// PopulateTokenEndpointResponse implements https://tools.ietf.org/html/rfc6749#section-4.3.3
func (c *ResourceOwnerPasswordCredentialsGrantHandler) PopulateTokenEndpointResponse(ctx context.Context, req *http.Request, requester fosite.AccessRequester, responder fosite.AccessResponder) error {
	if !requester.GetGrantTypes().Exact("password") {
		return errors.Wrap(fosite.ErrUnknownRequest, "")
	}

	var refresh, refreshSignature string
	if requester.GetGrantedScopes().Has("offline") {
		var err error
		refresh, refreshSignature, err = c.RefreshTokenStrategy.GenerateRefreshToken(ctx, requester)
		if err != nil {
			return errors.Wrap(fosite.ErrServerError, err.Error())
		} else if err := c.ResourceOwnerPasswordCredentialsGrantStorage.CreateRefreshTokenSession(ctx, refreshSignature, requester); err != nil {
			return errors.Wrap(fosite.ErrServerError, err.Error())
		}
	}

	if err := c.IssueAccessToken(ctx, req, requester, responder); err != nil {
		return err
	}

	if refresh != "" {
		responder.SetExtra("refresh_token", refresh)
	}

	return nil
}

// HandleTokenEndpointRequest implements https://tools.ietf.org/html/rfc6749#section-4.3.2
func (c *ResourceOwnerPasswordCredentialsGrantHandler) HandleTokenEndpointRequest(ctx context.Context, req *http.Request, request fosite.AccessRequester) error {
	// grant_type REQUIRED.
	// Value MUST be set to "password".
	if !request.GetGrantTypes().Exact("password") {
		return errors.Wrap(fosite.ErrUnknownRequest, "")
	}

	if !request.GetClient().GetGrantTypes().Has("password") {
		return errors.Wrap(fosite.ErrInvalidGrant, "The client is not allowed to use grant type password")
	}

	username := req.PostForm.Get("username")
	password := req.PostForm.Get("password")
	if username == "" || password == "" {
		return errors.Wrap(fosite.ErrInvalidRequest, "Username or password missing")
	} else if err := c.ResourceOwnerPasswordCredentialsGrantStorage.Authenticate(ctx, username, password); errors.Cause(err) == fosite.ErrNotFound {
		return errors.Wrap(fosite.ErrInvalidRequest, err.Error())
	} else if err != nil {
		return errors.Wrap(fosite.ErrServerError, err.Error())
	}

	client := request.GetClient()
	for _, scope := range request.GetRequestedScopes() {
		if !c.ScopeStrategy(client.GetScopes(), scope) {
			return errors.Wrap(fosite.ErrInvalidScope, fmt.Sprintf("The client is not allowed to request scope %s", scope))
		}
	}

	// Credentials must not be passed around, potentially leaking to the database!
	delete(request.GetRequestForm(), "password")
	return nil
}

// PopulateTokenEndpointResponse implements https://tools.ietf.org/html/rfc6749#section-6
func (c *RefreshTokenGrantHandler) PopulateTokenEndpointResponse(ctx context.Context, req *http.Request, requester fosite.AccessRequester, responder fosite.AccessResponder) error {
	if !requester.GetGrantTypes().Exact("refresh_token") {
		return errors.Wrap(fosite.ErrUnknownRequest, "")
	}

	accessToken, accessSignature, err := c.AccessTokenStrategy.GenerateAccessToken(ctx, requester)
	if err != nil {
		return errors.Wrap(fosite.ErrServerError, err.Error())
	}

	refreshToken, refreshSignature, err := c.RefreshTokenStrategy.GenerateRefreshToken(ctx, requester)
	if err != nil {
		return errors.Wrap(fosite.ErrServerError, err.Error())
	}

	signature := c.RefreshTokenStrategy.RefreshTokenSignature(req.PostForm.Get("refresh_token"))
	if err := c.RefreshTokenGrantStorage.PersistRefreshTokenGrantSession(ctx, signature, accessSignature, refreshSignature, requester); err != nil {
		return errors.Wrap(fosite.ErrServerError, err.Error())
	}

	responder.SetAccessToken(accessToken)
	responder.SetTokenType("bearer")
	responder.SetExpiresIn(getExpiresIn(requester, fosite.AccessToken, c.AccessTokenLifespan, time.Now()))
	responder.SetScopes(requester.GetGrantedScopes())
	responder.SetExtra("refresh_token", refreshToken)
	return nil
}

