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

namespace Admin.NET.Plugin.AiDOP.Infrastructure;

/// <summary>
/// ETL 执行机指派与实例注册表的写入侧。
///
/// <para><b>「最多一台执行机」由 <c>ado_etl_runner_designation</c> 的结构保证</b>：
/// 该表主键固定为 <see cref="AdoEtlRunnerDesignation.SingletonId"/>，放不下第二行，
/// 因此不再需要旧模型里「同一事务内先清后置」那套写入侧约束。
/// 并发指派会被主键与条件更新挡住，而不是依赖调用方守规矩。</para>
///
/// <para><b>指派的对象是槽位，不是实例</b>：实例标识含进程ID与启动时间，
/// 指派挂上去每次重启都会丢（见 <c>AdoEtlRunnerDesignation</c> 注释）。</para>
/// </summary>
public interface IEtlInstanceStore
{
    /// <summary>
    /// 把某个部署槽位指派为唯一执行机。槽位无需当前有存活实例——
    /// 指派可以先于部署，也可以在目标机器重启期间保持有效，这正是本模型的要点。
    /// </summary>
    Task AssignRunnerSlotAsync(string slotCode, string assignedBy, CancellationToken ct = default);

    /// <summary>取消指派。此后无人跑定时 ETL——这是允许的状态。</summary>
    Task ClearRunnerAsync(string clearedBy = null, CancellationToken ct = default);

    /// <summary>当前被指派的槽位；无指派返回 null。</summary>
    Task<string> GetDesignatedSlotAsync(CancellationToken ct = default);

    /// <summary>指派记录全文，供页面展示「谁在什么时候指派的」。无指派返回 null。</summary>
    Task<AdoEtlRunnerDesignation> GetDesignationAsync(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 AssignRunnerSlotAsync(string slotCode, string assignedBy, CancellationToken ct = default)
    {
        var slot = string.IsNullOrWhiteSpace(slotCode) ? null : slotCode.Trim().ToLowerInvariant();
        await UpsertDesignationAsync(slot, assignedBy, ct);
    }

    public async Task ClearRunnerAsync(string clearedBy = null, CancellationToken ct = default) =>
        await UpsertDesignationAsync(null, clearedBy, ct);

    public async Task<string> GetDesignatedSlotAsync(CancellationToken ct = default)
    {
        var row = await GetDesignationAsync(ct);
        return string.IsNullOrWhiteSpace(row?.SlotCode) ? null : row.SlotCode;
    }

    public Task<AdoEtlRunnerDesignation> GetDesignationAsync(CancellationToken ct = default) =>
        _db.Queryable<AdoEtlRunnerDesignation>()
            .Where(x => x.Id == AdoEtlRunnerDesignation.SingletonId)
            .FirstAsync(ct);

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

    /// <summary>
    /// 写唯一那一行。先 UPDATE 再按影响行数决定是否 INSERT：
    /// 两个超管同时指派时，后到的 INSERT 会撞主键而不是插出第二行，
    /// 撞了就退回 UPDATE 重写一次，最终仍是单行单值。
    /// </summary>
    private async Task UpsertDesignationAsync(string slot, string operatorName, CancellationToken ct)
    {
        var now = DateTime.Now;
        var by = string.IsNullOrWhiteSpace(operatorName) ? null : operatorName.Trim();

        // 三元运算符不放进表达式树：SqlSugar 要把 SetColumns 的初始化器翻成 SQL，
        // 取消指派时 assigned_at 应回到 NULL，这个判断在 C# 侧先算完更稳。
        DateTime? assignedAt = slot == null ? null : now;

        var updated = await UpdateDesignationAsync(slot, by, assignedAt, now, ct);
        if (updated > 0) return;

        try
        {
            await _db.Insertable(new AdoEtlRunnerDesignation
            {
                Id = AdoEtlRunnerDesignation.SingletonId,
                SlotCode = slot,
                AssignedBy = by,
                AssignedAt = assignedAt,
                CreateTime = now,
                UpdateTime = now
            }).ExecuteCommandAsync(ct);
        }
        catch
        {
            // 并发下另一方已插入，改写即可；再失败就让异常上抛给控制器。
            await UpdateDesignationAsync(slot, by, assignedAt, now, ct);
        }
    }

    private Task<int> UpdateDesignationAsync(string slot, string by, DateTime? assignedAt, DateTime now, CancellationToken ct) =>
        _db.Updateable<AdoEtlRunnerDesignation>()
            .SetColumns(x => new AdoEtlRunnerDesignation
            {
                SlotCode = slot,
                AssignedBy = by,
                AssignedAt = assignedAt,
                UpdateTime = now
            })
            .Where(x => x.Id == AdoEtlRunnerDesignation.SingletonId)
            .ExecuteCommandAsync(ct);
}