using System.Collections.Generic;

namespace XWorld.Server.Gateway
{
    public sealed class Matchmaker
    {
        public sealed class Seat { public int PlayerId; public bool IsAi; }
        public sealed class Match { public string GameId; public int Version; public List<Seat> Seats = new List<Seat>(); }

        private sealed class Waiter { public int Pid; public long EnqueuedTick; }
        private sealed class Bucket { public int PlayerCount; public List<Waiter> Waiters = new List<Waiter>(); }

        private readonly long _timeoutTicks;
        private int _aiSeq;
        private readonly Dictionary<string, Bucket> _buckets = new Dictionary<string, Bucket>();

        public Matchmaker(long timeoutTicks) { _timeoutTicks = timeoutTicks; }
        private static string Key(string g, int v) => $"{g}@{v}";

        public void Enqueue(int pid, string gameId, int version, int playerCount, long tick)
        {
            string k = Key(gameId, version);
            if (!_buckets.TryGetValue(k, out var b)) { b = new Bucket { PlayerCount = playerCount }; _buckets[k] = b; }
            b.Waiters.Add(new Waiter { Pid = pid, EnqueuedTick = tick });
        }

        // 从等待队列移除某玩家（断线时调用）；返回是否移除
        public bool Remove(int pid)
        {
            foreach (var kv in _buckets)
            {
                var ws = kv.Value.Waiters;
                for (int i = 0; i < ws.Count; i++)
                    if (ws[i].Pid == pid) { ws.RemoveAt(i); return true; }
            }
            return false;
        }

        // 返回本次可成形的对局（凑齐或超时 AI 补足）
        public IReadOnlyList<Match> Poll(long currentTick)
        {
            List<Match> formed = null;
            foreach (var kv in _buckets)
            {
                var b = kv.Value;
                string[] gv = kv.Key.Split('@');
                while (b.Waiters.Count > 0 &&
                       (b.Waiters.Count >= b.PlayerCount ||
                        currentTick - b.Waiters[0].EnqueuedTick >= _timeoutTicks))
                {
                    var m = new Match { GameId = gv[0], Version = int.Parse(gv[1]) };
                    int take = b.Waiters.Count >= b.PlayerCount ? b.PlayerCount : b.Waiters.Count;
                    for (int i = 0; i < take; i++)
                        m.Seats.Add(new Seat { PlayerId = b.Waiters[i].Pid, IsAi = false });
                    b.Waiters.RemoveRange(0, take);
                    while (m.Seats.Count < b.PlayerCount)
                        m.Seats.Add(new Seat { PlayerId = -(++_aiSeq), IsAi = true }); // AI 用负 pid
                    (formed ??= new List<Match>()).Add(m);
                }
            }
            return formed ?? (IReadOnlyList<Match>)System.Array.Empty<Match>();
        }
    }
}