package tracker

import (
	"encoding/json"
	"errors"
	"fmt"
	"os"
	"path/filepath"

	"github.com/vsariola/sointu"
	"github.com/vsariola/sointu/vm"
)

// Model implements the mutable state for the tracker program GUI.
//
// Go does not have immutable slices, so there's no efficient way to guarantee
// accidental mutations in the song. But at least the value members are
// protected.
// It is owned by the GUI thread (goroutine), while the player is owned by
// by the audioprocessing thread. They communicate using the two channels
type (
	// modelData is the part of the model that gets save to recovery file
	modelData struct {
		Song                    sointu.Song
		Cursor, Cursor2         Cursor
		LowNibble               bool
		InstrIndex, InstrIndex2 int
		UnitIndex, UnitIndex2   int
		ParamIndex              int
		UnitSearchIndex         int
		UnitSearchString        string
		UnitSearching           bool
		Octave                  int
		Step                    int
		FilePath                string
		ChangedSinceSave        bool
		RecoveryFilePath        string
		ChangedSinceRecovery    bool
	}

	Model struct {
		d modelData

		instrEnlarged   bool
		commentExpanded bool

		prevUndoKind    string
		undoSkipCounter int
		undoStack       []modelData
		redoStack       []modelData

		changeLevel    int
		changeCancel   bool
		changeSeverity ChangeSeverity
		changeType     ChangeType

		panic        bool
		recording    bool
		playing      bool
		playPosition sointu.SongPos
		noteTracking bool
		quitted      bool

		cachePatternUseCount [][]int

		voiceLevels [vm.MAX_VOICES]float32
		avgVolume   Volume
		peakVolume  Volume

		alerts  []Alert
		dialog  Dialog
		synther sointu.Synther // the synther used to create new synths

		PlayerMessages chan PlayerMsg
		modelMessages  chan<- interface{}
	}

	// Cursor identifies a row and a track in a song score.
	Cursor struct {
		Track int
		sointu.SongPos
	}

	Explore struct {
		IsSave       bool         // true if this is a save operation, false if open operation
		IsSong       bool         // true if this is a song, false if instrument
		Continuation func(string) // function to call with the selected file path
	}

	// Describes a note triggered either a track or an instrument
	// If Go had union or Either types, this would be it, but in absence
	// those, this uses a boolean to define if the instrument is defined or the track
	NoteID struct {
		IsInstr bool
		Instr   int
		Track   int
		Note    byte

		model *Model
	}

	IsPlayingMsg   struct{ bool }
	StartPlayMsg   struct{ sointu.SongPos }
	BPMMsg         struct{ int }
	RowsPerBeatMsg struct{ int }
	PanicMsg       struct{ bool }
	RecordingMsg   struct{ bool }
	NoteOnMsg      struct{ NoteID }
	NoteOffMsg     struct{ NoteID }

	ChangeSeverity int
	ChangeType     int

	Dialog int
)

const (
	MajorChange ChangeSeverity = iota
	MinorChange
)

const (
	NoChange    ChangeType = 0
	PatchChange ChangeType = 1 << iota
	ScoreChange
	BPMChange
	RowsPerBeatChange
	SongChange ChangeType = PatchChange | ScoreChange | BPMChange | RowsPerBeatChange
)

const (
	NoDialog = iota
	SaveAsExplorer
	NewSongChanges
	NewSongSaveExplorer
	OpenSongChanges
	OpenSongSaveExplorer
	OpenSongOpenExplorer
	Export
	ExportFloatExplorer
	ExportInt16Explorer
	QuitChanges
	QuitSaveExplorer
)

const maxUndo = 64

func (m *Model) AverageVolume() Volume        { return m.avgVolume }
func (m *Model) PeakVolume() Volume           { return m.peakVolume }
func (m *Model) PlayPosition() sointu.SongPos { return m.playPosition }
func (m *Model) PlaySongRow() int             { return m.d.Song.Score.SongRow(m.playPosition) }
func (m *Model) ChangedSinceSave() bool       { return m.d.ChangedSinceSave }
func (m *Model) Dialog() Dialog               { return m.dialog }
func (m *Model) Quitted() bool                { return m.quitted }

// NewModelPlayer creates a new model and a player that communicates with it
func NewModelPlayer(synther sointu.Synther, recoveryFilePath string) (*Model, *Player) {
	m := new(Model)
	m.synther = synther
	modelMessages := make(chan interface{}, 1024)
	playerMessages := make(chan PlayerMsg, 1024)
	m.modelMessages = modelMessages
	m.PlayerMessages = playerMessages
	m.d.Octave = 4
	m.d.RecoveryFilePath = recoveryFilePath
	m.resetSong()
	if recoveryFilePath != "" {
		if bytes2, err := os.ReadFile(m.d.RecoveryFilePath); err == nil {
			json.Unmarshal(bytes2, &m.d)
		}
	}
	p := &Player{
		playerMsgs:      playerMessages,
		modelMsgs:       modelMessages,
		synther:         synther,
		song:            m.d.Song.Copy(),
		avgVolumeMeter:  VolumeAnalyzer{Attack: 0.3, Release: 0.3, Min: -100, Max: 20},
		peakVolumeMeter: VolumeAnalyzer{Attack: 1e-4, Release: 1, Min: -100, Max: 20},
	}
	p.compileOrUpdateSynth()
	return m, p
}

