package coderd

import (
	"bytes"
	"context"
	"database/sql"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"net/http"
	"net/url"
	"slices"
	"strings"
	"time"

	"github.com/go-chi/chi/v5"
	"github.com/google/uuid"
	"golang.org/x/oauth2"
	"golang.org/x/xerrors"

	"cdr.dev/slog/v3"
	"github.com/coder/coder/v2/coderd/audit"
	"github.com/coder/coder/v2/coderd/database"
	"github.com/coder/coder/v2/coderd/database/dbauthz"
	"github.com/coder/coder/v2/coderd/database/dbtime"
	"github.com/coder/coder/v2/coderd/httpapi"
	"github.com/coder/coder/v2/coderd/httpmw"
	"github.com/coder/coder/v2/coderd/promoauth"
	"github.com/coder/coder/v2/coderd/rbac"
	"github.com/coder/coder/v2/coderd/rbac/policy"
	"github.com/coder/coder/v2/coderd/x/chatd/mcpclient"
	"github.com/coder/coder/v2/codersdk"
)

// mcpProtocolVersion is copied from the official SDK, which does not export
// protocol version constants.
const mcpProtocolVersion = "2026-07-28"

// oidcMCPTokenSource implements mcpclient.UserOIDCTokenSource using
// the same refresh strategy as provisionerdserver.ObtainOIDCAccessToken.
// The logic is duplicated to avoid importing provisionerdserver from
// coderd; keep the two in sync.
type oidcMCPTokenSource struct {
	db     database.Store
	config promoauth.OAuth2Config
	logger slog.Logger
}

// newOIDCMCPTokenSource returns nil when no OIDC provider is
// configured. mcpclient treats a nil source the same as "no token
// available" and omits the Authorization header.
func newOIDCMCPTokenSource(db database.Store, config promoauth.OAuth2Config, logger slog.Logger) mcpclient.UserOIDCTokenSource {
	if config == nil {
		return nil
	}
	return &oidcMCPTokenSource{
		db:     db,
		config: config,
		logger: logger,
	}
}

// OIDCAccessToken refreshes and persists the user's OIDC token.
func (s *oidcMCPTokenSource) OIDCAccessToken(ctx context.Context, userID uuid.UUID) (string, error) {
	//nolint:gocritic // user_links read needs system access; the
	// caller's user identity is supplied via the userID parameter.
	dbCtx := dbauthz.AsSystemRestricted(ctx)
	link, err := s.db.GetUserLinkByUserIDLoginType(dbCtx, database.GetUserLinkByUserIDLoginTypeParams{
		UserID:    userID,
		LoginType: database.LoginTypeOIDC,
	})
	if errors.Is(err, sql.ErrNoRows) {
		return "", nil
	}
	if err != nil {
		return "", xerrors.Errorf("get oidc user link: %w", err)
	}

	if shouldRefresh, expiresAt := shouldRefreshOIDCToken(link); shouldRefresh {
		token, err := s.config.TokenSource(ctx, &oauth2.Token{
			AccessToken:  link.OAuthAccessToken,
			RefreshToken: link.OAuthRefreshToken,
			// Use the expiresAt returned by shouldRefreshOIDCToken.
			// It will force a refresh with an expired time.
			Expiry: expiresAt,
		}).Token()
		if err != nil {
			// Don't fail the request; the upstream MCP server will see no
			// Authorization header and can return a 401 if it requires one.
			s.logger.Warn(ctx, "failed to refresh OIDC token for MCP request",
				slog.F("user_id", userID),
				slog.Error(err),
			)
			return "", nil
		}
		link.OAuthAccessToken = token.AccessToken
		link.OAuthRefreshToken = token.RefreshToken
		link.OAuthExpiry = token.Expiry

		// Persist on a detached context so a canceled chat request
		// cannot drop a refresh-token rotation, see PR #24332.
		persistCtx, persistCancel := context.WithTimeout(
			context.WithoutCancel(dbCtx), 10*time.Second,
		)
		link, err = s.db.UpdateUserLink(persistCtx, database.UpdateUserLinkParams{
			UserID:                 userID,
			LoginType:              database.LoginTypeOIDC,
			OAuthAccessToken:       link.OAuthAccessToken,
			OAuthAccessTokenKeyID:  sql.NullString{}, // set by dbcrypt if required
			OAuthRefreshToken:      link.OAuthRefreshToken,
			OAuthRefreshTokenKeyID: sql.NullString{}, // set by dbcrypt if required
			OAuthExpiry:            link.OAuthExpiry,
			Claims:                 link.Claims,
		})
		persistCancel()
		if err != nil {
			return "", xerrors.Errorf("update user link after oidc refresh: %w", err)
		}
		s.logger.Info(ctx, "refreshed expired OIDC token for MCP request",
			slog.F("user_id", userID),
		)
	}

	return link.OAuthAccessToken, nil
}

// shouldRefreshOIDCToken mirrors provisionerdserver.shouldRefreshOIDCToken.
// See that function for the rationale behind the 10-minute pre-expiry
// buffer.
func shouldRefreshOIDCToken(link database.UserLink) (bool, time.Time) {
	if link.OAuthRefreshToken == "" {
		return false, link.OAuthExpiry
	}
	if link.OAuthExpiry.IsZero() {
		// A zero expiry means the token never expires.
		return false, link.OAuthExpiry
	}
	expiresAt := link.OAuthExpiry.Add(-time.Minute * 10)
	return expiresAt.Before(dbtime.Now()), expiresAt
}

// @Summary List MCP server configs
// @ID list-mcp-server-configs
// @Security CoderSessionToken
// @Tags MCP
// @Produce json
// @Param organization path string true "Organization ID" format(uuid)
// @Success 200 {array} codersdk.MCPServerConfig
// @Router /api/experimental/organizations/{organization}/mcp-servers [get]
// @x-apidocgen {"skip": true}
// EXPERIMENTAL: this endpoint is experimental and is subject to change.
//
//nolint:revive // HTTP handler writes to ResponseWriter.
func (api *API) listMCPServerConfigs(rw http.ResponseWriter, r *http.Request) {
	ctx := r.Context()
	apiKey := httpmw.APIKey(r)
	organization := httpmw.OrganizationParam(r)

	// Full view: disabled configs included, management fields unredacted,
	// fetched with system access behind this gate. Auditors get it to
	// inspect audit-logged resources but stay subject to per-server ACLs
	// elsewhere. Other members see enabled ACL-granted configs, redacted.
	// The update leg also requires config read so a custom role granting
	// update without read cannot lift the read filtering below.
	hasFullView := ((api.Authorize(r, policy.ActionRead, rbac.ResourceMCPServerConfig.InOrg(organization.ID)) &&
		api.Authorize(r, policy.ActionUpdate, rbac.ResourceMCPServerConfig.InOrg(organization.ID))) ||
		api.Authorize(r, policy.ActionRead, rbac.ResourceAuditLog.InOrg(organization.ID))) &&
		api.mcpServerConfigReadInKeyScope(r, organization.ID)

	var configs []database.MCPServerConfig
	var err error
	if hasFullView {
		//nolint:gocritic // The update-or-audit gate above owns this authorization.
		configs, err = api.Database.GetMCPServerConfigsByOrganization(dbauthz.AsSystemRestricted(ctx), organization.ID)
	} else if api.mcpServerConfigReadInKeyScope(r, organization.ID) {
		seen := make(map[uuid.UUID]struct{})
		for _, action := range []policy.Action{policy.ActionRead, policy.ActionUpdate, policy.ActionDelete, policy.ActionShare} {
			prepared, prepareErr := api.HTTPAuth.AuthorizeSQLFilter(r, action, rbac.ResourceMCPServerConfig.Type)
			if prepareErr != nil {
				httpapi.InternalServerError(rw, prepareErr)
				return
			}
			authorized, queryErr := api.Database.GetAuthorizedMCPServerConfigs(ctx, organization.ID, prepared)
			if queryErr != nil {
				err = queryErr
				break
			}
			for _, config := range authorized {
				if _, ok := seen[config.ID]; ok {
					continue
				}
				seen[config.ID] = struct{}{}
				configs = append(configs, config)
			}
		}
		slices.SortFunc(configs, func(a, b database.MCPServerConfig) int {
			return strings.Compare(a.DisplayName, b.DisplayName)
		})
		// Management-authorized callers keep disabled configs in the redacted
		// list so they can still reach and manage them.
		configs = slices.DeleteFunc(configs, func(config database.MCPServerConfig) bool {
			return !config.Enabled &&
				!api.Authorize(r, policy.ActionUpdate, config) &&
				!api.Authorize(r, policy.ActionDelete, config) &&
				!api.Authorize(r, policy.ActionShare, config)
		})
	}
	if err != nil {
		httpapi.Write(ctx, rw, http.StatusInternalServerError, codersdk.Response{
			Message: "Failed to list MCP server configs.",
			Detail:  err.Error(),
		})
		return
	}

	// Read and refresh OAuth2 tokens only when the caller may view them.
	// Without that permission, auth_connected remains false.
	var userTokens []database.MCPServerUserToken
	tokenReadErr := api.HTTPAuth.Authorizer.Authorize(ctx, httpmw.UserAuthorization(ctx),
		policy.ActionReadPersonal, rbac.ResourceUserObject(apiKey.UserID).RBACObject())
	if tokenReadErr == nil {
		userTokens, err = api.Database.GetMCPServerUserTokensByUserID(ctx, apiKey.UserID)
		if err != nil {
			httpapi.Write(ctx, rw, http.StatusInternalServerError, codersdk.Response{
				Message: "Failed to get user tokens.",
				Detail:  err.Error(),
			})
			return
		}
	}

