// Package icon carries the talk icon for the desktop: the PNG is embedded
// in the binary and written next to the config so the OS can show it in
// notifications (Windows toast identity, freedesktop app_icon). The source
// is assets/icon/talk.svg; `go run assets/icon/gen.go` renders it, the
// Windows .ico and the resource objects for talk.exe.
package icon

import (
	"bytes"
	_ "embed"
	"errors"
	"os"
	"path/filepath"
)

//go:embed talk.png
var PNG []byte

// FileName is the icon's name in the config directory.
const FileName = "talk.png"

// Install writes the icon into dir (if missing or outdated) and returns its
// path. Idempotent: an unchanged file is not touched.
func Install(dir string) (string, error) {
	if dir == "" {
		return "", errors.New("icon: no directory")
	}
	path := filepath.Join(dir, FileName)
	if cur, err := os.ReadFile(path); err == nil && bytes.Equal(cur, PNG) {
		return path, nil
	}
	if err := os.MkdirAll(dir, 0o755); err != nil {
		return "", err
	}
	if err := os.WriteFile(path, PNG, 0o644); err != nil {
		return "", err
	}
	return path, nil
}