"""Accepted, paired pitch/rhythm examples; production uses contextual profiles."""
from __future__ import annotations

import dataclasses
import fractions
import hashlib
import json
import pathlib

import generator.harmony
import generator.model
import generator.solo.types as types

F = fractions.Fraction

@dataclasses.dataclass(frozen=True)
class ReferencePhrase:
  id: str
  version: str
  notes: tuple[types.Note, ...]
  decorated: tuple[types.Note, ...]
  duration: F
  tonic: int
  harmony: tuple[tuple[F, str], ...]
  features: tuple[tuple[str, F, F], ...]
  runs: tuple[tuple[F, F], ...]
  acceptance: str
  development: tuple[tuple[str, F, F, tuple[int, ...]], ...] = ()
  def windows(self):
    # Windows retain their parent and context; they are not separate approvals.
    result = []
    for length in (F(8), F(16)):
      for start in range(0, int(self.duration), int(length)):
        end = min(self.duration, start + length)
        selected = tuple(dataclasses.replace(n, start=n.start - start, end=n.end - start) for n in self.notes if start <= n.start and n.end <= end)
        if len(selected) >= 2:
          chords = tuple(chord for time, chord in self.harmony if start <= time < end)
          result.append(types.Motif(f'{self.id}:{start}:{end}', selected, end - start, chords, 'accepted reference profile'))
    return tuple(result)

def read(path):
  raw = path.read_bytes()
  data = json.loads(raw)
  if data['pitch_convention'] != 'sounding' or not data.get('acceptance'):
    raise ValueError(f'{path}: reference requires sounding pitches and explicit acceptance provenance')

  def notes(variant):
    result, cursor = [], F()
    for i, event in enumerate(data['variants'][variant]['events']):
      start, duration = F(event['onset_beats']), F(event['duration_beats'])
      if start != cursor or duration <= 0:
        raise ValueError(f'{path}: reference events must fill exact sequential time')
      cursor = start + duration
      if event['pitch'] is None:
        continue
      name = event['pitch']
      pitch = types.Pitch(name[0].lower(), F(1 if '#' in name else -1 if 'b' in name else 0), int(name[-1]))
      if pitch.number() != event['midi_pitch']:
        raise ValueError(f'{path}: inconsistent sounding pitch {name}')
      result.append(types.Note(start, cursor, pitch, (data['id'],), event_id=f'{variant}_{i}'))
    return tuple(result), cursor

  plain, duration = notes('lead_theme')
  decorated, other_duration = notes('lead_with_runs')
  if duration != other_duration or len(plain) != data['variants']['lead_theme']['attacks'] or len(decorated) != data['variants']['lead_with_runs']['attacks']:
    raise ValueError(f'{path}: inconsistent reference variants')
  tonic = generator.model.parse_pitch_name(data['tonic'])
  number = int(generator.model.NATURAL[tonic['letter']] + generator.model.alteration(tonic['alter']))
  harmony = tuple((F(4 * (h['bar'] - 1)), h['chord']) for h in data['harmony'])
  for _, chord in harmony:
    generator.harmony.parse_symbol(chord)
  return ReferencePhrase(data['id'], hashlib.sha256(raw).hexdigest(), plain, decorated, duration, number, harmony,
    tuple((f['id'], F(f['start']), F(f['end'])) for f in data['features']), tuple((F(w['start']), F(w['end'])) for w in data['run_windows']), data['acceptance'],
    tuple((d['role'], F(d['start']), F(d['end']), tuple(d.get('degrees', ()))) for d in data.get('development', ())))

def load_library(root: pathlib.Path):
  return tuple(read(path) for path in sorted(root.glob('*.json')))

def identifying_features(notes, source):
  """Select a characteristic leap followed by return, wherever it occurs."""
  notes = tuple(notes)
  candidates = []
  for i in range(len(notes) - 2):
    a, b, c = notes[i:i + 3]
    leap, reply = b.pitch.number() - a.pitch.number(), c.pitch.number() - b.pitch.number()
    if 3 <= abs(leap) <= 9 and leap * reply < 0 and c.start - a.start <= 4:
      group = notes[i:min(len(notes), i + 4)]
      rhythm = tuple((n.start - a.start, n.end - n.start) for n in group)
      intervals = tuple(y.pitch.number() - x.pitch.number() for x, y in zip(group, group[1:]))
      candidates.append(types.IdentifyingFeature(a.event_id + '_identity', tuple(n.event_id for n in group), rhythm, intervals, source))
  return tuple(candidates[:1])

def feature_error(feature, notes):
  by_id = {n.event_id: n for n in notes}
  actual = [by_id.get(identity) for identity in feature.events]
  if not all(actual):
    return 1.0
  first = actual[0].start
  rhythm = tuple((n.start - first, n.end - n.start) for n in actual)
  movement = tuple(b.pitch.number() - a.pitch.number() for a, b in zip(actual, actual[1:]))
  timing = sum(a != b for a, b in zip(rhythm, feature.rhythm)) / max(1, len(rhythm))
  contour = sum(((a > 0) - (a < 0)) != ((b > 0) - (b < 0)) or abs(a - b) > 2 for a, b in zip(movement, feature.intervals)) / max(1, len(movement))
  return (timing + contour) / 2

def relationship(notes, reference):
  """One joint relationship cost: timed movement, not absolute-pitch copying."""
  notes = tuple(notes)
  if len(notes) < 2 or len(reference.notes) < 2:
    return 0.0 if len(notes) == len(reference.notes) == 1 else 1.0
  actual = tuple(b.pitch.number() - a.pitch.number() for a, b in zip(notes, notes[1:]))
  expected = reference.contour()
  count = min(len(actual), len(expected))
  contour = sum(0.75 * (((a > 0) - (a < 0)) != ((b > 0) - (b < 0))) + 0.25 * min(1, max(0, abs(a - b) - 2) / 7) for a, b in zip(actual, expected)) / max(1, count)
  start, ref_start = notes[0].start, reference.notes[0].start
  rhythm = sum(min(1, float(abs((n.start - start) - (r.start - ref_start))) / 2) for n, r in zip(notes, reference.notes)) / min(len(notes), len(reference.notes))
  evidence = max(0, min(3, len(reference.notes)) - len(notes)) / 3
  return max(evidence, (contour + rhythm) / 2)