	// Build a config lookup for the refresh helper.
	configByID := make(map[uuid.UUID]database.MCPServerConfig, len(configs))
	for _, c := range configs {
		configByID[c.ID] = c
	}

	tokenMap := make(map[uuid.UUID]bool, len(userTokens))
	for _, tok := range userTokens {
		cfg, ok := configByID[tok.MCPServerConfigID]
		if !ok {
			continue
		}
		tokenMap[tok.MCPServerConfigID] = api.refreshMCPUserToken(ctx, cfg, tok)
	}

	resp := make([]codersdk.MCPServerConfig, 0, len(configs))
	for _, config := range configs {
		var sdkConfig codersdk.MCPServerConfig
		if hasFullView {
			sdkConfig = convertMCPServerConfig(config)
		} else {
			sdkConfig = convertMCPServerConfigRedacted(config)
		}
		if config.AuthType == "oauth2" {
			sdkConfig.AuthConnected = tokenMap[config.ID]
		}
		resp = append(resp, sdkConfig)
	}

	httpapi.Write(ctx, rw, http.StatusOK, resp)
}

// mcpServerConfigReadInKeyScope reports whether the caller's API key scope
// permits reading MCP server configs. The full-view list fetch bypasses row
// authorization with system access, so the key's scope must be enforced here.
// Owner roles make the authorize outcome depend only on the scope dimension.
func (api *API) mcpServerConfigReadInKeyScope(r *http.Request, organizationID uuid.UUID) bool {
	caller := httpmw.UserAuthorization(r.Context())
	scopeOnly := rbac.Subject{
		Type:         caller.Type,
		FriendlyName: caller.FriendlyName,
		ID:           caller.ID,
		Roles:        rbac.RoleIdentifiers{rbac.RoleOwner()},
		Scope:        caller.Scope,
	}
	err := api.HTTPAuth.Authorizer.Authorize(r.Context(), scopeOnly,
		policy.ActionRead, rbac.ResourceMCPServerConfig.InOrg(organizationID))
	return err == nil
}

// @Summary Create MCP server config
// @ID create-mcp-server-config
// @Security CoderSessionToken
// @Tags MCP
// @Accept json
// @Produce json
// @Param organization path string true "Organization ID" format(uuid)
// @Param request body codersdk.CreateMCPServerConfigRequest true "Create MCP server config request"
// @Success 201 {object} codersdk.MCPServerConfig
// @Router /api/experimental/organizations/{organization}/mcp-servers [post]
// @x-apidocgen {"skip": true}
// EXPERIMENTAL: this endpoint is experimental and is subject to change.
//
//nolint:revive // HTTP handler writes to ResponseWriter.
func (api *API) createMCPServerConfig(rw http.ResponseWriter, r *http.Request) {
	ctx := r.Context()
	apiKey := httpmw.APIKey(r)
	organization := httpmw.OrganizationParam(r)
	auditor := api.Auditor.Load()
	aReq, commitAudit := audit.InitRequest[database.MCPServerConfig](rw, &audit.RequestParams{
		Audit:          *auditor,
		Log:            api.Logger,
		Request:        r,
		Action:         database.AuditActionCreate,
		OrganizationID: organization.ID,
	})
	defer commitAudit()
	if !api.Authorize(r, policy.ActionCreate, rbac.ResourceMCPServerConfig.InOrg(organization.ID)) {
		httpapi.Forbidden(rw)
		return
	}

	var req codersdk.CreateMCPServerConfigRequest
	if !httpapi.Read(ctx, rw, r, &req) {
		return
	}

	if req.AuthType == "user_oidc" && !api.authorizeUserOIDCMCPServerConfig(rw, r) {
		return
	}

	if trimmed := strings.TrimSpace(req.OAuth2RevocationURL); trimmed != "" {
		if err := mcpclient.ValidateRevocationEndpoint(trimmed); err != nil {
			httpapi.Write(ctx, rw, http.StatusBadRequest, codersdk.Response{
				Message: "Invalid OAuth2 revocation URL.",
				Detail:  "oauth2_revocation_url must be an https URL (loopback hosts may use http).",
			})
			return
		}
	}

	configID := uuid.New()

	// Validate auth-type-dependent fields.
	switch req.AuthType {
	case "oauth2":
		// When the admin does not provide OAuth2 credentials, attempt
		// automatic discovery and Dynamic Client Registration (RFC 7591)
		// using the MCP server URL.  This follows the MCP authorization
		// spec: discover the authorization server via Protected Resource
		// Metadata (RFC 9728) and Authorization Server Metadata
		// (RFC 8414), then register a client dynamically.
		if req.OAuth2ClientID == "" && req.OAuth2AuthURL == "" && req.OAuth2TokenURL == "" {
			// Create-only callers cannot read configs. This pre-DCR check reveals nothing
			// beyond the insert's conflict response, which remains authoritative for races.
			//nolint:gocritic // Restrict system access to this existence check.
			_, err := api.Database.GetMCPServerConfigByOrganizationAndSlug(dbauthz.AsSystemRestricted(ctx), database.GetMCPServerConfigByOrganizationAndSlugParams{
				OrganizationID: organization.ID,
				Slug:           strings.TrimSpace(req.Slug),
			})
			switch {
			case err == nil:
				httpapi.Write(ctx, rw, http.StatusConflict, codersdk.Response{
					Message: "MCP server config already exists.",
				})
				return
			case !errors.Is(err, sql.ErrNoRows):
				httpapi.Write(ctx, rw, http.StatusInternalServerError, codersdk.Response{
					Message: "Failed to create MCP server config.",
					Detail:  err.Error(),
				})
				return
			}

			callbackURL := api.AccessURL.String() + mcpServerOAuth2CallbackPath(configID)
			// Discovery targets are attacker-influenced (the MCP
			// server URL and any endpoints or redirects it
			// advertises), so all discovery traffic goes through an
			// SSRF-guarded client that refuses private/internal
			// destinations (CDM-02-002).
			httpClient := newMCPDiscoveryHTTPClient(api.HTTPClient, api.MCPOAuth2DiscoveryAllowedIPRanges)
			result, err := discoverAndRegisterMCPOAuth2(ctx, httpClient, strings.TrimSpace(req.URL), callbackURL)
			if err != nil {
				api.Logger.Warn(ctx, "mcp oauth2 auto-discovery failed",
					slog.F("url", req.URL),
					slog.Error(err),
				)
				httpapi.Write(ctx, rw, http.StatusBadRequest, codersdk.Response{
					Message: "OAuth2 auto-discovery failed. Provide oauth2_client_id, oauth2_auth_url, and oauth2_token_url manually, or ensure the MCP server supports RFC 9728 (Protected Resource Metadata) and RFC 7591 (Dynamic Client Registration).",
					Detail:  err.Error(),
				})
				return
			}

			// Determine scopes: use the request value if provided,
			// otherwise fall back to the discovered value.
			oauth2Scopes := strings.TrimSpace(req.OAuth2Scopes)
			if oauth2Scopes == "" {
				oauth2Scopes = result.scopes
			}

			// A discovered endpoint that fails the HTTPS policy is
			// dropped instead of failing creation.
			oauth2RevocationURL := strings.TrimSpace(req.OAuth2RevocationURL)
			if oauth2RevocationURL == "" {
				oauth2RevocationURL = result.revocationURL
				if oauth2RevocationURL != "" {
					if err := mcpclient.ValidateRevocationEndpoint(oauth2RevocationURL); err != nil {
						api.Logger.Warn(ctx, "ignoring discovered MCP oauth2 revocation endpoint",
							slog.F("url", req.URL),
							slog.Error(err),
						)
						oauth2RevocationURL = ""
					}
				}
			}

			req.OAuth2ClientID = result.clientID
			req.OAuth2ClientSecret = result.clientSecret
			req.OAuth2AuthURL = result.authURL
			req.OAuth2TokenURL = result.tokenURL
			req.OAuth2RevocationURL = oauth2RevocationURL
			req.OAuth2Scopes = oauth2Scopes
		} else if req.OAuth2ClientID == "" || req.OAuth2AuthURL == "" || req.OAuth2TokenURL == "" {
			// Partial manual config: all three fields are required together.
			httpapi.Write(ctx, rw, http.StatusBadRequest, codersdk.Response{
				Message: "OAuth2 auth type requires either all of oauth2_client_id, oauth2_auth_url, and oauth2_token_url (manual configuration), or none of them (automatic discovery via RFC 7591).",
			})
			return
		}
	case "api_key":
		if req.APIKeyHeader == "" || req.APIKeyValue == "" {
			httpapi.Write(ctx, rw, http.StatusBadRequest, codersdk.Response{
				Message: "API key auth type requires api_key_header and api_key_value.",
			})
			return
		}
	case "custom_headers":
		if len(req.CustomHeaders) == 0 {
			httpapi.Write(ctx, rw, http.StatusBadRequest, codersdk.Response{
				Message: "Custom headers auth type requires at least one custom header.",
			})
			return
		}
	}

	customHeadersJSON, err := marshalCustomHeaders(req.CustomHeaders)
	if err != nil {
		httpapi.Write(ctx, rw, http.StatusBadRequest, codersdk.Response{
			Message: "Invalid custom headers.",
			Detail:  err.Error(),
		})
		return
	}

