// Copyright 2014 Hajime Hoshi
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package ebitenutil

import (
	"github.com/hajimehoshi/ebiten"
	"image"
	"image/color/palette"
	"image/draw"
	"image/gif"
	"io"
)

type recorder struct {
	inner        func(screen *ebiten.Image) error
	writer       io.Writer
	gif          *gif.GIF
	currentFrame int
}

func (r *recorder) update(screen *ebiten.Image) error {
	if err := r.inner(screen); err != nil {
		return err
	}
	if r.currentFrame == len(r.gif.Image) {
		return nil
	}
	img := image.NewPaletted(screen.Bounds(), palette.Plan9)
	// TODO: This is too slow.
	draw.Draw(img, img.Bounds(), screen, screen.Bounds().Min, draw.Src)
	r.gif.Image[r.currentFrame] = img
	// The actual FPS is 60, but GIF can't have such FPS. Set 50 FPS instead.
	r.gif.Delay[r.currentFrame] = 2

	r.currentFrame++
	if r.currentFrame == len(r.gif.Image) {
		if err := gif.EncodeAll(r.writer, r.gif); err != nil {
			return err
		}
	}
	return nil
}

// RecordScreenAsGIF returns updating function with recording the screen as an animation GIF image.
//
// This encodes each screen at each frame and may slows the application.
//
// Here is the example to record initial 120 frames of your game:
//
//     func update(screen *ebiten.Image) error {
//         // ...
//     }
//
//     func main() {
//         out, err := os.Create("output.gif")
//         if err != nil {
//             log.Fatal(err)
//         }
//         defer out.Close()
//
//         update := RecordScreenAsGIF(update, out, 120)
//         if err := ebiten.Run(update, 320, 240, 2, "Your game's title"); err != nil {
//             log.Fatal(err)
//         }
//     }
func RecordScreenAsGIF(update func(*ebiten.Image) error, out io.Writer, frameNum int) func(*ebiten.Image) error {
	r := &recorder{
		inner:  update,
		writer: out,
		gif: &gif.GIF{
			Image:     make([]*image.Paletted, frameNum),
			Delay:     make([]int, frameNum),
			LoopCount: -1,
		},
	}
	return r.update
}