"""Bounded comparison of completed source-related phrases."""
import collections
import dataclasses
import fractions
import time
import generator.solo.phrases
import generator.solo.selection
import generator.solo.sequences
import generator.solo.policy
import generator.vocabulary


class SearchExhausted(ValueError):
  pass


@dataclasses.dataclass(frozen=True)
class State:
  phrases: tuple = ()
  home: tuple = ()
  total: fractions.Fraction = fractions.Fraction()

  @property
  def notes(self):
    return tuple(n for p in self.phrases for n in p.notes)


class Builder:
  def __init__(self,analysis,measures,harmony,sequences,rhythms,end,seed,enabled=True,*,start=fractions.Fraction()):
    self.analysis,self.harmony = analysis,harmony
    self.start,self.end,self.seed = start,end,seed
    self.phrases = generator.solo.phrases.Phrases(analysis,harmony,sequences,rhythms,start,end,seed,enabled)
    self.rules = generator.vocabulary.data('solo')['search']
    self.timings = {}; self.frontiers = []; self.coverage = collections.defaultdict(collections.Counter); self.decisions = []
    self.failures = self.phrases.rejections

  def candidates(self,start,end,state):
    incoming = state.notes[-1] if state.notes else None
    values = {}
    for variant in range(self.rules['alternatives']):
      value = self.phrases.make(start,end,incoming,state.home,state.phrases,variant)
      if value is not None:
        phrase,introduced = value
        self.coverage[phrase.purpose]['valid'] += 1
        key = tuple((n.start,n.end,n.pitch.number()) for n in phrase.notes)
        values.setdefault(key,value)
    for phrase,_ in values.values():
      self.coverage[phrase.purpose]['distinct'] += 1
    return tuple(values.values())

  def rank(self,state):
    return state.total,generator.solo.policy.stable_rank(self.seed,tuple((n.start,n.end,n.pitch.number()) for n in state.notes))

  def compose(self):
    began = time.monotonic(); self.frontiers = []; self.decisions = []
    states = (State(),); start = self.start
    while start<self.end:
      end = self.phrases.horizon(start)
      successors = []
      for state in states:
        for phrase,introduced in self.candidates(start,end,state):
          total = state.total+phrase.evaluation.total*(end-start)
          successors.append(State((*state.phrases,phrase),state.home or (introduced if start>=0 and len(introduced)>=3 else ()),total))
      if not successors:
        raise SearchExhausted(f'No valid complete phrase at {start}–{end}; failures: {dict(self.failures)}')
      successors.sort(key=self.rank)
      states = tuple(generator.solo.sequences.diverse(successors,self.rank,
        lambda s:(s.phrases[-1].purpose,s.phrases[-1].direction,s.phrases[-1].ending),self.rules['histories']))
      for state in states:
        self.coverage[state.phrases[-1].purpose]['retained_histories'] += 1
      self.frontiers.append({'start':str(start),'end':str(end),'completed':len(successors),'retained':len(states),'best':str(min(s.total for s in states))})
      start = end
    self.completed = tuple(sorted(states,key=self.rank))
    winner = self.completed[0]
    self.timings['phrase_search_seconds'] = time.monotonic()-began
    self.winner_evaluation = generator.solo.selection.evaluate(winner.notes,self.start,self.end,self.harmony,
      home=winner.home,contracts=tuple(c for p in winner.phrases for c in p.expressions),center=self.phrases.center)
    for k,v in self.phrases.proposals.items():
      self.coverage[k]['proposed'] = v
    for p in winner.phrases:
      self.coverage[p.purpose]['selected'] += 1
    self.decisions = [{'start':str(p.start),'end':str(p.end),'purpose':p.purpose,'ending':p.ending,'evaluation':dataclasses.asdict(p.evaluation)} for p in winner.phrases]
    return winner.phrases