// Core song model. Time is stored in MIDI ticks against the song's ppq
// (pulses per quarter note); the tempo map converts to seconds.

export interface Note {
  id: string;
  tick: number; // start, in ticks
  duration: number; // in ticks, >= 1
  pitch: number; // MIDI note number 0..127
  velocity: number; // 1..127
}

export interface Track {
  id: string;
  name: string;
  instrumentId: string;
  volume: number; // 0..1.5, applied at mix time
  mute: boolean;
  solo: boolean;
  notes: Note[];
}

export interface TempoEvent {
  tick: number;
  usPerQuarter: number; // microseconds per quarter note
}

export interface TimeSigEvent {
  tick: number;
  numerator: number;
  denominator: number; // 4 = quarter gets the beat
}

export interface Song {
  ppq: number;
  tempo: TempoEvent[]; // sorted by tick, first at tick 0
  timeSig: TimeSigEvent[]; // sorted by tick, first at tick 0
  tracks: Track[];
}

export interface SongRecord {
  id: string;
  name: string;
  createdAt: number;
  updatedAt: number;
  song: Song;
}

export interface SongMeta {
  id: string;
  name: string;
  updatedAt: number;
  trackCount: number;
  noteCount: number;
}

let idCounter = 0;
export function newId(prefix = 'x'): string {
  idCounter += 1;
  return `${prefix}${Date.now().toString(36)}${idCounter.toString(36)}${Math.floor(Math.random() * 46656).toString(36)}`;
}

export const DEFAULT_PPQ = 480;

export function defaultSong(): Song {
  return {
    ppq: DEFAULT_PPQ,
    tempo: [{ tick: 0, usPerQuarter: 500000 }], // 120 bpm
    timeSig: [{ tick: 0, numerator: 4, denominator: 4 }],
    tracks: [
      {
        id: newId('t'),
        name: 'Track 1',
        instrumentId: 'pluck',
        volume: 1,
        mute: false,
        solo: false,
        notes: [],
      },
    ],
  };
}

export function songEndTick(song: Song): number {
  let end = 0;
  for (const t of song.tracks) for (const n of t.notes) end = Math.max(end, n.tick + n.duration);
  return end;
}