using System.Text.Json;
using Microsoft.EntityFrameworkCore;
using ZB.MOM.WW.Audit;
using ZB.MOM.WW.ScadaBridge.Commons.Interfaces.Repositories;
using ZB.MOM.WW.ScadaBridge.Commons.Types.Audit;
using ZB.MOM.WW.ScadaBridge.Commons.Types.Enums;
using ZB.MOM.WW.ScadaBridge.ConfigurationDatabase.Maintenance;
using ZB.MOM.WW.ScadaBridge.ConfigurationDatabase.Repositories;
using ZB.MOM.WW.ScadaBridge.ConfigurationDatabase.Tests.Migrations;

namespace ZB.MOM.WW.ScadaBridge.ConfigurationDatabase.Tests.Maintenance;

/// <summary>
/// SQL Server tests for AuditLog archive cleanup (ScadaBridge#109): a stale archive a retried
/// purge left behind is deleted only once a later purged archive provably holds all its rows;
/// a stale archive with a row no later archive holds, or a sole copy left at <c>Archived</c>, is
/// kept; retention deletes only expired archives whose partition is gone; deletion never
/// follows a path out of the archive folder.
/// </summary>
/// <remarks>Each test owns one month of the shared fixture database and its own archive directory.</remarks>
public sealed class AuditLogArchiveCleanupTests : IClassFixture<MsSqlMigrationFixture>, IDisposable
{
    private readonly MsSqlMigrationFixture _fixture;
    private readonly DirectoryInfo _root = Directory.CreateTempSubdirectory("auditlog-cleanup-");

    /// <summary>Creates the test class with the shared migrated SQL Server fixture.</summary>
    /// <param name="fixture">The shared migration fixture.</param>
    public AuditLogArchiveCleanupTests(MsSqlMigrationFixture fixture) => _fixture = fixture;

    /// <inheritdoc />
    public void Dispose() => _root.Delete(recursive: true);

    /// <summary>
    /// The retried purge: archive A goes stale (a row arrives and the chain advances), B purges.
    /// Dry run reports A as superseded and deletes nothing; the real pass deletes exactly A's
    /// three files and B still verifies.
    /// </summary>
    /// <returns>A task that represents the asynchronous operation.</returns>
    [SkippableFact]
    public async Task RetriedPurge_StaleArchiveIsDeleted_OnceALaterPurgedArchiveCoversIt()
    {
        Skip.IfNot(_fixture.Available, _fixture.SkipReason);
        var dir = Dir("retried");
        var month = Month(2027, 1);
        await InsertAsync(Enumerable.Range(1, 5).Select(i => NewEvent(month.AddDays(i))));
        await DrainAsync();
        await InsertAsync([NewEvent(month.AddDays(7))]); // unchained in A
        var stale = await ArchiveAsync(dir, month);
        Assert.Equal(1, stale.UnchainedRowCount);

        await InsertAsync([NewEvent(month.AddDays(9))]);
        await DrainAsync(); // A's unchained row is now chained; the chain moved past A's end
        await using (var ctx = CreateContext())
        {
            await Assert.ThrowsAsync<AuditArchiveStaleException>(() => Archive(ctx, dir).PurgeArchivedPartitionAsync(stale));
        }

        var fresh = await ArchiveAsync(dir, month);
        await using (var ctx = CreateContext())
        {
            Assert.Equal(7, await Archive(ctx, dir).PurgeArchivedPartitionAsync(fresh));
        }

        var dry = await CleanupAsync(dir, dryRun: true);
        var item = Assert.Single(dry.Items);
        Assert.Equal((stale.Name, AuditArchiveCleanupAction.DeletedSuperseded), (item.Name, item.Action));
        Assert.True(File.Exists(ManifestPath(dir, stale)));

        var real = await CleanupAsync(dir, dryRun: false);
        Assert.Equal(AuditArchiveCleanupAction.DeletedSuperseded, Assert.Single(real.Items).Action);
        Assert.False(File.Exists(ManifestPath(dir, stale)));
        Assert.False(File.Exists(Path.Combine(dir, "2027", stale.Name + ".parquet")));
        Assert.False(File.Exists(Path.Combine(dir, "2027", stale.Name + ".tombstones.parquet")));

        await using (var ctx = CreateContext())
        {
            var listed = Assert.Single(await Archive(ctx, dir).ListAsync());
            Assert.Equal(fresh.Name, listed.Name);
            Assert.True((await Archive(ctx, dir).VerifyAsync(fresh.Name)).Verified);
        }

