roadamp/internal/winamp/winamp.go

//go:build windows

// Package winamp provides IPC control of a running Winamp instance via
// Windows messages (WM_COMMAND / WM_USER), mirroring the TWinampControl
// Delphi component by SpECTre.
package winamp

import (
	"fmt"
	"syscall"
	"unsafe"
)

var (
	user32           = syscall.NewLazyDLL("user32.dll")
	findWindow       = user32.NewProc("FindWindowW")
	sendMessage      = user32.NewProc("SendMessageW")
	getWindowTextW   = user32.NewProc("GetWindowTextW")
)

const (
	wmCommand = 0x0111
	wmUser    = 0x0400

	// Winamp WM_COMMAND IDs
	cmdPrevTrack     = 40044
	cmdPlay          = 40045
	cmdPause         = 40046
	cmdStop          = 40047
	cmdNextTrack     = 40048
	cmdFadeStop      = 40147
	cmdStopAfter     = 40157
	cmdToggleRepeat  = 40022
	cmdToggleShuffle = 40023
	cmdClose         = 40001
	cmdVolumeUp      = 40058
	cmdVolumeDown    = 40059

	// Winamp WM_USER lParam IDs
	userGetVersion       = 0
	userGetPlayState     = 104
	userGetPosition      = 105
	userSeek             = 106
	userSetVolume        = 122
	userGetPlaylistPos   = 125
	userGetPlaylistLen   = 124
	userRestart          = 135
)

// Controller talks to a running Winamp instance.
type Controller struct{}

func New() *Controller { return &Controller{} }

func (c *Controller) handle() syscall.Handle {
	winampClass, _ := syscall.UTF16PtrFromString("Winamp v1.x")
	h, _, _ := findWindow.Call(
		uintptr(unsafe.Pointer(winampClass)),
		0,
	)
	return syscall.Handle(h)
}

func (c *Controller) IsRunning() bool {
	return c.handle() != 0
}

func send(h syscall.Handle, msg, wparam, lparam uintptr) uintptr {
	r, _, _ := sendMessage.Call(uintptr(h), msg, wparam, lparam)
	return r
}

func (c *Controller) cmd(id uintptr) bool {
	h := c.handle()
	if h == 0 {
		return false
	}
	send(h, wmCommand, id, 0)
	return true
}

func (c *Controller) user(wparam, lparam uintptr) (uintptr, bool) {
	h := c.handle()
	if h == 0 {
		return 0, false
	}
	return send(h, wmUser, wparam, lparam), true
}

// Playback controls
func (c *Controller) Play() bool      { return c.cmd(cmdPlay) }
func (c *Controller) Pause() bool     { return c.cmd(cmdPause) }
func (c *Controller) Stop() bool      { return c.cmd(cmdStop) }
func (c *Controller) NextTrack() bool { return c.cmd(cmdNextTrack) }
func (c *Controller) PrevTrack() bool { return c.cmd(cmdPrevTrack) }
func (c *Controller) Close() bool     { return c.cmd(cmdClose) }

// State: 0=stopped, 1=playing, 3=paused
func (c *Controller) PlayState() int {
	v, ok := c.user(0, userGetPlayState)
	if !ok {
		return 0
	}
	return int(v)
}

func (c *Controller) IsPlaying() bool { return c.PlayState() == 1 }
func (c *Controller) IsPaused() bool  { return c.PlayState() == 3 }
func (c *Controller) IsStopped() bool { return c.PlayState() == 0 }

// GetPosition returns current playback offset in seconds.
func (c *Controller) GetPosition() int {
	v, ok := c.user(0, userGetPosition)
	if !ok {
		return 0
	}
	return int(v) / 1000
}

// GetLength returns total track length in seconds.
func (c *Controller) GetLength() int {
	v, ok := c.user(1, userGetPosition)
	if !ok {
		return 0
	}
	return int(v)
}

// Seek sets the playback position to offsetSeconds.
func (c *Controller) Seek(offsetSeconds int) bool {
	h := c.handle()
	if h == 0 {
		return false
	}
	send(h, wmUser, uintptr(offsetSeconds*1000), userSeek)
	return true
}

// SetVolume sets Winamp's internal volume (0–255).
func (c *Controller) SetVolume(v int) bool {
	if v < 0 {
		v = 0
	}
	if v > 255 {
		v = 255
	}
	h := c.handle()
	if h == 0 {
		return false
	}
	send(h, wmUser, uintptr(v), userSetVolume)
	return true
}

// GetPlaylistPosition returns the 1-based current playlist index.
func (c *Controller) GetPlaylistPosition() int {
	v, ok := c.user(0, userGetPlaylistPos)
	if !ok {
		return 0
	}
	return int(v) + 1
}

// GetPlaylistLength returns the total number of tracks in the playlist.
func (c *Controller) GetPlaylistLength() int {
	v, ok := c.user(0, userGetPlaylistLen)
	if !ok {
		return 0
	}
	return int(v)
}

// GetVersion returns a human-readable Winamp version string (e.g. "5.66").
func (c *Controller) GetVersion() string {
	v, ok := c.user(0, userGetVersion)
	if !ok {
		return ""
	}
	hex := fmt.Sprintf("%04X", v)
	if len(hex) < 3 {
		return ""
	}
	return string(hex[0]) + "." + hex[1:3]
}

// GetTitle returns the title of the currently playing track by reading
// the Winamp window title (format: "N. Artist - Track - Winamp").
func (c *Controller) GetTitle() string {
	h := c.handle()
	if h == 0 {
		return ""
	}
	buf := make([]uint16, 512)
	getWindowTextW.Call(uintptr(h), uintptr(unsafe.Pointer(&buf[0])), 512)
	title := syscall.UTF16ToString(buf)

	// Strip trailing " - Winamp" suffix
	const suffix = " - Winamp"
	if idx := lastIndex(title, suffix); idx >= 0 {
		title = title[:idx]
	}
	// Strip leading playlist-number prefix "NNN. "
	if idx := indexOf(title, ". "); idx >= 0 {
		title = title[idx+2:]
	}
	return title
}

func lastIndex(s, sub string) int {
	last := -1
	for i := 0; i <= len(s)-len(sub); i++ {
		if s[i:i+len(sub)] == sub {
			last = i
		}
	}
	return last
}

func indexOf(s, sub string) int {
	for i := 0; i <= len(s)-len(sub); i++ {
		if s[i:i+len(sub)] == sub {
			return i
		}
	}
	return -1
}