package main

import (
	"encoding/binary"
	"fmt"
	"os"
	"path/filepath"
)

// mkico packs internal/gui/logo.png into a single-image ICO at cmd/tunnel/app.ico.
// Prefer replacing app.ico with a proper multi-size .ico from a designer tool;
// this helper is a quick path when you only have a PNG.
func main() {
	root, err := findRoot()
	if err != nil {
		panic(err)
	}
	pngPath := filepath.Join(root, "internal", "gui", "logo.png")
	icoPath := filepath.Join(root, "cmd", "tunnel", "app.ico")

	png, err := os.ReadFile(pngPath)
	if err != nil {
		panic(err)
	}
	var w, h uint32
	if len(png) >= 24 {
		w = binary.BigEndian.Uint32(png[16:20])
		h = binary.BigEndian.Uint32(png[20:24])
	}
	wb, hb := byte(w), byte(h)
	if w >= 256 {
		wb = 0
	}
	if h >= 256 {
		hb = 0
	}
	out := make([]byte, 22+len(png))
	binary.LittleEndian.PutUint16(out[2:], 1)
	binary.LittleEndian.PutUint16(out[4:], 1)
	out[6] = wb
	out[7] = hb
	binary.LittleEndian.PutUint16(out[10:], 1)
	binary.LittleEndian.PutUint16(out[12:], 32)
	binary.LittleEndian.PutUint32(out[14:], uint32(len(png)))
	binary.LittleEndian.PutUint32(out[18:], 22)
	copy(out[22:], png)
	if err := os.WriteFile(icoPath, out, 0o644); err != nil {
		panic(err)
	}
	fmt.Println("wrote", icoPath)
}

func findRoot() (string, error) {
	wd, err := os.Getwd()
	if err != nil {
		return "", err
	}
	dir := wd
	for {
		if _, err := os.Stat(filepath.Join(dir, "go.mod")); err == nil {
			return dir, nil
		}
		parent := filepath.Dir(dir)
		if parent == dir {
			return "", fmt.Errorf("go.mod not found from %s", wd)
		}
		dir = parent
	}
}