export type CombinationSearchCard = {
  id: string;
  characterId: string;
};

type BeamState<T extends CombinationSearchCard> = {
  cards: T[];
  score: number;
};

export type CombinationSearchLimits = {
  openSlots: number;
  screeningLimit: number;
  baseExactFinalistLimit: number;
  alternativeExactFinalistLimit: number;
};

export type CombinationScoringStrategy<T extends CombinationSearchCard> = {
  scoreCard: (card: T) => number;
  scoreCombination?: (cards: readonly T[]) => number;
};

const SCREENING_LIMIT_PER_OPEN_SLOT = 5_000;
const EXACT_FINALIST_LIMIT_PER_OPEN_SLOT = 56;

export function withinMediumProbabilityCardLimit(
  cards: readonly { details: { active: readonly { probabilityPercent?: number | null }[] } }[],
  maximum: number | null
): boolean {
  return maximum === null || cards.filter((card) =>
    card.details.active.some((level) => level.probabilityPercent === 46)
  ).length <= maximum;
}

export function combinationSearchLimits(fixedCardCount: number, targetSize = 5): CombinationSearchLimits {
  const normalizedTargetSize = Math.max(1, Math.floor(targetSize));
  const normalizedFixedCardCount = Math.min(normalizedTargetSize, Math.max(0, Math.floor(fixedCardCount)));
  const openSlots = Math.max(1, normalizedTargetSize - normalizedFixedCardCount);
  return {
    openSlots,
    screeningLimit: SCREENING_LIMIT_PER_OPEN_SLOT * openSlots,
    baseExactFinalistLimit: EXACT_FINALIST_LIMIT_PER_OPEN_SLOT * openSlots,
    alternativeExactFinalistLimit: EXACT_FINALIST_LIMIT_PER_OPEN_SLOT * openSlots
  };
}

export function resolveCandidateAwakening(
  configuredAwakening: number,
  owned: boolean,
  ownedAwakening: number
): number {
  return owned ? Math.max(configuredAwakening, ownedAwakening) : configuredAwakening;
}

export function generateCombinationCandidates<T extends CombinationSearchCard>(
  fixedCards: readonly T[],
  candidateCards: readonly T[],
  targetSize: number,
  scoreCard: (card: T) => number,
  beamWidth = 800,
  scoreCombination?: (cards: readonly T[]) => number,
  // Must accept valid partial combinations, as it is checked at every expansion.
  acceptsCombination?: (cards: readonly T[]) => boolean
): T[][] {
  if (targetSize < fixedCards.length) throw new Error('목표 카드 수가 고정 카드 수보다 작습니다.');
  if (new Set(fixedCards.map((card) => card.characterId)).size !== fixedCards.length) {
    throw new Error('같은 멤버를 두 번 고정할 수 없습니다.');
  }
  if (acceptsCombination && !acceptsCombination(fixedCards)) return [];
  const fixedIds = new Set(fixedCards.map((card) => card.id));
  const fixedCharacters = new Set(fixedCards.map((card) => card.characterId));
  const pool = candidateCards.filter((card) => !fixedIds.has(card.id) && !fixedCharacters.has(card.characterId));
  let beam: BeamState<T>[] = [{
    cards: Array.from(fixedCards),
    score: scoreCombination?.(fixedCards) ?? fixedCards.reduce((sum, card) => sum + scoreCard(card), 0)
  }];

  for (let size = fixedCards.length; size < targetSize; size += 1) {
    const expanded = new Map<string, BeamState<T>>();
    for (const state of beam) {
      const usedCharacters = new Set(state.cards.map((card) => card.characterId));
      const usedIds = new Set(state.cards.map((card) => card.id));
      for (const card of pool) {
        if (usedIds.has(card.id)) continue;
        if (usedCharacters.has(card.characterId)) continue;
        const cards = [...state.cards, card];
        if (acceptsCombination && !acceptsCombination(cards)) continue;
        const nextState = {
          cards,
          score: scoreCombination?.(cards) ?? state.score + scoreCard(card)
        };
        const key = nextState.cards.map((entry) => entry.id).sort().join('|');
        if (!expanded.has(key)) expanded.set(key, nextState);
      }
    }
    beam = Array.from(expanded.values())
      .sort((left, right) => right.score - left.score || left.cards.map((card) => card.id).join().localeCompare(right.cards.map((card) => card.id).join()))
      .slice(0, Math.max(1, beamWidth));
    if (beam.length === 0) break;
  }
  return beam
    .filter((state) => state.cards.length === targetSize)
    .sort((left, right) => right.score - left.score)
    .map((state) => state.cards);
}

export function generateAnchoredCombinationCandidates<T extends CombinationSearchCard>(
  fixedCards: readonly T[],
  candidateCards: readonly T[],
  targetSize: number,
  strategies: readonly CombinationScoringStrategy<T>[],
  perAnchorLimit: number,
  acceptsCombination?: (cards: readonly T[]) => boolean
): T[][] {
  if (strategies.length === 0 || perAnchorLimit <= 0 || fixedCards.length >= targetSize) return [];
  const fixedCharacters = new Set(fixedCards.map((card) => card.characterId));
  const anchors = candidateCards.filter((card) => !fixedCharacters.has(card.characterId));
  const perStrategyLimit = Math.max(1, Math.ceil(perAnchorLimit / strategies.length));
  const combined = new Map<string, T[]>();

  for (const anchor of anchors) {
    const anchored = new Map<string, T[]>();
    for (const strategy of strategies) {
      for (const cards of generateCombinationCandidates(
        [...fixedCards, anchor],
        candidateCards,
        targetSize,
        strategy.scoreCard,
        perStrategyLimit,
        strategy.scoreCombination,
        acceptsCombination
      )) {
        anchored.set(cards.map((card) => card.id).sort().join('|'), cards);
      }
    }
    for (const [key, cards] of Array.from(anchored.entries()).slice(0, perAnchorLimit)) {
      combined.set(key, cards);
    }
  }

  return Array.from(combined.values());
}

export function selectMemberDiverseCandidates<T>(
  candidates: readonly T[],
  cardsOf: (candidate: T) => readonly { id: string }[],
  scoreOf: (candidate: T) => number,
  fixedCardIds: readonly string[],
  limit: number
): T[] {
  if (limit <= 0) return [];
  const fixedIds = new Set(fixedCardIds);
  const ranked = [...candidates].sort((left, right) => scoreOf(right) - scoreOf(left));
  const bestByCardId = new Map<string, T>();
  for (const candidate of ranked) {
    for (const card of cardsOf(candidate)) {
      if (!fixedIds.has(card.id) && !bestByCardId.has(card.id)) bestByCardId.set(card.id, candidate);
    }
  }

  const selected = new Map<string, T>();
  for (const candidate of bestByCardId.values()) {
    const key = cardsOf(candidate).map((card) => card.id).sort().join('|');
    selected.set(key, candidate);
    if (selected.size >= limit) break;
  }
  return Array.from(selected.values());
}