from __future__ import annotations

from pathlib import Path


OUTPUT = Path(__file__).resolve().parents[1] / "sample_midi"


def variable_length(value: int) -> bytes:
    data = [value & 0x7F]
    value >>= 7
    while value:
        data.insert(0, (value & 0x7F) | 0x80)
        value >>= 7
    return bytes(data)


def track(events: list[tuple[int, bytes]], tempo: int = 500_000, program: int = 0) -> bytes:
    body = bytearray()
    body.extend(b"\x00\xff\x51\x03" + tempo.to_bytes(3, "big"))
    body.extend(b"\x00\xff\x58\x04\x04\x02\x18\x08")
    body.extend(bytes([0, 0xC0, program]))
    for delta, message in events:
        body.extend(variable_length(delta))
        body.extend(message)
    body.extend(b"\x00\xff\x2f\x00")
    return b"MTrk" + len(body).to_bytes(4, "big") + body


def midi_file(events: list[tuple[int, bytes]], tempo: int = 500_000) -> bytes:
    header = b"MThd" + (6).to_bytes(4, "big") + (0).to_bytes(2, "big") + (1).to_bytes(2, "big") + (480).to_bytes(2, "big")
    return header + track(events, tempo)


def melody(notes: list[int], beats: int = 1, velocity: int = 82) -> list[tuple[int, bytes]]:
    result: list[tuple[int, bytes]] = []
    for note in notes:
        result.append((0, bytes([0x90, note, velocity])))
        result.append((480 * beats, bytes([0x80, note, 0])))
    return result


def chord_progression(chords: list[list[int]], melody_notes: list[int]) -> list[tuple[int, bytes]]:
    result: list[tuple[int, bytes]] = []
    for index, note in enumerate(melody_notes):
        chord = chords[(index // 4) % len(chords)]
        for chord_note in chord:
            result.append((0, bytes([0x90, chord_note, 52])))
        result.append((0, bytes([0x90, note, 86])))
        result.append((480, bytes([0x80, note, 0])))
        for chord_note in chord:
            result.append((0, bytes([0x80, chord_note, 0])))
    return result


def main() -> None:
    OUTPUT.mkdir(parents=True, exist_ok=True)
    first_snow = [64, 67, 69, 67, 64, 62, 60, 62, 64, 67, 72, 71, 69, 67, 64, 60]
    blue_breeze = [60, 62, 64, 67, 69, 67, 64, 62, 64, 65, 67, 72, 69, 67, 64, 60]
    morning_waltz = [64, 67, 72, 71, 67, 64, 62, 65, 69, 67, 64, 62, 60, 64, 67, 72]
    (OUTPUT / "first-snow-melody.mid").write_bytes(midi_file(melody(first_snow), 560_000))
    (OUTPUT / "first-snow-accompaniment.mid").write_bytes(
        midi_file(chord_progression([[48, 52, 55], [45, 48, 52], [41, 45, 48], [43, 47, 50]], first_snow), 560_000)
    )
    (OUTPUT / "blue-breeze-walk.mid").write_bytes(midi_file(melody(blue_breeze), 470_000))
    (OUTPUT / "little-morning-waltz.mid").write_bytes(
        midi_file(chord_progression([[48, 52, 55], [43, 47, 50], [45, 48, 52]], morning_waltz), 620_000)
    )


if __name__ == "__main__":
    main()