// Copyright (c) 2017 Mattermost, Inc. All Rights Reserved.
// See License.txt for license information.

package app

import (
	"bytes"
	"crypto/sha256"
	"encoding/base64"
	"fmt"
	"io"
	"io/ioutil"
	"net/url"
	"os"
	"path"
	"path/filepath"
	"strings"
	"sync"

	l4g "github.com/alecthomas/log4go"
	"github.com/mattermost/platform/model"
	"github.com/mattermost/platform/utils"

	s3 "github.com/minio/minio-go"
)

func ReadFile(path string) ([]byte, *model.AppError) {
	if utils.Cfg.FileSettings.DriverName == model.IMAGE_DRIVER_S3 {
		endpoint := utils.Cfg.FileSettings.AmazonS3Endpoint
		accessKey := utils.Cfg.FileSettings.AmazonS3AccessKeyId
		secretKey := utils.Cfg.FileSettings.AmazonS3SecretAccessKey
		secure := *utils.Cfg.FileSettings.AmazonS3SSL
		s3Clnt, err := s3.New(endpoint, accessKey, secretKey, secure)
		if err != nil {
			return nil, model.NewLocAppError("ReadFile", "api.file.read_file.s3.app_error", nil, err.Error())
		}
		bucket := utils.Cfg.FileSettings.AmazonS3Bucket
		minioObject, err := s3Clnt.GetObject(bucket, path)
		defer minioObject.Close()
		if err != nil {
			return nil, model.NewLocAppError("ReadFile", "api.file.read_file.s3.app_error", nil, err.Error())
		}
		if f, err := ioutil.ReadAll(minioObject); err != nil {
			return nil, model.NewLocAppError("ReadFile", "api.file.read_file.s3.app_error", nil, err.Error())
		} else {
			return f, nil
		}
	} else if utils.Cfg.FileSettings.DriverName == model.IMAGE_DRIVER_LOCAL {
		if f, err := ioutil.ReadFile(utils.Cfg.FileSettings.Directory + path); err != nil {
			return nil, model.NewLocAppError("ReadFile", "api.file.read_file.reading_local.app_error", nil, err.Error())
		} else {
			return f, nil
		}
	} else {
		return nil, model.NewLocAppError("ReadFile", "api.file.read_file.configured.app_error", nil, "")
	}
}

func MoveFile(oldPath, newPath string) *model.AppError {
	if utils.Cfg.FileSettings.DriverName == model.IMAGE_DRIVER_S3 {
		endpoint := utils.Cfg.FileSettings.AmazonS3Endpoint
		accessKey := utils.Cfg.FileSettings.AmazonS3AccessKeyId
		secretKey := utils.Cfg.FileSettings.AmazonS3SecretAccessKey
		secure := *utils.Cfg.FileSettings.AmazonS3SSL
		s3Clnt, err := s3.New(endpoint, accessKey, secretKey, secure)
		if err != nil {
			return model.NewLocAppError("moveFile", "api.file.write_file.s3.app_error", nil, err.Error())
		}
		bucket := utils.Cfg.FileSettings.AmazonS3Bucket

		var copyConds = s3.NewCopyConditions()
		if err = s3Clnt.CopyObject(bucket, newPath, "/"+path.Join(bucket, oldPath), copyConds); err != nil {
			return model.NewLocAppError("moveFile", "api.file.move_file.delete_from_s3.app_error", nil, err.Error())
		}
		if err = s3Clnt.RemoveObject(bucket, oldPath); err != nil {
			return model.NewLocAppError("moveFile", "api.file.move_file.delete_from_s3.app_error", nil, err.Error())
		}
	} else if utils.Cfg.FileSettings.DriverName == model.IMAGE_DRIVER_LOCAL {
		if err := os.MkdirAll(filepath.Dir(utils.Cfg.FileSettings.Directory+newPath), 0774); err != nil {
			return model.NewLocAppError("moveFile", "api.file.move_file.rename.app_error", nil, err.Error())
		}