	inserted, err := api.Database.InsertMCPServerConfig(ctx, database.InsertMCPServerConfigParams{
		ID:                      configID,
		OrganizationID:          organization.ID,
		DisplayName:             strings.TrimSpace(req.DisplayName),
		Slug:                    strings.TrimSpace(req.Slug),
		Description:             strings.TrimSpace(req.Description),
		IconURL:                 strings.TrimSpace(req.IconURL),
		Transport:               strings.TrimSpace(req.Transport),
		Url:                     strings.TrimSpace(req.URL),
		AuthType:                strings.TrimSpace(req.AuthType),
		OAuth2ClientID:          strings.TrimSpace(req.OAuth2ClientID),
		OAuth2ClientSecret:      strings.TrimSpace(req.OAuth2ClientSecret),
		OAuth2ClientSecretKeyID: sql.NullString{},
		OAuth2AuthURL:           strings.TrimSpace(req.OAuth2AuthURL),
		OAuth2TokenURL:          strings.TrimSpace(req.OAuth2TokenURL),
		OAuth2RevocationURL:     strings.TrimSpace(req.OAuth2RevocationURL),
		OAuth2Scopes:            strings.TrimSpace(req.OAuth2Scopes),
		APIKeyHeader:            strings.TrimSpace(req.APIKeyHeader),
		APIKeyValue:             strings.TrimSpace(req.APIKeyValue),
		APIKeyValueKeyID:        sql.NullString{},
		CustomHeaders:           customHeadersJSON,
		CustomHeadersKeyID:      sql.NullString{},
		ToolAllowList:           coalesceStringSlice(trimStringSlice(req.ToolAllowList)),
		ToolDenyList:            coalesceStringSlice(trimStringSlice(req.ToolDenyList)),
		Availability:            strings.TrimSpace(req.Availability),
		Enabled:                 req.Enabled,
		ModelIntent:             req.ModelIntent,
		AllowInPlanMode:         req.AllowInPlanMode,
		ForwardCoderHeaders:     req.ForwardCoderHeaders,
		GroupACL: database.ChatACL{
			organization.ID.String(): {Permissions: []policy.Action{policy.ActionRead}},
		},
		UserACL:   database.ChatACL{},
		CreatedBy: apiKey.UserID,
		UpdatedBy: apiKey.UserID,
	})
	if err != nil {
		switch {
		case database.IsUniqueViolation(err):
			httpapi.Write(ctx, rw, http.StatusConflict, codersdk.Response{
				Message: "MCP server config already exists.",
				Detail:  err.Error(),
			})
			return
		case database.IsCheckViolation(err):
			httpapi.Write(ctx, rw, http.StatusBadRequest, codersdk.Response{
				Message: "Invalid MCP server config.",
				Detail:  err.Error(),
			})
			return
		default:
			httpapi.Write(ctx, rw, http.StatusInternalServerError, codersdk.Response{
				Message: "Failed to create MCP server config.",
				Detail:  err.Error(),
			})
			return
		}
	}

	aReq.New = inserted

	httpapi.Write(ctx, rw, http.StatusCreated, convertMCPServerConfig(inserted))
}

// @Summary Get MCP server config
// @ID get-mcp-server-config
// @Security CoderSessionToken
// @Tags MCP
// @Produce json
// @Param organization path string true "Organization ID" format(uuid)
// @Param mcpserverconfig path string true "MCP server config ID" format(uuid)
// @Success 200 {object} codersdk.MCPServerConfig
// @Router /api/experimental/organizations/{organization}/mcp-servers/{mcpserverconfig} [get]
// @x-apidocgen {"skip": true}
// EXPERIMENTAL: this endpoint is experimental and is subject to change.
//
//nolint:revive // HTTP handler writes to ResponseWriter.
func (api *API) getMCPServerConfig(rw http.ResponseWriter, r *http.Request) {
	ctx := r.Context()
	apiKey := httpmw.APIKey(r)
	config := httpmw.MCPServerConfigParam(r)
	if !api.mcpServerConfigReadInKeyScope(r, config.OrganizationID) {
		httpapi.ResourceNotFound(rw)
		return
	}

	// Same full-view rule as listMCPServerConfigs: admins and auditors.
	hasFullView := api.Authorize(r, policy.ActionUpdate, config) ||
		api.Authorize(r, policy.ActionRead, rbac.ResourceAuditLog.InOrg(config.OrganizationID))
	if !hasFullView && !config.Enabled &&
		!api.Authorize(r, policy.ActionDelete, config) {
		httpapi.ResourceNotFound(rw)
		return
	}

	var sdkConfig codersdk.MCPServerConfig
	if hasFullView {
		sdkConfig = convertMCPServerConfig(config)
	} else {
		sdkConfig = convertMCPServerConfigRedacted(config)
	}

	// Refresh readable token state so AuthConnected reflects the current
	// OAuth status.
	if config.AuthType == "oauth2" {
		tok, err := api.Database.GetMCPServerUserToken(ctx, database.GetMCPServerUserTokenParams{
			MCPServerConfigID: config.ID,
			UserID:            apiKey.UserID,
		})
		if err == nil {
			sdkConfig.AuthConnected = api.refreshMCPUserToken(ctx, config, tok)
			// Token visibility is separately scoped, so denial means disconnected here.
		} else if !errors.Is(err, sql.ErrNoRows) && !dbauthz.IsNotAuthorizedError(err) {
			httpapi.Write(ctx, rw, http.StatusInternalServerError, codersdk.Response{
				Message: "Failed to get user token.",
				Detail:  err.Error(),
			})
			return
		}
	}

	httpapi.Write(ctx, rw, http.StatusOK, sdkConfig)
}

var errUserOIDCRequiresDeploymentPerms = xerrors.New("managing user_oidc MCP server configs requires deployment-level permissions")

var errMCPConfigSupersededDuringAuth = xerrors.New("MCP server config superseded during authorization")

// authorizeUserOIDCMCPServerConfig requires deployment-level permission because
// user_oidc sends each chat owner's upstream OIDC access token to the configured
// URL without a per-user consent step.
func (api *API) authorizeUserOIDCMCPServerConfig(rw http.ResponseWriter, r *http.Request) bool {
	if api.Authorize(r, policy.ActionUpdate, rbac.ResourceDeploymentConfig) {
		return true
	}
	httpapi.Write(r.Context(), rw, http.StatusForbidden, codersdk.Response{
		Message: "Managing user_oidc MCP server configs requires deployment-level permissions.",
	})
	return false
}

// Preserve the param middleware's 404 concealment. Write denial is a 403.
func (api *API) getMCPServerConfigForMutation(rw http.ResponseWriter, r *http.Request, action policy.Action) (database.MCPServerConfig, bool) {
	config := httpmw.MCPServerConfigParam(r)
	if !api.Authorize(r, action, config) {
		httpapi.Forbidden(rw)
		return database.MCPServerConfig{}, false
	}
	return config, true
}

// @Summary Update MCP server config
// @ID update-mcp-server-config
// @Security CoderSessionToken
// @Tags MCP
// @Accept json
// @Produce json
// @Param organization path string true "Organization ID" format(uuid)
// @Param mcpserverconfig path string true "MCP server config ID" format(uuid)
// @Param request body codersdk.UpdateMCPServerConfigRequest true "Update MCP server config request"
// @Success 200 {object} codersdk.MCPServerConfig
// @Router /api/experimental/organizations/{organization}/mcp-servers/{mcpserverconfig} [patch]
// @x-apidocgen {"skip": true}
// EXPERIMENTAL: this endpoint is experimental and is subject to change.
//
//nolint:revive // HTTP handler writes to ResponseWriter.
func (api *API) updateMCPServerConfig(rw http.ResponseWriter, r *http.Request) {
	ctx := r.Context()
	apiKey := httpmw.APIKey(r)
	auditor := api.Auditor.Load()
	aReq, commitAudit := audit.InitRequest[database.MCPServerConfig](rw, &audit.RequestParams{
		Audit:   *auditor,
		Log:     api.Logger,
		Request: r,
		Action:  database.AuditActionWrite,
	})
	defer commitAudit()

	// Set Old before the requested-action check so callers admitted for a
	// different action are audited when this handler denies them with 403.
	aReq.Old = httpmw.MCPServerConfigParam(r)
	aReq.UpdateOrganizationID(aReq.Old.OrganizationID)

	existing, ok := api.getMCPServerConfigForMutation(rw, r, policy.ActionUpdate)
	if !ok {
		return
	}

	var req codersdk.UpdateMCPServerConfigRequest
	if !httpapi.Read(ctx, rw, r, &req) {
		return
	}

	// Validated here rather than via a struct tag because an empty
	// string is a valid value that clears the stored URL.
	if req.OAuth2RevocationURL != nil {
		if trimmed := strings.TrimSpace(*req.OAuth2RevocationURL); trimmed != "" {
			if err := httpapi.Validate.VarCtx(ctx, trimmed, "url"); err != nil {
				httpapi.Write(ctx, rw, http.StatusBadRequest, codersdk.Response{
					Message: "Invalid OAuth2 revocation URL.",
					Detail:  "oauth2_revocation_url must be a valid URL or an empty string.",
				})
				return
			}
			// Same policy as RevokeOAuth2Token, so stored URLs are
			// not refused later at disconnect time.
			if err := mcpclient.ValidateRevocationEndpoint(trimmed); err != nil {
				httpapi.Write(ctx, rw, http.StatusBadRequest, codersdk.Response{
					Message: "Invalid OAuth2 revocation URL.",
					Detail:  "oauth2_revocation_url must be an https URL (loopback hosts may use http).",
				})
				return
			}
		}
	}

