from __future__ import annotations

import dataclasses
import fractions

import generator.model

@dataclasses.dataclass(frozen=True)
class ChordSpan:
  start: fractions.Fraction
  end: fractions.Fraction
  measure: int
  source_measure: str
  beat: fractions.Fraction
  key: dict
  chord: dict | None

def read(staff: dict, *, initial: dict | None = None) -> tuple[ChordSpan, ...]:
  result = []
  absolute = fractions.Fraction()
  active = initial
  for number, measure in enumerate(staff['measures'], 1):
    length = generator.model.fraction(measure['duration'])
    harmonies = {generator.model.fraction(h['onset']): h for h in measure['harmonies']}
    changes = {generator.model.fraction(a['onset']): a['key'] for a in measure.get('attributes', []) if 'key' in a}
    boundaries = sorted({fractions.Fraction(), length} | set(harmonies) | set(changes))
    key = measure['key']
    for start, end in zip(boundaries, boundaries[1:]):
      key = changes.get(start, key)
      active = harmonies.get(start, active)
      result.append(ChordSpan(absolute + start, absolute + end, number, str(measure['number']), start + 1, key, active if active and active['kind'] != 'none' else None))
    absolute += length
  return tuple(result)