from __future__ import annotations

from itertools import product

from generator.transposition import mod12
from generator import harmony
from generator.model import NATURAL, alteration
from generator.guitar import MAX_FRET, MIN_FRET, STANDARD_TUNING, TabPosition, WRITTEN_GUITAR_OCTAVE_OFFSET, within_fret_span

def chord_pitch_classes(symbol: str | dict) -> tuple[int, ...]:
  return harmony.pitch_classes(harmony.parse_symbol(symbol) if isinstance(symbol, str) else symbol)

def positions_for_string(string_number: int, open_midi: int, pitch_classes: tuple[int, ...]) -> list[TabPosition]:
  result: list[TabPosition] = []
  for fret in range(MIN_FRET, MAX_FRET + 1):
    midi = open_midi + fret
    if mod12(midi) in pitch_classes:
      result.append(TabPosition(string_number, fret, midi))
  return result

def candidate_score(candidate: tuple[TabPosition, ...], pitch_classes: tuple[int, ...]) -> int:
  fretted = [position.fret for position in candidate if position.fret > 0]
  if not fretted:
    span = 0
    low = 0
  else:
    span = max(fretted) - min(fretted)
    low = min(fretted)
  covered = {mod12(position.midi) for position in candidate}
  missing = len(set(pitch_classes) - covered)
  open_penalty = sum(1 for position in candidate if position.fret == 0)
  return missing * 1000 + span * 80 + abs(low - 5) * 12 + open_penalty * 8 + sum(position.fret for position in candidate)

def find_playable_voicing(symbol: str | dict) -> list[TabPosition]:
  definition = harmony.parse_symbol(symbol) if isinstance(symbol, str) else symbol
  semantic_degrees = harmony.degrees(definition)
  voicing = dict(semantic_degrees)
  if 7 in voicing and voicing.get(5) == 0:
    del voicing[5]
  if len(voicing) > 4:
    for degree in (11, 9, 5):
      if len(voicing) > 4 and voicing.get(degree) == 0:
        del voicing[degree]
  root = definition.get('root', {'letter': 'c', 'alter': 0})
  root_pc = NATURAL[root['letter']] + alteration(root['alter'])
  pitch_classes = tuple(dict.fromkeys((root_pc + harmony.degree_semitones(d, a)) % 12 for d, a in voicing.items()))
  bass = definition.get('bass')
  bass_pc = (NATURAL[bass['letter']] + alteration(bass['alter'])) % 12 if bass else None
  if bass_pc is not None and bass_pc not in pitch_classes:
    pitch_classes += (bass_pc,)
  if not pitch_classes:
    return []
  string_sets = ((6, 4, 3, 2), (5, 4, 3, 2), (4, 3, 2, 1), (6, 5, 4, 3), (5, 3, 2, 1))
  by_string = {string_number: positions_for_string(string_number, open_midi, pitch_classes) for string_number, open_midi in STANDARD_TUNING}
  best: tuple[TabPosition, ...] | None = None
  best_score = 10**9
  for string_set in string_sets:
    options = [by_string[string_number] for string_number in string_set]
    if any(not item for item in options):
      continue
    for candidate in product(*options):
      if bass_pc is not None and min(candidate, key=lambda p: p.midi).midi % 12 != bass_pc:
        continue
      if not within_fret_span(candidate):
        continue
      covered = {mod12(position.midi) for position in candidate}
      if not set(pitch_classes).issubset(covered):
        continue
      score = candidate_score(candidate, pitch_classes)
      if score < best_score:
        best = candidate
        best_score = score
  return sorted(best or [], key=lambda item: item.midi)

def pitches_for_voicing(symbol: str | dict) -> list[dict[str, int | str]]:
  definition = harmony.parse_symbol(symbol) if isinstance(symbol, str) else symbol
  from generator.transposition import shift_pitch
  root = definition.get('root', {'letter': 'c', 'alter': 0})
  spellings = {}
  for degree, alter in harmony.degrees(definition).items():
    p = shift_pitch(root, degree - 1, harmony.degree_semitones(degree, alter))
    spellings[(NATURAL[p['letter']] + alteration(p['alter'])) % 12] = p
  if bass := definition.get('bass'):
    spellings[(NATURAL[bass['letter']] + alteration(bass['alter'])) % 12] = bass
  result = []
  for position in find_playable_voicing(definition):
    midi = position.midi + WRITTEN_GUITAR_OCTAVE_OFFSET
    p = spellings[midi % 12].copy()
    p['octave'] = int((midi - NATURAL[p['letter']] - alteration(p['alter'])) // 12 - 1)
    result.append(p)
  return result