	// Pre-validate custom headers before entering the transaction.
	var customHeadersJSON string
	if req.CustomHeaders != nil {
		var chErr error
		customHeadersJSON, chErr = marshalCustomHeaders(*req.CustomHeaders)
		if chErr != nil {
			httpapi.Write(ctx, rw, http.StatusBadRequest, codersdk.Response{
				Message: "Invalid custom headers.",
				Detail:  chErr.Error(),
			})
			return
		}
	}

	var updated database.MCPServerConfig
	err := api.Database.InTx(func(tx database.Store) error {
		// Lock and re-fetch the row so omitted fields and the audit baseline
		// match the row this update replaces, and so grant invalidation
		// serializes with in-flight OAuth callbacks verifying the config.
		//nolint:gocritic // The update write reauthorizes the locked row.
		current, err := tx.GetMCPServerConfigByIDForUpdate(dbauthz.AsSystemRestricted(ctx), existing.ID)
		if err != nil {
			return err
		}
		existing = current
		aReq.Old = current

		touchesUserOIDC := existing.AuthType == "user_oidc" ||
			(req.AuthType != nil && *req.AuthType == "user_oidc")
		if touchesUserOIDC && !api.Authorize(r, policy.ActionUpdate, rbac.ResourceDeploymentConfig) {
			return errUserOIDCRequiresDeploymentPerms
		}

		displayName := existing.DisplayName
		if req.DisplayName != nil {
			displayName = strings.TrimSpace(*req.DisplayName)
		}

		slug := existing.Slug
		if req.Slug != nil {
			slug = strings.TrimSpace(*req.Slug)
		}

		description := existing.Description
		if req.Description != nil {
			description = strings.TrimSpace(*req.Description)
		}

		iconURL := existing.IconURL
		if req.IconURL != nil {
			iconURL = strings.TrimSpace(*req.IconURL)
		}

		transport := existing.Transport
		if req.Transport != nil {
			transport = strings.TrimSpace(*req.Transport)
		}

		serverURL := existing.Url
		if req.URL != nil {
			serverURL = strings.TrimSpace(*req.URL)
		}

		authType := existing.AuthType
		if req.AuthType != nil {
			authType = strings.TrimSpace(*req.AuthType)
		}

		oauth2ClientID := existing.OAuth2ClientID
		if req.OAuth2ClientID != nil {
			oauth2ClientID = strings.TrimSpace(*req.OAuth2ClientID)
		}

		oauth2ClientSecret := existing.OAuth2ClientSecret
		oauth2ClientSecretKeyID := existing.OAuth2ClientSecretKeyID
		if req.OAuth2ClientSecret != nil {
			oauth2ClientSecret = strings.TrimSpace(*req.OAuth2ClientSecret)
			// Clear the key ID when the secret is explicitly updated.
			oauth2ClientSecretKeyID = sql.NullString{}
		}

		oauth2AuthURL := existing.OAuth2AuthURL
		if req.OAuth2AuthURL != nil {
			oauth2AuthURL = strings.TrimSpace(*req.OAuth2AuthURL)
		}

		oauth2TokenURL := existing.OAuth2TokenURL
		if req.OAuth2TokenURL != nil {
			oauth2TokenURL = strings.TrimSpace(*req.OAuth2TokenURL)
		}

		oauth2RevocationURL := existing.OAuth2RevocationURL
		if req.OAuth2RevocationURL != nil {
			oauth2RevocationURL = strings.TrimSpace(*req.OAuth2RevocationURL)
		}

		oauth2Scopes := existing.OAuth2Scopes
		if req.OAuth2Scopes != nil {
			oauth2Scopes = strings.TrimSpace(*req.OAuth2Scopes)
		}

		apiKeyHeader := existing.APIKeyHeader
		if req.APIKeyHeader != nil {
			apiKeyHeader = strings.TrimSpace(*req.APIKeyHeader)
		}

		apiKeyValue := existing.APIKeyValue
		apiKeyValueKeyID := existing.APIKeyValueKeyID
		if req.APIKeyValue != nil {
			apiKeyValue = strings.TrimSpace(*req.APIKeyValue)
			// Clear the key ID when the value is explicitly updated.
			apiKeyValueKeyID = sql.NullString{}
		}

		customHeaders := existing.CustomHeaders
		customHeadersKeyID := existing.CustomHeadersKeyID
		if req.CustomHeaders != nil {
			customHeaders = customHeadersJSON
			// Clear the key ID when headers are explicitly updated.
			customHeadersKeyID = sql.NullString{}
		}

		toolAllowList := existing.ToolAllowList
		if req.ToolAllowList != nil {
			toolAllowList = coalesceStringSlice(trimStringSlice(*req.ToolAllowList))
		}

		toolDenyList := existing.ToolDenyList
		if req.ToolDenyList != nil {
			toolDenyList = coalesceStringSlice(trimStringSlice(*req.ToolDenyList))
		}

		availability := existing.Availability
		if req.Availability != nil {
			availability = strings.TrimSpace(*req.Availability)
		}

		enabled := existing.Enabled
		if req.Enabled != nil {
			enabled = *req.Enabled
		}

		modelIntent := existing.ModelIntent
		if req.ModelIntent != nil {
			modelIntent = *req.ModelIntent
		}

		allowInPlanMode := existing.AllowInPlanMode
		if req.AllowInPlanMode != nil {
			allowInPlanMode = *req.AllowInPlanMode
		}

		forwardCoderHeaders := existing.ForwardCoderHeaders
		if req.ForwardCoderHeaders != nil {
			forwardCoderHeaders = *req.ForwardCoderHeaders
		}

		// When auth_type changes, clear fields belonging to the
		// previous auth type so stale secrets don't persist.
		if authType != existing.AuthType {
			switch authType {
			case "none":
				oauth2ClientID = ""
				oauth2ClientSecret = ""
				oauth2ClientSecretKeyID = sql.NullString{}
				oauth2AuthURL = ""
				oauth2TokenURL = ""
				oauth2RevocationURL = ""
				oauth2Scopes = ""
				apiKeyHeader = ""
				apiKeyValue = ""
				apiKeyValueKeyID = sql.NullString{}
				customHeaders = "{}"
				customHeadersKeyID = sql.NullString{}
			case "oauth2":
				apiKeyHeader = ""
				apiKeyValue = ""
				apiKeyValueKeyID = sql.NullString{}
				customHeaders = "{}"
				customHeadersKeyID = sql.NullString{}
			case "api_key":
				oauth2ClientID = ""
				oauth2ClientSecret = ""
				oauth2ClientSecretKeyID = sql.NullString{}
				oauth2AuthURL = ""
				oauth2TokenURL = ""
				oauth2RevocationURL = ""
				oauth2Scopes = ""
				customHeaders = "{}"
				customHeadersKeyID = sql.NullString{}
			case "custom_headers":
				oauth2ClientID = ""
				oauth2ClientSecret = ""
				oauth2ClientSecretKeyID = sql.NullString{}
				oauth2AuthURL = ""
				oauth2TokenURL = ""
				oauth2RevocationURL = ""
				oauth2Scopes = ""
				apiKeyHeader = ""
				apiKeyValue = ""
				apiKeyValueKeyID = sql.NullString{}
			case "user_oidc":
				// user_oidc forwards the calling user's OIDC access token
				// from user_links at request time, so no admin-configured
				// secrets are stored on the row.
				oauth2ClientID = ""
				oauth2ClientSecret = ""
				oauth2ClientSecretKeyID = sql.NullString{}
				oauth2AuthURL = ""
				oauth2TokenURL = ""
				oauth2RevocationURL = ""
				oauth2Scopes = ""
				apiKeyHeader = ""
				apiKeyValue = ""
				apiKeyValueKeyID = sql.NullString{}
				customHeaders = "{}"
				customHeadersKeyID = sql.NullString{}
			}
		}

		// User grants are bound to the destination, auth flow, token and revocation
		// endpoints, and OAuth client. Invalidate them when any of these change so
		// stored tokens cannot be sent to another endpoint or client.
		if serverURL != existing.Url || authType != existing.AuthType ||
			oauth2TokenURL != existing.OAuth2TokenURL || oauth2RevocationURL != existing.OAuth2RevocationURL ||
			oauth2ClientID != existing.OAuth2ClientID {
			if err := tx.DeleteMCPServerUserTokensByConfigID(ctx, existing.ID); err != nil {
				return xerrors.Errorf("invalidate MCP server user tokens: %w", err)
			}
		}

		updatedConfig, err := tx.UpdateMCPServerConfig(ctx, database.UpdateMCPServerConfigParams{
			DisplayName:             displayName,
			Slug:                    slug,
			Description:             description,
			IconURL:                 iconURL,
			Transport:               transport,
			Url:                     serverURL,
			AuthType:                authType,
			OAuth2ClientID:          oauth2ClientID,
			OAuth2ClientSecret:      oauth2ClientSecret,
			OAuth2ClientSecretKeyID: oauth2ClientSecretKeyID,
			OAuth2AuthURL:           oauth2AuthURL,
			OAuth2TokenURL:          oauth2TokenURL,
			OAuth2RevocationURL:     oauth2RevocationURL,
			OAuth2Scopes:            oauth2Scopes,
			APIKeyHeader:            apiKeyHeader,
			APIKeyValue:             apiKeyValue,
			APIKeyValueKeyID:        apiKeyValueKeyID,
			CustomHeaders:           customHeaders,
			CustomHeadersKeyID:      customHeadersKeyID,
			ToolAllowList:           toolAllowList,
			ToolDenyList:            toolDenyList,
			Availability:            availability,
			Enabled:                 enabled,
			ModelIntent:             modelIntent,
			AllowInPlanMode:         allowInPlanMode,
			ForwardCoderHeaders:     forwardCoderHeaders,
			UpdatedBy:               apiKey.UserID,
			ID:                      existing.ID,
		})
		if err != nil {
			return err
		}
		updated = updatedConfig
		return nil
	}, nil)
	if err != nil {
		switch {
		case errors.Is(err, errUserOIDCRequiresDeploymentPerms):
			httpapi.Write(ctx, rw, http.StatusForbidden, codersdk.Response{
				Message: "Managing user_oidc MCP server configs requires deployment-level permissions.",
			})
			return
		case httpapi.Is404Error(err):
			httpapi.ResourceNotFound(rw)
			return
		case database.IsUniqueViolation(err):
			httpapi.Write(ctx, rw, http.StatusConflict, codersdk.Response{
				Message: "MCP server config slug already exists.",
				Detail:  err.Error(),
			})
			return
		case database.IsCheckViolation(err):
			httpapi.Write(ctx, rw, http.StatusBadRequest, codersdk.Response{
				Message: "Invalid MCP server config.",
				Detail:  err.Error(),
			})
			return
		default:
			httpapi.Write(ctx, rw, http.StatusInternalServerError, codersdk.Response{
				Message: "Failed to update MCP server config.",
				Detail:  err.Error(),
			})
			return
		}
	}

	aReq.New = updated

	httpapi.Write(ctx, rw, http.StatusOK, convertMCPServerConfig(updated))
}

// @Summary Delete MCP server config
// @ID delete-mcp-server-config
// @Security CoderSessionToken
// @Tags MCP
// @Param organization path string true "Organization ID" format(uuid)
// @Param mcpserverconfig path string true "MCP server config ID" format(uuid)
// @Success 204
// @Router /api/experimental/organizations/{organization}/mcp-servers/{mcpserverconfig} [delete]
// @x-apidocgen {"skip": true}
// EXPERIMENTAL: this endpoint is experimental and is subject to change.
func (api *API) deleteMCPServerConfig(rw http.ResponseWriter, r *http.Request) {
	ctx := r.Context()
	auditor := api.Auditor.Load()
	aReq, commitAudit := audit.InitRequest[database.MCPServerConfig](rw, &audit.RequestParams{
		Audit:   *auditor,
		Log:     api.Logger,
		Request: r,
		Action:  database.AuditActionDelete,
	})
	defer commitAudit()

