package main

import (
	"encoding/base64"
	"errors"
	"image"
	_ "image/gif"
	"image/jpeg"
	_ "image/png"
	"io"
	"os"
	"path"
	"sort"
	"time"

	"github.com/nfnt/resize"
)

type PictureExplorer struct {
	FileBackend
	PublishedImgDir string
	NextImgDir      string
}

type Picture struct {
	path       string
	basename   string
	Name       string    `json:"name"`
	UploadTime time.Time `json:"upload_time"`
}

type ByUploadTime []*Picture

func (a ByUploadTime) Len() int      { return len(a) }
func (a ByUploadTime) Swap(i, j int) { a[i], a[j] = a[j], a[i] }
func (a ByUploadTime) Less(i, j int) bool {
	return a[i].UploadTime.Sub(a[j].UploadTime).Nanoseconds() < 0
}

func (e *PictureExplorer) GetNextImages() (pictures []*Picture, err error) {
	pictures, err = e.ListPictures(e.NextImgDir)
	sort.Sort(ByUploadTime(pictures))
	return
}

func (e *PictureExplorer) GetPublishedImages() (pictures []*Picture, err error) {
	pictures, err = e.ListPictures(e.PublishedImgDir)
	sort.Sort(ByUploadTime(pictures))
	return
}

func (e *PictureExplorer) GetLastImage() (*Picture, error) {
	picts, err := e.GetPublishedImages()
	if err != nil {
		return nil, err
	}

	return picts[len(picts)-1], nil
}

func (e *PictureExplorer) GetPublishedImage(fname string) (*Picture, error) {
	return e.GetPictureInfo(e.PublishedImgDir, fname)
}

func (e *PictureExplorer) GetNextImage(fname string) (*Picture, error) {
	return e.GetPictureInfo(e.NextImgDir, fname)
}

func (e *PictureExplorer) IsUniqueName(filename string) bool {
	if pict, _ := e.GetPublishedImage(filename); pict != nil {
		return false
	}

	if pict, _ := e.GetNextImage(filename); pict != nil {
		return false
	}

	return true
}

func (e *PictureExplorer) AddImage(filename string, blob io.ReadCloser) error {
	// Check the name is not already used
	if ok := e.IsUniqueName(filename); !ok {
		return errors.New("This filename is already used, please choose another one.")
	}

	// Convert to JPEG
	img, _, err := image.Decode(base64.NewDecoder(base64.StdEncoding, blob))
	if err != nil {
		return err
	}

	// Save file
	if err := e.PutPicture(e.NextImgDir, filename, &img); err != nil {
		return err
	}

	thumb := resize.Thumbnail(300, 185, img, resize.Lanczos3)

	// Save thumbnail
	fw, err := os.Create(path.Join(ThumbsDir, filename+".jpg"))
	if err != nil {
		return err
	}
	defer fw.Close()

	return jpeg.Encode(fw, thumb, nil)
}

func (e *PictureExplorer) Publish(p *Picture) error {
	return e.MovePicture(e.NextImgDir, e.PublishedImgDir, p.Name)
}

func (e *PictureExplorer) Unpublish(p *Picture) error {
	return e.MovePicture(e.PublishedImgDir, e.NextImgDir, p.Name)
}

func (e *PictureExplorer) Remove(p *Picture) error {
	return e.DeletePicture(path.Dir(p.path), p.Name)
}