package server

import (
	"encoding/json"
	"fmt"
	"io"
	"io/ioutil"
	"log"
	"net/http"
	"os"
	"path/filepath"
	"strings"

	"github.com/aws/aws-sdk-go/aws"
	"github.com/aws/aws-sdk-go/aws/awserr"
	"github.com/aws/aws-sdk-go/aws/session"
	"github.com/aws/aws-sdk-go/service/s3"
	"github.com/aws/aws-sdk-go/service/s3/s3manager"
	"golang.org/x/net/context"
	"golang.org/x/oauth2"
	"golang.org/x/oauth2/google"
	"google.golang.org/api/drive/v3"
	"google.golang.org/api/googleapi"
)

type Storage interface {
	Get(token string, filename string) (reader io.ReadCloser, contentLength uint64, err error)
	Head(token string, filename string) (contentLength uint64, err error)
	Put(token string, filename string, reader io.Reader, contentType string, contentLength uint64) error
	Delete(token string, filename string) error
	IsNotExist(err error) bool

	Type() string
}

type LocalStorage struct {
	Storage
	basedir string
	logger  *log.Logger
}

func NewLocalStorage(basedir string, logger *log.Logger) (*LocalStorage, error) {
	return &LocalStorage{basedir: basedir, logger: logger}, nil
}

func (s *LocalStorage) Type() string {
	return "local"
}

func (s *LocalStorage) Head(token string, filename string) (contentLength uint64, err error) {
	path := filepath.Join(s.basedir, token, filename)

	var fi os.FileInfo
	if fi, err = os.Lstat(path); err != nil {
		return
	}

	contentLength = uint64(fi.Size())

	return
}

func (s *LocalStorage) Get(token string, filename string) (reader io.ReadCloser, contentLength uint64, err error) {
	path := filepath.Join(s.basedir, token, filename)

	// content type , content length
	if reader, err = os.Open(path); err != nil {
		return
	}

	var fi os.FileInfo
	if fi, err = os.Lstat(path); err != nil {
		return
	}

	contentLength = uint64(fi.Size())

	return
}

func (s *LocalStorage) Delete(token string, filename string) (err error) {
	metadata := filepath.Join(s.basedir, token, fmt.Sprintf("%s.metadata", filename))
	os.Remove(metadata)

	path := filepath.Join(s.basedir, token, filename)
	err = os.Remove(path)
	return
}

func (s *LocalStorage) IsNotExist(err error) bool {
	if err == nil {
		return false
	}

	return os.IsNotExist(err)
}

func (s *LocalStorage) Put(token string, filename string, reader io.Reader, contentType string, contentLength uint64) error {
	var f io.WriteCloser
	var err error

	path := filepath.Join(s.basedir, token)

	if err = os.MkdirAll(path, 0700); err != nil && !os.IsExist(err) {
		return err
	}

	if f, err = os.OpenFile(filepath.Join(path, filename), os.O_RDWR|os.O_CREATE|os.O_TRUNC, 0600); err != nil {
		return err
	}

	defer f.Close()

	if _, err = io.Copy(f, reader); err != nil {
		return err
	}

	return nil
}

type S3Storage struct {
	Storage
	bucket      string
	session     *session.Session
	s3          *s3.S3
	logger      *log.Logger
	noMultipart bool
}

func NewS3Storage(accessKey, secretKey, bucketName, region, endpoint string, logger *log.Logger, disableMultipart bool, forcePathStyle bool) (*S3Storage, error) {
	sess := getAwsSession(accessKey, secretKey, region, endpoint, forcePathStyle)

	return &S3Storage{bucket: bucketName, s3: s3.New(sess), session: sess, logger: logger, noMultipart: disableMultipart}, nil
}

func (s *S3Storage) Type() string {
	return "s3"
}

func (s *S3Storage) Head(token string, filename string) (contentLength uint64, err error) {
	key := fmt.Sprintf("%s/%s", token, filename)

	headRequest := &s3.HeadObjectInput{
		Bucket: aws.String(s.bucket),
		Key:    aws.String(key),
	}

	// content type , content length
	response, err := s.s3.HeadObject(headRequest)
	if err != nil {
		return
	}

	if response.ContentLength != nil {
		contentLength = uint64(*response.ContentLength)
	}

	return
}

func (s *S3Storage) IsNotExist(err error) bool {
	if err == nil {
		return false
	}

	if aerr, ok := err.(awserr.Error); ok {
		switch aerr.Code() {
		case s3.ErrCodeNoSuchKey:
			return true
		}
	}

	return false
}

func (s *S3Storage) Get(token string, filename string) (reader io.ReadCloser, contentLength uint64, err error) {
	key := fmt.Sprintf("%s/%s", token, filename)

	getRequest := &s3.GetObjectInput{
		Bucket: aws.String(s.bucket),
		Key:    aws.String(key),
	}

	response, err := s.s3.GetObject(getRequest)
	if err != nil {
		return
	}

	if response.ContentLength != nil {
		contentLength = uint64(*response.ContentLength)
	}

	reader = response.Body
	return
}

func (s *S3Storage) Delete(token string, filename string) (err error) {
	metadata := fmt.Sprintf("%s/%s.metadata", token, filename)
	deleteRequest := &s3.DeleteObjectInput{
		Bucket: aws.String(s.bucket),
		Key:    aws.String(metadata),
	}