		if err := os.Rename(utils.Cfg.FileSettings.Directory+oldPath, utils.Cfg.FileSettings.Directory+newPath); err != nil {
			return model.NewLocAppError("moveFile", "api.file.move_file.rename.app_error", nil, err.Error())
		}
	} else {
		return model.NewLocAppError("moveFile", "api.file.move_file.configured.app_error", nil, "")
	}

	return nil
}

func WriteFile(f []byte, path string) *model.AppError {
	if utils.Cfg.FileSettings.DriverName == model.IMAGE_DRIVER_S3 {
		endpoint := utils.Cfg.FileSettings.AmazonS3Endpoint
		accessKey := utils.Cfg.FileSettings.AmazonS3AccessKeyId
		secretKey := utils.Cfg.FileSettings.AmazonS3SecretAccessKey
		secure := *utils.Cfg.FileSettings.AmazonS3SSL
		s3Clnt, err := s3.New(endpoint, accessKey, secretKey, secure)
		if err != nil {
			return model.NewLocAppError("WriteFile", "api.file.write_file.s3.app_error", nil, err.Error())
		}
		bucket := utils.Cfg.FileSettings.AmazonS3Bucket
		ext := filepath.Ext(path)

		if model.IsFileExtImage(ext) {
			_, err = s3Clnt.PutObject(bucket, path, bytes.NewReader(f), model.GetImageMimeType(ext))
		} else {
			_, err = s3Clnt.PutObject(bucket, path, bytes.NewReader(f), "binary/octet-stream")
		}
		if err != nil {
			return model.NewLocAppError("WriteFile", "api.file.write_file.s3.app_error", nil, err.Error())
		}
	} else if utils.Cfg.FileSettings.DriverName == model.IMAGE_DRIVER_LOCAL {
		if err := writeFileLocally(f, utils.Cfg.FileSettings.Directory+path); err != nil {
			return err
		}
	} else {
		return model.NewLocAppError("WriteFile", "api.file.write_file.configured.app_error", nil, "")
	}

	return nil
}

func writeFileLocally(f []byte, path string) *model.AppError {
	if err := os.MkdirAll(filepath.Dir(path), 0774); err != nil {
		directory, _ := filepath.Abs(filepath.Dir(path))
		return model.NewLocAppError("WriteFile", "api.file.write_file_locally.create_dir.app_error", nil, "directory="+directory+", err="+err.Error())
	}

	if err := ioutil.WriteFile(path, f, 0644); err != nil {
		return model.NewLocAppError("WriteFile", "api.file.write_file_locally.writing.app_error", nil, err.Error())
	}

	return nil
}

func openFileWriteStream(path string) (io.Writer, *model.AppError) {
	if utils.Cfg.FileSettings.DriverName == model.IMAGE_DRIVER_S3 {
		return nil, model.NewLocAppError("openFileWriteStream", "api.file.open_file_write_stream.s3.app_error", nil, "")
	} else if utils.Cfg.FileSettings.DriverName == model.IMAGE_DRIVER_LOCAL {
		if err := os.MkdirAll(filepath.Dir(utils.Cfg.FileSettings.Directory+path), 0774); err != nil {
			return nil, model.NewLocAppError("openFileWriteStream", "api.file.open_file_write_stream.creating_dir.app_error", nil, err.Error())
		}

		if fileHandle, err := os.Create(utils.Cfg.FileSettings.Directory + path); err != nil {
			return nil, model.NewLocAppError("openFileWriteStream", "api.file.open_file_write_stream.local_server.app_error", nil, err.Error())
		} else {
			fileHandle.Chmod(0644)
			return fileHandle, nil
		}
	}

	return nil, model.NewLocAppError("openFileWriteStream", "api.file.open_file_write_stream.configured.app_error", nil, "")
}

