using System;
using System.Collections.Concurrent;
using IvfTl.Hardware;
namespace IvfTl.ControlHost.Debug
{
    /// <summary>
    /// control 端调试会话后端:会话表 + 借用/归还 + 心跳续约 + 超时自动回收 + 命令分发。
    /// 安全地基(spec §5):绝不指望 operate 主动还,SweepExpired 超时回收兜底。
    /// </summary>
    public sealed class DebugSessionManager
    {
        private readonly Func<int, IHouseGate> _gateOf;
        private readonly Func<DateTime> _clock;
        private readonly int _ttlMs;
        private readonly Action<string> _log;
        private readonly ConcurrentDictionary<string, DebugSession> _sessions = new ConcurrentDictionary<string, DebugSession>();
        public DebugSessionManager(Func<int, IHouseGate> gateOf, Func<DateTime> clock, int ttlMs, Action<string> log)
        {
            _gateOf = gateOf; _clock = clock; _ttlMs = ttlMs; _log = log ?? (_ => { });
        }
        public DebugCommandResult Acquire(int houseSn)
        {
            var gate = _gateOf(houseSn);
            if (gate == null) return DebugCommandResult.Fail("NO_HANDLE", $"舱{houseSn}无闸门");
            var lease = gate.Acquire(HardwareUser.OperateDebug);
            if (lease == null) return DebugCommandResult.Fail("BUSY", $"舱{houseSn}被占用,借用超时");
            string sid = Guid.NewGuid().ToString("N");
            _sessions[sid] = new DebugSession(sid, houseSn, lease, _clock());
            _log($"[debug] acquire 舱{houseSn} sid={sid}");
            return DebugCommandResult.Okay(sid);
        }
        public DebugCommandResult Heartbeat(string sid)
        {
            if (sid != null && _sessions.TryGetValue(sid, out var s)) { s.LastSeen = _clock(); return DebugCommandResult.Okay(); }
            return DebugCommandResult.Fail("SESSION_EXPIRED", "会话不存在或已过期");
        }
        public DebugCommandResult Release(string sid)
        {
            if (sid != null && _sessions.TryRemove(sid, out var s))
            {
                try { s.Lease.Dispose(); } catch { }
                _log($"[debug] release sid={sid} 舱{s.HouseSn}");
            }
            return DebugCommandResult.Okay();
        }
        /// <summary>超时回收:LastSeen + ttl < now 的会话自动归还(spec §5.1)。</summary>
        public int SweepExpired()
        {
            int n = 0; var now = _clock();
            foreach (var kv in _sessions)
            {
                if ((now - kv.Value.LastSeen).TotalMilliseconds > _ttlMs)
                {
                    if (_sessions.TryRemove(kv.Key, out var s))
                    {
                        try { s.Lease.Dispose(); } catch { }
                        _log($"[debug] 会话超时自动回收 sid={kv.Key} 舱{s.HouseSn}");
                        n++;
                    }
                }
            }
            return n;
        }
    }
}