import type { Instrument, LiveVoice, NoteSpec, TrackRenderRequest, TrackRenderResult } from './types.ts';
import { brassNote, drumNote, epianoNote, leadNote, organNote, pianoNote, pluckNote, stringsNote, synthBassNote } from './dsp.ts';

// Built-in instruments, each constructed from a pure per-note DSP function.
// The render path sums per-note buffers; the live path plays one note's
// buffer through a gain node whose release implements noteOff. A custom
// instrument with its own rendering logic does not have to go through
// this helper; it only has to satisfy the Instrument interface.

export type NoteDsp = (sr: number, pitch: number, velocity: number, durationSec: number) => Float32Array;

interface DspOpts {
  sustains: boolean; // if true, live voices are rendered long and gated by noteOff
  liveDurationSec?: number;
}

export function instrumentFromNoteDsp(id: string, name: string, dsp: NoteDsp, opts: DspOpts): Instrument {
  return {
    id,
    name,
    renderTrack(req: TrackRenderRequest): Promise<TrackRenderResult> {
      // lengthSamples is a minimum: a release that outlives the last note
      // is kept rather than clipped.
      const rendered: { off: number; buf: Float32Array }[] = [];
      let length = req.lengthSamples;
      for (const note of req.notes) {
        const buf = dsp(req.sampleRate, note.pitch, note.velocity, note.durationSec);
        const off = Math.round(note.timeSec * req.sampleRate);
        rendered.push({ off, buf });
        length = Math.max(length, off + buf.length);
      }
      const out = new Float32Array(length);
      for (const r of rendered) {
        const end = Math.min(out.length, r.off + r.buf.length);
        for (let i = Math.max(0, r.off); i < end; i++) out[i] += r.buf[i - r.off];
      }
      return Promise.resolve({ audio: out });
    },
    noteOn(ctx, dest, pitch, velocity, whenSec): LiveVoice {
      const dur = opts.sustains ? (opts.liveDurationSec ?? 20) : 0.25;
      const data = dsp(ctx.sampleRate, pitch, velocity, dur);
      const buffer = ctx.createBuffer(1, data.length, ctx.sampleRate);
      buffer.copyToChannel(data as Float32Array<ArrayBuffer>, 0);
      const src = ctx.createBufferSource();
      src.buffer = buffer;
      const gain = ctx.createGain();
      src.connect(gain);
      gain.connect(dest);
      src.start(whenSec);
      let done = false;
      const finish = (fadeSec: number) => {
        if (done) return;
        done = true;
        const t = Math.max(ctx.currentTime, whenSec);
        gain.gain.setValueAtTime(gain.gain.value, t);
        gain.gain.setTargetAtTime(0, t, fadeSec / 4);
        src.stop(t + fadeSec + 0.1);
      };
      src.onended = () => { done = true; };
      return {
        noteOff: () => { if (opts.sustains) finish(0.15); },
        cut: () => finish(0.02),
      };
    },
  };
}

// The cheap synthetic set: one instrument per broad General MIDI family,
// so an imported MIDI file is playable without a soundfont.
export const builtinInstruments: Instrument[] = [
  instrumentFromNoteDsp('piano', 'Piano (FM)', pianoNote, { sustains: true, liveDurationSec: 10 }),
  instrumentFromNoteDsp('epiano', 'E-Piano (FM)', epianoNote, { sustains: true, liveDurationSec: 8 }),
  instrumentFromNoteDsp('organ', 'Organ (drawbar)', organNote, { sustains: true, liveDurationSec: 20 }),
  instrumentFromNoteDsp('pluck', 'Pluck (Karplus-Strong)', pluckNote, { sustains: true, liveDurationSec: 3 }),
  instrumentFromNoteDsp('synthbass', 'Synth Bass', synthBassNote, { sustains: true, liveDurationSec: 6 }),
  instrumentFromNoteDsp('strings', 'Strings (pad)', stringsNote, { sustains: true, liveDurationSec: 20 }),
  instrumentFromNoteDsp('brass', 'Brass (saw)', brassNote, { sustains: true, liveDurationSec: 20 }),
  instrumentFromNoteDsp('lead', 'Lead (square)', leadNote, { sustains: true, liveDurationSec: 20 }),
  instrumentFromNoteDsp('drumkit', 'Drum kit (GM)', drumNote, { sustains: false }),
];

export function noteSpecVelocity(velocity127: number): number {
  return Math.max(0, Math.min(1, velocity127 / 127));
}

export type { NoteSpec };