package main

import (
	"errors"
	"io"
	"io/ioutil"
	"image"
	_ "image/gif"
	"image/jpeg"
	_ "image/png"
	"os"
	"path/filepath"
	"sort"
	"strconv"
	"time"

	"github.com/nfnt/resize"
)

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 getImages(dir string) ([]Picture, error) {
	if files, err := ioutil.ReadDir(dir); err != nil {
		return nil, err
	} else {
		pictures := make([]Picture, 0)
		for _, file := range files {
			if !file.IsDir() {
				filename := file.Name()
				pictures = append(pictures, Picture{
					filepath.Join(dir, filename), // Path
					filename, // Basename
					filename[:len(filename) - len(filepath.Ext(filename))], // Sanitized filename
					file.ModTime(), // UploadTime
				})
			}
		}
		sort.Sort(ByUploadTime(pictures))
		return pictures, nil
	}
}

func GetNextImages() ([]Picture, error) {
	return getImages(NextImgDir)
}

func GetPublishedImages() ([]Picture, error) {
	return getImages(PublishedImgDir)
}

func GetLastImage() (Picture, error) {
	if picts, err := GetPublishedImages(); err != nil {
		return Picture{}, err
	} else {
		return picts[len(picts)-1], nil
	}
}

func getImage(flist func() ([]Picture, error), fname string) (Picture, error) {
	if picts, err := flist(); err != nil {
		return Picture{}, err
	} else if pid, err := strconv.Atoi(fname); err == nil {
		if pid < len(picts) {
			return picts[pid], nil
		} else {
			return Picture{}, errors.New("Invalid picture identifier")
		}
	} else {
		for _, pict := range picts {
			if pict.Name == fname || pict.basename == fname {
				return pict, nil
			}
		}
		return Picture{}, errors.New("No such picture")
	}
}

func GetPublishedImage(fname string) (Picture, error) {
	return getImage(GetPublishedImages, fname)
}

func GetNextImage(fname string) (Picture, error) {
	return getImage(GetNextImages, fname)
}

func UniqueImage(filename string) (bool) {
	if pict, _ := GetPublishedImage(filename); pict.path != "" {
		return false
	} else {
		if pict, _ := GetNextImage(filename); pict.path != "" {
			return false
		} else {
			return true
		}
	}
}

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

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

	// Save file
	} else if fw, err := os.Create(filepath.Join(NextImgDir, filename + ".jpg")); err != nil {
		return err
	} else if err := jpeg.Encode(fw, img, nil); err != nil {
		return err
	} else {
		fw.Close()

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

		// Save thumbnail
		if fw, err := os.Create(filepath.Join(ThumbsDir, filename + ".jpg")); err != nil {
			return err
		} else if err := jpeg.Encode(fw, thumb, nil); err != nil {
			return err
		} else {
			fw.Close()
		}
	}

	return nil
}

func (p Picture) Publish() (error) {
	npath := filepath.Join(PublishedImgDir, p.basename)
	if err := os.Rename(p.path, npath); err != nil {
		return err
	} else if err := os.Chtimes(npath, time.Now(), time.Now()); err != nil {
		return err
	} else {
		return nil
	}
}

func (p Picture) Unpublish() (error) {
	if err := os.Rename(p.path, filepath.Join(NextImgDir, p.basename)); err != nil {
		return err
	} else {
		return nil
	}
}

func (p Picture) Remove() (error) {
	if err := os.Remove(p.path); err != nil {
		return err
	} else {
		return nil
	}
}