"""Sounding-register references and hard solo instrument domains."""
from __future__ import annotations

import dataclasses
from fractions import Fraction as F

import generator.fretboard
import generator.vocabulary


@dataclasses.dataclass(frozen=True)
class Instrument:
  part: str = ''
  strings: tuple[int, ...] = (1, 2, 3, 4, 5, 6)
  reference: int | None = None
  melody_range: tuple[int, int] | None = None

  @property
  def register(self):
    tuning = [p for s, p in generator.fretboard.STANDARD_TUNING if s in self.strings]
    return min(tuning) + 1, max(tuning) + 12

  def permits(self, number):
    return any(p.string_number in self.strings for p in generator.fretboard.single_positions_for_pitch(F(number)))

  def cost(self, number):
    return .5 * min(1., max(0, abs(number - self.reference) - 7) / 12) if self.reference is not None else 0.


UNRESTRICTED = Instrument()


def weighted_center(notes):
  values = sorted((n.pitch.number(), n.end - n.start) for n in notes)
  total = sum((d for _, d in values), F())
  elapsed = F()
  for number, duration in values:
    elapsed += duration
    if elapsed >= total / 2:
      return number
  return 60


def for_part(part, analysis=None):
  if part not in ('acoustic', 'electric'):
    raise ValueError('unknown solo instrument: ' + part)
  strings = (1, 2, 3, 4, 5, 6)
  if analysis is None or not analysis.melody:
    return Instrument(part, strings)
  # Analysis contains the prepared concert source. Electric melody is written
  # two octaves up and sounds one down (parts.build_measure), hence +12.
  # Use the source voice, never the highest added harmonization voice.
  shift = generator.vocabulary.role(part + '_solo').get('register_offset', 12 if part == 'electric' else 0)
  notes = tuple(n for n in analysis.melody if n.end > analysis.body_offset)
  return Instrument(part, strings, weighted_center(notes) + shift,
    (min(n.pitch.number() for n in notes) + shift, max(n.pitch.number() for n in notes) + shift))