package main

import (
	"bytes"
	"fmt"
	"image"
	"image/color"
	_ "image/jpeg"
	"image/png"
	"io/ioutil"
	"os"
)

func main() {
	data, err := ioutil.ReadFile("input.jpg")

	if err != nil {
		panic(err)
	}

	img, _, err := image.Decode(bytes.NewReader(data))

	if err != nil {
		panic(err)
	}

	improved := ImproveQuality(img)
	f, err := os.Create("output.png")

	if err != nil {
		panic(err)
	}

	defer f.Close()
	png.Encode(f, improved)
}

const max = float64(65535)

// Pixel ...
type Pixel struct {
	X int
	Y int
}

// Area ...
type Area struct {
	Pixels []Pixel
	totalR uint64
	totalG uint64
	totalB uint64
	totalA uint64
}

// Add ...
func (area *Area) Add(x, y int, r, g, b, a uint32) {
	area.Pixels = append(area.Pixels, Pixel{
		X: x,
		Y: y,
	})

	area.totalR += uint64(r)
	area.totalG += uint64(g)
	area.totalB += uint64(b)
	area.totalA += uint64(a)
}

// AverageColor ...
func (area *Area) AverageColor() color.Color {
	if len(area.Pixels) == 0 {
		return color.Transparent
	}

	return color.RGBA64{
		R: uint16(area.totalR / uint64(len(area.Pixels))),
		G: uint16(area.totalG / uint64(len(area.Pixels))),
		B: uint16(area.totalB / uint64(len(area.Pixels))),
		A: uint16(area.totalA / uint64(len(area.Pixels))),
	}
}

const (
	tolerance = uint32(10000)
)

func diffAbs(a uint32, b uint32) uint32 {
	if a > b {
		return a - b
	}

	return b - a
}

// ImproveQuality returns the average color of an image in HSL format.
func ImproveQuality(img image.Image) *image.NRGBA {
	width := img.Bounds().Dx()
	height := img.Bounds().Dy()
	clone := image.NewNRGBA(image.Rect(0, 0, width, height))
	areas := []*Area{}
	areaIndexMap := make([]int, width*height)

	for x := 0; x < width; x++ {
		for y := 0; y < height; y++ {
			color := img.At(x, y)
			r, g, b, a := color.RGBA()
			areaIndex := -1

			// Find similar area
			for i := 0; i < len(areas); i++ {
				area := areas[i]
				avgR, avgG, avgB, _ := area.AverageColor().RGBA()

				// Is the color similar?
				if diffAbs(r, avgR) <= tolerance && diffAbs(g, avgG) <= tolerance && diffAbs(b, avgB) <= tolerance {
					areaIndex = i
					break
				}
			}

			// Insert new area
			if areaIndex == -1 {
				areaIndex = len(areas)
				areas = append(areas, &Area{})
			}

			areaIndexMap[y*width+x] = areaIndex
			areas[areaIndex].Add(x, y, r, g, b, a)
		}
	}

	fmt.Println(len(areas), "areas")

	pixelCount := 0

	for _, area := range areas {
		pixelCount += len(area.Pixels)
	}

	// fmt.Println(pixelCount, "pixels", width*height)

	// Reduce noise
	noiseCount := 0

	for areaIndex, area := range areas {
		removals := []int{}
		areaSurroundedBy := map[int]int{}

		for i := 0; i < len(area.Pixels); i++ {
			// If pixel is surrounded by 4 different areas, remove it
			pixel := area.Pixels[i]
			x := pixel.X
			y := pixel.Y
			left := areaIndex
			right := areaIndex
			top := areaIndex
			bottom := areaIndex

			if x > 0 {
				left = areaIndexMap[y*width+(x-1)]
			}

			if x < width-1 {
				right = areaIndexMap[y*width+(x+1)]
			}

			if y > 0 {
				top = areaIndexMap[(y-1)*width+x]
			}

			if y < height-1 {
				bottom = areaIndexMap[(y+1)*width+x]
			}

			differentNeighbors := 0

			if left != areaIndex {
				differentNeighbors++
			}

			if right != areaIndex {
				differentNeighbors++
			}

			if top != areaIndex {
				differentNeighbors++
			}

			if bottom != areaIndex {
				differentNeighbors++
			}

			// Determine surrounding area
			areaIndexScore := map[int]int{}

			areaIndexScore[left]++
			areaIndexScore[right]++
			areaIndexScore[top]++
			areaIndexScore[bottom]++

			areaSurroundedBy[left]++
			areaSurroundedBy[right]++
			areaSurroundedBy[top]++
			areaSurroundedBy[bottom]++

			newAreaIndex := -1
			bestScore := 0

			for checkIndex, score := range areaIndexScore {
				if score > bestScore {
					bestScore = score
					newAreaIndex = checkIndex
				}
			}

			if differentNeighbors >= 3 && bestScore >= 3 {
				noiseCount++
				removals = append(removals, i)

				// Add to surrounding area
				r, g, b, a := img.At(x, y).RGBA()
				areas[newAreaIndex].Add(x, y, r, g, b, a)
			}
		}

		// Remove noise pixels
		// offset := 0

		// for _, removal := range removals {
		// 	index := removal - offset
		// 	area.Pixels = append(area.Pixels[:index], area.Pixels[index+1:]...)
		// 	// area.Pixels = area.Pixels[:index+copy(area.Pixels[index:], area.Pixels[index+1:])]
		// 	offset++
		// }

		// Determine surrounding area
		surroundingAreaIndex := -1
		bestScore := 0

		for checkIndex, score := range areaSurroundedBy {
			if score > bestScore {
				bestScore = score
				surroundingAreaIndex = checkIndex
			}
		}

		if areaIndex != surroundingAreaIndex {
			// fmt.Println(areaIndex, "surrounded by", surroundingAreaIndex, "|", len(area.Pixels), len(areas[surroundingAreaIndex].Pixels))

			// // Add pixels to surrounding area
			// for _, pixel := range area.Pixels {
			// 	r, g, b, a := img.At(pixel.X, pixel.Y).RGBA()
			// 	areas[surroundingAreaIndex].Add(pixel.X, pixel.Y, r, g, b, a)
			// }

			// // Remove this area
			// area.Pixels = nil
			// area.totalR = 0
			// area.totalG = 0
			// area.totalB = 0
			// area.totalA = 0
		}
	}

	fmt.Println(noiseCount, "noise pixels")

	pixelCount = 0

	for _, area := range areas {
		pixelCount += len(area.Pixels)
	}

	fmt.Println(pixelCount, "pixels", width*height)

	// Build image from areas
	for _, area := range areas {
		avgColor := area.AverageColor()

		for _, pixel := range area.Pixels {
			clone.Set(pixel.X, pixel.Y, avgColor)
		}
	}

	return clone
}