	_, err = s.s3.DeleteObject(deleteRequest)
	if err != nil {
		return
	}

	key := fmt.Sprintf("%s/%s", token, filename)
	deleteRequest = &s3.DeleteObjectInput{
		Bucket: aws.String(s.bucket),
		Key:    aws.String(key),
	}

	_, err = s.s3.DeleteObject(deleteRequest)

	return
}

func (s *S3Storage) Put(token string, filename string, reader io.Reader, contentType string, contentLength uint64) (err error) {
	key := fmt.Sprintf("%s/%s", token, filename)

	s.logger.Printf("Uploading file %s to S3 Bucket", filename)
	var concurrency int
	if !s.noMultipart {
		concurrency = 20
	} else {
		concurrency = 1
	}

	// Create an uploader with the session and custom options
	uploader := s3manager.NewUploader(s.session, func(u *s3manager.Uploader) {
		u.Concurrency = concurrency // default is 5
		u.LeavePartsOnError = false
	})

	_, err = uploader.Upload(&s3manager.UploadInput{
		Bucket: aws.String(s.bucket),
		Key:    aws.String(key),
		Body:   reader,
	})

	return
}

type GDrive struct {
	service         *drive.Service
	rootId          string
	basedir         string
	localConfigPath string
	chunkSize       int
	logger          *log.Logger
}

func NewGDriveStorage(clientJsonFilepath string, localConfigPath string, basedir string, chunkSize int, logger *log.Logger) (*GDrive, error) {
	b, err := ioutil.ReadFile(clientJsonFilepath)
	if err != nil {
		return nil, err
	}

	// If modifying these scopes, delete your previously saved client_secret.json.
	config, err := google.ConfigFromJSON(b, drive.DriveScope, drive.DriveMetadataScope)
	if err != nil {
		return nil, err
	}

	srv, err := drive.New(getGDriveClient(config, localConfigPath, logger))
	if err != nil {
		return nil, err
	}

	chunkSize = chunkSize * 1024 * 1024
	storage := &GDrive{service: srv, basedir: basedir, rootId: "", localConfigPath: localConfigPath, chunkSize: chunkSize, logger: logger}
	err = storage.setupRoot()
	if err != nil {
		return nil, err
	}

	return storage, nil
}

const GDriveRootConfigFile = "root_id.conf"
const GDriveTokenJsonFile = "token.json"
const GDriveDirectoryMimeType = "application/vnd.google-apps.folder"

func (s *GDrive) setupRoot() error {
	rootFileConfig := filepath.Join(s.localConfigPath, GDriveRootConfigFile)

	rootId, err := ioutil.ReadFile(rootFileConfig)
	if err != nil && !os.IsNotExist(err) {
		return err
	}

	if string(rootId) != "" {
		s.rootId = string(rootId)
		return nil
	}

	dir := &drive.File{
		Name:     s.basedir,
		MimeType: GDriveDirectoryMimeType,
	}

	di, err := s.service.Files.Create(dir).Fields("id").Do()
	if err != nil {
		return err
	}

	s.rootId = di.Id
	err = ioutil.WriteFile(rootFileConfig, []byte(s.rootId), os.FileMode(0600))
	if err != nil {
		return err
	}

	return nil
}

func (s *GDrive) hasChecksum(f *drive.File) bool {
	return f.Md5Checksum != ""
}

func (s *GDrive) list(nextPageToken string, q string) (*drive.FileList, error) {
	return s.service.Files.List().Fields("nextPageToken, files(id, name, mimeType)").Q(q).PageToken(nextPageToken).Do()
}

func (s *GDrive) findId(filename string, token string) (string, error) {
	filename = strings.Replace(filename, `'`, `\'`, -1)
	filename = strings.Replace(filename, `"`, `\"`, -1)

	fileId, tokenId, nextPageToken := "", "", ""

	q := fmt.Sprintf("'%s' in parents and name='%s' and mimeType='%s' and trashed=false", s.rootId, token, GDriveDirectoryMimeType)
	l, err := s.list(nextPageToken, q)
	if err != nil {
		return "", err
	}

	for 0 < len(l.Files) {
		for _, fi := range l.Files {
			tokenId = fi.Id
			break
		}

		if l.NextPageToken == "" {
			break
		}

		l, err = s.list(l.NextPageToken, q)
	}

	if filename == "" {
		return tokenId, nil
	} else if tokenId == "" {
		return "", fmt.Errorf("Cannot find file %s/%s", token, filename)
	}

	q = fmt.Sprintf("'%s' in parents and name='%s' and mimeType!='%s' and trashed=false", tokenId, filename, GDriveDirectoryMimeType)
	l, err = s.list(nextPageToken, q)
	if err != nil {
		return "", err
	}