	// Set Old before the requested-action check so callers admitted for a
	// different action are audited when this handler denies them with 403.
	aReq.Old = httpmw.MCPServerConfigParam(r)
	aReq.UpdateOrganizationID(aReq.Old.OrganizationID)

	config, ok := api.getMCPServerConfigForMutation(rw, r, policy.ActionDelete)
	if !ok {
		return
	}

	err := api.Database.InTx(func(tx database.Store) error {
		// Re-fetch under a row lock so the audit record describes the
		// row this request actually removes, not a middleware snapshot
		// that a concurrent update may have made stale.
		//nolint:gocritic // The delete write reauthorizes the locked row.
		current, err := tx.GetMCPServerConfigByIDForUpdate(dbauthz.AsSystemRestricted(ctx), config.ID)
		if err != nil {
			return err
		}
		aReq.Old = current
		return tx.DeleteMCPServerConfigByID(ctx, current.ID)
	}, nil)
	if err != nil {
		if httpapi.Is404Error(err) {
			httpapi.ResourceNotFound(rw)
			return
		}
		httpapi.Write(ctx, rw, http.StatusInternalServerError, codersdk.Response{
			Message: "Failed to delete MCP server config.",
			Detail:  err.Error(),
		})
		return
	}

	rw.WriteHeader(http.StatusNoContent)
}

// @Summary Initiate MCP server OAuth2 connect
// @ID initiate-mcp-server-oauth2-connect
// @Security CoderSessionToken
// @Tags MCP
// @Param organization path string true "Organization ID" format(uuid)
// @Param mcpserverconfig path string true "MCP server config ID" format(uuid)
// @Success 307
// @Router /api/experimental/organizations/{organization}/mcp-servers/{mcpserverconfig}/oauth2/connect [get]
// @x-apidocgen {"skip": true}
// EXPERIMENTAL: this endpoint is experimental and is subject to change.
// Redirects the user to the MCP server's OAuth2 authorization URL.
//
//nolint:revive // HTTP handler writes to ResponseWriter.
func (api *API) mcpServerOAuth2Connect(rw http.ResponseWriter, r *http.Request) {
	ctx := r.Context()
	config := httpmw.MCPServerConfigParam(r)

	if !config.Enabled {
		httpapi.Write(ctx, rw, http.StatusBadRequest, codersdk.Response{
			Message: "MCP server is not enabled.",
		})
		return
	}

	if config.AuthType != "oauth2" {
		httpapi.Write(ctx, rw, http.StatusBadRequest, codersdk.Response{
			Message: "MCP server does not use OAuth2 authentication.",
		})
		return
	}

	if config.OAuth2AuthURL == "" {
		httpapi.Write(ctx, rw, http.StatusBadRequest, codersdk.Response{
			Message: "MCP server OAuth2 authorization URL is not configured.",
		})
		return
	}

	// Do not start an authorization flow when its grant cannot be persisted.
	if !api.Authorize(r, policy.ActionUpdatePersonal, rbac.ResourceUserObject(httpmw.APIKey(r).UserID)) {
		httpapi.Forbidden(rw)
		return
	}

	// Build the authorization URL. The frontend opens this in a popup.
	// The callback URL is on our server; after the exchange we store
	// the token and close the popup.
	state := uuid.New().String()
	callbackPath := mcpServerOAuth2CallbackPath(config.ID)
	http.SetCookie(rw, api.DeploymentValues.HTTPCookies.Apply(&http.Cookie{
		Name:     "mcp_oauth2_state_" + config.ID.String(),
		Value:    state,
		Path:     callbackPath,
		MaxAge:   600, // 10 minutes
		HttpOnly: true,
		SameSite: http.SameSiteLaxMode,
	}))

	// PKCE (RFC 7636) is required by many OAuth2 providers (e.g.
	// Linear). We always send it because it is harmless when the
	// server ignores it and essential when it does not.
	verifier := oauth2.GenerateVerifier()
	http.SetCookie(rw, api.DeploymentValues.HTTPCookies.Apply(&http.Cookie{
		Name:     "mcp_oauth2_verifier_" + config.ID.String(),
		Value:    verifier,
		Path:     callbackPath,
		MaxAge:   600, // 10 minutes
		HttpOnly: true,
		SameSite: http.SameSiteLaxMode,
	}))

	oauth2Config := &oauth2.Config{
		ClientID:     config.OAuth2ClientID,
		ClientSecret: config.OAuth2ClientSecret,
		Endpoint: oauth2.Endpoint{
			AuthURL:  config.OAuth2AuthURL,
			TokenURL: config.OAuth2TokenURL,
		},
		RedirectURL: fmt.Sprintf("%s%s", api.AccessURL.String(), callbackPath),
	}
	var scopes []string
	if config.OAuth2Scopes != "" {
		scopes = strings.Split(config.OAuth2Scopes, " ")
	}
	oauth2Config.Scopes = scopes
	authURL := oauth2Config.AuthCodeURL(state, oauth2.S256ChallengeOption(verifier))
	http.Redirect(rw, r, authURL, http.StatusTemporaryRedirect)
}

// @Summary Handle MCP server OAuth2 callback
// @ID handle-mcp-server-oauth2-callback
// @Security CoderSessionToken
// @Tags MCP
// @Produce html
// @Param mcpServer path string true "MCP server config ID" format(uuid)
// @Param code query string false "Authorization code issued by the provider. Required together with state on success."
// @Param state query string false "Opaque state issued by the connect endpoint. Required together with code on success."
// @Param error query string false "Provider error code. Present instead of code when authorization fails."
// @Param error_description query string false "Provider error description accompanying error."
// @Success 200
// @Router /api/experimental/mcp/servers/{mcpServer}/oauth2/callback [get]
// @x-apidocgen {"skip": true}
// EXPERIMENTAL: this endpoint is experimental and is subject to change.
// Exchanges the authorization code for tokens and stores them.
//
//nolint:revive // HTTP handler writes to ResponseWriter.
func (api *API) mcpServerOAuth2Callback(rw http.ResponseWriter, r *http.Request) {
	ctx := r.Context()
	apiKey := httpmw.APIKey(r)

	mcpServerID, ok := parseMCPServerConfigID(rw, r)
	if !ok {
		return
	}

	// Authorization codes are one-time credentials. Do not consume one when
	// the resulting token cannot be persisted.
	if !api.Authorize(r, policy.ActionUpdatePersonal, rbac.ResourceUserObject(apiKey.UserID)) {
		httpapi.Forbidden(rw)
		return
	}

	config, err := api.Database.GetMCPServerConfigByID(ctx, mcpServerID)
	if err != nil {
		if httpapi.Is404Error(err) {
			httpapi.ResourceNotFound(rw)
			return
		}
		httpapi.InternalServerError(rw, err)
		return
	}

	if !config.Enabled {
		httpapi.Write(ctx, rw, http.StatusBadRequest, codersdk.Response{
			Message: "MCP server is not enabled.",
		})
		return
	}

	if config.AuthType != "oauth2" {
		httpapi.Write(ctx, rw, http.StatusBadRequest, codersdk.Response{
			Message: "MCP server does not use OAuth2 authentication.",
		})
		return
	}

	// Check if the OAuth2 provider returned an error (e.g., user
	// denied consent).
	if oauthError := r.URL.Query().Get("error"); oauthError != "" {
		desc := r.URL.Query().Get("error_description")
		if desc == "" {
			desc = oauthError
		}
		httpapi.Write(ctx, rw, http.StatusBadRequest, codersdk.Response{
			Message: "OAuth2 provider returned an error.",
			Detail:  desc,
		})
		return
	}

	code := r.URL.Query().Get("code")
	if code == "" {
		httpapi.Write(ctx, rw, http.StatusBadRequest, codersdk.Response{
			Message: "Missing authorization code.",
		})
		return
	}

	// Validate the state parameter for CSRF protection.
	expectedState := ""
	if cookie, err := r.Cookie("mcp_oauth2_state_" + config.ID.String()); err == nil {
		expectedState = cookie.Value
	}
	actualState := r.URL.Query().Get("state")
	if expectedState == "" || actualState != expectedState {
		httpapi.Write(ctx, rw, http.StatusBadRequest, codersdk.Response{
			Message: "Invalid or missing OAuth2 state parameter.",
		})
		return
	}
	// Clear the state cookie.
	callbackPath := mcpServerOAuth2CallbackPath(config.ID)
	http.SetCookie(rw, api.DeploymentValues.HTTPCookies.Apply(&http.Cookie{
		Name:     "mcp_oauth2_state_" + config.ID.String(),
		Value:    "",
		Path:     callbackPath,
		MaxAge:   -1,
		HttpOnly: true,
		SameSite: http.SameSiteLaxMode,
	}))

