import { useSyncExternalStore } from 'react';
import type { Song, SongMeta, SongRecord, Track } from '../types.ts';
import { defaultSong, newId } from '../types.ts';
import * as db from '../storage/db.ts';
import { parseMidi } from '../midi/parse.ts';
import { TempoMap } from '../midi/time.ts';
import { quantizeNotes } from '../midi/ops.ts';
import { player } from '../audio/player.ts';
import { Recorder, type CapturedNote } from '../input/recorder.ts';

// Application state and every action that edits it. Song edits go through
// beginEdit/editSong/endEdit so a whole drag gesture is one undo step;
// mutateSong wraps the three for one-shot edits. Songs autosave to
// IndexedDB shortly after each committed edit.

export interface AppState {
  ready: boolean;
  rec: SongRecord | null;
  songs: SongMeta[];
  activeTrackId: string | null;
  armedTrackId: string | null;
  selection: string[];
  snapBeats: number; // snap grid in quarter notes; 0 = off
  libraryOpen: boolean;
  status: string;
}

const LAST_SONG_KEY = 'midiboot:lastSong';
const UNDO_CAP = 200;

class Store {
  state: AppState = {
    ready: false,
    rec: null,
    songs: [],
    activeTrackId: null,
    armedTrackId: null,
    selection: [],
    snapBeats: 0.25,
    libraryOpen: false,
    status: '',
  };
  recorder = new Recorder();

  private listeners = new Set<() => void>();
  private undoStack: Song[] = [];
  private redoStack: Song[] = [];
  private pendingUndo: Song | null = null;
  private saveTimer: ReturnType<typeof setTimeout> | null = null;

  subscribe = (cb: () => void): (() => void) => {
    this.listeners.add(cb);
    return () => this.listeners.delete(cb);
  };

  getSnapshot = (): AppState => this.state;

  private set(patch: Partial<AppState>) {
    this.state = { ...this.state, ...patch };
    for (const cb of this.listeners) cb();
  }

  song(): Song | null { return this.state.rec?.song ?? null; }

  tempoMap(): TempoMap | null {
    const song = this.song();
    return song ? new TempoMap(song.ppq, song.tempo, song.timeSig) : null;
  }

  snapTicks(): number {
    const song = this.song();
    if (!song || this.state.snapBeats <= 0) return 0;
    return Math.round(song.ppq * this.state.snapBeats);
  }

  async init(): Promise<void> {
    const songs = await db.listSongs();
    let rec: SongRecord | null = null;
    try {
      const last = localStorage.getItem(LAST_SONG_KEY);
      if (last) rec = await db.getSong(last);
    } catch { /* localStorage unavailable */ }
    if (!rec && songs.length > 0) rec = await db.getSong(songs[0].id);
    if (!rec) {
      rec = this.freshRecord('Untitled song');
      await db.putSong(rec);
    }
    this.set({ ready: true, songs, rec, activeTrackId: rec.song.tracks[0]?.id ?? null });
    this.rememberLast(rec.id);
  }

  private freshRecord(name: string, song?: Song): SongRecord {
    const now = Date.now();
    return { id: newId('s'), name, createdAt: now, updatedAt: now, song: song ?? defaultSong() };
  }

  private rememberLast(id: string) {
    try { localStorage.setItem(LAST_SONG_KEY, id); } catch { /* ignore */ }
  }

  private scheduleSave() {
    if (this.saveTimer !== null) clearTimeout(this.saveTimer);
    this.saveTimer = setTimeout(() => {
      this.saveTimer = null;
      void this.saveNow();
    }, 400);
  }

  private async saveNow() {
    const rec = this.state.rec;
    if (!rec) return;
    await db.putSong(rec);
    this.set({ songs: await db.listSongs() });
  }

