feat(coderd): refactors github pr sync functionality (#22715)

- Adds `_API_BASE_URL` to `CODER_EXTERNAL_AUTH_CONFIG_`
- Extracts and refactors existing GitHub PR sync logic to new packages
`coderd/gitsync` and `coderd/externalauth/gitprovider`
- Associated wiring and tests

Created using Opus 4.6

coderd/gitsync/gitsync.go

@@ -0,0 +1,230 @@
+package gitsync
+
+import (
+	"context"
+	"database/sql"
+	"errors"
+	"fmt"
+	"time"
+
+	"github.com/google/uuid"
+	"golang.org/x/xerrors"
+
+	"cdr.dev/slog/v3"
+	"github.com/coder/coder/v2/coderd/database"
+	"github.com/coder/coder/v2/coderd/externalauth/gitprovider"
+	"github.com/coder/quartz"
+)
+
+const (
+	// DiffStatusTTL is how long a successfully refreshed
+	// diff status remains fresh before becoming stale again.
+	DiffStatusTTL = 120 * time.Second
+)
+
+// ProviderResolver maps a git remote origin to the gitprovider
+// that handles it. Returns nil if no provider matches.
+type ProviderResolver func(origin string) gitprovider.Provider
+
+var ErrNoTokenAvailable error = errors.New("no token available")
+
+// TokenResolver obtains the user's git access token for a given
+// remote origin. Should return nil if no token is available, in
+// which case ErrNoTokenAvailable will be returned.
+type TokenResolver func(
+	ctx context.Context,
+	userID uuid.UUID,
+	origin string,
+) (*string, error)
+
+// Refresher contains the stateless business logic for fetching
+// fresh PR data from a git provider given a stale
+// database.ChatDiffStatus row.
+type Refresher struct {
+	providers ProviderResolver
+	tokens    TokenResolver
+	logger    slog.Logger
+	clock     quartz.Clock
+}
+
+// NewRefresher creates a Refresher with the given dependency
+// functions.
+func NewRefresher(
+	providers ProviderResolver,
+	tokens TokenResolver,
+	logger slog.Logger,
+	clock quartz.Clock,
+) *Refresher {
+	return &Refresher{
+		providers: providers,
+		tokens:    tokens,
+		logger:    logger,
+		clock:     clock,
+	}
+}
+
+// RefreshRequest pairs a stale row with the chat owner who
+// holds the git token needed for API calls.
+type RefreshRequest struct {
+	Row     database.ChatDiffStatus
+	OwnerID uuid.UUID
+}
+
+// RefreshResult is the outcome for a single row.
+//   - Params != nil, Error == nil  → success, caller should upsert.
+//   - Params == nil, Error == nil  → no PR yet, caller should skip.
+//   - Params == nil, Error != nil  → row-level failure.
+type RefreshResult struct {
+	Request RefreshRequest
+	Params  *database.UpsertChatDiffStatusParams
+	Error   error
+}
+
+// groupKey identifies a unique (owner, origin) pair so that
+// provider and token resolution happen once per group.
+type groupKey struct {
+	ownerID uuid.UUID
+	origin  string
+}
+
+// Refresh fetches fresh PR data for a batch of stale rows.
+// Rows are grouped internally by (ownerID, origin) so that
+// provider and token resolution happen once per group. A
+// top-level error is returned only when the entire batch
+// fails catastrophically. Per-row outcomes are in the
+// returned RefreshResult slice (one per input request, same
+// order).
+func (r *Refresher) Refresh(
+	ctx context.Context,
+	requests []RefreshRequest,
+) ([]RefreshResult, error) {
+	results := make([]RefreshResult, len(requests))
+	for i, req := range requests {
+		results[i].Request = req
+	}
+
+	// Group request indices by (ownerID, origin).
+	groups := make(map[groupKey][]int)
+	for i, req := range requests {
+		key := groupKey{
