// Copyright 2017 The Ebiten Authors
//
// 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 restorable

import (
	"image"
	"image/color"
	"image/draw"
	"runtime"
)

// CopyImage copies origImg to a new RGBA image.
//
// Basically CopyImage just calls draw.Draw.
// If origImg is a paletted image, an optimized copying method is used.
//
// CopyImage is used only internally but it is exposed for testing.
//
// TODO: CopyImage should return []byte (#521)
func CopyImage(origImg image.Image) *image.RGBA {
	size := origImg.Bounds().Size()
	w, h := size.X, size.Y
	newImg := image.NewRGBA(image.Rect(0, 0, w, h))
	switch origImg := origImg.(type) {
	case *image.Paletted:
		b := origImg.Bounds()
		x0 := b.Min.X
		y0 := b.Min.Y
		x1 := b.Max.X
		y1 := b.Max.Y
		palette := make([]uint8, len(origImg.Palette)*4)
		for i, c := range origImg.Palette {
			rgba := color.RGBAModel.Convert(c).(color.RGBA)
			palette[4*i] = rgba.R
			palette[4*i+1] = rgba.G
			palette[4*i+2] = rgba.B
			palette[4*i+3] = rgba.A
		}
		index0 := 0
		index1 := 0
		d0 := origImg.Stride - (x1 - x0)
		d1 := newImg.Stride - (x1-x0)*4
		pix0 := origImg.Pix
		pix1 := newImg.Pix
		for j := 0; j < y1-y0; j++ {
			for i := 0; i < x1-x0; i++ {
				p := int(pix0[index0])
				pix1[index1] = palette[4*p]
				pix1[index1+1] = palette[4*p+1]
				pix1[index1+2] = palette[4*p+2]
				pix1[index1+3] = palette[4*p+3]
				index0++
				index1 += 4
			}
			index0 += d0
			index1 += d1
		}
	default:
		draw.Draw(newImg, image.Rect(0, 0, w, h), origImg, origImg.Bounds().Min, draw.Src)
	}
	runtime.Gosched()
	return newImg
}