	// Recover the PKCE code_verifier set during the connect step.
	var exchangeOpts []oauth2.AuthCodeOption
	if verifierCookie, err := r.Cookie("mcp_oauth2_verifier_" + config.ID.String()); err == nil {
		exchangeOpts = append(exchangeOpts, oauth2.VerifierOption(verifierCookie.Value))
	}
	// Clear the verifier cookie regardless of whether it was present.
	http.SetCookie(rw, api.DeploymentValues.HTTPCookies.Apply(&http.Cookie{
		Name:     "mcp_oauth2_verifier_" + config.ID.String(),
		Value:    "",
		Path:     callbackPath,
		MaxAge:   -1,
		HttpOnly: true,
		SameSite: http.SameSiteLaxMode,
	}))

	// Exchange the authorization code for tokens.
	oauth2Config := &oauth2.Config{
		ClientID:     config.OAuth2ClientID,
		ClientSecret: config.OAuth2ClientSecret,
		Endpoint: oauth2.Endpoint{
			AuthURL:  config.OAuth2AuthURL,
			TokenURL: config.OAuth2TokenURL,
		},
		RedirectURL: fmt.Sprintf("%s%s", api.AccessURL.String(), callbackPath),
	}
	var scopes []string
	if config.OAuth2Scopes != "" {
		scopes = strings.Split(config.OAuth2Scopes, " ")
	}
	oauth2Config.Scopes = scopes

	// Use the deployment's HTTP client for the token exchange to
	// respect proxy settings and avoid using http.DefaultClient.
	// Guard against nil so the oauth2 library falls back to the
	// default client instead of panicking.
	exchangeCtx := ctx
	if api.HTTPClient != nil {
		exchangeCtx = context.WithValue(ctx, oauth2.HTTPClient, api.HTTPClient)
	}
	token, err := oauth2Config.Exchange(exchangeCtx, code, exchangeOpts...)
	if err != nil {
		httpapi.Write(ctx, rw, http.StatusBadGateway, codersdk.Response{
			Message: "Failed to exchange authorization code for token.",
			Detail:  "The OAuth2 token exchange with the upstream provider failed.",
		})
		return
	}

	// Store the token for the user.
	refreshToken := ""
	if token.RefreshToken != "" {
		refreshToken = token.RefreshToken
	}

	var expiry sql.NullTime
	if !token.Expiry.IsZero() {
		expiry = sql.NullTime{Time: token.Expiry, Valid: true}
	}

	err = api.Database.InTx(func(tx database.Store) error {
		// Hold the config lock through the grant write so a concurrent update
		// cannot invalidate grants and then have this callback recreate one
		// for the old config.
		current, err := tx.GetMCPServerConfigByIDForUpdate(ctx, config.ID)
		if err != nil {
			return xerrors.Errorf("re-read MCP server config: %w", err)
		}
		if current.Url != config.Url || current.AuthType != config.AuthType ||
			current.OAuth2TokenURL != config.OAuth2TokenURL || current.OAuth2RevocationURL != config.OAuth2RevocationURL ||
			current.OAuth2ClientID != config.OAuth2ClientID {
			return errMCPConfigSupersededDuringAuth
		}
		_, err = tx.UpsertMCPServerUserToken(ctx, database.UpsertMCPServerUserTokenParams{
			MCPServerConfigID: config.ID,
			UserID:            apiKey.UserID,
			AccessToken:       token.AccessToken,
			AccessTokenKeyID:  sql.NullString{},
			RefreshToken:      refreshToken,
			RefreshTokenKeyID: sql.NullString{},
			TokenType:         token.TokenType,
			Expiry:            expiry,
		})
		return err
	}, nil)
	if errors.Is(err, errMCPConfigSupersededDuringAuth) {
		httpapi.Write(ctx, rw, http.StatusConflict, codersdk.Response{
			Message: "MCP server configuration changed during authorization.",
			Detail:  "The server's destination or OAuth settings were updated while the connection was in progress. Reconnect to authorize against the current configuration.",
		})
		return
	}
	if err != nil {
		httpapi.Write(ctx, rw, http.StatusInternalServerError, codersdk.Response{
			Message: "Failed to store OAuth2 token.",
			Detail:  err.Error(),
		})
		return
	}

	// Respond with a simple HTML page that closes the popup window.
	rw.Header().Set("Content-Security-Policy", "default-src 'none'; script-src 'unsafe-inline'")
	rw.Header().Set("Content-Type", "text/html; charset=utf-8")
	rw.WriteHeader(http.StatusOK)
	_, _ = rw.Write([]byte(`<!DOCTYPE html><html><body><script>
		if (window.opener) {
			window.opener.postMessage({type: "mcp-oauth2-complete", serverID: "` + config.ID.String() + `"}, "` + api.AccessURL.String() + `");
			window.close();
		} else {
			document.body.innerText = "Authentication successful. You may close this window.";
		}
	</script></body></html>`))
}

// @Summary Disconnect MCP server OAuth2 token
// @ID disconnect-mcp-server-oauth2-token
// @Security CoderSessionToken
// @Tags MCP
// @Produce json
// @Param mcpServer path string true "MCP server config ID" format(uuid)
// @Success 200 {object} codersdk.MCPServerOAuth2DisconnectResponse
// @Router /api/experimental/mcp/servers/{mcpServer}/oauth2/disconnect [delete]
// @x-apidocgen {"skip": true}
// EXPERIMENTAL: this endpoint is experimental and is subject to change.
// Removes the user's stored OAuth2 token for an MCP server.
// Provider revocation is best-effort and cannot block local deletion.
func (api *API) mcpServerOAuth2Disconnect(rw http.ResponseWriter, r *http.Request) {
	ctx := r.Context()
	apiKey := httpmw.APIKey(r)

	configID, parsed := httpmw.ParseUUIDParam(rw, r, "mcpServer")
	if !parsed {
		return
	}

	if !api.Authorize(r, policy.ActionUpdatePersonal, rbac.ResourceUserObject(apiKey.UserID)) {
		httpapi.Forbidden(rw)
		return
	}

	var (
		config database.MCPServerConfig
		token  database.MCPServerUserToken
	)
	// Serializable isolation keeps the revoked token aligned with the row deleted locally.
	err := api.Database.InTx(func(tx database.Store) error {
		//nolint:gocritic // Update permission permits this revocation read.
		dbToken, err := tx.GetMCPServerUserToken(dbauthz.AsSystemRestricted(ctx), database.GetMCPServerUserTokenParams{
			MCPServerConfigID: configID,
			UserID:            apiKey.UserID,
		})
		if err != nil {
			return err
		}
		// Load the config only after the token is found so callers
		// without a token cannot probe which config IDs exist. The
		// system context keeps disconnect available to token owners
		// who can no longer read the config, such as users removed
		// from the organization.
		//nolint:gocritic // Token owners keep disconnect access without config read.
		dbConfig, err := tx.GetMCPServerConfigByID(dbauthz.AsSystemRestricted(ctx), configID)
		if err != nil {
			return err
		}
		if err := tx.DeleteMCPServerUserToken(ctx, database.DeleteMCPServerUserTokenParams{
			MCPServerConfigID: configID,
			UserID:            apiKey.UserID,
		}); err != nil {
			return err
		}
		config = dbConfig
		token = dbToken
		return nil
	}, &database.TxOptions{Isolation: sql.LevelSerializable})
	if err != nil {
		if errors.Is(err, sql.ErrNoRows) {
			// Nonexistent config IDs take the same path, so they
			// cannot be probed either.
			httpapi.Write(ctx, rw, http.StatusOK, codersdk.MCPServerOAuth2DisconnectResponse{})
			return
		}
		if dbauthz.IsNotAuthorizedError(err) {
			httpapi.Forbidden(rw)
			return
		}
		httpapi.Write(ctx, rw, http.StatusInternalServerError, codersdk.Response{
			Message: "Failed to disconnect OAuth2 token.",
			Detail:  err.Error(),
		})
		return
	}

	resp := codersdk.MCPServerOAuth2DisconnectResponse{}
	if config.AuthType == "oauth2" {
		// The local token is already deleted, so a client abort must
		// not cancel the provider revocation; it has its own timeout.
		revoked, err := mcpclient.RevokeOAuth2Token(context.WithoutCancel(ctx), api.HTTPClient, config, token)
		resp.TokenRevoked = revoked
		if err != nil {
			api.Logger.Warn(ctx, "failed to revoke MCP oauth2 token at provider",
				slog.F("server_slug", config.Slug),
				slog.Error(err),
			)
			// Provider error bodies may echo the client secret, so
			// callers only get a generic message.
			resp.TokenRevocationError = "The OAuth provider rejected the revocation request."
		}
	}

	httpapi.Write(ctx, rw, http.StatusOK, resp)
}

// refreshMCPUserToken attempts to refresh an expired OAuth2 token
// for the given MCP server config. Returns true when the token is
// valid (either still fresh or successfully refreshed), false when
// the token is expired and cannot be refreshed. Permanent refresh
// failures (e.g. revoked grants) are persisted so subsequent calls
// skip the provider without a network call.
func (api *API) refreshMCPUserToken(
	ctx context.Context,
	cfg database.MCPServerConfig,
	tok database.MCPServerUserToken,
) bool {
	if cfg.AuthType != "oauth2" {
		return true
	}
	if tok.OauthRefreshFailureReason != "" {
		return false
	}
	if tok.RefreshToken == "" {
		// No refresh token; connected only if not expired (or no
		// expiry set).
		return !tok.Expiry.Valid || tok.Expiry.Time.After(time.Now())
	}

	result, err := mcpclient.RefreshOAuth2Token(ctx, cfg, tok)
	if err != nil {
		api.Logger.Warn(ctx, "failed to refresh MCP oauth2 token",
			slog.F("server_slug", cfg.Slug),
			slog.Error(err),
		)
		if mcpclient.IsPermanentRefreshError(err) {
			return api.markMCPTokenRefreshFailure(ctx, cfg, tok, err)
		}
		// Transient failure; the token is unusable right now but a
		// later refresh may succeed.
		return false
	}

	if result.Refreshed {
		var expiry sql.NullTime
		if !result.Expiry.IsZero() {
			expiry = sql.NullTime{Time: result.Expiry, Valid: true}
		}

