"""MIDI serialization: write ChartData to a GH-format .mid file."""

import mido

from midmid.datatypes import ChartData, NoteEvent

DIFFICULTY_OFFSETS = {"easy": 60, "medium": 72, "hard": 84, "expert": 96}
HOPO_NOTE = {"easy": 65, "medium": 77, "hard": 89, "expert": 101}
NOTE_VELOCITY = 100


def write_midi(chart: ChartData, output_path: str) -> None:
    mid = mido.MidiFile(ticks_per_beat=chart.resolution)

    mid.tracks.append(_build_tempo_track(chart))
    mid.tracks.append(_build_events_track(chart))
    mid.tracks.append(_build_guitar_track(chart))
    if chart.beats:
        mid.tracks.append(_build_beat_track(chart))

    mid.save(output_path)


def _build_tempo_track(chart):
    track = mido.MidiTrack()
    events = []

    for tick, bpm in chart.tempo_events:
        events.append((tick, mido.MetaMessage(
            "set_tempo", tempo=mido.bpm2tempo(bpm), time=0)))

    for tick, num, den in chart.time_signatures:
        events.append((tick, mido.MetaMessage(
            "time_signature", numerator=num, denominator=den, time=0)))

    _write_sorted_events(track, events)
    return track


def _build_events_track(chart):
    track = mido.MidiTrack()
    track.append(mido.MetaMessage("track_name", name="EVENTS", time=0))

    events = []
    for tick, label in chart.sections:
        events.append((tick, mido.MetaMessage(
            "text", text=f"[section {label}]", time=0)))

    _write_sorted_events(track, events)
    return track


def _build_guitar_track(chart):
    track = mido.MidiTrack()
    track.append(mido.MetaMessage("track_name", name="PART GUITAR", time=0))

    events = []
    for difficulty, offset in DIFFICULTY_OFFSETS.items():
        if difficulty not in chart.notes:
            continue

        for note in chart.notes[difficulty]:
            for fret in note.fret_set:
                midi_note = offset + fret
                events.append((note.tick, mido.Message(
                    "note_on", note=midi_note, velocity=NOTE_VELOCITY, time=0)))
                off_tick = note.tick + max(note.sustain_ticks, 1)
                events.append((off_tick, mido.Message(
                    "note_off", note=midi_note, velocity=0, time=0)))

            if note.is_hopo:
                hopo_note = HOPO_NOTE[difficulty]
                events.append((note.tick, mido.Message(
                    "note_on", note=hopo_note, velocity=NOTE_VELOCITY, time=0)))
                events.append((note.tick + 1, mido.Message(
                    "note_off", note=hopo_note, velocity=0, time=0)))

    _write_sorted_events(track, events)
    return track


def _build_beat_track(chart):
    track = mido.MidiTrack()
    track.append(mido.MetaMessage("track_name", name="BEAT", time=0))

    events = []
    for tick, is_downbeat in chart.beats:
        midi_note = 12 if is_downbeat else 13
        events.append((tick, mido.Message(
            "note_on", note=midi_note, velocity=NOTE_VELOCITY, time=0)))
        events.append((tick + 1, mido.Message(
            "note_off", note=midi_note, velocity=0, time=0)))

    _write_sorted_events(track, events)
    return track


def _write_sorted_events(track, events):
    events.sort(key=lambda e: e[0])
    prev_tick = 0
    for abs_tick, msg in events:
        msg.time = abs_tick - prev_tick
        track.append(msg)
        prev_tick = abs_tick