"""Source-derived ending geometry, independent of instrument composition."""
import copy
import fractions

import generator.model

BARS = 3

def template(source):
  result = copy.deepcopy(source[-1])
  # An ending is three full bars in the final active meter, never a pickup.
  for change in result.get('attributes', []):
    for key in ('meter', 'key', 'clef', 'transpose', 'staff_details'):
      if key in change:
        result[key] = copy.deepcopy(change[key])
  result.update(duration=generator.model.rational(generator.model.meter_length(result['meter'])), implicit=False,
    attributes=[], harmonies=[], voices=[], tempos=[], section_label='')
  result['time_signature'] = generator.model.meter_label(result['meter'])
  return result

def duration(source):
  return BARS * generator.model.fraction(template(source)['duration']) if source else fractions.Fraction()