using Microsoft.Extensions.Configuration;

namespace Admin.NET.Plugin.AiDOP.Infrastructure.S8;

/// <summary>S8 后台自动任务标识。每个 Job 一个独立开关节。</summary>
public enum S8BackgroundJob
{
    /// <summary>S8 自动监控主链调度（<c>S8:WatchScheduler:Enabled</c>）。</summary>
    WatchScheduler,

    /// <summary>SLA 超时自动升级（<c>S8:TimeoutAutoEscalation:Enabled</c>）。</summary>
    TimeoutAutoEscalation,

    /// <summary>ActiveFlow 卡死扫描（<c>S8:ActiveFlowStuckScan:Enabled</c>）。</summary>
    ActiveFlowStuckScan,
}

/// <summary>
/// S8-P0-2-PER-JOB-KILL-SWITCH-1：S8 后台任务三级开关求值。
///
/// <para><b>为什么需要</b>：修复前三个 Job（WatchScheduler / TimeoutAutoEscalation / ActiveFlowStuckScan）
/// 读的是**完全相同**的两个键 <c>Scheduler:Enabled</c> + <c>S8:Scheduler:Enabled</c>，
/// 没有任何 per-job 键。于是「只想跑 Watch」在配置层不可表达 —— 2026-09-02 的受控启动里，
/// 打开总开关同时放行了另外两个 Job，其中 <c>ActiveFlowStuckScan</c> 因带 <c>RunOnStart = true</c>
/// 在重启瞬间就写入了 499 行告警日志。当时只能靠「先暂停 trigger 再重启」隔离，
/// 而该手段实测**不可靠**（两次重启结果相反：一次暂停态丢失、一次存活）。</para>
///
/// <para><b>生效语义</b>（三级与，任一 false 即停）：</para>
/// <code>
/// Effective = Scheduler:Enabled          // 环境级 master kill switch，默认 true
///          &amp;&amp; S8:Scheduler:Enabled       // S8 业务级 master kill switch，默认 false
///          &amp;&amp; S8:{Job}:Enabled           // 单 Job 开关，默认 false
/// </code>
///
/// <para><b>默认 false 是刻意的</b>：新增 per-job 键后，任何未显式声明该键的部署都保持不执行，
/// 宁可「本该跑却没跑」也不要「本不该跑却跑了」——本模块的事故类型全部属于后者。</para>
///
/// <para><b>env override</b>：Furion 4.9.8.24 把 <c>Configuration/*.json</c> 装配在 ASP.NET Core
/// EnvironmentVariables provider **之后**，JSON 会盖掉 env，故所有开关都改用
/// <see cref="Environment.GetEnvironmentVariable"/> 直读，命名沿用既有 <c>AIDOP_</c> 前缀约定。
/// env 不存在 / 空白 → 沿用 JSON；存在但 <c>bool.TryParse</c> 失败 → 保留 JSON 值并回报
/// <see cref="S8JobSwitchDecision.ParseFailEnvName"/>（由调用方做单次 warn，不输出 value）。</para>
///
/// <para><b>与 RunOnStart 的关系</b>：本类只做纯计算、不碰 DB / service。调用方必须在
/// <c>ExecuteAsync</c> 的**第一步**求值并在 false 时 <c>return</c>，因此即便
/// <c>[Period(..., RunOnStart = true)]</c> 在启动瞬间触发，也会在进入任何业务扫描 / 写入之前退出。
/// 不再需要、也不得依赖 trigger 暂停作为隔离手段。</para>
/// </summary>
public static class S8JobSwitch
{
    /// <summary>环境级总开关配置键。默认 true（保持既有部署行为）。</summary>
    public const string EnvironmentEnabledKey = "Scheduler:Enabled";

    /// <summary>S8 业务级总开关配置键。默认 false。</summary>
    public const string MasterEnabledKey = "S8:Scheduler:Enabled";

    public const string EnvEnvironmentEnabled = "AIDOP_SCHEDULER_ENABLED";
    public const string EnvMasterEnabled = "AIDOP_S8_SCHEDULER_ENABLED";

