"""Four-fret hand windows shared by chord and single-note placement.

This describes playable regions, not an anatomical fingering solver. Chord
and single tones may occupy any frets within the window. Only shifting the
window is movement. Actual sounded-note limits remain in fretboard.py.
"""
import functools
import typing

import generator.fretboard

VERSION = 'hand-window-2'

class Motion(typing.NamedTuple):
  shift: int = 0
  fingers: int = 0
  strings: int = 0
  @property
  def ergonomics(self):
    return self.fingers + self.strings

def base(shape):
  return min((p.fret for p in shape), default=0)

@functools.lru_cache(maxsize=4096)
def regions(shape):
  if not shape:
    return tuple([0])
  return tuple(range(max(1, max(p.fret for p in shape) - 3), min(base(shape), generator.fretboard.MAX_ANCHOR_FRET) + 1))

@functools.lru_cache(maxsize=32768)
def motion(previous, current, old_hand, hand, acoustic=False):
  if not previous or not current:
    return Motion()
  if len(previous) == len(current) == 1:
    pairs = ((previous[0], current[0]),)
    unmatched = 0
  else:

    def voices(shape):
      return {('bass' if acoustic and p.string_number in (5, 6) else p.string_number): p for p in shape}

    a, b = voices(previous), voices(current)
    pairs = tuple((a[s], b[s]) for s in a.keys() & b.keys())
    unmatched = len(a.keys() ^ b.keys())
  return Motion(abs(hand - old_hand),
    unmatched + sum(abs((a.fret - old_hand) - (b.fret - hand)) for a, b in pairs),
    sum(abs(a.string_number - b.string_number) for a, b in pairs))

def summary(shifts):
  shifts = tuple(shifts)
  return {'total_travel': sum(shifts), 'shift_count': sum(s > 0 for s in shifts), 'largest_shift': max(shifts, default=0)}