package jukebox

import (
	"errors"
	"math/rand"
	"os/exec"
	"sync"
)

// ErrUnavailable is returned by every action when no mpv binary was
// found at startup — the jukebox is administratively unavailable rather
// than pretending to control playback it can't.
var ErrUnavailable = errors.New("jukebox: no playback backend available (mpv not found)")

// State mirrors what the Subsonic jukeboxControl "status"/"get" actions
// report.
type State struct {
	CurrentIndex int
	Playing      bool
	Gain         float64
	PositionSecs int
	SongIDs      []string // playlist order, VibeSonic song IDs
}

// Jukebox is a real server-side playback controller backed by mpv. One
// instance serves the whole server (Subsonic's jukebox is inherently a
// single shared "device", not per-user).
type Jukebox struct {
	Available bool

	mpv *mpvClient

	mu      sync.Mutex
	songIDs []string
	gain    float64
}

// New probes for an mpv binary and returns a Jukebox. If mpv isn't
// found, Available is false and every action returns ErrUnavailable —
// callers (the Subsonic handler) should surface that as a clear "not
// configured" error, never as fake success.
func New(mpvPath string) *Jukebox {
	if mpvPath == "" {
		mpvPath = "mpv"
	}
	j := &Jukebox{gain: 1.0}
	if _, err := exec.LookPath(mpvPath); err != nil {
		return j
	}
	j.Available = true
	j.mpv = newMPVClient(mpvPath)
	return j
}

// Close stops the backing mpv process, if one was started.
func (j *Jukebox) Close() {
	if j.mpv != nil {
		j.mpv.close()
	}
}

func (j *Jukebox) requireAvailable() error {
	if !j.Available {
		return ErrUnavailable
	}
	return nil
}

// Status returns the current playback state without changing anything.
func (j *Jukebox) Status() (State, error) {
	if err := j.requireAvailable(); err != nil {
		return State{}, err
	}
	j.mu.Lock()
	defer j.mu.Unlock()
	return j.stateLocked()
}

func (j *Jukebox) stateLocked() (State, error) {
	pauseVal, err := j.mpv.getProperty("pause")
	if err != nil {
		return State{}, err
	}
	paused, _ := pauseVal.(bool)

	idx := 0
	if v, err := j.mpv.getProperty("playlist-pos"); err == nil {
		if f, ok := v.(float64); ok && f >= 0 {
			idx = int(f)
		}
	}
	pos := 0
	if v, err := j.mpv.getProperty("time-pos"); err == nil {
		if f, ok := v.(float64); ok {
			pos = int(f)
		}
	}

	return State{
		CurrentIndex: idx,
		Playing:      !paused && len(j.songIDs) > 0,
		Gain:         j.gain,
		PositionSecs: pos,
		SongIDs:      append([]string(nil), j.songIDs...),
	}, nil
}

// resolvePath maps a VibeSonic song ID to a playable filesystem path.
// The Subsonic handler supplies this since path resolution needs
// database + folder-permission context this package doesn't have.
type ResolveFunc func(songID string) (path string, err error)

// Set replaces the entire jukebox playlist with songIDs and starts
// playing from the beginning.
func (j *Jukebox) Set(songIDs []string, resolve ResolveFunc) (State, error) {
	if err := j.requireAvailable(); err != nil {
		return State{}, err
	}
	j.mu.Lock()
	defer j.mu.Unlock()

	if _, err := j.mpv.command("playlist-clear"); err != nil {
		return State{}, err
	}
	if _, err := j.mpv.command("stop"); err != nil {
		return State{}, err
	}
	j.songIDs = nil

	for i, id := range songIDs {
		path, err := resolve(id)
		if err != nil {
			continue // skip songs we can't resolve rather than failing the whole playlist
		}
		mode := "append-play"
		if i == 0 {
			mode = "replace"
		}
		if _, err := j.mpv.command("loadfile", path, mode); err != nil {
			continue
		}
		j.songIDs = append(j.songIDs, id)
	}

	return j.stateLocked()
}

// Add appends songIDs to the end of the current playlist.
func (j *Jukebox) Add(songIDs []string, resolve ResolveFunc) (State, error) {
	if err := j.requireAvailable(); err != nil {
		return State{}, err
	}
	j.mu.Lock()
	defer j.mu.Unlock()

	for _, id := range songIDs {
		path, err := resolve(id)
		if err != nil {
			continue
		}
		mode := "append-play"
		if len(j.songIDs) == 0 {
			mode = "replace"
		}
		if _, err := j.mpv.command("loadfile", path, mode); err != nil {
			continue
		}
		j.songIDs = append(j.songIDs, id)
	}
	return j.stateLocked()
}

