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"
	"strings"
	"syscall"
	"unsafe"
)

var (
	user32                   = syscall.NewLazyDLL("user32.dll")
	kernel32                 = syscall.NewLazyDLL("kernel32.dll")
	findWindow               = user32.NewProc("FindWindowW")
	sendMessage              = user32.NewProc("SendMessageW")
	getWindowTextW           = user32.NewProc("GetWindowTextW")
	getWindowThreadProcessId = user32.NewProc("GetWindowThreadProcessId")
	openProcess              = kernel32.NewProc("OpenProcess")
	readProcessMemory        = kernel32.NewProc("ReadProcessMemory")
	multiByteToWideChar      = kernel32.NewProc("MultiByteToWideChar")
)

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
	userSetPlaylistPos   = 121
	userGetPlaylistTitle = 212
	userRestart          = 135

	// OpenProcess access right
	processVMRead = 0x0010
)

// 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.
// Returns 0 when stopped (Winamp returns 0xFFFFFFFF in that state).
func (c *Controller) GetPosition() int {
	v, ok := c.user(0, userGetPosition)
	if !ok || v > 0xF0000000 { // 0xFFFFFFFF = stopped/no track
		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.
//
// Winamp 5.x formats the window title as one of:
//
//	"N. Artist - Title - Winamp"   (playing)
//	"Winamp"                        (stopped, no playlist)
//
// We strip the " - Winamp" suffix and the leading "N. " playlist prefix.
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 " - Winamp" suffix (use last occurrence so track titles
	// containing " - Winamp" are handled correctly).
	const suffix = " - Winamp"
	if idx := strings.LastIndex(title, suffix); idx >= 0 {
		title = title[:idx]
	} else {
		// Title is just "Winamp" (stopped, empty playlist).
		return ""
	}

	// Strip leading playlist-number prefix: digits followed by ". "
	// e.g. "4. " or "12. "
	if dot := strings.Index(title, ". "); dot >= 0 && dot <= 4 {
		title = title[dot+2:]
	}
	return title
}

// ── Playlist ──────────────────────────────────────────────────────────────────

// TrackInfo is one entry in the Winamp playlist.
type TrackInfo struct {
	Index int    `json:"index"` // 1-based
	Title string `json:"title"`
}

// readRemoteString reads a null-terminated ANSI string from another process
// and converts it to UTF-8 via MultiByteToWideChar (CP_ACP = 0) so that
// umlauts and other non-ASCII characters are handled correctly regardless of
// the active Windows code page.
func readRemoteString(proc syscall.Handle, ptr uintptr) string {
	if ptr == 0 {
		return ""
	}
	buf := make([]byte, 512)
	var read uintptr
	ok, _, _ := readProcessMemory.Call(
		uintptr(proc),
		ptr,
		uintptr(unsafe.Pointer(&buf[0])),
		uintptr(len(buf)),
		uintptr(unsafe.Pointer(&read)),
	)
	if ok == 0 || read == 0 {
		return ""
	}

	// Trim to null terminator.
	ansi := buf[:read]
	for i, b := range ansi {
		if b == 0 {
			ansi = ansi[:i]
			break
		}
	}
	if len(ansi) == 0 {
		return ""
	}

	// First call: query required UTF-16 buffer size.
	const cpACP = 0
	n, _, _ := multiByteToWideChar.Call(
		cpACP, 0,
		uintptr(unsafe.Pointer(&ansi[0])), uintptr(len(ansi)),
		0, 0,
	)
	if n == 0 {
		return string(ansi) // fallback: treat as latin-1
	}

	// Second call: do the conversion.
	wide := make([]uint16, n)
	multiByteToWideChar.Call(
		cpACP, 0,
		uintptr(unsafe.Pointer(&ansi[0])), uintptr(len(ansi)),
		uintptr(unsafe.Pointer(&wide[0])), n,
	)
	return syscall.UTF16ToString(wide)
}

// GetPlaylist returns all titles in the current Winamp playlist.
// Titles are read from Winamp's process memory via ReadProcessMemory.
func (c *Controller) GetPlaylist() []TrackInfo {
	h := c.handle()
	if h == 0 {
		return nil
	}
	n := int(send(h, wmUser, 0, userGetPlaylistLen))
	if n <= 0 {
		return nil
	}

	var pid uint32
	getWindowThreadProcessId.Call(uintptr(h), uintptr(unsafe.Pointer(&pid)))

	proc, _, _ := openProcess.Call(processVMRead, 0, uintptr(pid))
	if proc == 0 {
		return nil
	}
	defer syscall.CloseHandle(syscall.Handle(proc))

	tracks := make([]TrackInfo, n)
	for i := 0; i < n; i++ {
		ptr := send(h, wmUser, uintptr(i), userGetPlaylistTitle)
		tracks[i] = TrackInfo{
			Index: i + 1,
			Title: readRemoteString(syscall.Handle(proc), ptr),
		}
	}
	return tracks
}

// JumpToTrack sets the playlist position (0-based) and starts playback.
func (c *Controller) JumpToTrack(zeroBasedIndex int) bool {
	h := c.handle()
	if h == 0 {
		return false
	}
	send(h, wmUser, uintptr(zeroBasedIndex), userSetPlaylistPos)
	send(h, wmCommand, cmdPlay, 0)
	return true
}