/*
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 ebiten

import (
	"image/color"
	"math"
)

const ColorMatrixDim = 5

type ColorMatrix struct {
	Elements [ColorMatrixDim - 1][ColorMatrixDim]float64
}

func ColorMatrixI() ColorMatrix {
	return ColorMatrix{
		[ColorMatrixDim - 1][ColorMatrixDim]float64{
			{1, 0, 0, 0, 0},
			{0, 1, 0, 0, 0},
			{0, 0, 1, 0, 0},
			{0, 0, 0, 1, 0},
		},
	}
}

func (c *ColorMatrix) dim() int {
	return ColorMatrixDim
}

func (c *ColorMatrix) Concat(other ColorMatrix) {
	result := ColorMatrix{}
	mul(&other, c, &result)
	*c = result
}

func (c *ColorMatrix) IsIdentity() bool {
	return isIdentity(c)
}

func (c *ColorMatrix) element(i, j int) float64 {
	return c.Elements[i][j]
}

func (c *ColorMatrix) setElement(i, j int, element float64) {
	c.Elements[i][j] = element
}

func Monochrome() ColorMatrix {
	const r float64 = 6968.0 / 32768.0
	const g float64 = 23434.0 / 32768.0
	const b float64 = 2366.0 / 32768.0
	return ColorMatrix{
		[ColorMatrixDim - 1][ColorMatrixDim]float64{
			{r, g, b, 0, 0},
			{r, g, b, 0, 0},
			{r, g, b, 0, 0},
			{0, 0, 0, 1, 0},
		},
	}
}

func rgba(clr color.Color) (float64, float64, float64, float64) {
	r, g, b, a := clr.RGBA()
	rf := float64(r) / float64(math.MaxUint16)
	gf := float64(g) / float64(math.MaxUint16)
	bf := float64(b) / float64(math.MaxUint16)
	af := float64(a) / float64(math.MaxUint16)
	return rf, gf, bf, af
}

func (c *ColorMatrix) Scale(clr color.Color) {
	rf, gf, bf, af := rgba(clr)
	for i, e := range []float64{rf, gf, bf, af} {
		for j := 0; j < 4; j++ {
			c.Elements[i][j] *= e
		}
	}
}

func (c *ColorMatrix) Translate(clr color.Color) {
	rf, gf, bf, af := rgba(clr)
	c.Elements[0][4] = rf
	c.Elements[1][4] = gf
	c.Elements[2][4] = bf
	c.Elements[3][4] = af
}