using Admin.NET.Plugin.AiDOP.Entity.SmartOps;

namespace Admin.NET.Plugin.AiDOP.Infrastructure;

/// <summary>
/// ETL 执行机实例注册表的写入侧。
///
/// <para><b>「最多一台执行机」这条不变式由本类保证</b>，不要在控制器、前端或数据库约束里另做一份：
/// MySQL 没有部分索引，无法用唯一索引表达「最多一行 <c>is_runner=1</c>」；
/// 而前端保证等于没有保证（两个超管同时点两台就会破）。
/// 故 <see cref="AssignRunnerAsync"/> 在**同一事务内**先清后置。</para>
/// </summary>
public interface IEtlInstanceStore
{
    /// <summary>把指定实例指派为唯一执行机。同一事务内先把其余行置 0。</summary>
    /// <returns>false 表示该 instanceId 不存在（进程可能已退出并被清理）。</returns>
    Task<bool> AssignRunnerAsync(string instanceId, CancellationToken ct = default);

    /// <summary>取消所有指派。此后无人跑定时 ETL——这是允许的状态。</summary>
    Task ClearRunnerAsync(CancellationToken ct = default);

    Task<List<AdoEtlInstance>> ListAsync(CancellationToken ct = default);
}

public sealed class EtlInstanceStore : IEtlInstanceStore, ITransient
{
    private readonly ISqlSugarClient _db;

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

    public async Task<bool> AssignRunnerAsync(string instanceId, CancellationToken ct = default)
    {
        if (string.IsNullOrWhiteSpace(instanceId))
            return false;

        var id = instanceId.Trim();
        var assigned = false;

        // 事务边界不可省：先清后置若被拆成两个自动提交语句，
        // 中间那一瞬会出现「零台执行机」或（并发指派时）「两台执行机」。
        await _db.Ado.UseTranAsync(async () =>
        {
            var now = DateTime.Now;

            await _db.Updateable<AdoEtlInstance>()
                .SetColumns(x => new AdoEtlInstance { IsRunner = false, UpdateTime = now })
                .Where(x => x.IsRunner && x.InstanceId != id)
                .ExecuteCommandAsync(ct);

            var n = await _db.Updateable<AdoEtlInstance>()
                .SetColumns(x => new AdoEtlInstance { IsRunner = true, UpdateTime = now })
                .Where(x => x.InstanceId == id)
                .ExecuteCommandAsync(ct);

            assigned = n > 0;
        });

        return assigned;
    }

    public async Task ClearRunnerAsync(CancellationToken ct = default)
    {
        var now = DateTime.Now;
        await _db.Updateable<AdoEtlInstance>()
            .SetColumns(x => new AdoEtlInstance { IsRunner = false, UpdateTime = now })
            .Where(x => x.IsRunner)
            .ExecuteCommandAsync(ct);
    }

    public Task<List<AdoEtlInstance>> ListAsync(CancellationToken ct = default) =>
        _db.Queryable<AdoEtlInstance>()
            .OrderBy(x => x.MachineName)
            .OrderBy(x => x.ProcessId)
            .ToListAsync(ct);
}