		// The caller can read the token, but a read-only key cannot persist refresh
		// results. System access permits storing rotated credentials after a
		// successful refresh.
		//nolint:gocritic // Token refresh persistence follows an authorized read of the same token.
		persistCtx := dbauthz.AsSystemRestricted(ctx)
		_, err = api.Database.UpdateMCPServerUserTokenFromRefresh(
			persistCtx,
			database.UpdateMCPServerUserTokenFromRefreshParams{
				ID:                tok.ID,
				UpdatedAt:         tok.UpdatedAt,
				AccessToken:       result.AccessToken,
				AccessTokenKeyID:  sql.NullString{},
				RefreshToken:      result.RefreshToken,
				RefreshTokenKeyID: sql.NullString{},
				TokenType:         result.TokenType,
				Expiry:            expiry,
			},
		)
		if err != nil {
			if errors.Is(err, sql.ErrNoRows) {
				connected, readErr := api.currentMCPUserTokenConnected(ctx, tok)
				if readErr == nil {
					return connected
				}
				err = readErr
			}
			api.Logger.Warn(ctx, "failed to persist refreshed MCP oauth2 token",
				slog.F("server_slug", cfg.Slug),
				slog.Error(err),
			)
		}
	}

	return true
}

func (api *API) currentMCPUserTokenConnected(
	ctx context.Context,
	tok database.MCPServerUserToken,
) (bool, error) {
	//nolint:gocritic // Refresh reconciliation follows an authorized read of the same token.
	current, err := api.Database.GetMCPServerUserToken(
		dbauthz.AsSystemRestricted(ctx),
		database.GetMCPServerUserTokenParams{
			MCPServerConfigID: tok.MCPServerConfigID,
			UserID:            tok.UserID,
		},
	)
	if errors.Is(err, sql.ErrNoRows) {
		return false, nil
	}
	if err != nil {
		return false, err
	}
	return current.OauthRefreshFailureReason == "" &&
		current.AccessToken != "" &&
		(!current.Expiry.Valid || current.Expiry.Time.After(time.Now())), nil
}

// markMCPTokenRefreshFailure persists a permanent refresh failure so
// later status checks skip the provider. The updated_at optimistic
// lock loses to concurrent refreshes: in that case the winner's row
// determines whether the token is still usable.
func (api *API) markMCPTokenRefreshFailure(
	ctx context.Context,
	cfg database.MCPServerConfig,
	tok database.MCPServerUserToken,
	refreshErr error,
) bool {
	//nolint:gocritic // Refresh failure recording follows an authorized read of the same token.
	_, err := api.Database.MarkMCPServerUserTokenRefreshFailure(
		dbauthz.AsSystemRestricted(ctx),
		database.MarkMCPServerUserTokenRefreshFailureParams{
			ID:                        tok.ID,
			UpdatedAt:                 tok.UpdatedAt,
			OauthRefreshFailureReason: mcpclient.RefreshFailureReason(refreshErr),
		},
	)
	if err == nil {
		return false
	}

	if xerrors.Is(err, sql.ErrNoRows) {
		connected, readErr := api.currentMCPUserTokenConnected(ctx, tok)
		if readErr == nil {
			return connected
		}
		err = readErr
	}

	api.Logger.Warn(ctx, "failed to persist MCP oauth2 refresh failure",
		slog.F("server_slug", cfg.Slug),
		slog.Error(err),
	)
	return false
}

// mcpServerOAuth2CallbackPath returns the OAuth2 callback path for a
// config. This path is frozen: it is the redirect URI registered with
// external authorization servers, so it must not change when other MCP
// routes move. The route registration in coderd.go and the OAuth cookie
// Path values must stay aligned with it.
func mcpServerOAuth2CallbackPath(configID uuid.UUID) string {
	return fmt.Sprintf("/api/experimental/mcp/servers/%s/oauth2/callback", configID)
}

// parseMCPServerConfigID extracts the MCP server config UUID from the
// "mcpServer" path parameter, which is part of the frozen callback
// route shape.
func parseMCPServerConfigID(rw http.ResponseWriter, r *http.Request) (uuid.UUID, bool) {
	mcpServerID, err := uuid.Parse(chi.URLParam(r, "mcpServer"))
	if err != nil {
		httpapi.Write(r.Context(), rw, http.StatusBadRequest, codersdk.Response{
			Message: "Invalid MCP server config ID.",
			Detail:  err.Error(),
		})
		return uuid.Nil, false
	}
	return mcpServerID, true
}

// convertMCPServerConfig converts a database MCP server config to the
// SDK type. Secrets are never returned; only has_* booleans are set.
// Admin-only fields (OAuth2 client ID, auth URLs, etc.) are included.
func convertMCPServerConfig(config database.MCPServerConfig) codersdk.MCPServerConfig {
	return codersdk.MCPServerConfig{
		ID:             config.ID,
		OrganizationID: config.OrganizationID,
		DisplayName:    config.DisplayName,
		Slug:           config.Slug,
		Description:    config.Description,
		IconURL:        config.IconURL,

		Transport: config.Transport,
		URL:       config.Url,

		AuthType:            config.AuthType,
		OAuth2ClientID:      config.OAuth2ClientID,
		HasOAuth2Secret:     config.OAuth2ClientSecret != "",
		OAuth2AuthURL:       config.OAuth2AuthURL,
		OAuth2TokenURL:      config.OAuth2TokenURL,
		OAuth2RevocationURL: config.OAuth2RevocationURL,
		OAuth2Scopes:        config.OAuth2Scopes,

		APIKeyHeader: config.APIKeyHeader,
		HasAPIKey:    config.APIKeyValue != "",

		HasCustomHeaders: len(config.CustomHeaders) > 0 && config.CustomHeaders != "{}",

		ToolAllowList: coalesceStringSlice(config.ToolAllowList),
		ToolDenyList:  coalesceStringSlice(config.ToolDenyList),

		Availability: config.Availability,

		Enabled:             config.Enabled,
		ModelIntent:         config.ModelIntent,
		AllowInPlanMode:     config.AllowInPlanMode,
		ForwardCoderHeaders: config.ForwardCoderHeaders,
		CreatedAt:           config.CreatedAt,
		UpdatedAt:           config.UpdatedAt,

		// Default per-user auth state. Handlers that know the
		// calling user's token state (list/get) overwrite this.
		AuthConnected: config.AuthType != "oauth2",
	}
}

// convertMCPServerConfigRedacted is the same as convertMCPServerConfig
// but strips admin-only fields (OAuth2 details, API key header) for
// non-admin callers.
func convertMCPServerConfigRedacted(config database.MCPServerConfig) codersdk.MCPServerConfig {
	c := convertMCPServerConfig(config)
	c.URL = ""
	c.Transport = ""
	c.OAuth2ClientID = ""
	c.OAuth2AuthURL = ""
	c.OAuth2TokenURL = ""
	c.OAuth2RevocationURL = ""
	c.OAuth2Scopes = ""
	c.APIKeyHeader = ""
	return c
}

// marshalCustomHeaders encodes a map of custom headers to JSON for
// database storage. A nil map produces an empty JSON object.
func marshalCustomHeaders(headers map[string]string) (string, error) {
	if headers == nil {
		return "{}", nil
	}
	encoded, err := json.Marshal(headers)
	if err != nil {
		return "", err
	}
	return string(encoded), nil
}

// trimStringSlice trims whitespace from each element and drops empty
// strings.
func trimStringSlice(ss []string) []string {
	if ss == nil {
		return nil
	}
	out := make([]string, 0, len(ss))
	for _, s := range ss {
		if trimmed := strings.TrimSpace(s); trimmed != "" {
			out = append(out, trimmed)
		}
	}
	return out
}

// coalesceStringSlice returns ss if non-nil, otherwise an empty
// non-nil slice. This prevents pq.Array from sending NULL for
// NOT NULL text[] columns.
func coalesceStringSlice(ss []string) []string {
	if ss == nil {
		return []string{}
	}
	return ss
}

// mcpOAuth2Discovery holds the result of MCP OAuth2 auto-discovery
// and Dynamic Client Registration.
type mcpOAuth2Discovery struct {
	clientID      string
	clientSecret  string
	authURL       string
	tokenURL      string
	revocationURL string
	scopes        string // space-separated
}

// protectedResourceMetadata represents the response from a
// Protected Resource Metadata endpoint per RFC 9728 §2.
type protectedResourceMetadata struct {
	Resource             string   `json:"resource"`
	AuthorizationServers []string `json:"authorization_servers"`
	ScopesSupported      []string `json:"scopes_supported,omitempty"`
}

// authServerMetadata represents the response from an Authorization
// Server Metadata endpoint per RFC 8414 §2.
type authServerMetadata struct {
	Issuer                string   `json:"issuer"`
	AuthorizationEndpoint string   `json:"authorization_endpoint"`
	TokenEndpoint         string   `json:"token_endpoint"`
	RegistrationEndpoint  string   `json:"registration_endpoint,omitempty"`
	RevocationEndpoint    string   `json:"revocation_endpoint,omitempty"`
	ScopesSupported       []string `json:"scopes_supported,omitempty"`
}