func closeFileWriteStream(file io.Writer) {
	file.(*os.File).Close()
}

func GetInfoForFilename(post *model.Post, teamId string, filename string) *model.FileInfo {
	// Find the path from the Filename of the form /{channelId}/{userId}/{uid}/{nameWithExtension}
	split := strings.SplitN(filename, "/", 5)
	if len(split) < 5 {
		l4g.Error(utils.T("api.file.migrate_filenames_to_file_infos.unexpected_filename.error"), post.Id, filename)
		return nil
	}

	channelId := split[1]
	userId := split[2]
	oldId := split[3]
	name, _ := url.QueryUnescape(split[4])

	if split[0] != "" || split[1] != post.ChannelId || split[2] != post.UserId || strings.Contains(split[4], "/") {
		l4g.Warn(utils.T("api.file.migrate_filenames_to_file_infos.mismatched_filename.warn"), post.Id, post.ChannelId, post.UserId, filename)
	}

	pathPrefix := fmt.Sprintf("teams/%s/channels/%s/users/%s/%s/", teamId, channelId, userId, oldId)
	path := pathPrefix + name

	// Open the file and populate the fields of the FileInfo
	var info *model.FileInfo
	if data, err := ReadFile(path); err != nil {
		l4g.Error(utils.T("api.file.migrate_filenames_to_file_infos.file_not_found.error"), post.Id, filename, path, err)
		return nil
	} else {
		var err *model.AppError
		info, err = model.GetInfoForBytes(name, data)
		if err != nil {
			l4g.Warn(utils.T("api.file.migrate_filenames_to_file_infos.info.app_error"), post.Id, filename, err)
		}
	}

	// Generate a new ID because with the old system, you could very rarely get multiple posts referencing the same file
	info.Id = model.NewId()
	info.CreatorId = post.UserId
	info.PostId = post.Id
	info.CreateAt = post.CreateAt
	info.UpdateAt = post.UpdateAt
	info.Path = path

	if info.IsImage() {
		nameWithoutExtension := name[:strings.LastIndex(name, ".")]
		info.PreviewPath = pathPrefix + nameWithoutExtension + "_preview.jpg"
		info.ThumbnailPath = pathPrefix + nameWithoutExtension + "_thumb.jpg"
	}

	return info
}

func FindTeamIdForFilename(post *model.Post, filename string) string {
	split := strings.SplitN(filename, "/", 5)
	id := split[3]
	name, _ := url.QueryUnescape(split[4])

	// This post is in a direct channel so we need to figure out what team the files are stored under.
	if result := <-Srv.Store.Team().GetTeamsByUserId(post.UserId); result.Err != nil {
		l4g.Error(utils.T("api.file.migrate_filenames_to_file_infos.teams.app_error"), post.Id, result.Err)
	} else if teams := result.Data.([]*model.Team); len(teams) == 1 {
		// The user has only one team so the post must've been sent from it
		return teams[0].Id
	} else {
		for _, team := range teams {
			path := fmt.Sprintf("teams/%s/channels/%s/users/%s/%s/%s", team.Id, post.ChannelId, post.UserId, id, name)
			if _, err := ReadFile(path); err == nil {
				// Found the team that this file was posted from
				return team.Id
			}
		}
	}

	return ""
}

var fileMigrationLock sync.Mutex

// Creates and stores FileInfos for a post created before the FileInfos table existed.
func MigrateFilenamesToFileInfos(post *model.Post) []*model.FileInfo {
	if len(post.Filenames) == 0 {
		l4g.Warn(utils.T("api.file.migrate_filenames_to_file_infos.no_filenames.warn"), post.Id)
		return []*model.FileInfo{}
	}

	cchan := Srv.Store.Channel().Get(post.ChannelId, true)

	// There's a weird bug that rarely happens where a post ends up with duplicate Filenames so remove those
	filenames := utils.RemoveDuplicatesFromStringArray(post.Filenames)

	var channel *model.Channel
	if result := <-cchan; result.Err != nil {
		l4g.Error(utils.T("api.file.migrate_filenames_to_file_infos.channel.app_error"), post.Id, post.ChannelId, result.Err)
		return []*model.FileInfo{}
	} else {
		channel = result.Data.(*model.Channel)
	}

