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

import copy
import fractions

import generator.accompaniment
import generator.acoustic
import generator.acoustic_voicing
import generator.electric
import generator.guitar
import generator.fretboard
import generator.model
import generator.parts
import generator.score
import generator.arrange.form
import generator.arrange.pickup

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):
  """Compare music, not generated IDs, at every reused form position."""
  authored = generator.score.source_staff(source)['measures']
  result = {}
  for part, document in documents.items():
    if part == 'vocal':
      continue
    sections = generator.arrange.form.full_arrangement_sections(authored, part)
    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 != 'accompaniment':
          continue
        m = measures[offset + j]
        if 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
        key = (section.source_measure_index + j, repr(harmonic_key(m, carried[offset + j])))
        signature = tuple((generator.model.fraction(n['onset']), generator.model.fraction(n['duration']),
          tuple((generator.model.pitch_number(p), p['tablature']['string'], p['tablature']['fret']) for p in n['pitches']))
          for n in generator.score.measure_notes(m))
        if key in seen:
          if signature != seen[key]:
            raise ValueError(f'{part}, arrangement measure {m["number"]}: canonical accompaniment changed')
          reused += 1
        else:
          if any(k[0] == key[0] for k in seen):
            exceptions.append({'measure': m['number'], 'reason': 'changed effective harmony or duration'})
          seen[key] = signature
      offset += section.measure_count
    result[part] = {'reused_bars': reused, 'distinct_form_bars': len(seen), 'exceptions': exceptions}
  return result