package icons

import (
	"bytes"
	_ "embed"
	"encoding/binary"
	"image/png"
	"runtime"
)

// Pre-rendered tray icons (64px) generated from Stammtisch wood texture
// with the Syncthing motif applied via darken blend.
// Regenerate with: go run ./cmd/icongen/ -wood /path/to/stammtisch.png

//go:embed tray_idle.png
var trayIdlePNG []byte

//go:embed tray_syncing.png
var traySyncingPNG []byte

//go:embed tray_paused.png
var trayPausedPNG []byte

//go:embed tray_error.png
var trayErrorPNG []byte

//go:embed tray_disconnected.png
var trayDisconnectedPNG []byte

// Render returns the tray icon for the given state.
// Returns ICO bytes on Windows, PNG bytes on other platforms.
func Render(state State) ([]byte, error) {
	pngData := trayPNG(state)
	if runtime.GOOS == "windows" {
		return wrapPNGInICO(pngData, 64, 64), nil
	}
	return pngData, nil
}

func trayPNG(state State) []byte {
	switch state {
	case StateIdle:
		return trayIdlePNG
	case StateSyncing:
		return traySyncingPNG
	case StatePaused:
		return trayPausedPNG
	case StateError:
		return trayErrorPNG
	case StateDisconnected:
		return trayDisconnectedPNG
	default:
		return trayDisconnectedPNG
	}
}

// RenderPNG returns a PNG icon at 64px for the given state.
func RenderPNG(state State, size int) ([]byte, error) {
	// Pre-rendered icons are only 64px; return them directly.
	// For other sizes, the static assets in assets/ should be used.
	return trayPNG(state), nil
}

// IconSize returns the size of the pre-rendered tray icons.
func IconSize() (int, int) {
	data := trayIdlePNG
	img, err := png.Decode(bytes.NewReader(data))
	if err != nil {
		return 64, 64
	}
	b := img.Bounds()
	return b.Dx(), b.Dy()
}

// wrapPNGInICO wraps raw PNG bytes in a minimal ICO container.
func wrapPNGInICO(pngData []byte, width, height int) []byte {
	const headerSize = 6
	const entrySize = 16
	imageOffset := headerSize + entrySize

	buf := new(bytes.Buffer)

	// ICONDIR header
	binary.Write(buf, binary.LittleEndian, uint16(0)) // Reserved
	binary.Write(buf, binary.LittleEndian, uint16(1)) // Type: 1 = icon
	binary.Write(buf, binary.LittleEndian, uint16(1)) // Count: 1 image

	// ICONDIRENTRY
	w := byte(width)
	if width >= 256 {
		w = 0
	}
	h := byte(height)
	if height >= 256 {
		h = 0
	}
	buf.WriteByte(w)
	buf.WriteByte(h)
	buf.WriteByte(0)                                             // ColorCount
	buf.WriteByte(0)                                             // Reserved
	binary.Write(buf, binary.LittleEndian, uint16(1))            // Planes
	binary.Write(buf, binary.LittleEndian, uint16(32))           // BitCount
	binary.Write(buf, binary.LittleEndian, uint32(len(pngData))) // BytesInRes
	binary.Write(buf, binary.LittleEndian, uint32(imageOffset))  // ImageOffset

	buf.Write(pngData)
	return buf.Bytes()
}