/*
 * Copyright © 2015-2018 Aeneas Rekkas <aeneas+oss@aeneas.io>
 *
 * 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.
 *
 * @author		Aeneas Rekkas <aeneas+oss@aeneas.io>
 * @copyright 	2015-2018 Aeneas Rekkas <aeneas+oss@aeneas.io>
 * @license 	Apache-2.0
 *
 */

package oauth2

import (
	"context"
	"fmt"
	"strings"
	"time"

	"github.com/ory/x/errorsx"

	"github.com/pkg/errors"

	"github.com/ory/fosite"
	"github.com/ory/fosite/storage"
)

type RefreshTokenGrantHandler struct {
	AccessTokenStrategy    AccessTokenStrategy
	RefreshTokenStrategy   RefreshTokenStrategy
	TokenRevocationStorage TokenRevocationStorage

	// AccessTokenLifespan defines the lifetime of an access token.
	AccessTokenLifespan time.Duration

	// RefreshTokenLifespan defines the lifetime of a refresh token.
	RefreshTokenLifespan time.Duration

	ScopeStrategy            fosite.ScopeStrategy
	AudienceMatchingStrategy fosite.AudienceMatchingStrategy
	RefreshTokenScopes       []string
}

// HandleTokenEndpointRequest implements https://tools.ietf.org/html/rfc6749#section-6
func (c *RefreshTokenGrantHandler) HandleTokenEndpointRequest(ctx context.Context, request fosite.AccessRequester) error {
	if !c.CanHandleTokenEndpointRequest(request) {
		return errorsx.WithStack(fosite.ErrUnknownRequest)
	}

	if !request.GetClient().GetGrantTypes().Has("refresh_token") {
		return errorsx.WithStack(fosite.ErrUnauthorizedClient.WithHint("The OAuth 2.0 Client is not allowed to use authorization grant 'refresh_token'."))
	}

	refresh := request.GetRequestForm().Get("refresh_token")
	signature := c.RefreshTokenStrategy.RefreshTokenSignature(refresh)
	originalRequest, err := c.TokenRevocationStorage.GetRefreshTokenSession(ctx, signature, request.GetSession())
	if errors.Is(err, fosite.ErrInactiveToken) {
		// Detected refresh token reuse
		if rErr := c.handleRefreshTokenReuse(ctx, signature, originalRequest); rErr != nil {
			return errorsx.WithStack(fosite.ErrServerError.WithWrap(rErr).WithDebug(rErr.Error()))
		}

		return errorsx.WithStack(fosite.ErrInactiveToken.WithWrap(err).WithDebug(err.Error()))
	} else if errors.Is(err, fosite.ErrNotFound) {
		return errorsx.WithStack(fosite.ErrInvalidGrant.WithWrap(err).WithDebugf("The refresh token has not been found: %s", err.Error()))
	} else if err != nil {
		return errorsx.WithStack(fosite.ErrServerError.WithWrap(err).WithDebug(err.Error()))
	} else if err := c.RefreshTokenStrategy.ValidateRefreshToken(ctx, originalRequest, refresh); err != nil {
		// The authorization server MUST ... validate the refresh token.
		// This needs to happen after store retrieval for the session to be hydrated properly
		if errors.Is(err, fosite.ErrTokenExpired) {
			return errorsx.WithStack(fosite.ErrInvalidGrant.WithWrap(err).WithDebug(err.Error()))
		}
		return errorsx.WithStack(fosite.ErrInvalidRequest.WithWrap(err).WithDebug(err.Error()))
	}

	if !(len(c.RefreshTokenScopes) == 0 || originalRequest.GetGrantedScopes().HasOneOf(c.RefreshTokenScopes...)) {
		scopeNames := strings.Join(c.RefreshTokenScopes, " or ")
		hint := fmt.Sprintf("The OAuth 2.0 Client was not granted scope %s and may thus not perform the 'refresh_token' authorization grant.", scopeNames)
		return errorsx.WithStack(fosite.ErrScopeNotGranted.WithHint(hint))

	}

	// The authorization server MUST ... and ensure that the refresh token was issued to the authenticated client
	if originalRequest.GetClient().GetID() != request.GetClient().GetID() {
		return errorsx.WithStack(fosite.ErrInvalidGrant.WithHint("The OAuth 2.0 Client ID from this request does not match the ID during the initial token issuance."))
	}

	request.SetSession(originalRequest.GetSession().Clone())
	request.SetRequestedScopes(originalRequest.GetRequestedScopes())
	request.SetRequestedAudience(originalRequest.GetRequestedAudience())

	for _, scope := range originalRequest.GetGrantedScopes() {
		if !c.ScopeStrategy(request.GetClient().GetScopes(), scope) {
			return errorsx.WithStack(fosite.ErrInvalidScope.WithHintf("The OAuth 2.0 Client is not allowed to request scope '%s'.", scope))
		}
		request.GrantScope(scope)
	}

	if err := c.AudienceMatchingStrategy(request.GetClient().GetAudience(), originalRequest.GetGrantedAudience()); err != nil {
		return err
	}

	for _, audience := range originalRequest.GetGrantedAudience() {
		request.GrantAudience(audience)
	}

	request.GetSession().SetExpiresAt(fosite.AccessToken, time.Now().UTC().Add(c.AccessTokenLifespan).Round(time.Second))
	if c.RefreshTokenLifespan > -1 {
		request.GetSession().SetExpiresAt(fosite.RefreshToken, time.Now().UTC().Add(c.RefreshTokenLifespan).Round(time.Second))
	}

