from __future__ import annotations

import dataclasses
import fractions
import functools

import generator.fretboard
import generator.solo.types

def travel(previous: generator.solo.types.Note | None, current: generator.solo.types.Note, tempo: fractions.Fraction) -> int:
  if previous is None:
    return 0
  return transition(previous.position, current.position, current.start - previous.start, tempo)

@functools.lru_cache(maxsize=16384)
def transition(previous, current, duration, tempo):
  distance = abs(previous.fret - current.fret) + abs(previous.string_number - current.string_number)
  seconds = float(duration * 60 / tempo)
  # Movement is a preference, not an unsupported claim about a player's limits.
  return round(100 * distance / max(seconds, 0.05))

@functools.lru_cache(maxsize=4096)
def place(notes: tuple[generator.solo.types.Note, ...], tempo: fractions.Fraction, previous: generator.solo.types.Note | None = None) -> tuple[int, tuple[generator.solo.types.Note, ...]] | None:
  states = [(0, ())]
  for note in notes:
    following = []
    for position in positions(note.pitch.number()):
      current = dataclasses.replace(note, position=position)
      candidates = []
      for cost, path in states:
        prior = path[-1] if path else previous
        if note.continuation and (prior is None or prior.pitch != note.pitch or prior.position != position or prior.end != note.start):
          continue
        candidates.append((cost + (0 if note.continuation else travel(prior, current, tempo)), (*path, current)))
      if candidates:
        following.append(min(candidates, key=lambda item: (item[0], tuple(n.position for n in item[1]))))
    if not following:
      return None
    states = following
  return min(states, key=lambda item: (item[0], tuple(n.position for n in item[1])))

@functools.lru_cache(maxsize=128)
def positions(number: int):
  return generator.fretboard.positions_for_pitch(fractions.Fraction(number))