"""One learned accompaniment per instrument, reused at authored form positions."""
from __future__ import annotations

import fractions

import generator.accompaniment
import generator.arrange.form
import generator.arrange.pickup
import generator.model
import generator.score

def harmonic_key(measure, previous):

  def key(chord):
    return repr({k: chord.get(k) for k in ('root', 'kind', 'degrees', 'bass', 'inversion')}) if chord else ''

  active = generator.accompaniment.active_chord(measure, fractions.Fraction(), previous)
  return (key(active), tuple((generator.model.fraction(h['onset']), key(h)) for h in measure['harmonies']
    if generator.model.fraction(h['onset']) > 0), measure['duration'], measure['time_signature'])

def audit(source, documents, *, role_documents=False):
  """Compare music, not generated IDs, at every reused form position."""
  authored = generator.score.source_staff(source)['measures']
  result = {}
  for name, document in documents.items():
    part = name.split('_')[0] if role_documents else name
    wanted = {'solo': 'slash', 'melody': 'vocal' if part == 'vocal' else 'melody'}.get(name.split('_')[-1], 'accompaniment') if role_documents else 'accompaniment'
    if part == 'vocal' and not role_documents:
      continue
    sections = generator.arrange.form.full_arrangement_sections(authored, part)
    entry_positions = {s.source_measure_index for s in sections if s.role == wanted}
    measures = document['staves'][0]['measures']
    carried = generator.accompaniment.carried_chords(measures)
    seen, exceptions, offset, reused = {}, [], 0, 0
    for si, section in enumerate(sections):
      following = sections[si + 1] if si + 1 < len(sections) else None
      for j in range(section.measure_count):
        if section.role != wanted:
          continue
        m = measures[offset + j]
        if wanted == 'accompaniment' and j == section.measure_count - 1 and following and following.role == 'melody' and generator.arrange.pickup.enters(following, authored):
          exceptions.append({'measure': m['number'], 'reason': 'protected melody pickup'})
          continue
        if wanted == 'accompaniment' and j == section.measure_count - 1 and following and following.role == 'slash' and generator.score.body_start_measure_index(authored):
          exceptions.append({'measure': m['number'], 'reason': 'source-defined solo pickup allocation'})
          continue
        position = section.source_measure_index + j
        # A complete figure depends on both measures' effective harmony and
        # source-defined participation. Changed final turnarounds/pickups are
        # explicit contexts, not incidental changes between iterations.
        first = generator.score.body_start_measure_index(authored)
        block_start = first + 2 * ((position - first) // 2)
        neighbors = range(max(section.source_measure_index, block_start), min(section.source_measure_index + section.measure_count, block_start + 2))
        context = tuple(repr(harmonic_key(measures[offset + k - section.source_measure_index], carried[offset + k - section.source_measure_index])) for k in neighbors)
        boundary = following.role if following and block_start + 2 >= section.source_measure_index + section.measure_count and generator.score.body_start_measure_index(authored) and following.role in ('slash', 'melody') else ''
        key = (position, context, boundary)
        signature = tuple((v['id'], generator.model.fraction(n['onset']), generator.model.fraction(n['duration']),
          tuple((generator.model.pitch_number(p), generator.model.fraction(p['duration']), p.get('tablature', {}).get('string'), p.get('tablature', {}).get('fret'), bool(p.get('tie_from')) if position not in entry_positions or generator.model.fraction(n['onset']) else False, bool(p.get('tie_to'))) for p in n['pitches']))
          for v in m['voices'] for n in v['notes'])
        if key in seen:
          if signature != seen[key]:
            raise ValueError(f'{name}, arrangement measure {m["number"]}: canonical {wanted} changed')
          reused += 1
        else:
          if any(k[0] == key[0] for k in seen):
            exceptions.append({'measure': m['number'], 'reason': 'changed two-bar harmony, duration, or protected participation'})
          seen[key] = signature
      offset += section.measure_count
    result[name] = {'reused_bars': reused, 'distinct_form_bars': len(seen), 'exceptions': exceptions}
  return result