// Clear empties the playlist and stops playback.
func (j *Jukebox) Clear() (State, error) {
	if err := j.requireAvailable(); err != nil {
		return State{}, err
	}
	j.mu.Lock()
	defer j.mu.Unlock()
	if _, err := j.mpv.command("playlist-clear"); err != nil {
		return State{}, err
	}
	if _, err := j.mpv.command("stop"); err != nil {
		return State{}, err
	}
	j.songIDs = nil
	return j.stateLocked()
}

// Remove removes the playlist entry at index.
func (j *Jukebox) Remove(index int) (State, error) {
	if err := j.requireAvailable(); err != nil {
		return State{}, err
	}
	j.mu.Lock()
	defer j.mu.Unlock()
	if index < 0 || index >= len(j.songIDs) {
		return j.stateLocked()
	}
	if _, err := j.mpv.command("playlist-remove", index); err != nil {
		return State{}, err
	}
	j.songIDs = append(j.songIDs[:index], j.songIDs[index+1:]...)
	return j.stateLocked()
}

// Shuffle reshuffles the playlist order and rebuilds mpv's queue to
// match. mpv's own playlist-shuffle command shuffles in place without
// reporting the resulting order back, so instead this reshuffles our
// song-ID tracking directly and rebuilds mpv's queue from it.
func (j *Jukebox) Shuffle(resolve ResolveFunc) (State, error) {
	if err := j.requireAvailable(); err != nil {
		return State{}, err
	}
	j.mu.Lock()
	defer j.mu.Unlock()

	if len(j.songIDs) == 0 {
		return j.stateLocked()
	}
	rand.Shuffle(len(j.songIDs), func(i, k int) { j.songIDs[i], j.songIDs[k] = j.songIDs[k], j.songIDs[i] })

	if _, err := j.mpv.command("playlist-clear"); err != nil {
		return State{}, err
	}
	if _, err := j.mpv.command("stop"); err != nil {
		return State{}, err
	}
	kept := j.songIDs
	j.songIDs = nil
	for i, id := range kept {
		path, err := resolve(id)
		if err != nil {
			continue
		}
		mode := "append-play"
		if i == 0 {
			mode = "replace"
		}
		if _, err := j.mpv.command("loadfile", path, mode); err != nil {
			continue
		}
		j.songIDs = append(j.songIDs, id)
	}
	return j.stateLocked()
}

// SkipTo jumps to playlist index and seeks offsetSecs into it.
func (j *Jukebox) SkipTo(index int, offsetSecs float64) (State, error) {
	if err := j.requireAvailable(); err != nil {
		return State{}, err
	}
	j.mu.Lock()
	defer j.mu.Unlock()
	if index < 0 || index >= len(j.songIDs) {
		return j.stateLocked()
	}
	if _, err := j.mpv.command("playlist-play-index", index); err != nil {
		return State{}, err
	}
	if offsetSecs > 0 {
		_, _ = j.mpv.command("seek", offsetSecs, "absolute")
	}
	if err := j.mpv.setProperty("pause", false); err != nil {
		return State{}, err
	}
	return j.stateLocked()
}

// Start resumes/starts playback.
func (j *Jukebox) Start() (State, error) {
	if err := j.requireAvailable(); err != nil {
		return State{}, err
	}
	j.mu.Lock()
	defer j.mu.Unlock()
	if err := j.mpv.setProperty("pause", false); err != nil {
		return State{}, err
	}
	return j.stateLocked()
}

// Stop pauses playback.
func (j *Jukebox) Stop() (State, error) {
	if err := j.requireAvailable(); err != nil {
		return State{}, err
	}
	j.mu.Lock()
	defer j.mu.Unlock()
	if err := j.mpv.setProperty("pause", true); err != nil {
		return State{}, err
	}
	return j.stateLocked()
}

// SetGain sets playback volume, gain in [0.0, 1.0] mapped onto mpv's
// 0-100 volume property.
func (j *Jukebox) SetGain(gain float64) (State, error) {
	if err := j.requireAvailable(); err != nil {
		return State{}, err
	}
	if gain < 0 {
		gain = 0
	}
	if gain > 1 {
		gain = 1
	}
	j.mu.Lock()
	defer j.mu.Unlock()
	if err := j.mpv.setProperty("volume", gain*100); err != nil {
		return State{}, err
	}
	j.gain = gain
	return j.stateLocked()
}