from __future__ import annotations

import dataclasses
import fractions
import pathlib
import types

import generator.model
import generator.musicxml

@dataclasses.dataclass(frozen=True)
class Event:
  onset: fractions.Fraction
  duration: fractions.Fraction
  sounding: bool
  written_type: str
  dots: int = 0
  beams: tuple[tuple[int, str], ...] = ()
  continuation: bool = False
  ratio: fractions.Fraction = fractions.Fraction(1)

@dataclasses.dataclass(frozen=True)
class Bar:
  events: tuple[Event, ...]
  length: fractions.Fraction
  def attacks(self) -> tuple[fractions.Fraction, ...]:
    return tuple(e.onset for e in self.events if e.sounding and not e.continuation)
  def beat(self, number: int) -> tuple:
    return tuple((max(e.onset, number) - number, min(e.onset + e.duration, number + 1) - max(e.onset, number), e.sounding, e.continuation or e.onset < number) for e in self.events if e.onset < number + 1 and e.onset + e.duration > number)

@dataclasses.dataclass(frozen=True)
class Snippet:
  id: str
  meter: str
  bars: tuple[Bar, ...]

@dataclasses.dataclass(frozen=True, init=False)
class Library:
  snippets: types.MappingProxyType
  def __init__(self, snippets: tuple[Snippet, ...]):
    grouped = {}
    identities = set()
    for snippet in sorted(snippets, key=lambda s: s.id):
      if snippet.id in identities:
        raise ValueError(f'duplicate rhythm identity: {snippet.id}')
      identities.add(snippet.id)
      grouped.setdefault(snippet.meter, []).append(snippet)
    object.__setattr__(self, 'snippets', types.MappingProxyType({meter: tuple(values) for meter, values in grouped.items()}))
  def for_meter(self, meter: str) -> tuple[Snippet, ...]:
    if meter not in ('2/4', '3/4', '4/4', '5/4') or meter not in self.snippets:
      raise ValueError(f'accompaniment requires rhythm snippets for {meter}; supported meters are 2/4, 3/4, 4/4, and 5/4')
    return self.snippets[meter]

def read_snippet(path: pathlib.Path, identifier: str) -> Snippet:
  document = generator.musicxml.load_musicxml(path)
  staff = document['staves'][0]
  if len(staff['measures']) not in (1, 2):
    raise ValueError(f'{path}: rhythm snippets require one or two bars')
  meter = staff['measures'][0]['time_signature']
  bars = []
  for measure in staff['measures']:
    length = generator.model.fraction(measure['duration'])
    if measure['time_signature'] != meter or length != generator.model.meter_length(measure['meter']):
      raise ValueError(f'{path}, measure {measure["number"]}: rhythm bars must be complete and use one meter')
    if len(measure['voices']) != 1 or any('meter' in a for a in measure.get('attributes', [])):
      raise ValueError(f'{path}: rhythm snippets require one voice without meter changes')
    events = []
    cursor = fractions.Fraction()
    for note in measure['voices'][0]['notes']:
      onset, duration = generator.model.fraction(note['onset']), generator.model.fraction(note['duration'])
      if onset != cursor or duration <= 0 or note.get('grace') or note['kind'] not in ('note', 'rest') or note.get('tremolo'):
        raise ValueError(f'{path}, measure {measure["number"]}: rhythm events must fill the bar sequentially')
      events.append(Event(onset, duration, note['kind'] == 'note', note['written']['type'], note['written'].get('dots', 0), tuple((b['level'], b['type']) for b in note.get('beams', [])), any('tie_from' in p for p in note['pitches']), generator.model.fraction(note['written'].get('ratio',generator.model.rational(1)))))
      cursor += duration
    if cursor != length:
      raise ValueError(f'{path}: rhythm events do not fill the bar')
    bars.append(Bar(tuple(events), length))
  return Snippet(identifier, meter, tuple(bars))

def load_library(root: pathlib.Path) -> Library:
  if not root.is_dir():
    raise ValueError(f'{root}: rhythm library not found')
  snippets = []
  for path in sorted(root.rglob('*.xml')):
    relative = path.relative_to(root)
    if len(relative.parts) != 3 or relative.parts[0] not in ('2_4', '3_4', '4_4', '5_4') or relative.parts[1] not in ('1', '2', '3'):
      raise ValueError(f'{path}: rhythm sources belong under meter/series')
    snippet = read_snippet(path, relative.as_posix())
    if snippet.meter != relative.parts[0].replace('_', '/'):
      raise ValueError(f'{path}: rhythm meter disagrees with its directory')
    snippets.append(snippet)
  if not snippets:
    raise ValueError(f'{root}: rhythm library is empty')
  return Library(tuple(snippets))