import { Player } from "./Player";
  
interface PairingResult {
    playerId: string;
    opponentId: string;
    isResting: boolean; // 是否为轮空玩家
  }
  
  class Matchmaker {
    private mPlayers: Map<string, Player>;
    private currentRound: number = 0;
    private restingHistory: Map<string, number> = new Map(); // 记录每个玩家的轮空次数
  
    constructor(players: Map<string, Player>) {
      this.mPlayers = players;
    }
  
    /**
     * 为当前轮次生成配对
     * @returns 配对结果数组
     */
    public generatePairings(): PairingResult[] {
      const playerIds = Array.from(this.mPlayers.keys()); // 只使用当前存活的玩家
      const playerCount = playerIds.length;
      
      if (playerCount === 0) {
        return [];
      }
      
      if (playerCount === 1) {
        // 只有一个玩家时，与自己配对（轮空）
        return [{
          playerId: playerIds[0],
          opponentId: playerIds[0],
          isResting: true
        }];
      }
  
      const pairings = this.createRandomPairings(playerIds);
      this.currentRound++;
      
      return pairings;
    }
  
    /**
     * 创建随机配对 - 使用 Fisher-Yates 洗牌算法
     * @param playerIds 玩家ID数组
     * @returns 配对结果
     */
    private createRandomPairings(playerIds: string[]): PairingResult[] {
      const playerCount = playerIds.length;
      const isOddCount = playerCount % 2 === 1;
      
      // 如果是奇数，需要找一个玩家轮空
      let restingPlayer: string | null = null;
      let activePlayers = [...playerIds];
      
      if (isOddCount) {
        restingPlayer = this.selectRestingPlayer(playerIds);
        activePlayers = playerIds.filter(id => id !== restingPlayer);
      }
  
      // Fisher-Yates 洗牌算法 - O(n) 时间复杂度
      const shuffled = this.shuffleArray(activePlayers);
      
      const pairings: PairingResult[] = [];
      
      // 按顺序两两配对 - O(n) 时间复杂度
      for (let i = 0; i < shuffled.length; i += 2) {
        if (i + 1 < shuffled.length) {
          const player1 = shuffled[i];
          const player2 = shuffled[i + 1];
          
          pairings.push({
            playerId: player1,
            opponentId: player2,
            isResting: false
          });
          pairings.push({
            playerId: player2,
            opponentId: player1,
            isResting: false
          });
        }
      }
  
      // 处理轮空玩家
      if (restingPlayer) {
        const ghostOpponent = this.selectGhostOpponent(restingPlayer, playerIds);
        pairings.push({
          playerId: restingPlayer,
          opponentId: ghostOpponent,
          isResting: true
        });
      }
  
      return pairings;
    }
    
    /**
     * Fisher-Yates 洗牌算法 - 完全随机且高效
     * @param array 要洗牌的数组
     * @returns 洗牌后的新数组
     */
    private shuffleArray<T>(array: T[]): T[] {
      const result = [...array];
      for (let i = result.length - 1; i > 0; i--) {
        const j = Math.floor(Math.random() * (i + 1));
        [result[i], result[j]] = [result[j], result[i]];
      }
      return result;
    }
  
    /**
     * 选择轮空玩家（轮换制，确保每个玩家都有机会轮空）
     * @param playerIds 玩家ID数组（当前存活的玩家）
     * @returns 轮空玩家ID
     */
    private selectRestingPlayer(playerIds: string[]): string {
      // 初始化轮空次数记录
      playerIds.forEach(id => {
        if (!this.restingHistory.has(id)) {
          this.restingHistory.set(id, 0);
        }
      });
      
      // 找到轮空次数最少的玩家
      let minRestingCount = Infinity;
      playerIds.forEach(id => {
        const count = this.restingHistory.get(id) || 0;
        if (count < minRestingCount) {
          minRestingCount = count;
        }
      });
  
      const candidatePlayers = playerIds.filter(id => {
        const count = this.restingHistory.get(id) || 0;
        return count === minRestingCount;
      });
  
      // 在轮空次数最少的玩家中随机选择
      const selectedIndex = Math.floor(Math.random() * candidatePlayers.length);
      const selectedPlayer = candidatePlayers[selectedIndex];
      
      // 增加该玩家的轮空次数
      this.restingHistory.set(selectedPlayer, (this.restingHistory.get(selectedPlayer) || 0) + 1);
      
      return selectedPlayer;
    }
  
    /**
     * 为轮空玩家选择一个"幽灵对手"（用于显示）
     * @param restingPlayer 轮空玩家ID
     * @param allPlayers 所有当前存活的玩家ID
     * @returns 幽灵对手ID
     */
    private selectGhostOpponent(restingPlayer: string, allPlayers: string[]): string {
      // 只在当前存活的玩家中选择幽灵对手
      const alivePlayers = allPlayers.filter(id => id !== restingPlayer);
      
      if (alivePlayers.length === 0) {
        return restingPlayer; // 如果没有其他存活玩家，返回自己
      }
      
      // 随机选择一个幽灵对手
      const randomIndex = Math.floor(Math.random() * alivePlayers.length);
      return alivePlayers[randomIndex];
    }
  
    /**
     * 重置配对历史（新游戏开始时调用）
     */
    public resetHistory(): void {
      this.restingHistory.clear();
      this.currentRound = 0;
    }
  
    /**
     * 更新玩家列表（当有玩家加入或退出时调用）
     * @param newPlayers 新的玩家Map
     */
    public updatePlayers(newPlayers: Map<string, Player>): void {
      this.mPlayers = newPlayers;
      
      // 清理已死亡玩家的轮空历史记录
      const alivePlayerIds = new Set(newPlayers.keys());
      for (const playerId of this.restingHistory.keys()) {
        if (!alivePlayerIds.has(playerId)) {
          this.restingHistory.delete(playerId);
        }
      }
    }

    public deletePlayer(playerId: string) {
      if (this.mPlayers.has(playerId)) {
        this.mPlayers.delete(playerId);
      }
      // 清理该玩家的轮空历史
      this.restingHistory.delete(playerId);
    }
  }
  
  // 使用示例和辅助函数
  function createMatchmaker(mPlayers: Map<string, Player>): Matchmaker {
    return new Matchmaker(mPlayers);
  }
  
  // 显示配对结果的辅助函数
  function displayPairings(pairings: PairingResult[]): void {
    console.log(`=== 第${pairings.length > 0 ? '当前' : '0'}轮配对结果 ===`);
    
    const processedPairs = new Set<string>();
    
    pairings.forEach(pairing => {
      const pairKey = [pairing.playerId, pairing.opponentId].sort().join('-');
      
      if (!processedPairs.has(pairKey)) {
        console.log(`${pairing.playerId} VS ${pairing.opponentId}`);
        processedPairs.add(pairKey);
      }
    });
  }
  
  export { Matchmaker, PairingResult, createMatchmaker, displayPairings };