// Command releaseicon creates the small deterministic PNG used only by the
// Windows release resource generator. Keeping the source rather than a binary
// asset makes the icon reproducible in the pinned toolchain.
package main

import (
	"flag"
	"image"
	"image/color"
	"image/png"
	"os"
	"path/filepath"
)

const canvasSize = 256

func main() {
	output := flag.String("out", "", "absolute PNG output path")
	flag.Parse()
	if *output == "" || !filepath.IsAbs(*output) {
		panic("--out must be an absolute path")
	}
	if err := os.MkdirAll(filepath.Dir(*output), 0o700); err != nil {
		panic(err)
	}
	file, err := os.OpenFile(*output, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0o600)
	if err != nil {
		panic(err)
	}
	defer file.Close()

	image := image.NewNRGBA(image.Rect(0, 0, canvasSize, canvasSize))
	fill(image, color.NRGBA{R: 15, G: 28, B: 48, A: 255})
	fillRoundedRect(image, 18, 18, 238, 238, 42, color.NRGBA{R: 28, G: 56, B: 92, A: 255})
	// A compact outlined box and terminal prompt remain recognizable at the
	// 16-pixel size Windows Explorer generates from this source image.
	strokeRect(image, 57, 62, 199, 194, 12, color.NRGBA{R: 54, G: 211, B: 189, A: 255})
	fillRect(image, 79, 105, 96, 121, color.NRGBA{R: 240, G: 249, B: 255, A: 255})
	fillRect(image, 95, 121, 112, 137, color.NRGBA{R: 240, G: 249, B: 255, A: 255})
	fillRect(image, 79, 137, 96, 153, color.NRGBA{R: 240, G: 249, B: 255, A: 255})
	fillRect(image, 126, 150, 176, 166, color.NRGBA{R: 240, G: 249, B: 255, A: 255})
	if err := png.Encode(file, image); err != nil {
		panic(err)
	}
}

func fill(image *image.NRGBA, value color.NRGBA) {
	for y := 0; y < canvasSize; y++ {
		for x := 0; x < canvasSize; x++ {
			image.SetNRGBA(x, y, value)
		}
	}
}

func fillRoundedRect(image *image.NRGBA, left, top, right, bottom, radius int, value color.NRGBA) {
	for y := top; y < bottom; y++ {
		for x := left; x < right; x++ {
			dx, dy := 0, 0
			if x < left+radius {
				dx = left + radius - x
			} else if x >= right-radius {
				dx = x - (right - radius - 1)
			}
			if y < top+radius {
				dy = top + radius - y
			} else if y >= bottom-radius {
				dy = y - (bottom - radius - 1)
			}
			if dx*dx+dy*dy <= radius*radius {
				image.SetNRGBA(x, y, value)
			}
		}
	}
}

func strokeRect(image *image.NRGBA, left, top, right, bottom, width int, value color.NRGBA) {
	fillRect(image, left, top, right, top+width, value)
	fillRect(image, left, bottom-width, right, bottom, value)
	fillRect(image, left, top, left+width, bottom, value)
	fillRect(image, right-width, top, right, bottom, value)
}

func fillRect(image *image.NRGBA, left, top, right, bottom int, value color.NRGBA) {
	for y := top; y < bottom; y++ {
		for x := left; x < right; x++ {
			image.SetNRGBA(x, y, value)
		}
	}
}