  // --- edit protocol ---

  beginEdit(): void {
    if (!this.state.rec || this.pendingUndo) return;
    this.pendingUndo = structuredClone(this.state.rec.song);
  }

  editSong(fn: (song: Song) => void): void {
    const rec = this.state.rec;
    if (!rec) return;
    const song = structuredClone(rec.song);
    fn(song);
    this.set({ rec: { ...rec, song, updatedAt: Date.now() } });
  }

  endEdit(): void {
    if (this.pendingUndo) {
      this.undoStack.push(this.pendingUndo);
      if (this.undoStack.length > UNDO_CAP) this.undoStack.shift();
      this.redoStack = [];
      this.pendingUndo = null;
    }
    this.scheduleSave();
  }

  mutateSong(fn: (song: Song) => void): void {
    this.beginEdit();
    this.editSong(fn);
    this.endEdit();
  }

  undo(): void {
    const rec = this.state.rec;
    const prev = this.undoStack.pop();
    if (!rec || !prev) return;
    this.redoStack.push(structuredClone(rec.song));
    this.set({ rec: { ...rec, song: prev, updatedAt: Date.now() }, selection: [] });
    this.scheduleSave();
  }

  redo(): void {
    const rec = this.state.rec;
    const next = this.redoStack.pop();
    if (!rec || !next) return;
    this.undoStack.push(structuredClone(rec.song));
    this.set({ rec: { ...rec, song: next, updatedAt: Date.now() }, selection: [] });
    this.scheduleSave();
  }

  private resetHistory() {
    this.undoStack = [];
    this.redoStack = [];
    this.pendingUndo = null;
  }

  // --- library ---

  setLibraryOpen(v: boolean): void { this.set({ libraryOpen: v }); }

  async newSong(): Promise<void> {
    player.stop();
    const rec = this.freshRecord('Untitled song');
    await db.putSong(rec);
    this.resetHistory();
    this.set({ rec, songs: await db.listSongs(), activeTrackId: rec.song.tracks[0]?.id ?? null, armedTrackId: null, selection: [], libraryOpen: false });
    player.seek(0);
    this.rememberLast(rec.id);
  }

  async openSong(id: string): Promise<void> {
    const rec = await db.getSong(id);
    if (!rec) return;
    player.stop();
    this.resetHistory();
    this.set({ rec, activeTrackId: rec.song.tracks[0]?.id ?? null, armedTrackId: null, selection: [], libraryOpen: false });
    player.seek(0);
    this.rememberLast(rec.id);
  }

  async deleteSongById(id: string): Promise<void> {
    await db.deleteSong(id);
    const songs = await db.listSongs();
    this.set({ songs });
    if (this.state.rec?.id === id) {
      if (songs.length > 0) await this.openSong(songs[0].id);
      else await this.newSong();
    }
  }

  renameSong(name: string): void {
    const rec = this.state.rec;
    if (!rec) return;
    this.set({ rec: { ...rec, name, updatedAt: Date.now() } });
    this.scheduleSave();
  }

  async duplicateSong(id: string): Promise<void> {
    const src = await db.getSong(id);
    if (!src) return;
    const rec = this.freshRecord(`${src.name} copy`, structuredClone(src.song));
    await db.putSong(rec);
    this.set({ songs: await db.listSongs() });
  }

  async importMidi(fileName: string, data: Uint8Array): Promise<void> {
    let song: Song;
    try {
      song = parseMidi(data);
    } catch (err) {
      this.set({ status: `Import failed: ${err instanceof Error ? err.message : String(err)}` });
      return;
    }
    if (song.tracks.length === 0) {
      this.set({ status: 'Import: no notes found in file' });
      return;
    }
    player.stop();
    const name = fileName.replace(/\.(mid|midi)$/i, '') || 'Imported song';
    const rec = this.freshRecord(name, song);
    await db.putSong(rec);
    this.resetHistory();
    this.set({ rec, songs: await db.listSongs(), activeTrackId: song.tracks[0].id, armedTrackId: null, selection: [], libraryOpen: false, status: `Imported ${song.tracks.length} track(s)` });
    player.seek(0);
    this.rememberLast(rec.id);
  }