	// Find the team that was used to make this post since its part of the file path that isn't saved in the Filename
	var teamId string
	if channel.TeamId == "" {
		// This post was made in a cross-team DM channel so we need to find where its files were saved
		teamId = FindTeamIdForFilename(post, filenames[0])
	} else {
		teamId = channel.TeamId
	}

	// Create FileInfo objects for this post
	infos := make([]*model.FileInfo, 0, len(filenames))
	if teamId == "" {
		l4g.Error(utils.T("api.file.migrate_filenames_to_file_infos.team_id.error"), post.Id, filenames)
	} else {
		for _, filename := range filenames {
			info := GetInfoForFilename(post, teamId, filename)
			if info == nil {
				continue
			}

			infos = append(infos, info)
		}
	}

	// Lock to prevent only one migration thread from trying to update the post at once, preventing duplicate FileInfos from being created
	fileMigrationLock.Lock()
	defer fileMigrationLock.Unlock()

	if result := <-Srv.Store.Post().Get(post.Id); result.Err != nil {
		l4g.Error(utils.T("api.file.migrate_filenames_to_file_infos.get_post_again.app_error"), post.Id, result.Err)
		return []*model.FileInfo{}
	} else if newPost := result.Data.(*model.PostList).Posts[post.Id]; len(newPost.Filenames) != len(post.Filenames) {
		// Another thread has already created FileInfos for this post, so just return those
		if result := <-Srv.Store.FileInfo().GetForPost(post.Id); result.Err != nil {
			l4g.Error(utils.T("api.file.migrate_filenames_to_file_infos.get_post_file_infos_again.app_error"), post.Id, result.Err)
			return []*model.FileInfo{}
		} else {
			l4g.Debug(utils.T("api.file.migrate_filenames_to_file_infos.not_migrating_post.debug"), post.Id)
			return result.Data.([]*model.FileInfo)
		}
	}

	l4g.Debug(utils.T("api.file.migrate_filenames_to_file_infos.migrating_post.debug"), post.Id)

	savedInfos := make([]*model.FileInfo, 0, len(infos))
	fileIds := make([]string, 0, len(filenames))
	for _, info := range infos {
		if result := <-Srv.Store.FileInfo().Save(info); result.Err != nil {
			l4g.Error(utils.T("api.file.migrate_filenames_to_file_infos.save_file_info.app_error"), post.Id, info.Id, info.Path, result.Err)
			continue
		}

		savedInfos = append(savedInfos, info)
		fileIds = append(fileIds, info.Id)
	}

	// Copy and save the updated post
	newPost := &model.Post{}
	*newPost = *post

	newPost.Filenames = []string{}
	newPost.FileIds = fileIds

	// Update Posts to clear Filenames and set FileIds
	if result := <-Srv.Store.Post().Update(newPost, post); result.Err != nil {
		l4g.Error(utils.T("api.file.migrate_filenames_to_file_infos.save_post.app_error"), post.Id, newPost.FileIds, post.Filenames, result.Err)
		return []*model.FileInfo{}
	} else {
		return savedInfos
	}
}

func GeneratePublicLink(siteURL string, info *model.FileInfo) string {
	hash := GeneratePublicLinkHash(info.Id, *utils.Cfg.FileSettings.PublicLinkSalt)
	return fmt.Sprintf("%s%s/public/files/%v/get?h=%s", siteURL, model.API_URL_SUFFIX, info.Id, hash)
}

func GeneratePublicLinkHash(fileId, salt string) string {
	hash := sha256.New()
	hash.Write([]byte(salt))
	hash.Write([]byte(fileId))

	return base64.RawURLEncoding.EncodeToString(hash.Sum(nil))
}