// Copyright 2019 Drone IO, 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 contents

import (
	"context"
	"strings"
	"time"

	"github.com/drone/drone/core"
	"github.com/drone/go-scm/scm"
)

// default number of backoff attempts.
var attempts = 3

// default time to wait after failed attempt.
var wait = time.Second * 15

// New returns a new FileService.
func New(client *scm.Client, renewer core.Renewer) core.FileService {
	return &service{
		client:   client,
		renewer:  renewer,
		attempts: attempts,
		wait:     wait,
	}
}

type service struct {
	renewer  core.Renewer
	client   *scm.Client
	attempts int
	wait     time.Duration
}

func (s *service) Find(ctx context.Context, user *core.User, repo, commit, ref, path string) (*core.File, error) {
	// TODO(gogs) ability to fetch a yaml by pull request ref.
	// it is not currently possible to fetch the yaml
	// configuration file from a pull request sha. This
	// workaround defaults to master.
	if s.client.Driver == scm.DriverGogs &&
		strings.HasPrefix(ref, "refs/pull") {
		commit = "master"
	}
	// TODO(gogs) ability to fetch a file in tag from commit sha.
	// this is a workaround for gogs which does not allow
	// fetching a file by commit sha for a tag. This forces
	// fetching a file by reference instead.
	if s.client.Driver == scm.DriverGogs &&
		strings.HasPrefix(ref, "refs/tag") {
		commit = ref
	}
	err := s.renewer.Renew(ctx, user, false)
	if err != nil {
		return nil, err
	}
	ctx = context.WithValue(ctx, scm.TokenKey{}, &scm.Token{
		Token:   user.Token,
		Refresh: user.Refresh,
	})
	content, err := s.findRetry(ctx, repo, path, commit)
	if err != nil {
		return nil, err
	}
	return &core.File{
		Data: content.Data,
		Hash: []byte{},
	}, nil
}

// helper function attempts to get the yaml configuration file
// with backoff on failure. This may be required due to eventual
// consistency issues with the github datastore.
func (s *service) findRetry(ctx context.Context, repo, path, commit string) (content *scm.Content, err error) {
	for i := 0; i < s.attempts; i++ {
		content, _, err = s.client.Contents.Find(ctx, repo, path, commit)
		// if no error is returned we can exit immediately.
		if err == nil {
			return
		}
		// wait a few seconds before retry. according to github
		// support 30 seconds total should be enough time. we
		// try 3 x 15 seconds, giving a total of 45 seconds.
		time.Sleep(s.wait)
	}
	return
}