	for 0 < len(l.Files) {
		for _, fi := range l.Files {

			fileId = fi.Id
			break
		}

		if l.NextPageToken == "" {
			break
		}

		l, err = s.list(l.NextPageToken, q)
	}

	if fileId == "" {
		return "", fmt.Errorf("Cannot find file %s/%s", token, filename)
	}

	return fileId, nil
}

func (s *GDrive) Type() string {
	return "gdrive"
}

func (s *GDrive) Head(token string, filename string) (contentLength uint64, err error) {
	var fileId string
	fileId, err = s.findId(filename, token)
	if err != nil {
		return
	}

	var fi *drive.File
	if fi, err = s.service.Files.Get(fileId).Fields("size").Do(); err != nil {
		return
	}

	contentLength = uint64(fi.Size)

	return
}

func (s *GDrive) Get(token string, filename string) (reader io.ReadCloser, contentLength uint64, err error) {
	var fileId string
	fileId, err = s.findId(filename, token)
	if err != nil {
		return
	}

	var fi *drive.File
	fi, err = s.service.Files.Get(fileId).Fields("size", "md5Checksum").Do()
	if !s.hasChecksum(fi) {
		err = fmt.Errorf("Cannot find file %s/%s", token, filename)
		return
	}

	contentLength = uint64(fi.Size)

	ctx := context.Background()
	var res *http.Response
	res, err = s.service.Files.Get(fileId).Context(ctx).Download()
	if err != nil {
		return
	}

	reader = res.Body

	return
}

func (s *GDrive) Delete(token string, filename string) (err error) {
	metadata, _ := s.findId(fmt.Sprintf("%s.metadata", filename), token)
	s.service.Files.Delete(metadata).Do()

	var fileId string
	fileId, err = s.findId(filename, token)
	if err != nil {
		return
	}

	err = s.service.Files.Delete(fileId).Do()
	return
}

func (s *GDrive) IsNotExist(err error) bool {
	if err != nil {
		if e, ok := err.(*googleapi.Error); ok {
			return e.Code == http.StatusNotFound
		}
	}

	return false
}

func (s *GDrive) Put(token string, filename string, reader io.Reader, contentType string, contentLength uint64) error {
	dirId, err := s.findId("", token)
	if err != nil {
		return err
	}

	if dirId == "" {
		dir := &drive.File{
			Name:     token,
			Parents:  []string{s.rootId},
			MimeType: GDriveDirectoryMimeType,
		}

		di, err := s.service.Files.Create(dir).Fields("id").Do()
		if err != nil {
			return err
		}

		dirId = di.Id
	}

	// Instantiate empty drive file
	dst := &drive.File{
		Name:     filename,
		Parents:  []string{dirId},
		MimeType: contentType,
	}

	ctx := context.Background()
	_, err = s.service.Files.Create(dst).Context(ctx).Media(reader, googleapi.ChunkSize(s.chunkSize)).Do()

	if err != nil {
		return err
	}

	return nil
}

// Retrieve a token, saves the token, then returns the generated client.
func getGDriveClient(config *oauth2.Config, localConfigPath string, logger *log.Logger) *http.Client {
	tokenFile := filepath.Join(localConfigPath, GDriveTokenJsonFile)
	tok, err := gDriveTokenFromFile(tokenFile)
	if err != nil {
		tok = getGDriveTokenFromWeb(config, logger)
		saveGDriveToken(tokenFile, tok, logger)
	}

	return config.Client(context.Background(), tok)
}

// Request a token from the web, then returns the retrieved token.
func getGDriveTokenFromWeb(config *oauth2.Config, logger *log.Logger) *oauth2.Token {
	authURL := config.AuthCodeURL("state-token", oauth2.AccessTypeOffline)
	fmt.Printf("Go to the following link in your browser then type the "+
		"authorization code: \n%v\n", authURL)

	var authCode string
	if _, err := fmt.Scan(&authCode); err != nil {
		logger.Fatalf("Unable to read authorization code %v", err)
	}

	tok, err := config.Exchange(context.TODO(), authCode)
	if err != nil {
		logger.Fatalf("Unable to retrieve token from web %v", err)
	}
	return tok
}

// Retrieves a token from a local file.
func gDriveTokenFromFile(file string) (*oauth2.Token, error) {
	f, err := os.Open(file)
	defer f.Close()
	if err != nil {
		return nil, err
	}
	tok := &oauth2.Token{}
	err = json.NewDecoder(f).Decode(tok)
	return tok, err
}

// Saves a token to a file path.
func saveGDriveToken(path string, token *oauth2.Token, logger *log.Logger) {
	logger.Printf("Saving credential file to: %s\n", path)
	f, err := os.OpenFile(path, os.O_RDWR|os.O_CREATE|os.O_TRUNC, 0600)
	defer f.Close()
	if err != nil {
		logger.Fatalf("Unable to cache oauth token: %v", err)
	}

	json.NewEncoder(f).Encode(token)
}