    /// <summary>单 Job 配置键，形如 <c>S8:WatchScheduler:Enabled</c>。</summary>
    public static string JobEnabledKey(S8BackgroundJob job) => $"S8:{SectionOf(job)}:Enabled";

    /// <summary>单 Job env override 名，形如 <c>AIDOP_S8_WATCH_SCHEDULER_ENABLED</c>。</summary>
    public static string JobEnvName(S8BackgroundJob job) => job switch
    {
        S8BackgroundJob.WatchScheduler => "AIDOP_S8_WATCH_SCHEDULER_ENABLED",
        S8BackgroundJob.TimeoutAutoEscalation => "AIDOP_S8_TIMEOUT_AUTO_ESCALATION_ENABLED",
        S8BackgroundJob.ActiveFlowStuckScan => "AIDOP_S8_ACTIVE_FLOW_STUCK_SCAN_ENABLED",
        _ => throw new ArgumentOutOfRangeException(nameof(job), job, null),
    };

    private static string SectionOf(S8BackgroundJob job) => job switch
    {
        S8BackgroundJob.WatchScheduler => "WatchScheduler",
        S8BackgroundJob.TimeoutAutoEscalation => "TimeoutAutoEscalation",
        S8BackgroundJob.ActiveFlowStuckScan => "ActiveFlowStuckScan",
        _ => throw new ArgumentOutOfRangeException(nameof(job), job, null),
    };

    /// <summary>求值三级开关。纯函数：不访问数据库、不解析租户、不产生副作用。</summary>
    public static S8JobSwitchDecision Evaluate(IConfiguration configuration, S8BackgroundJob job)
    {
        ArgumentNullException.ThrowIfNull(configuration);

        string? parseFailEnvName = null;

        var environmentEnabled = ResolveBool(
            configuration.GetValue(EnvironmentEnabledKey, true), EnvEnvironmentEnabled, ref parseFailEnvName);

        var masterEnabled = ResolveBool(
            configuration.GetValue(MasterEnabledKey, false), EnvMasterEnabled, ref parseFailEnvName);

        var jobEnabled = ResolveBool(
            configuration.GetValue(JobEnabledKey(job), false), JobEnvName(job), ref parseFailEnvName);

        return new S8JobSwitchDecision(
            EnvironmentEnabled: environmentEnabled,
            MasterEnabled: masterEnabled,
            JobEnabled: jobEnabled,
            ParseFailEnvName: parseFailEnvName);
    }

    private static bool ResolveBool(bool fromJson, string envName, ref string? parseFailEnvName)
    {
        var raw = Environment.GetEnvironmentVariable(envName);
        if (string.IsNullOrWhiteSpace(raw)) return fromJson;
        if (bool.TryParse(raw, out var parsed)) return parsed;
        parseFailEnvName ??= envName;
        return fromJson;
    }
}

/// <summary>三级开关求值结果。<see cref="Enabled"/> 为 false 时调用方必须立即 return。</summary>
/// <param name="EnvironmentEnabled">环境级总开关 <c>Scheduler:Enabled</c> 的生效值。</param>
/// <param name="MasterEnabled">S8 业务级总开关 <c>S8:Scheduler:Enabled</c> 的生效值。</param>
/// <param name="JobEnabled">单 Job 开关 <c>S8:{Job}:Enabled</c> 的生效值。</param>
/// <param name="ParseFailEnvName">首个 <c>bool.TryParse</c> 失败的 env 名；无失败为 null。</param>
public sealed record S8JobSwitchDecision(
    bool EnvironmentEnabled,
    bool MasterEnabled,
    bool JobEnabled,
    string? ParseFailEnvName)
{
    /// <summary>三级与：任一为 false 即不执行业务体。</summary>
    public bool Enabled => EnvironmentEnabled && MasterEnabled && JobEnabled;
}