// HandleTokenEndpointRequest implements https://tools.ietf.org/html/rfc6749#section-6
func (c *RefreshTokenGrantHandler) HandleTokenEndpointRequest(ctx context.Context, req *http.Request, requester fosite.AccessRequester, responder fosite.AccessResponder) error {
	if requester.GetGrantType() != "refresh_token" {
		return nil
	}

	accessToken, accessSignature, err := c.AccessTokenStrategy.GenerateAccessToken(ctx, req, requester)
	if err != nil {
		return errors.New(fosite.ErrServerError)
	} else if err := c.Store.CreateAccessTokenSession(accessSignature, requester); err != nil {
		return errors.New(fosite.ErrServerError)
	}

	refreshToken, refreshSignature, err := c.RefreshTokenStrategy.GenerateRefreshToken(ctx, req, requester)
	if err != nil {
		return errors.New(fosite.ErrServerError)
	} else if err := c.Store.CreateRefreshTokenSession(refreshSignature, requester); err != nil {
		return errors.New(fosite.ErrServerError)
	}

	signature, err := c.RefreshTokenStrategy.ValidateRefreshToken(req.PostForm.Get("refresh_token"), ctx, req, requester)
	if err != nil {
		return errors.New(fosite.ErrInvalidRequest)
	}

	if err := c.Store.DeleteRefreshTokenSession(signature); err != nil {
		return errors.New(fosite.ErrServerError)
	}

	responder.SetAccessToken(accessToken)
	responder.SetTokenType("bearer")
	responder.SetExtra("expires_in", strconv.Itoa(int(c.AccessTokenLifespan/time.Second)))
	responder.SetExtra("scope", strings.Join(requester.GetGrantedScopes(), " "))
	responder.SetExtra("refresh_token", refreshToken)
	return nil
}

// PopulateTokenEndpointResponse implements https://tools.ietf.org/html/rfc6749#section-4.4.3
func (c *ClientCredentialsGrantHandler) PopulateTokenEndpointResponse(ctx context.Context, r *http.Request, request fosite.AccessRequester, response fosite.AccessResponder) error {
	if !request.GetGrantTypes().Exact("client_credentials") {
		return errors.Wrap(fosite.ErrUnknownRequest, "")
	}

	if !request.GetClient().GetGrantTypes().Has("client_credentials") {
		return errors.Wrap(fosite.ErrInvalidGrant, "The client is not allowed to use grant type client_credentials")
	}

	return c.IssueAccessToken(ctx, r, request, response)
}

func (c *CoreValidator) introspectAuthorizeCode(ctx context.Context, token string, accessRequest fosite.AccessRequester) error {
	sig := c.CoreStrategy.AuthorizeCodeSignature(token)
	if or, err := c.CoreStorage.GetAuthorizeCodeSession(ctx, sig, accessRequest.GetSession()); err != nil {
		return errors.Wrap(err, fosite.ErrRequestUnauthorized.Error())
	} else if err := c.CoreStrategy.ValidateAuthorizeCode(ctx, or, token); err != nil {
		return err
	} else {
		accessRequest.Merge(or)
	}

	return nil
}

// IntrospectTokenEndpointRequest implements https://tools.ietf.org/html/rfc6749#section-4.4.2
func (c *ClientCredentialsGrantHandler) HandleTokenEndpointRequest(_ context.Context, r *http.Request, request fosite.AccessRequester) error {
	// grant_type REQUIRED.
	// Value MUST be set to "client_credentials".
	if !request.GetGrantTypes().Exact("client_credentials") {
		return errors.Wrap(fosite.ErrUnknownRequest, "")
	}

	client := request.GetClient()
	for _, scope := range request.GetRequestedScopes() {
		if !c.ScopeStrategy(client.GetScopes(), scope) {
			return errors.Wrap(fosite.ErrInvalidScope, fmt.Sprintf("The client is not allowed to request scope %s", scope))
		}
	}

	// The client MUST authenticate with the authorization server as described in Section 3.2.1.
	// This requirement is already fulfilled because fosite requries all token requests to be authenticated as described
	// in https://tools.ietf.org/html/rfc6749#section-3.2.1
	if client.IsPublic() {
		return errors.Wrap(fosite.ErrInvalidGrant, "The client is public and thus not allowed to use grant type client_credentials")
	}
	// if the client is not public, he has already been authenticated by the access request handler.