func (m *Model) change(kind string, t ChangeType, severity ChangeSeverity) func() {
	if m.changeLevel == 0 {
		m.changeType = NoChange
		m.undoStack = append(m.undoStack, m.d.Copy())
		m.changeCancel = false
		m.changeSeverity = severity
	} else {
		if m.changeSeverity < severity {
			m.changeSeverity = severity
		}
	}
	m.changeType |= t
	m.changeLevel++
	return func() {
		m.changeLevel--
		if m.changeLevel < 0 {
			panic("changeLevel < 0, mismatched change() calls")
		}
		if m.changeLevel == 0 {
			if m.changeCancel || m.d.Song.BPM <= 0 || m.d.Song.RowsPerBeat <= 0 || m.d.Song.Score.Length <= 0 {
				// the change was cancelled or put the song in invalid state, so we don't save it
				m.d = m.undoStack[len(m.undoStack)-1]
				m.undoStack = m.undoStack[:len(m.undoStack)-1]
				return
			}
			m.d.ChangedSinceSave = true
			m.d.ChangedSinceRecovery = true
			if m.changeType&ScoreChange != 0 {
				m.updatePatternUseCount()
				m.d.Cursor.SongPos = m.d.Song.Score.Wrap(m.d.Cursor.SongPos)
				m.d.Cursor2.SongPos = m.d.Song.Score.Wrap(m.d.Cursor2.SongPos)
				m.send(m.d.Song.Score.Copy())
			}
			if m.changeType&PatchChange != 0 {
				m.d.InstrIndex = clamp(m.d.InstrIndex, 0, len(m.d.Song.Patch)-1)
				m.d.InstrIndex2 = clamp(m.d.InstrIndex2, 0, len(m.d.Song.Patch)-1)
				unitCount := 0
				if m.d.InstrIndex >= 0 && m.d.InstrIndex < len(m.d.Song.Patch) {
					unitCount = len(m.d.Song.Patch[m.d.InstrIndex].Units)
				}
				m.d.UnitIndex = clamp(m.d.UnitIndex, 0, unitCount-1)
				m.d.UnitIndex2 = clamp(m.d.UnitIndex2, 0, unitCount-1)
				m.d.UnitSearching = false // if we change anything in the patch, reset the unit searching
				m.d.UnitSearchString = ""
				m.send(m.d.Song.Patch.Copy())
			}
			if m.changeType&BPMChange != 0 {
				m.send(BPMMsg{m.d.Song.BPM})
			}
			if m.changeType&RowsPerBeatChange != 0 {
				m.send(RowsPerBeatMsg{m.d.Song.RowsPerBeat})
			}
			m.undoSkipCounter++
			var limit int
			switch m.changeSeverity {
			default:
			case MajorChange:
				limit = 1
			case MinorChange:
				limit = 10
			}
			if m.prevUndoKind == kind && m.undoSkipCounter < limit {
				m.undoStack = m.undoStack[:len(m.undoStack)-1]
				return
			}
			m.undoSkipCounter = 0
			m.prevUndoKind = kind
			m.redoStack = m.redoStack[:0]
			if len(m.undoStack) > maxUndo {
				copy(m.undoStack, m.undoStack[len(m.undoStack)-maxUndo:])
				m.undoStack = m.undoStack[:maxUndo]
			}
		}
	}
}

func (m *Model) MarshalRecovery() []byte {
	out, err := json.Marshal(m.d)
	if err != nil {
		return nil
	}
	if m.d.RecoveryFilePath != "" {
		os.Remove(m.d.RecoveryFilePath)
	}
	m.d.ChangedSinceRecovery = false
	return out
}

func (m *Model) SaveRecovery() error {
	if !m.d.ChangedSinceRecovery {
		return nil
	}
	if m.d.RecoveryFilePath == "" {
		return errors.New("no backup file path")
	}
	out, err := json.Marshal(m.d)
	if err != nil {
		return fmt.Errorf("could not marshal recovery data: %w", err)
	}
	dir := filepath.Dir(m.d.RecoveryFilePath)
	if _, err := os.Stat(dir); os.IsNotExist(err) {
		os.MkdirAll(dir, os.ModePerm)
	}
	file, err := os.Create(m.d.RecoveryFilePath)
	if err != nil {
		return fmt.Errorf("could not create recovery file: %w", err)
	}
	_, err = file.Write(out)
	if err != nil {
		return fmt.Errorf("could not write recovery file: %w", err)
	}
	m.d.ChangedSinceRecovery = false
	return nil
}