+			ownerID: req.OwnerID,
+			origin:  req.Row.GitRemoteOrigin,
+		}
+		groups[key] = append(groups[key], i)
+	}
+
+	for key, indices := range groups {
+		provider := r.providers(key.origin)
+		if provider == nil {
+			err := xerrors.Errorf("no provider for origin %q", key.origin)
+			for _, i := range indices {
+				results[i].Error = err
+			}
+			continue
+		}
+
+		token, err := r.tokens(ctx, key.ownerID, key.origin)
+		if err != nil {
+			err = xerrors.Errorf("resolve token: %w", err)
+		} else if token == nil || len(*token) == 0 {
+			err = ErrNoTokenAvailable
+		}
+		if err != nil {
+			for _, i := range indices {
+				results[i].Error = err
+			}
+			continue
+		}
+		// This is technically unnecessary but kept here as a future molly-guard.
+		if token == nil {
+			continue
+		}
+
+		for i, idx := range indices {
+			req := requests[idx]
+			params, err := r.refreshOne(ctx, provider, *token, req.Row)
+			results[idx] = RefreshResult{Request: req, Params: params, Error: err}
+
+			// If rate-limited, skip remaining rows in this group.
+			var rlErr *gitprovider.RateLimitError
+			if errors.As(err, &rlErr) {
+				for _, remaining := range indices[i+1:] {
+					results[remaining] = RefreshResult{
+						Request: requests[remaining],
+						Error:   fmt.Errorf("skipped: %w", rlErr),
+					}
+				}
+				break
+			}
+		}
+	}
+
+	return results, nil
+}
+
+// refreshOne processes a single row using an already-resolved
+// provider and token. This is the old Refresh logic, unchanged.
+func (r *Refresher) refreshOne(
+	ctx context.Context,
+	provider gitprovider.Provider,
+	token string,
+	row database.ChatDiffStatus,
+) (*database.UpsertChatDiffStatusParams, error) {
+	var ref gitprovider.PRRef
+	var prURL string
+
+	if row.Url.Valid && row.Url.String != "" {
+		// Row already has a PR URL — parse it directly.
+		parsed, ok := provider.ParsePullRequestURL(row.Url.String)
+		if !ok {
+			return nil, xerrors.Errorf("parse pull request URL %q", row.Url.String)
+		}
+		ref = parsed
+		prURL = row.Url.String
+	} else {
+		// No PR URL — resolve owner/repo from the remote origin,
+		// then look up the open PR for this branch.
+		owner, repo, _, ok := provider.ParseRepositoryOrigin(row.GitRemoteOrigin)
+		if !ok {
+			return nil, xerrors.Errorf("parse repository origin %q", row.GitRemoteOrigin)
+		}
+
+		resolved, err := provider.ResolveBranchPullRequest(ctx, token, gitprovider.BranchRef{
+			Owner:  owner,
+			Repo:   repo,
+			Branch: row.GitBranch,
+		})
+		if err != nil {
+			return nil, xerrors.Errorf("resolve branch pull request: %w", err)
+		}
+		if resolved == nil {
+			// No PR exists yet for this branch.
+			return nil, nil
+		}
+		ref = *resolved
+		prURL = provider.BuildPullRequestURL(ref)
+	}
+
+	status, err := provider.FetchPullRequestStatus(ctx, token, ref)
+	if err != nil {
+		return nil, xerrors.Errorf("fetch pull request status: %w", err)
+	}
+
+	now := r.clock.Now().UTC()
+	params := &database.UpsertChatDiffStatusParams{
+		ChatID: row.ChatID,
+		Url:    sql.NullString{String: prURL, Valid: prURL != ""},
+		PullRequestState: sql.NullString{
+			String: string(status.State),
+			Valid:  status.State != "",
+		},
+		ChangesRequested: status.ChangesRequested,
+		Additions:        status.DiffStats.Additions,
+		Deletions:        status.DiffStats.Deletions,
+		ChangedFiles:     status.DiffStats.ChangedFiles,
+		RefreshedAt:      now,
+		StaleAt:          now.Add(DiffStatusTTL),
+	}
+
+	return params, nil
+}