	request.GetSession().SetExpiresAt(fosite.AccessToken, time.Now().Add(c.AccessTokenLifespan))
	return nil
}

func (h *HandleHelper) IssueAccessToken(ctx context.Context, req *http.Request, requester fosite.AccessRequester, responder fosite.AccessResponder) error {
	token, signature, err := h.AccessTokenStrategy.GenerateAccessToken(ctx, requester)
	if err != nil {
		return err
	} else if err := h.AccessTokenStorage.CreateAccessTokenSession(ctx, signature, requester); err != nil {
		return err
	}

	responder.SetAccessToken(token)
	responder.SetTokenType("bearer")
	responder.SetExpiresIn(getExpiresIn(requester, fosite.AccessToken, h.AccessTokenLifespan, time.Now()))
	responder.SetScopes(requester.GetGrantedScopes())
	return nil
}

// HandleTokenEndpointRequest implements https://tools.ietf.org/html/rfc6749#section-6
func (c *RefreshTokenGrantHandler) HandleTokenEndpointRequest(ctx context.Context, req *http.Request, requester fosite.AccessRequester, responder fosite.AccessResponder, session interface{}) error {
	if requester.GetGrantType() != "refresh_token" {
		return nil
	}

	access, err := c.Enigma.GenerateChallenge(requester.GetClient().GetHashedSecret())
	if err != nil {
		return errors.New(fosite.ErrServerError)
	} else if err := c.Store.CreateAccessTokenSession(access.Signature, requester, &core.TokenSession{Extra: session}); err != nil {
		return errors.New(fosite.ErrServerError)
	}

	refresh, err := c.Enigma.GenerateChallenge(requester.GetClient().GetHashedSecret())
	if err != nil {
		return errors.New(fosite.ErrServerError)
	} else if err := c.Store.CreateRefreshTokenSession(refresh.Signature, requester, &core.TokenSession{Extra: session}); err != nil {
		return errors.New(fosite.ErrServerError)
	}

	challenge := new(enigma.Challenge)
	challenge.FromString(req.Form.Get("refresh_token"))
	if err := c.Store.DeleteRefreshTokenSession(challenge.Signature); err != nil {
		return errors.New(fosite.ErrServerError)
	}

	responder.SetAccessToken(access.String())
	responder.SetTokenType("bearer")
	responder.SetExtra("expires_in", strconv.Itoa(int(c.AccessTokenLifespan/time.Second)))
	responder.SetExtra("scope", strings.Join(requester.GetGrantedScopes(), " "))
	responder.SetExtra("refresh_token", refresh.String())
	return nil
}

// ValidateTokenEndpointRequest implements https://tools.ietf.org/html/rfc6749#section-6
func (c *RefreshTokenGrantHandler) ValidateTokenEndpointRequest(_ context.Context, req *http.Request, request fosite.AccessRequester, session interface{}) error {
	// grant_type REQUIRED.
	// Value MUST be set to "client_credentials".
	if request.GetGrantType() != "refresh_token" {
		return nil
	}

	// The authorization server MUST ... validate the refresh token.
	challenge := new(enigma.Challenge)
	challenge.FromString(req.Form.Get("refresh_token"))
	if err := c.Enigma.ValidateChallenge(request.GetClient().GetHashedSecret(), challenge); err != nil {
		return errors.New(fosite.ErrInvalidRequest)
	}

	ar, err := c.Store.GetRefreshTokenSession(challenge.Signature, &core.TokenSession{Extra: session})
	if err == pkg.ErrNotFound {
		return errors.New(fosite.ErrInvalidRequest)
	} else if err != nil {
		return errors.New(fosite.ErrServerError)
	}

	// The authorization server MUST ... and ensure that the refresh token was issued to the authenticated client
	if ar.GetClient().GetID() != request.GetClient().GetID() {
		return errors.New(fosite.ErrInvalidRequest)
	}

	request.SetGrantTypeHandled("refresh_token")
	return nil
}

func (c *OpenIDConnectExplicitHandler) PopulateTokenEndpointResponse(ctx context.Context, req *http.Request, requester fosite.AccessRequester, responder fosite.AccessResponder) error {
	if !requester.GetGrantTypes().Exact("authorization_code") {
		return errors.Wrap(fosite.ErrUnknownRequest, "")
	}