func (m *Model) UnmarshalRecovery(bytes []byte) {
	err := json.Unmarshal(bytes, &m.d)
	if err != nil {
		return
	}
	if m.d.RecoveryFilePath != "" { // check if there's a recovery file on disk and load it instead
		if bytes2, err := os.ReadFile(m.d.RecoveryFilePath); err == nil {
			json.Unmarshal(bytes2, &m.d)
		}
	}
	m.d.ChangedSinceRecovery = false
	m.send(m.d.Song.Copy())
	m.updatePatternUseCount()
}

func (m *Model) ProcessPlayerMessage(msg PlayerMsg) {
	m.playPosition = msg.SongPosition
	m.voiceLevels = msg.VoiceLevels
	m.avgVolume = msg.AverageVolume
	m.peakVolume = msg.PeakVolume
	if m.playing && m.noteTracking {
		m.d.Cursor.SongPos = msg.SongPosition
		m.d.Cursor2.SongPos = msg.SongPosition
	}
	m.panic = msg.Panic
	switch e := msg.Inner.(type) {
	case func():
		e()
	case Recording:
		if e.BPM == 0 {
			e.BPM = float64(m.d.Song.BPM)
		}
		score, err := e.Score(m.d.Song.Patch, m.d.Song.RowsPerBeat, m.d.Song.Score.RowsPerPattern)
		if err != nil || score.Length <= 0 {
			break
		}
		defer m.change("Recording", SongChange, MajorChange)()
		m.d.Song.Score = score
		m.d.Song.BPM = int(e.BPM + 0.5)
		m.instrEnlarged = false
	case Alert:
		m.Alerts().AddAlert(e)
	default:
	}
}

func (m *Model) TrackNoteOn(track int, note byte) (id NoteID) {
	id = NoteID{IsInstr: false, Track: track, Note: note, model: m}
	m.send(NoteOnMsg{id})
	return id
}

func (m *Model) InstrNoteOn(instr int, note byte) (id NoteID) {
	id = NoteID{IsInstr: true, Instr: instr, Note: note, model: m}
	m.send(NoteOnMsg{id})
	return id
}

func (n NoteID) NoteOff() {
	n.model.send(NoteOffMsg{n})
}

func (m *Model) FindUnit(id int) (instrIndex, unitIndex int, err error) {
	// TODO: this only used for choosing send target; find a better way for this
	return m.d.Song.Patch.FindUnit(id)
}

func (m *Model) Instrument(index int) sointu.Instrument {
	// TODO: this only used for choosing send target; find a better way for this
	// we make a copy just so that the gui can't accidentally modify the song
	if index < 0 || index >= len(m.d.Song.Patch) {
		return sointu.Instrument{}
	}
	return m.d.Song.Patch[index].Copy()
}

func (d *modelData) Copy() modelData {
	ret := *d
	ret.Song = d.Song.Copy()
	return ret
}

func (m *Model) resetSong() {
	m.d.Song = defaultSong.Copy()
	for _, instr := range m.d.Song.Patch {
		(*Model)(m).assignUnitIDs(instr.Units)
	}
	m.d.FilePath = ""
	m.d.ChangedSinceSave = false
}

// send sends a message to the player
func (m *Model) send(message interface{}) {
	m.modelMessages <- message
}

func (m *Model) assignUnitIDs(units []sointu.Unit) {
	maxId := 0
	usedIds := make(map[int]bool)
	for _, instr := range m.d.Song.Patch {
		for _, unit := range instr.Units {
			usedIds[unit.ID] = true
			if maxId < unit.ID {
				maxId = unit.ID
			}
		}
	}
	rewrites := map[int]int{}
	for i := range units {
		if id := units[i].ID; id == 0 || usedIds[id] {
			maxId++
			if id > 0 {
				rewrites[id] = maxId
			}
			units[i].ID = maxId
		}
		usedIds[units[i].ID] = true
		if maxId < units[i].ID {
			maxId = units[i].ID
		}
	}
	for i, u := range units {
		if target, ok := u.Parameters["target"]; u.Type == "send" && ok {
			if newId, ok := rewrites[target]; ok {
				units[i].Parameters["target"] = newId
			}
		}
	}
}

func (m *Model) updatePatternUseCount() {
	for i, track := range m.d.Song.Score.Tracks {
		for len(m.cachePatternUseCount) <= i {
			m.cachePatternUseCount = append(m.cachePatternUseCount, nil)
		}
		for j := range m.cachePatternUseCount[i] {
			m.cachePatternUseCount[i][j] = 0
		}
		for j := 0; j < m.d.Song.Score.Length; j++ {
			if j >= len(track.Order) {
				break
			}
			p := track.Order[j]
			for len(m.cachePatternUseCount[i]) <= p {
				m.cachePatternUseCount[i] = append(m.cachePatternUseCount[i], 0)
			}
			if p < 0 {
				continue
			}
			m.cachePatternUseCount[i][p]++
		}
	}
}

func clamp(a, min, max int) int {
	if a > max {
		return max
	}
	if a < min {
		return min
	}
	return a
}

func intMax(a, b int) int {
	if a > b {
		return a
	}
	return b
}

func intMin(a, b int) int {
	if a < b {
		return a
	}
	return b
}