// fetchJSON performs a GET request to the given URL with the
// standard MCP OAuth2 discovery headers and decodes the JSON
// response into dest. It returns nil on success or an error
// if the request fails or the server returns a non-200 status.
func fetchJSON(ctx context.Context, httpClient *http.Client, rawURL string, dest any) error {
	req, err := http.NewRequestWithContext(
		ctx, http.MethodGet, rawURL, nil,
	)
	if err != nil {
		return xerrors.Errorf("create request for %s: %w", rawURL, err)
	}
	req.Header.Set("Accept", "application/json")
	req.Header.Set("MCP-Protocol-Version", mcpProtocolVersion)

	resp, err := httpClient.Do(req)
	if err != nil {
		return xerrors.Errorf("GET %s: %w", rawURL, err)
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusOK {
		return xerrors.Errorf(
			"GET %s returned HTTP %d", rawURL, resp.StatusCode,
		)
	}

	body, err := io.ReadAll(io.LimitReader(resp.Body, 1<<20))
	if err != nil {
		return xerrors.Errorf(
			"read response from %s: %w", rawURL, err,
		)
	}

	if err := json.Unmarshal(body, dest); err != nil {
		return xerrors.Errorf(
			"decode JSON from %s: %w", rawURL, err,
		)
	}

	return nil
}

// discoverProtectedResource discovers the Protected Resource
// Metadata for the given MCP server per RFC 9728 §3.1. It
// tries the path-aware well-known URL first, then falls back
// to the root-level URL.
//
// Path-aware: GET {origin}/.well-known/oauth-protected-resource{path}
// Root:       GET {origin}/.well-known/oauth-protected-resource
func discoverProtectedResource(
	ctx context.Context, httpClient *http.Client, origin, path string,
) (*protectedResourceMetadata, error) {
	var urls []string

	// Per RFC 9728 §3.1, when the resource URL contains a
	// path component, the well-known URI is constructed by
	// inserting the well-known prefix before the path.
	if path != "" && path != "/" {
		urls = append(
			urls,
			origin+"/.well-known/oauth-protected-resource"+path,
		)
	}
	// Always try the root-level URL as a fallback.
	urls = append(
		urls, origin+"/.well-known/oauth-protected-resource",
	)

	var lastErr error
	for _, u := range urls {
		var meta protectedResourceMetadata
		if err := fetchJSON(ctx, httpClient, u, &meta); err != nil {
			lastErr = err
			continue
		}
		if len(meta.AuthorizationServers) == 0 {
			lastErr = xerrors.Errorf(
				"protected resource metadata at %s "+
					"has no authorization_servers", u,
			)
			continue
		}
		return &meta, nil
	}

	return nil, xerrors.Errorf(
		"discover protected resource metadata: %w", lastErr,
	)
}

// discoverAuthServerMetadata discovers the Authorization Server
// Metadata per RFC 8414 §3.1. When the authorization server
// issuer URL has a path component, the metadata URL is
// path-aware. Falls back to root-level and OpenID Connect
// discovery as a last resort.
//
// Path-aware: {origin}/.well-known/oauth-authorization-server{path}
// Root:       {origin}/.well-known/oauth-authorization-server
// OpenID:     {issuer}/.well-known/openid-configuration
func discoverAuthServerMetadata(
	ctx context.Context, httpClient *http.Client, authServerURL string,
) (*authServerMetadata, error) {
	parsed, err := url.Parse(authServerURL)
	if err != nil {
		return nil, xerrors.Errorf(
			"parse auth server URL: %w", err,
		)
	}
	asOrigin := fmt.Sprintf(
		"%s://%s", parsed.Scheme, parsed.Host,
	)
	asPath := parsed.Path

	var urls []string

	// Per RFC 8414 §3.1, if the issuer URL has a path,
	// insert the well-known prefix before the path.
	if asPath != "" && asPath != "/" {
		urls = append(
			urls,
			asOrigin+"/.well-known/oauth-authorization-server"+asPath,
		)
	}
	// Root-level fallback.
	urls = append(
		urls,
		asOrigin+"/.well-known/oauth-authorization-server",
	)
	// OpenID Connect discovery as a last resort. Note: this is
	// tried after RFC 8414 (unlike the previous mcp-go code that
	// tried OIDC first) because RFC 8414 is the MCP spec's
	// recommended discovery mechanism.
	// Per OpenID Connect Discovery 1.0 §4, the well-known URL
	// is formed by appending to the full issuer (including
	// path), not just the origin.
	urls = append(
		urls,
		strings.TrimRight(authServerURL, "/")+
			"/.well-known/openid-configuration",
	)

	var lastErr error
	for _, u := range urls {
		var meta authServerMetadata
		if err := fetchJSON(ctx, httpClient, u, &meta); err != nil {
			lastErr = err
			continue
		}
		if meta.AuthorizationEndpoint == "" || meta.TokenEndpoint == "" {
			lastErr = xerrors.Errorf(
				"auth server metadata at %s missing required "+
					"endpoints", u,
			)
			continue
		}
		return &meta, nil
	}

	return nil, xerrors.Errorf(
		"discover auth server metadata: %w", lastErr,
	)
}

// registerOAuth2Client performs Dynamic Client Registration per
// RFC 7591 by POSTing client metadata to the registration
// endpoint and returning the assigned client_id and optional
// client_secret.
func registerOAuth2Client(
	ctx context.Context, httpClient *http.Client,
	registrationEndpoint, callbackURL, clientName string,
) (clientID string, clientSecret string, err error) {
	payload := map[string]any{
		"client_name":                clientName,
		"redirect_uris":              []string{callbackURL},
		"token_endpoint_auth_method": "none",
		"grant_types":                []string{"authorization_code", "refresh_token"},
		"response_types":             []string{"code"},
	}

	body, err := json.Marshal(payload)
	if err != nil {
		return "", "", xerrors.Errorf(
			"marshal registration request: %w", err,
		)
	}

	req, err := http.NewRequestWithContext(
		ctx, http.MethodPost,
		registrationEndpoint, bytes.NewReader(body),
	)
	if err != nil {
		return "", "", xerrors.Errorf(
			"create registration request: %w", err,
		)
	}
	req.Header.Set("Content-Type", "application/json")
	req.Header.Set("Accept", "application/json")

	resp, err := httpClient.Do(req)
	if err != nil {
		return "", "", xerrors.Errorf(
			"POST %s: %w", registrationEndpoint, err,
		)
	}
	defer resp.Body.Close()

	respBody, err := io.ReadAll(io.LimitReader(resp.Body, 1<<20))
	if err != nil {
		return "", "", xerrors.Errorf(
			"read registration response: %w", err,
		)
	}

	if resp.StatusCode != http.StatusOK &&
		resp.StatusCode != http.StatusCreated {
		// Truncate to avoid leaking verbose upstream errors
		// through the API.
		const maxErrBody = 512
		errMsg := string(respBody)
		if len(errMsg) > maxErrBody {
			errMsg = errMsg[:maxErrBody] + "..."
		}
		return "", "", xerrors.Errorf(
			"registration endpoint returned HTTP %d: %s",
			resp.StatusCode, errMsg,
		)
	}

	var result struct {
		ClientID     string `json:"client_id"`
		ClientSecret string `json:"client_secret"`
	}
	if err := json.Unmarshal(respBody, &result); err != nil {
		return "", "", xerrors.Errorf(
			"decode registration response: %w", err,
		)
	}
	if result.ClientID == "" {
		return "", "", xerrors.New(
			"registration response missing client_id",
		)
	}

	return result.ClientID, result.ClientSecret, nil
}

// discoverAndRegisterMCPOAuth2 performs the full MCP OAuth2
// discovery and Dynamic Client Registration flow:
//
//  1. Discover the authorization server via Protected Resource
//     Metadata (RFC 9728).
//  2. Fetch Authorization Server Metadata (RFC 8414).
//  3. Register a client via Dynamic Client Registration
//     (RFC 7591).
//  4. Return the discovered endpoints and credentials.
//
// Unlike a root-only approach, this implementation follows the
// path-aware well-known URI construction rules from RFC 9728
// §3.1 and RFC 8414 §3.1, which is required for servers that
// serve metadata at path-specific URLs (e.g.
// https://api.githubcopilot.com/mcp/).
func discoverAndRegisterMCPOAuth2(ctx context.Context, httpClient *http.Client, mcpServerURL, callbackURL string) (*mcpOAuth2Discovery, error) {
	// Parse the MCP server URL into origin and path.
	parsed, err := url.Parse(mcpServerURL)
	if err != nil {
		return nil, xerrors.Errorf(
			"parse MCP server URL: %w", err,
		)
	}
	origin := fmt.Sprintf("%s://%s", parsed.Scheme, parsed.Host)
	path := parsed.Path

	// Step 1: Discover the Protected Resource Metadata
	// (RFC 9728) to find the authorization server.
	prm, err := discoverProtectedResource(ctx, httpClient, origin, path)
	if err != nil {
		return nil, xerrors.Errorf(
			"protected resource discovery: %w", err,
		)
	}

	// Step 2: Fetch Authorization Server Metadata (RFC 8414)
	// from the first advertised authorization server.
	asMeta, err := discoverAuthServerMetadata(
		ctx, httpClient, prm.AuthorizationServers[0],
	)
	if err != nil {
		return nil, xerrors.Errorf(
			"auth server metadata discovery: %w", err,
		)
	}

	// Only RegistrationEndpoint needs checking here;
	// discoverAuthServerMetadata already validates that
	// AuthorizationEndpoint and TokenEndpoint are present.
	if asMeta.RegistrationEndpoint == "" {
		return nil, xerrors.New(
			"authorization server does not advertise a " +
				"registration_endpoint (dynamic client " +
				"registration may not be supported)",
		)
	}

	// Step 3: Register via Dynamic Client Registration
	// (RFC 7591).
	clientID, clientSecret, err := registerOAuth2Client(
		ctx, httpClient, asMeta.RegistrationEndpoint, callbackURL, "Coder",
	)
	if err != nil {
		return nil, xerrors.Errorf(
			"dynamic client registration: %w", err,
		)
	}

	scopes := strings.Join(asMeta.ScopesSupported, " ")

	return &mcpOAuth2Discovery{
		clientID:      clientID,
		clientSecret:  clientSecret,
		authURL:       asMeta.AuthorizationEndpoint,
		tokenURL:      asMeta.TokenEndpoint,
		revocationURL: asMeta.RevocationEndpoint,
		scopes:        scopes,
	}, nil
}