	authorize, err := c.OpenIDConnectRequestStorage.GetOpenIDConnectSession(ctx, requester.GetRequestForm().Get("code"), requester)
	if errors.Cause(err) == ErrNoSessionFound {
		return errors.Wrap(fosite.ErrUnknownRequest, err.Error())
	} else if err != nil {
		return errors.Wrap(fosite.ErrServerError, err.Error())
	}

	if !authorize.GetGrantedScopes().Has("openid") {
		return errors.Wrap(fosite.ErrMisconfiguration, "The an openid connect session was found but the openid scope is missing in it")
	}

	if !requester.GetClient().GetGrantTypes().Has("authorization_code") {
		return errors.Wrap(fosite.ErrInvalidGrant, "The client is not allowed to use the authorization_code grant type")
	}

	if !requester.GetClient().GetResponseTypes().Has("id_token") {
		return errors.Wrap(fosite.ErrInvalidGrant, "The client is not allowed to use response type id_token")
	}

	return c.IssueExplicitIDToken(ctx, req, authorize, responder)
}

// ValidateTokenEndpointRequest implements https://tools.ietf.org/html/rfc6749#section-4.4.2
func (c *ClientCredentialsGrantHandler) ValidateTokenEndpointRequest(_ context.Context, req *http.Request, request fosite.AccessRequester, session interface{}) error {
	// grant_type REQUIRED.
	// Value MUST be set to "client_credentials".
	if request.GetGrantType() != "client_credentials" {
		return nil
	}

	// The client MUST authenticate with the authorization server as described in Section 3.2.1.
	// This requirement is already fulfilled because fosite requries all token requests to be authenticated as described
	// in https://tools.ietf.org/html/rfc6749#section-3.2.1

	// There's nothing else to do. All other security considerations are for the client side.

	request.SetGrantTypeHandled("client_credentials")
	return nil
}

// ValidateTokenEndpointRequest implements https://tools.ietf.org/html/rfc6749#section-4.3.2
func (c *ResourceOwnerPasswordCredentialsGrantHandler) ValidateTokenEndpointRequest(_ context.Context, req *http.Request, request fosite.AccessRequester, session interface{}) error {
	// grant_type REQUIRED.
	// Value MUST be set to "password".
	if request.GetGrantType() != "password" {
		return nil
	}

	username := req.PostForm.Get("username")
	password := req.PostForm.Get("password")
	if username == "" || password == "" {
		return errors.New(fosite.ErrInvalidRequest)
	} else if err := c.Store.DoCredentialsAuthenticate(username, password); err == pkg.ErrNotFound {
		return errors.New(fosite.ErrInvalidRequest)
	} else if err != nil {
		return errors.New(fosite.ErrServerError)
	}

	request.SetGrantTypeHandled("password")
	return nil
}

// ValidateTokenEndpointRequest implements https://tools.ietf.org/html/rfc6749#section-6
func (c *RefreshTokenGrantHandler) ValidateTokenEndpointRequest(ctx context.Context, req *http.Request, request fosite.AccessRequester) error {
	// grant_type REQUIRED.
	// Value MUST be set to "client_credentials".
	if request.GetGrantType() != "refresh_token" {
		return nil
	}

	// The authorization server MUST ... validate the refresh token.
	signature, err := c.RefreshTokenStrategy.ValidateRefreshToken(req.Form.Get("refresh_token"), ctx, req, request)
	if err != nil {
		return errors.New(fosite.ErrInvalidRequest)
	}

	accessRequest, err := c.Store.GetRefreshTokenSession(signature, nil)
	if err == pkg.ErrNotFound {
		return errors.New(fosite.ErrInvalidRequest)
	} else if err != nil {
		return errors.New(fosite.ErrServerError)
	}

	// The authorization server MUST ... and ensure that the refresh token was issued to the authenticated client
	if accessRequest.GetClient().GetID() != request.GetClient().GetID() {
		return errors.New(fosite.ErrInvalidRequest)
	}

	request.SetGrantTypeHandled("refresh_token")
	return nil
}

func (c *CoreValidator) introspectAccessToken(ctx context.Context, token string, accessRequest fosite.AccessRequester, scopes []string) error {
	sig := c.CoreStrategy.AccessTokenSignature(token)
	or, err := c.CoreStorage.GetAccessTokenSession(ctx, sig, accessRequest.GetSession())
	if err != nil {
		return errors.Wrap(fosite.ErrRequestUnauthorized, err.Error())
	} else if err := c.CoreStrategy.ValidateAccessToken(ctx, or, token); err != nil {
		return err
	}

