using System.Security.Cryptography;
using Admin.NET.Core.Update;
using Xunit;

namespace Admin.NET.Plugin.AiDOP.Tests.Migration;

/// <summary>
/// 已知失败迁移「重跑前恢复」的策略契约。
///
/// <para>被守护的核心不变量只有一条：<b>这条破坏性通道必须极其难以被误触发。</b>
/// 它会 TRUNCATE 一张真实的表且不可回滚，所以四道闸门里任意一道松掉都是事故：
///   · 版本没登记 → 不能动；
///   · 从未跑过 / 已经成功 → 不能动（尤其「已成功」，动了就是破坏别人正常的库）；
///   · 日志 hash 或磁盘 hash 与已发布的原始脚本对不上 → 必须显式拒绝，不能沉默放行。</para>
///
/// <para>策略是纯函数，因此这些用例不需要数据库；副作用（TRUNCATE / 抛异常）由
/// AutoVersionUpdate 执行，其真实运行结果另由本地 runtime 验证覆盖。</para>
/// </summary>
public class MigrationRecoveryPolicyTests
{
    private const string V = "1.0.517";
    private const string OriginalHash = "EF2722954B4BB5BEA465F63E764C927F01E9E52109738478E89CE94145ECB50B";

    // ── CASE A：Failed + 原始 hash ⇒ 允许恢复 ──────────────────────────────────────
    [Fact]
    public void CaseA_FailedWithOriginalHash_Truncates()
    {
        var outcome = MigrationRecoveryPolicy.Decide(V, "Failed", OriginalHash, diskHashMatchesOriginal: true);

        Assert.Equal(MigrationRecoveryDecision.Truncate, outcome.Decision);
        Assert.Equal("dwd_requirement_examine_detail", outcome.Plan!.TableName);
        Assert.Equal("DWD_TRUNCATE_PRE_RETRY", outcome.Plan.Strategy);
        Assert.Null(outcome.RejectReason);
    }

    /// <summary>大小写与首尾空白不应改变裁决 —— 不同驱动回读 hash 的形态不一致。</summary>
    [Theory]
    [InlineData("Failed")]
    [InlineData("failed")]
    [InlineData("FAILED")]
    public void CaseA_StatusComparisonIsCaseInsensitive(string status)
    {
        Assert.Equal(MigrationRecoveryDecision.Truncate,
            MigrationRecoveryPolicy.Decide(V, status, "  " + OriginalHash.ToLowerInvariant() + "  ", true).Decision);
    }

    // ── CASE B：已 Success ⇒ 绝不触碰 ─────────────────────────────────────────────
    /// <summary>
    /// 这是整组测试里最重要的一条。已成功的环境说明该迁移在那里本来就跑对了，
    /// 恢复通道一旦在这种环境上生效，就是把别人正常的库清空。
    /// </summary>
    [Fact]
    public void CaseB_AlreadySucceeded_IsNeverTouched()
    {
        var outcome = MigrationRecoveryPolicy.Decide(V, "Success", OriginalHash, diskHashMatchesOriginal: true);

        Assert.Equal(MigrationRecoveryDecision.None, outcome.Decision);
        Assert.Null(outcome.RejectReason);
    }

    [Theory]
    [InlineData("Success")]
    [InlineData("Running")]
    [InlineData("Skipped")]
    public void CaseB_AnyNonFailedStatus_IsNeverTouched(string status)
    {
        Assert.Equal(MigrationRecoveryDecision.None,
            MigrationRecoveryPolicy.Decide(V, status, OriginalHash, true).Decision);
    }

    // ── CASE C：Failed 但 hash 不是登记的那一个 ⇒ 显式拒绝 ────────────────────────
    /// <summary>
    /// 不能沉默跳过：沉默会让人以为「恢复没生效但也没坏事」，
    /// 实际是我们对一个来历不明的 1.0.517 做了判断却没说。TRUNCATE 不可回滚，必须停机报错。
    /// </summary>
    [Fact]
    public void CaseC_FailedWithUnknownLoggedHash_IsRejected_NotSilentlySkipped()
    {
        var outcome = MigrationRecoveryPolicy.Decide(
            V, "Failed", "0000000000000000000000000000000000000000000000000000000000000000", true);

        Assert.Equal(MigrationRecoveryDecision.Reject, outcome.Decision);
        Assert.Contains("SHA256", outcome.RejectReason!, StringComparison.Ordinal);
    }

    /// <summary>日志 hash 对得上，但磁盘脚本被改过 —— 同样拒绝。</summary>
    [Fact]
    public void CaseC_FailedButDiskScriptModified_IsRejected()
    {
        var outcome = MigrationRecoveryPolicy.Decide(V, "Failed", OriginalHash, diskHashMatchesOriginal: false);