  // --- tracks ---

  setActiveTrack(id: string): void { this.set({ activeTrackId: id, selection: [] }); }

  setArmedTrack(id: string | null): void { this.set({ armedTrackId: id }); }

  addTrack(): void {
    const id = newId('t');
    this.mutateSong((song) => {
      song.tracks.push({ id, name: `Track ${song.tracks.length + 1}`, instrumentId: 'pluck', volume: 1, mute: false, solo: false, notes: [] });
    });
    this.set({ activeTrackId: id });
  }

  removeTrack(id: string): void {
    this.mutateSong((song) => {
      song.tracks = song.tracks.filter((t) => t.id !== id);
    });
    const song = this.song();
    if (this.state.activeTrackId === id) this.set({ activeTrackId: song?.tracks[0]?.id ?? null });
    if (this.state.armedTrackId === id) this.set({ armedTrackId: null });
  }

  updateTrack(id: string, patch: Partial<Track>, undoable = true): void {
    const fn = (song: Song) => {
      const t = song.tracks.find((x) => x.id === id);
      if (t) Object.assign(t, patch);
    };
    if (undoable) this.mutateSong(fn);
    else {
      this.editSong(fn);
      this.scheduleSave();
    }
  }

  setSelection(ids: string[]): void { this.set({ selection: ids }); }

  setSnapBeats(v: number): void { this.set({ snapBeats: v }); }

  deleteSelection(): void {
    if (this.state.selection.length === 0) return;
    const sel = new Set(this.state.selection);
    this.mutateSong((song) => {
      for (const t of song.tracks) t.notes = t.notes.filter((n) => !sel.has(n.id));
    });
    this.set({ selection: [] });
  }

  quantize(): void {
    const grid = this.snapTicks();
    if (grid <= 0) { this.set({ status: 'Quantize: snap is off' }); return; }
    const sel = this.state.selection.length > 0 ? new Set(this.state.selection) : null;
    const activeId = this.state.activeTrackId;
    this.mutateSong((song) => {
      for (const t of song.tracks) {
        if (sel) t.notes = quantizeNotes(t.notes, grid, sel);
        else if (t.id === activeId) t.notes = quantizeNotes(t.notes, grid);
      }
    });
  }

  // --- transport ---

  async togglePlay(): Promise<void> {
    const song = this.song();
    if (!song) return;
    if (player.state !== 'stopped') this.stopTransport();
    else await player.play(song);
  }

  async record(): Promise<void> {
    const song = this.song();
    if (!song) return;
    if (player.state !== 'stopped') this.stopTransport();
    const armed = this.state.armedTrackId ?? this.state.activeTrackId;
    if (!armed) { this.set({ status: 'Record: no track to record into' }); return; }
    this.set({ armedTrackId: armed });
    await player.play(song, { record: true, countInBars: 1 });
    this.recorder.start();
  }

  stopTransport(): void {
    if (player.state === 'recording') {
      const endSec = Math.max(0, player.getPositionSec());
      const take = this.recorder.stop(endSec);
      player.stop();
      this.commitTake(take);
    } else {
      player.stop();
    }
  }

  private commitTake(take: CapturedNote[]): void {
    if (take.length === 0) return;
    const song = this.song();
    const armed = this.state.armedTrackId;
    if (!song || !armed) return;
    const tm = new TempoMap(song.ppq, song.tempo, song.timeSig);
    const ids: string[] = [];
    this.mutateSong((s) => {
      const track = s.tracks.find((t) => t.id === armed);
      if (!track) return;
      for (const c of take) {
        const tick = Math.max(0, Math.round(tm.secToTick(Math.max(0, c.startSec))));
        const endTick = Math.round(tm.secToTick(Math.max(0, c.endSec)));
        const id = newId('n');
        ids.push(id);
        track.notes.push({ id, tick, duration: Math.max(Math.round(s.ppq / 16), endTick - tick), pitch: c.pitch, velocity: c.velocity });
      }
      track.notes.sort((a, b) => a.tick - b.tick || a.pitch - b.pitch);
    });
    this.set({ selection: ids, status: `Recorded ${take.length} note(s)` });
  }

  seekTo(sec: number): void {
    if (player.state === 'recording') return;
    const song = this.song();
    if (player.state === 'playing' && song) {
      player.stop();
      player.seek(sec);
      void player.play(song);
    } else {
      player.seek(sec);
    }
  }
}

export const store = new Store();

export function useApp(): AppState {
  return useSyncExternalStore(store.subscribe, store.getSnapshot);
}

export function usePlayerVersion(): number {
  return useSyncExternalStore(player.subscribe, () => player.version);
}