import fs from "node:fs";
import path from "node:path";
import { fileURLToPath } from "node:url";
import midiPackage from "../frontend/node_modules/@tonejs/midi/build/Midi.js";

const { Midi } = midiPackage;
const projectRoot = path.resolve(path.dirname(fileURLToPath(import.meta.url)), "..");
const sampleRoot = path.join(projectRoot, "backend", "sample_midi");

function load(name) {
  return new Midi(fs.readFileSync(path.join(sampleRoot, name)));
}

function createVariant(source, options) {
  const result = new Midi();
  const header = source.header.toJSON();
  result.header.fromJSON({
    ...header,
    name: options.name,
    tempos: [{ ticks: 0, bpm: options.tempo }],
    meta: [],
  });

  const originalTempo = source.header.tempos[0]?.bpm ?? options.tempo;
  const timeScale = originalTempo / options.tempo;
  for (const trackIndex of options.trackIndexes) {
    const sourceTrack = source.tracks[trackIndex];
    if (!sourceTrack) continue;
    const targetTrack = result.addTrack();
    targetTrack.name = sourceTrack.name;
    targetTrack.channel = sourceTrack.channel;
    targetTrack.instrument.number = sourceTrack.instrument.number;

    let notes = sourceTrack.notes.filter((note) => note.time < options.endTime);
    if (options.leftHandRoots && trackIndex === 1) {
      const measureSeconds = (60 / originalTempo) * (header.timeSignatures[0]?.timeSignature[0] ?? 4);
      const roots = new Map();
      for (const note of notes) {
        const measure = Math.floor(note.time / measureSeconds);
        const current = roots.get(measure);
        if (!current || note.midi < current.midi) roots.set(measure, note);
      }
      notes = [...roots.values()];
    }

    for (const note of notes) {
      targetTrack.addNote({
        midi: note.midi,
        time: note.time * timeScale,
        duration: options.leftHandRoots && trackIndex === 1
          ? Math.max(note.duration * timeScale, 0.8)
          : note.duration * timeScale,
        velocity: note.velocity,
      });
    }
  }
  return result;
}

function write(name, midi) {
  fs.writeFileSync(path.join(sampleRoot, name), Buffer.from(midi.toArray()));
}

const furElise = load("fur-elise.mid");
write(
  "fur-elise-beginner.mid",
  createVariant(furElise, {
    name: "엘리제를 위하여 입문 양손 연습",
    tempo: 60,
    endTime: 32,
    trackIndexes: [0, 1],
    leftHandRoots: true,
  }),
);
write(
  "fur-elise-easy.mid",
  createVariant(furElise, {
    name: "엘리제를 위하여 쉬운 양손 연습",
    tempo: 66,
    endTime: 45,
    trackIndexes: [0, 1],
    leftHandRoots: true,
  }),
);

const bachMinuet = load("minuet-bwv-anh-114.mid");
write(
  "minuet-bwv-anh-114-beginner.mid",
  createVariant(bachMinuet, {
    name: "미뉴에트 사장조 입문 양손 연습",
    tempo: 100,
    endTime: bachMinuet.duration + 1,
    trackIndexes: [0, 1],
    leftHandRoots: true,
  }),
);

const beethovenMinuet = load("menuett-woo-82.mid");
write(
  "menuett-woo-82-easy.mid",
  createVariant(beethovenMinuet, {
    name: "미뉴에트 내림마장조 쉬운 양손 연습",
    tempo: 88,
    endTime: beethovenMinuet.duration + 1,
    trackIndexes: [0, 1],
    leftHandRoots: true,
  }),
);

console.log("양손이 포함된 난이도별 연습 MIDI 4개를 만들었습니다.");