        Assert.Equal(MigrationRecoveryDecision.Reject, outcome.Decision);
        Assert.NotNull(outcome.RejectReason);
    }

    [Fact]
    public void CaseC_FailedWithNullOrEmptyLoggedHash_IsRejected()
    {
        Assert.Equal(MigrationRecoveryDecision.Reject, MigrationRecoveryPolicy.Decide(V, "Failed", null, true).Decision);
        Assert.Equal(MigrationRecoveryDecision.Reject, MigrationRecoveryPolicy.Decide(V, "Failed", "", true).Decision);
    }

    // ── 未登记版本 / 从未跑过 ⇒ 什么都不做 ────────────────────────────────────────
    [Theory]
    [InlineData("1.0.516")]
    [InlineData("1.0.518")]
    [InlineData("1.0.510")]
    public void UnregisteredVersion_IsNeverTouched_EvenWhenFailed(string version)
    {
        var outcome = MigrationRecoveryPolicy.Decide(version, "Failed", OriginalHash, true);

        Assert.Equal(MigrationRecoveryDecision.None, outcome.Decision);
        Assert.Null(outcome.Plan);
    }

    /// <summary>从未跑过（无日志行）= 正常首次执行，不是抢救场景。</summary>
    [Fact]
    public void NeverRun_IsNeverTouched()
    {
        Assert.Equal(MigrationRecoveryDecision.None, MigrationRecoveryPolicy.Decide(V, null, null, true).Decision);
        Assert.Equal(MigrationRecoveryDecision.None, MigrationRecoveryPolicy.Decide(V, "  ", null, true).Decision);
    }

    // ── 幂等 ──────────────────────────────────────────────────────────────────────
    /// <summary>
    /// 恢复不写迁移日志，所以「TRUNCATE 完成后进程崩溃」时下次启动的输入完全相同，
    /// 裁决必须仍然是 Truncate（对空表再清一次，无副作用），而不是变成 Reject 或 None。
    /// </summary>
    [Fact]
    public void Decision_IsIdempotent_AcrossRepeatedStartups()
    {
        for (var i = 0; i < 3; i++)
            Assert.Equal(MigrationRecoveryDecision.Truncate,
                MigrationRecoveryPolicy.Decide(V, "Failed", OriginalHash, true).Decision);
    }

    // ── 登记表与真实脚本必须一致 ──────────────────────────────────────────────────
    /// <summary>
    /// 登记的 hash 必须等于仓库里那份 1.0.517.sql 的真实 SHA256。
    ///
    /// <para>这条防的是最隐蔽的一种走样：有人改了已发布的 1.0.517.sql 却忘了同步登记表。
    /// 那时闸门 4 会对所有环境判 Reject，恢复通道静默失效，而故障现场看起来只是「又起不来」。</para>
    /// </summary>
    [Fact]
    public void RegisteredHash_MatchesTheActualPublishedScript()
    {
        var plan = Assert.Single(MigrationRecoveryPolicy.KnownFailedRecoveries, x => x.Version == V);

        var path = FindScript($"{V}.sql");
        var actual = Convert.ToHexString(SHA256.HashData(NormalizeToLf(File.ReadAllBytes(path))));

        Assert.Equal(plan.OriginalFileHash, actual, ignoreCase: true);
    }

    /// <summary>登记表是破坏性授权清单：新增一条等于授权一次不可回滚操作，必须显式评审。</summary>
    [Fact]
    public void Registry_ContainsOnlyTheDeliberatelyReviewedEntries()
    {
        Assert.Single(MigrationRecoveryPolicy.KnownFailedRecoveries);
        Assert.All(MigrationRecoveryPolicy.KnownFailedRecoveries,
            x => Assert.Equal(64, x.OriginalFileHash.Length));
    }

    private static byte[] NormalizeToLf(byte[] content)
    {
        var output = new byte[content.Length];
        var length = 0;
        for (var i = 0; i < content.Length; i++)
        {
            if (content[i] == 0x0D)
            {
                if (i + 1 < content.Length && content[i + 1] == 0x0A) i++;
                output[length++] = 0x0A;
                continue;
            }
            output[length++] = content[i];
        }
        return output.AsSpan(0, length).ToArray();
    }

    private static string FindScript(string fileName)
    {
        var dir = new DirectoryInfo(AppContext.BaseDirectory);
        while (dir != null)
        {
            var candidate = Path.Combine(dir.FullName, "server", "Admin.NET.Web.Entry", "UpdateScripts", fileName);
            if (File.Exists(candidate)) return candidate;
            dir = dir.Parent;
        }
        throw new FileNotFoundException(fileName);
    }
}