namespace Admin.NET.Plugin.AiDOP.DataPlatform.MdpRebuild;

public interface IModuleRebuildLease : IAsyncDisposable
{
    Task HeartbeatAsync(CancellationToken ct = default);
}

public interface IModuleRebuildLock
{
    Task<IModuleRebuildLease?> TryAcquireAsync(MdpRebuildScope scope, string holderId, long? jobId = null, CancellationToken ct = default);
}

public sealed class ModuleRebuildLock : IModuleRebuildLock, ITransient
{
    public static readonly TimeSpan StaleAfter = TimeSpan.FromMinutes(30);
    private readonly ISqlSugarClient _db;

    public ModuleRebuildLock(ISqlSugarClient db) => _db = db;

    public async Task<IModuleRebuildLease?> TryAcquireAsync(MdpRebuildScope scope, string holderId, long? jobId = null, CancellationToken ct = default)
    {
        scope = MdpRebuildScope.Create(scope.ModuleCode, scope.TenantId, scope.FactoryId);
        if (string.IsNullOrWhiteSpace(holderId))
            throw new InvalidOperationException("重算锁持有者不能为空");
        var now = DateTime.Now;
        var staleBefore = now - StaleAfter;
        await _db.Ado.ExecuteCommandAsync(
            """
            INSERT INTO ado_mdp_rebuild_lock
            (lock_name, module_code, tenant_id, factory_id, status, create_time, update_time)
            SELECT @LockName, @ModuleCode, @TenantId, @FactoryId, 'FREE', @Now, @Now
            FROM DUAL
            WHERE NOT EXISTS (SELECT 1 FROM ado_mdp_rebuild_lock WHERE lock_name=@LockName)
            """,
            new SugarParameter("@LockName", scope.LockName),
            new SugarParameter("@ModuleCode", scope.ModuleCode),
            new SugarParameter("@TenantId", scope.TenantId),
            new SugarParameter("@FactoryId", scope.FactoryId),
            new SugarParameter("@Now", now));
        var n = await _db.Ado.ExecuteCommandAsync(
            """
            UPDATE ado_mdp_rebuild_lock
            SET holder_id=@HolderId, job_id=@JobId, status='HELD',
                acquired_at=@Now, heartbeat_at=@Now, update_time=@Now
            WHERE lock_name=@LockName
              AND (status='FREE' OR heartbeat_at IS NULL OR heartbeat_at < @StaleBefore)
            """,
            new SugarParameter("@HolderId", holderId),
            new SugarParameter("@JobId", (object?)jobId ?? DBNull.Value),
            new SugarParameter("@Now", now),
            new SugarParameter("@LockName", scope.LockName),
            new SugarParameter("@StaleBefore", staleBefore));
        if (n <= 0)
            return null;
        return new DbLease(_db, scope.LockName, holderId);
    }

    private sealed class DbLease : IModuleRebuildLease
    {
        private readonly ISqlSugarClient _db;
        private readonly string _lockName;
        private readonly string _holderId;
        private int _released;

        public DbLease(ISqlSugarClient db, string lockName, string holderId)
        {
            _db = db;
            _lockName = lockName;
            _holderId = holderId;
        }

        public async Task HeartbeatAsync(CancellationToken ct = default)
        {
            using var db = _db.CopyNew();
            await db.Ado.ExecuteCommandAsync(
                """
                UPDATE ado_mdp_rebuild_lock
                SET heartbeat_at=@Now, update_time=@Now
                WHERE lock_name=@LockName AND holder_id=@HolderId AND status='HELD'
                """,
                new SugarParameter("@Now", DateTime.Now),
                new SugarParameter("@LockName", _lockName),
                new SugarParameter("@HolderId", _holderId));
        }

        public async ValueTask DisposeAsync()
        {
            if (Interlocked.Exchange(ref _released, 1) == 1)
                return;
            try
            {
                using var db = _db.CopyNew();
                await db.Ado.ExecuteCommandAsync(
                    """
                    UPDATE ado_mdp_rebuild_lock
                    SET status='FREE', holder_id=NULL, job_id=NULL, update_time=@Now
                    WHERE lock_name=@LockName AND holder_id=@HolderId
                    """,
                    new SugarParameter("@Now", DateTime.Now),
                    new SugarParameter("@LockName", _lockName),
                    new SugarParameter("@HolderId", _holderId));
            }
            catch
            {
                // 释放失败留给租约过期
            }
        }
    }
}

public sealed class InMemoryModuleRebuildLock : IModuleRebuildLock
{
    private readonly Dictionary<string, string> _holders = new(StringComparer.Ordinal);

    public Task<IModuleRebuildLease?> TryAcquireAsync(MdpRebuildScope scope, string holderId, long? jobId = null, CancellationToken ct = default)
    {
        var lockName = MdpRebuildScope.Create(scope.ModuleCode, scope.TenantId, scope.FactoryId).LockName;
        lock (this)
        {
            if (_holders.ContainsKey(lockName))
                return Task.FromResult<IModuleRebuildLease?>(null);
            _holders[lockName] = holderId;
            return Task.FromResult<IModuleRebuildLease?>(new MemoryLease(this, lockName));
        }
    }

    private sealed class MemoryLease : IModuleRebuildLease
    {
        private readonly InMemoryModuleRebuildLock _owner;
        private readonly string _lockName;
        public MemoryLease(InMemoryModuleRebuildLock owner, string lockName)
        {
            _owner = owner;
            _lockName = lockName;
        }
        public Task HeartbeatAsync(CancellationToken ct = default) => Task.CompletedTask;
        public ValueTask DisposeAsync()
        {
            lock (_owner) _owner._holders.Remove(_lockName);
            return ValueTask.CompletedTask;
        }
    }
}