	return nil
}

// PopulateTokenEndpointResponse implements https://tools.ietf.org/html/rfc6749#section-6
func (c *RefreshTokenGrantHandler) PopulateTokenEndpointResponse(ctx context.Context, requester fosite.AccessRequester, responder fosite.AccessResponder) (err error) {
	if !c.CanHandleTokenEndpointRequest(requester) {
		return errorsx.WithStack(fosite.ErrUnknownRequest)
	}

	accessToken, accessSignature, err := c.AccessTokenStrategy.GenerateAccessToken(ctx, requester)
	if err != nil {
		return errorsx.WithStack(fosite.ErrServerError.WithWrap(err).WithDebug(err.Error()))
	}

	refreshToken, refreshSignature, err := c.RefreshTokenStrategy.GenerateRefreshToken(ctx, requester)
	if err != nil {
		return errorsx.WithStack(fosite.ErrServerError.WithWrap(err).WithDebug(err.Error()))
	}

	signature := c.RefreshTokenStrategy.RefreshTokenSignature(requester.GetRequestForm().Get("refresh_token"))

	ctx, err = storage.MaybeBeginTx(ctx, c.TokenRevocationStorage)
	if err != nil {
		return errorsx.WithStack(fosite.ErrServerError.WithWrap(err).WithDebug(err.Error()))
	}
	defer func() {
		err = c.handleRefreshTokenEndpointStorageError(ctx, err)
	}()

	ts, err := c.TokenRevocationStorage.GetRefreshTokenSession(ctx, signature, nil)
	if err != nil {
		return err
	} else if err := c.TokenRevocationStorage.RevokeAccessToken(ctx, ts.GetID()); err != nil {
		return err
	}

	if err := c.TokenRevocationStorage.RevokeRefreshTokenMaybeGracePeriod(ctx, ts.GetID(), signature); err != nil {
		return err
	}

	storeReq := requester.Sanitize([]string{})
	storeReq.SetID(ts.GetID())

	if err = c.TokenRevocationStorage.CreateAccessTokenSession(ctx, accessSignature, storeReq); err != nil {
		return err
	}

	if err = c.TokenRevocationStorage.CreateRefreshTokenSession(ctx, refreshSignature, storeReq); err != nil {
		return err
	}

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

	if err = storage.MaybeCommitTx(ctx, c.TokenRevocationStorage); err != nil {
		return err
	}

	return nil
}

// Reference: https://tools.ietf.org/html/rfc6819#section-5.2.2.3
//
//     The basic idea is to change the refresh token
//     value with every refresh request in order to detect attempts to
//     obtain access tokens using old refresh tokens.  Since the
//     authorization server cannot determine whether the attacker or the
//     legitimate client is trying to access, in case of such an access
//     attempt the valid refresh token and the access authorization
//     associated with it are both revoked.
//
func (c *RefreshTokenGrantHandler) handleRefreshTokenReuse(ctx context.Context, signature string, req fosite.Requester) (err error) {
	ctx, err = storage.MaybeBeginTx(ctx, c.TokenRevocationStorage)
	if err != nil {
		return errorsx.WithStack(fosite.ErrServerError.WithWrap(err).WithDebug(err.Error()))
	}
	defer func() {
		err = c.handleRefreshTokenEndpointStorageError(ctx, err)
	}()

	if err = c.TokenRevocationStorage.DeleteRefreshTokenSession(ctx, signature); err != nil {
		return err
	} else if err = c.TokenRevocationStorage.RevokeRefreshToken(
		ctx, req.GetID(),
	); err != nil && !errors.Is(err, fosite.ErrNotFound) {
		return err
	} else if err = c.TokenRevocationStorage.RevokeAccessToken(
		ctx, req.GetID(),
	); err != nil && !errors.Is(err, fosite.ErrNotFound) {
		return err
	}

	if err = storage.MaybeCommitTx(ctx, c.TokenRevocationStorage); err != nil {
		return err
	}

	return nil
}

func (c *RefreshTokenGrantHandler) handleRefreshTokenEndpointStorageError(ctx context.Context, storageErr error) (err error) {
	if storageErr == nil {
		return nil
	}

	defer func() {
		if rollBackTxnErr := storage.MaybeRollbackTx(ctx, c.TokenRevocationStorage); rollBackTxnErr != nil {
			err = errorsx.WithStack(fosite.ErrServerError.WithWrap(err).WithDebugf("error: %s; rollback error: %s", err, rollBackTxnErr))
		}
	}()

	if errors.Is(storageErr, fosite.ErrSerializationFailure) {
		return errorsx.WithStack(fosite.ErrInvalidRequest.
			WithDebugf(storageErr.Error()).
			WithHint("Failed to refresh token because of multiple concurrent requests using the same token which is not allowed."))
	}

	if errors.Is(storageErr, fosite.ErrNotFound) || errors.Is(storageErr, fosite.ErrInactiveToken) {
		return errorsx.WithStack(fosite.ErrInvalidRequest.
			WithDebugf(storageErr.Error()).
			WithHint("Failed to refresh token because of multiple concurrent requests using the same token which is not allowed."))
	}

	return errorsx.WithStack(fosite.ErrServerError.WithWrap(storageErr).WithDebug(storageErr.Error()))
}

func (c *RefreshTokenGrantHandler) CanSkipClientAuth(requester fosite.AccessRequester) bool {
	return false
}

func (c *RefreshTokenGrantHandler) CanHandleTokenEndpointRequest(requester fosite.AccessRequester) bool {
	// grant_type REQUIRED.
	// Value MUST be set to "refresh_token".
	return requester.GetGrantTypes().ExactOne("refresh_token")
}