	for _, scope := range scopes {
		if scope == "" {
			continue
		}

		if !c.ScopeStrategy(or.GetGrantedScopes(), scope) {
			return errors.Wrap(fosite.ErrInvalidScope, "")
		}
	}

	accessRequest.Merge(or)
	return nil
}

// HandleTokenEndpointRequest implements https://tools.ietf.org/html/rfc6749#section-4.4.3
func (c *ClientCredentialsGrantHandler) HandleTokenEndpointRequest(ctx context.Context, r *http.Request, request fosite.AccessRequester, response fosite.AccessResponder) error {
	if request.GetGrantType() != "client_credentials" {
		return nil
	}

	token, signature, err := c.AccessTokenStrategy.GenerateAccessToken(ctx, r, request)
	if err != nil {
		return errors.New(fosite.ErrServerError)
	} else if err := c.Store.CreateAccessTokenSession(signature, request); err != nil {
		return errors.New(fosite.ErrServerError)
	}

	response.SetAccessToken(token)
	response.SetTokenType("bearer")
	response.SetExtra("expires_in", strconv.Itoa(int(c.AccessTokenLifespan/time.Second)))
	response.SetExtra("scope", strings.Join(request.GetGrantedScopes(), " "))

	// "A refresh token SHOULD NOT be included."
	// -> we won't issue one

	return nil
}

// HandleTokenEndpointRequest implements https://tools.ietf.org/html/rfc6749#section-4.3.3
func (c *ResourceOwnerPasswordCredentialsGrantHandler) HandleTokenEndpointRequest(ctx context.Context, req *http.Request, requester fosite.AccessRequester, responder fosite.AccessResponder) error {
	if requester.GetGrantType() != "password" {
		return nil
	}

	token, signature, err := c.AccessTokenStrategy.GenerateAccessToken(ctx, req, requester)
	if err != nil {
		return errors.New(fosite.ErrServerError)
	} else if err := c.Store.CreateAccessTokenSession(signature, requester); err != nil {
		return errors.New(fosite.ErrServerError)
	}

	responder.SetAccessToken(token)
	responder.SetTokenType("bearer")
	responder.SetExtra("expires_in", strconv.Itoa(int(c.AccessTokenLifespan/time.Second)))
	responder.SetExtra("scope", strings.Join(requester.GetGrantedScopes(), " "))

	// As of https://tools.ietf.org/html/rfc6819#section-5.2.2.1 and
	// https://tools.ietf.org/html/rfc6819#section-4.4.3.3 we decided not to include refresh tokens
	// as part of the resource owner grant

	return nil
}

func (c *AuthorizeExplicitGrantHandler) PopulateTokenEndpointResponse(ctx context.Context, req *http.Request, requester fosite.AccessRequester, responder fosite.AccessResponder) error {
	// grant_type REQUIRED.
	// Value MUST be set to "authorization_code".
	if !requester.GetGrantTypes().Exact("authorization_code") {
		return errors.Wrap(fosite.ErrUnknownRequest, "")
	}

	code := req.PostForm.Get("code")
	signature := c.AuthorizeCodeStrategy.AuthorizeCodeSignature(code)
	authorizeRequest, err := c.AuthorizeCodeGrantStorage.GetAuthorizeCodeSession(ctx, signature, requester.GetSession())
	if err != nil {
		return errors.Wrap(fosite.ErrServerError, err.Error())
	} else if err := c.AuthorizeCodeStrategy.ValidateAuthorizeCode(ctx, requester, code); err != nil {
		return errors.Wrap(fosite.ErrInvalidRequest, err.Error())
	}

	access, accessSignature, err := c.AccessTokenStrategy.GenerateAccessToken(ctx, requester)
	if err != nil {
		return errors.Wrap(fosite.ErrServerError, err.Error())
	}

	for _, scope := range authorizeRequest.GetGrantedScopes() {
		requester.GrantScope(scope)
	}

	var refresh, refreshSignature string
	if authorizeRequest.GetGrantedScopes().Has("offline") {
		refresh, refreshSignature, err = c.RefreshTokenStrategy.GenerateRefreshToken(ctx, requester)
		if err != nil {
			return errors.Wrap(fosite.ErrServerError, err.Error())
		}
	}

	if err := c.AuthorizeCodeGrantStorage.PersistAuthorizeCodeGrantSession(ctx, signature, accessSignature, refreshSignature, requester); err != nil {
		return errors.Wrap(fosite.ErrServerError, err.Error())
	}

