/*
Copyright 2017-2021 Gravitational, Inc.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package auth

import (
	"context"
	"encoding/json"
	"net/url"

	"github.com/gravitational/trace"

	"github.com/gravitational/teleport/api/types"
	apievents "github.com/gravitational/teleport/api/types/events"
	"github.com/gravitational/teleport/lib/authz"
	"github.com/gravitational/teleport/lib/events"
)

type OIDCService interface {
	CreateOIDCAuthRequest(ctx context.Context, req types.OIDCAuthRequest) (*types.OIDCAuthRequest, error)
	ValidateOIDCAuthCallback(ctx context.Context, q url.Values) (*OIDCAuthResponse, error)
}

var errOIDCNotImplemented = trace.AccessDenied("OIDC is only available in enterprise subscriptions")

// UpsertOIDCConnector creates or updates an OIDC connector.
func (a *Server) UpsertOIDCConnector(ctx context.Context, connector types.OIDCConnector) error {
	if err := a.Services.UpsertOIDCConnector(ctx, connector); err != nil {
		return trace.Wrap(err)
	}
	if err := a.emitter.EmitAuditEvent(ctx, &apievents.OIDCConnectorCreate{
		Metadata: apievents.Metadata{
			Type: events.OIDCConnectorCreatedEvent,
			Code: events.OIDCConnectorCreatedCode,
		},
		UserMetadata: authz.ClientUserMetadata(ctx),
		ResourceMetadata: apievents.ResourceMetadata{
			Name: connector.GetName(),
		},
	}); err != nil {
		log.WithError(err).Warn("Failed to emit OIDC connector create event.")
	}

	return nil
}

// DeleteOIDCConnector deletes an OIDC connector by name.
func (a *Server) DeleteOIDCConnector(ctx context.Context, connectorName string) error {
	if err := a.Services.DeleteOIDCConnector(ctx, connectorName); err != nil {
		return trace.Wrap(err)
	}
	if err := a.emitter.EmitAuditEvent(ctx, &apievents.OIDCConnectorDelete{
		Metadata: apievents.Metadata{
			Type: events.OIDCConnectorDeletedEvent,
			Code: events.OIDCConnectorDeletedCode,
		},
		UserMetadata: authz.ClientUserMetadata(ctx),
		ResourceMetadata: apievents.ResourceMetadata{
			Name: connectorName,
		},
	}); err != nil {
		log.WithError(err).Warn("Failed to emit OIDC connector delete event.")
	}
	return nil
}

func (a *Server) CreateOIDCAuthRequest(ctx context.Context, req types.OIDCAuthRequest) (*types.OIDCAuthRequest, error) {
	if a.oidcAuthService == nil {
		return nil, errOIDCNotImplemented
	}

	rq, err := a.oidcAuthService.CreateOIDCAuthRequest(ctx, req)
	return rq, trace.Wrap(err)
}

func (a *Server) ValidateOIDCAuthCallback(ctx context.Context, q url.Values) (*OIDCAuthResponse, error) {
	if a.oidcAuthService == nil {
		return nil, errOIDCNotImplemented
	}

	resp, err := a.oidcAuthService.ValidateOIDCAuthCallback(ctx, q)
	return resp, trace.Wrap(err)
}

// OIDCAuthResponse is returned when auth server validated callback parameters
// returned from OIDC provider
type OIDCAuthResponse struct {
	// Username is authenticated teleport username
	Username string `json:"username"`
	// Identity contains validated OIDC identity
	Identity types.ExternalIdentity `json:"identity"`
	// Web session will be generated by auth server if requested in OIDCAuthRequest
	Session types.WebSession `json:"session,omitempty"`
	// Cert will be generated by certificate authority
	Cert []byte `json:"cert,omitempty"`
	// TLSCert is PEM encoded TLS certificate
	TLSCert []byte `json:"tls_cert,omitempty"`
	// Req is original oidc auth request
	Req OIDCAuthRequest `json:"req"`
	// HostSigners is a list of signing host public keys
	// trusted by proxy, used in console login
	HostSigners []types.CertAuthority `json:"host_signers"`
}

// OIDCAuthRequest is an OIDC auth request that supports standard json marshaling.
type OIDCAuthRequest struct {
	// ConnectorID is ID of OIDC connector this request uses
	ConnectorID string `json:"connector_id"`
	// CSRFToken is associated with user web session token
	CSRFToken string `json:"csrf_token"`
	// PublicKey is an optional public key, users want these
	// keys to be signed by auth servers user CA in case
	// of successful auth
	PublicKey []byte `json:"public_key"`
	// CreateWebSession indicates if user wants to generate a web
	// session after successful authentication
	CreateWebSession bool `json:"create_web_session"`
	// ClientRedirectURL is a URL client wants to be redirected
	// after successful authentication
	ClientRedirectURL string `json:"client_redirect_url"`
}

// ValidateOIDCAuthCallbackReq is the request made by the proxy to validate
// and activate a login via OIDC.
type ValidateOIDCAuthCallbackReq struct {
	Query url.Values `json:"query"`
}

// OIDCAuthRawResponse is returned when auth server validated callback parameters
// returned from OIDC provider
type OIDCAuthRawResponse struct {
	// Username is authenticated teleport username
	Username string `json:"username"`
	// Identity contains validated OIDC identity
	Identity types.ExternalIdentity `json:"identity"`
	// Web session will be generated by auth server if requested in OIDCAuthRequest
	Session json.RawMessage `json:"session,omitempty"`
	// Cert will be generated by certificate authority
	Cert []byte `json:"cert,omitempty"`
	// TLSCert is PEM encoded TLS certificate
	TLSCert []byte `json:"tls_cert,omitempty"`
	// Req is original oidc auth request
	Req OIDCAuthRequest `json:"req"`
	// HostSigners is a list of signing host public keys
	// trusted by proxy, used in console login
	HostSigners []json.RawMessage `json:"host_signers"`
}