/*

Package webdav implements sharing with WebDAV servers.

Copyright (c) 2018 - 2021 Michael Mayer <hello@photoprism.org>

    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU Affero General Public License as published
    by the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU Affero General Public License for more details.

    You should have received a copy of the GNU Affero General Public License
    along with this program.  If not, see <https://www.gnu.org/licenses/>.

    PhotoPrism® is a registered trademark of Michael Mayer.  You may use it as required
    to describe our software, run your own server, for educational purposes, but not for
    offering commercial goods, products, or services without prior written permission.
    In other words, please ask.

Feel free to send an e-mail to hello@photoprism.org if you have questions,
want to support our work, or just want to say hello.

Additional information can be found in our Developer Guide:
https://docs.photoprism.org/developer-guide/

*/
package webdav

import (
	"fmt"
	"os"
	"path"
	"runtime/debug"
	"time"

	"github.com/photoprism/photoprism/internal/event"
	"github.com/photoprism/photoprism/pkg/fs"
	"github.com/studio-b12/gowebdav"
)

var log = event.Log

const SyncTimeout = time.Second * 45
const AsyncTimeout = time.Minute * 20

type Client struct {
	client *gowebdav.Client
}

// New creates a new WebDAV client.
func New(url, user, pass string) Client {
	clt := gowebdav.NewClient(url, user, pass)

	clt.SetTimeout(10 * time.Minute) // TODO: Change timeout if needed

	result := Client{
		client: clt,
	}

	return result
}

func (c Client) readDir(path string) ([]os.FileInfo, error) {
	if path == "" {
		path = "/"
	}

	return c.client.ReadDir(path)
}

// Files returns all files in a directory as string slice.
func (c Client) Files(dir string) (result fs.FileInfos, err error) {
	defer func() {
		if r := recover(); r != nil {
			err = fmt.Errorf("webdav: %s (panic while listing files)\nstack: %s", r, debug.Stack())
		}
	}()

	files, err := c.readDir(dir)

	if err != nil {
		return result, err
	}

	for _, file := range files {
		if !file.Mode().IsRegular() {
			continue
		}

		info := fs.NewFileInfo(file, dir)

		result = append(result, info)
	}

	return result, nil
}

// Directories returns all sub directories in path as string slice.
func (c Client) Directories(root string, recursive bool, timeout time.Duration) (result fs.FileInfos, err error) {
	start := time.Now()

	result, err = c.fetchDirs(root, recursive, start, timeout)

	if time.Now().Sub(start) >= timeout {
		log.Warnf("webdav: read dir timeout reached")
	}

	return result, err
}

// fetchDirs recursively fetches all directories until the timeout is reached.
func (c Client) fetchDirs(root string, recursive bool, start time.Time, timeout time.Duration) (result fs.FileInfos, err error) {
	files, err := c.readDir(root)

	if err != nil {
		return result, err
	}

	if root == "/" {
		root = ""
	}

	for _, file := range files {
		if !file.Mode().IsDir() {
			continue
		}

		info := fs.NewFileInfo(file, root)

		result = append(result, info)

		if recursive && time.Now().Sub(start) < timeout {
			subDirs, err := c.fetchDirs(info.Abs, true, start, timeout)

			if err != nil {
				return result, err
			}

			result = append(result, subDirs...)
		}
	}

	return result, nil
}

// Download downloads a single file to the given location.
func (c Client) Download(from, to string, force bool) (err error) {
	defer func() {
		if r := recover(); r != nil {
			err = fmt.Errorf("webdav: %s (panic while downloading)\nstack: %s", r, debug.Stack())
		}
	}()

	if _, err := os.Stat(to); err == nil && !force {
		return fmt.Errorf("webdav: download skipped, %s already exists", to)
	}

	dir := path.Dir(to)
	dirInfo, err := os.Stat(dir)

	if err != nil {
		// Create directory
		if err := os.MkdirAll(dir, os.ModePerm); err != nil {
			return fmt.Errorf("webdav: can't create %s (%s)", dir, err)
		}
	} else if !dirInfo.IsDir() {
		return fmt.Errorf("webdav: %s is not a folder", dir)
	}

	var bytes []byte

	bytes, err = c.client.Read(from)

	if err != nil {
		return err
	}

	return os.WriteFile(to, bytes, 0644)
}

// DownloadDir downloads all files from a remote to a local directory.
func (c Client) DownloadDir(from, to string, recursive, force bool) (errs []error) {
	files, err := c.Files(from)

	if err != nil {
		return append(errs, err)
	}

	for _, file := range files {
		dest := to + string(os.PathSeparator) + file.Abs

		if _, err = os.Stat(dest); err == nil {
			// File already exists.
			msg := fmt.Errorf("webdav: %s exists", dest)
			errs = append(errs, msg)
			log.Warn(msg)
			continue
		}

		if err = c.Download(file.Abs, dest, force); err != nil {
			// Failed to download file.
			errs = append(errs, err)
			log.Error(err)
			continue
		}
	}

	if !recursive {
		return errs
	}

	dirs, err := c.Directories(from, false, AsyncTimeout)

	for _, dir := range dirs {
		errs = append(errs, c.DownloadDir(dir.Abs, to, true, force)...)
	}

	return errs
}

// CreateDir recursively creates directories if they don't exist.
func (c Client) CreateDir(dir string) error {
	if dir == "" || dir == "/" || dir == "." {
		return nil
	}

	return c.client.MkdirAll(dir, os.ModePerm)
}

// Upload uploads a single file to the remote server.
func (c Client) Upload(from, to string) (err error) {
	defer func() {
		if r := recover(); r != nil {
			err = fmt.Errorf("webdav: %s (panic while uploading)\nstack: %s", r, debug.Stack())
		}
	}()

	file, err := os.Open(from)

	if err != nil || file == nil {
		return err
	}

	defer func(file *os.File) {
		_ = file.Close()
	}(file)

	return c.client.WriteStream(to, file, 0644)
}

// Delete deletes a single file or directory on a remote server.
func (c Client) Delete(path string) error {
	return c.client.Remove(path)
}