	responder.SetAccessToken(access)
	responder.SetTokenType("bearer")
	responder.SetExpiresIn(getExpiresIn(requester, fosite.AccessToken, c.AccessTokenLifespan, time.Now()))
	responder.SetScopes(requester.GetGrantedScopes())
	if refresh != "" {
		responder.SetExtra("refresh_token", refresh)
	}

	return nil
}

// HandleTokenEndpointRequest implements https://tools.ietf.org/html/rfc6749#section-4.4.3
func (c *ClientCredentialsGrantHandler) HandleTokenEndpointRequest(ctx context.Context, req *http.Request, requester fosite.AccessRequester, responder fosite.AccessResponder, session interface{}) error {
	if requester.GetGrantType() != "client_credentials" {
		return nil
	}

	access, err := c.Enigma.GenerateChallenge(requester.GetClient().GetHashedSecret())
	if err != nil {
		return errors.New(fosite.ErrServerError)
	} else if err := c.Store.CreateAccessTokenSession(access.Signature, requester, &core.TokenSession{Extra: session}); err != nil {
		return errors.New(fosite.ErrServerError)
	}

	responder.SetAccessToken(access.String())
	responder.SetTokenType("bearer")
	responder.SetExtra("expires_in", strconv.Itoa(int(c.AccessTokenLifespan/time.Second)))
	responder.SetExtra("scope", strings.Join(requester.GetGrantedScopes(), " "))

	// "A refresh token SHOULD NOT be included."
	// -> we won't issue one

	return nil
}

// HandleTokenEndpointRequest implements
// * https://tools.ietf.org/html/rfc6749#section-4.1.3 (everything)
func (c *AuthorizeExplicitGrantHandler) HandleTokenEndpointRequest(ctx context.Context, r *http.Request, request fosite.AccessRequester) error {
	// grant_type REQUIRED.
	// Value MUST be set to "authorization_code".
	if !request.GetGrantTypes().Exact("authorization_code") {
		return errors.Wrap(fosite.ErrUnknownRequest, "")
	}

	if !request.GetClient().GetGrantTypes().Has("authorization_code") {
		return errors.Wrap(fosite.ErrInvalidGrant, "The client is not allowed to use grant type authorization_code")
	}

	code := r.PostForm.Get("code")
	signature := c.AuthorizeCodeStrategy.AuthorizeCodeSignature(code)
	authorizeRequest, err := c.AuthorizeCodeGrantStorage.GetAuthorizeCodeSession(ctx, signature, request.GetSession())
	if errors.Cause(err) == fosite.ErrNotFound {
		return errors.Wrap(fosite.ErrInvalidRequest, err.Error())
	} else if err != nil {
		return errors.Wrap(fosite.ErrServerError, err.Error())
	}

	// The authorization server MUST verify that the authorization code is valid
	if err := c.AuthorizeCodeStrategy.ValidateAuthorizeCode(ctx, request, code); err != nil {
		return errors.Wrap(fosite.ErrInvalidRequest, err.Error())
	}

	// Override scopes
	request.SetRequestedScopes(authorizeRequest.GetRequestedScopes())

	// The authorization server MUST ensure that the authorization code was issued to the authenticated
	// confidential client, or if the client is public, ensure that the
	// code was issued to "client_id" in the request,
	if authorizeRequest.GetClient().GetID() != request.GetClient().GetID() {
		return errors.Wrap(fosite.ErrInvalidRequest, "Client ID mismatch")
	}

	// ensure that the "redirect_uri" parameter is present if the
	// "redirect_uri" parameter was included in the initial authorization
	// request as described in Section 4.1.1, and if included ensure that
	// their values are identical.
	forcedRedirectURI := authorizeRequest.GetRequestForm().Get("redirect_uri")
	if forcedRedirectURI != "" && forcedRedirectURI != r.PostForm.Get("redirect_uri") {
		return errors.Wrap(fosite.ErrInvalidRequest, "Redirect URI mismatch")
	}

	// Checking of POST client_id skipped, because:
	// If the client type is confidential or the client was issued client
	// credentials (or assigned other authentication requirements), the
	// client MUST authenticate with the authorization server as described
	// in Section 3.2.1.
	request.SetSession(authorizeRequest.GetSession())
	request.GetSession().SetExpiresAt(fosite.AccessToken, time.Now().Add(c.AccessTokenLifespan))
	return nil
}