from __future__ import annotations

from fractions import Fraction
from pathlib import Path

from generator.guitar import validate_tuning
from generator.model import beat_lengths, fraction, make_event
from generator.pitch import concert_document, shift_pitch
from generator.score import copy_source_voices, make_measure, slugify, source_staff

PART_TYPES = ('acoustic', 'electric', 'vocal')

def source_paths(directory: Path, *, practice: bool = False) -> list[Path]:
  if not directory.is_dir():
    raise ValueError(f'{"practice" if practice else "performance"} source directory not found: {directory}')
  paths = sorted(directory.rglob('*.xml'))
  identities = {}
  for path in paths:
    if practice:
      if path.parent != directory or len(path.stem) != 3 or not path.stem.isascii() or not path.stem.isdecimal():
        raise ValueError(f'{path}: practice sources require a three-digit filename directly under data/practice')
    elif path.parent != directory:
      raise ValueError(f'{path}: performance sources belong directly under data/songs')
    identity = path.stem if practice else slugify(path.stem)
    if identity in identities:
      raise ValueError(f'{identities[identity]} and {path}: conflicting output path {identity}-acoustic.json')
    identities[identity] = path
  return paths

def prepare_document(document: dict, *, practice: bool = False) -> dict:
  validate_source(document, practice=practice)
  return concert_document(document, octave_transposing=True)

def propagated_chords(measures: list[dict], *, include_optional: bool = True) -> list[dict | None]:
  result = []
  current = None
  for measure in measures:
    result.append(current)
    for h in measure.get('harmonies', []):
      if include_optional or not h.get('chord_optional'):
        current = h
  return result

def active_chord(measure: dict, onset: Fraction, previous: dict | None) -> dict | None:
  active = previous
  for h in measure['harmonies']:
    if fraction(h['onset']) > onset:
      break
    active = h
  return active if active and active['kind'] != 'none' else None

def generated_voice(measure: dict, role: str, previous: dict | None) -> list[dict]:
  length = fraction(measure['duration'])
  if role == 'rest':
    return [make_event('rest', Fraction(), length, 'rest', written={'type': 'whole', 'dots': 0}) | {'measure_rest': True}]
  common_time = measure['time_signature'] == '4/4' and not any('meter' in a for a in measure.get('attributes', []))
  if role == 'rhythm' and common_time:
    attacks = [(Fraction(n, 2), Fraction(1, 2)) for n in (0, 3, 4, 5, 7)]
  elif role == 'accompaniment':
    boundaries = sorted({Fraction(), length} | {fraction(h['onset']) for h in measure['harmonies'] if fraction(h['onset']) < length})
    attacks = [(start, end - start) for start, end in zip(boundaries, boundaries[1:])]
  else:
    attacks = []
    states = [(Fraction(), measure['meter'])]
    states.extend((fraction(a['onset']), a['meter']) for a in measure.get('attributes', []) if 'meter' in a)
    for index, (onset, meter) in enumerate(states):
      end = states[index + 1][0] if index + 1 < len(states) else length
      beats = beat_lengths(meter)
      beat_index = 0
      while onset < end:
        beat = min(beats[beat_index % len(beats)] if beats else end - onset, end - onset)
        duration = beat if role == 'slash' or not beats else min(beat / 2, Fraction(1, 2))
        attacks.append((onset, duration))
        onset += beat
        beat_index += 1
  events = []
  cursor = Fraction()
  for onset, duration in attacks:
    if onset >= length:
      break
    if onset > cursor:
      events.append(make_event(f'rest-{len(events)}', cursor, onset - cursor, 'rest'))
    duration = min(duration, length - onset)
    chord = active_chord(measure, onset, previous)
    if role == 'slash':
      event = make_event(f'slash-{len(events)}', onset, duration, 'note')
      event['notehead'] = 'slash'
    elif not chord:
      event = make_event(f'rest-{len(events)}', onset, duration, 'rest')
    else:
      event = make_event(f'chord-{len(events)}', onset, duration, 'note')
      event['_harmony'] = chord
    events.append(event)
    cursor = onset + duration
  if cursor < length:
    events.append(make_event(f'rest-{len(events)}', cursor, length - cursor, 'rest'))
  return events

def validate_source(document: dict, *, practice: bool = False) -> None:
  voices = set()
  for measure in source_staff(document)['measures']:
    for state in [measure, *measure.get('attributes', [])]:
      if state.get('clef', {}).get('sign') in ('TAB', 'percussion'):
        raise ValueError(f'{measure["id"]}: parts require a pitched, non-TAB source')
      if 'staff_details' in state:
        validate_tuning(state, measure['id'])
    for voice in measure['voices']:
      voices.add(voice['id'])
      for note in voice['notes']:
        if practice and len(note['pitches']) > 1:
          raise ValueError(f'{measure["id"]}: practice requires a monophonic melody, not chord stacks')
        if any('tablature' in p or 'unpitched' in p for p in note['pitches']):
          raise ValueError(f'{measure["id"]}: authored TAB and percussion are unsupported')
  if practice and len(voices) > 1:
    raise ValueError('practice requires one monophonic voice')

def build_measure(source: dict, identifier: str, role: str, part: str, previous: dict | None, label: str = '') -> dict:
  voices = copy_source_voices(source, strip_lyrics=role == 'melody') if role in ('vocal', 'melody') else None
  notes = [n for v in voices for n in v['notes']] if voices else generated_voice(source, role, previous)
  if role in ('melody', 'vocal'):
    for note in notes:
      note['pitches'] = [shift_pitch(p, 7, 12) for p in note['pitches']]
  result = make_measure(identifier, source, [] if voices else notes, section_label=label)
  if voices:
    result['voices'] = voices
  result['transpose'] = {'diatonic': 0, 'chromatic': 0, 'octave_change': -1, 'explicit': True}
  result['clef']['octave_change'] = 0
  for change in result.get('attributes', []):
    change.pop('transpose', None)
    if 'clef' in change:
      change['clef']['octave_change'] = 0
  if part != 'vocal':
    result['clef'] = {'sign': 'G', 'line': 2, 'octave_change': 0}
    result['staff_details'] = {'lines': 5, 'tunings': [], 'capo': 0}
    for change in result.get('attributes', []):
      change.pop('clef', None)
      change.pop('staff_details', None)
  return result