        Assert.Empty((await CleanupAsync(dir, dryRun: false)).Items);
    }

    /// <summary>
    /// A stale archive holding an unchained row that a per-channel purge removed before the
    /// later archive (no tombstone for an unchained row) is the only copy of that row: kept.
    /// </summary>
    /// <returns>A task that represents the asynchronous operation.</returns>
    [SkippableFact]
    public async Task StaleArchive_WithARowNoLaterArchiveHolds_IsKept()
    {
        Skip.IfNot(_fixture.Available, _fixture.SkipReason);
        var dir = Dir("kept");
        var month = Month(2027, 3);
        await InsertAsync(Enumerable.Range(1, 3).Select(i => NewEvent(month.AddDays(i))));
        await DrainAsync();
        await InsertAsync([NewEvent(month.AddHours(1), AuditChannel.DbOutbound)]); // unchained
        var stale = await ArchiveAsync(dir, month);

        await using (var ctx = CreateContext())
        {
            Assert.Equal(1, await new AuditLogRepository(ctx).PurgeChannelOlderThanAsync("DbOutbound", month.AddDays(1), 100));
            await Assert.ThrowsAsync<AuditArchiveStaleException>(() => Archive(ctx, dir).PurgeArchivedPartitionAsync(stale));
        }

        var fresh = await ArchiveAsync(dir, month);
        await using (var ctx = CreateContext())
        {
            await Archive(ctx, dir).PurgeArchivedPartitionAsync(fresh);
        }

        var result = await CleanupAsync(dir, dryRun: false);

        var kept = Assert.Single(result.Items);
        Assert.Equal((stale.Name, AuditArchiveCleanupAction.KeptStale), (kept.Name, kept.Action));
        Assert.Contains("unchained row", kept.Detail);
        Assert.True(File.Exists(ManifestPath(dir, stale)));
    }

    /// <summary>
    /// An archive left at <c>Archived</c> although its partition WAS switched out (the node
    /// stopped before the manifest update) has no later purged archive: it is the sole copy, kept.
    /// </summary>
    /// <returns>A task that represents the asynchronous operation.</returns>
    [SkippableFact]
    public async Task SoleCopyLeftAtArchived_IsNotTouched()
    {
        Skip.IfNot(_fixture.Available, _fixture.SkipReason);
        var dir = Dir("sole");
        var month = Month(2027, 4);
        await InsertAsync(Enumerable.Range(1, 3).Select(i => NewEvent(month.AddDays(i))));
        await DrainAsync();
        var manifest = await ArchiveAsync(dir, month);
        await using (var ctx = CreateContext())
        {
            await Archive(ctx, dir).PurgeArchivedPartitionAsync(manifest);
        }

        await SetStatusAsync(dir, manifest, AuditArchiveStatus.Archived);

        Assert.Empty((await CleanupAsync(dir, dryRun: false)).Items);
        Assert.True(File.Exists(ManifestPath(dir, manifest)));
    }

    /// <summary>
    /// Retention: 0 never deletes; a purged archive is kept until its month ended more than
    /// RetentionDays ago, then deleted; an expired archive whose partition still holds rows is kept.
    /// </summary>
    /// <returns>A task that represents the asynchronous operation.</returns>
    [SkippableFact]
    public async Task Retention_DeletesOnlyExpiredArchivesWhosePartitionIsGone()
    {
        Skip.IfNot(_fixture.Available, _fixture.SkipReason);
        var dir = Dir("retention");
        var purgedMonth = Month(2027, 5);
        await InsertAsync(Enumerable.Range(1, 2).Select(i => NewEvent(purgedMonth.AddDays(i))));
        var purged = await ArchiveAsync(dir, purgedMonth);
        await using (var ctx = CreateContext())
        {
            await Archive(ctx, dir).PurgeArchivedPartitionAsync(purged);
        }

        var liveMonth = Month(2027, 6);
        await InsertAsync([NewEvent(liveMonth.AddDays(1))]);
        var live = await ArchiveAsync(dir, liveMonth); // never purged: rows still in the table

        var monthEnd = purgedMonth.AddMonths(1);
        var farFuture = liveMonth.AddMonths(1).AddDays(1000);
        Assert.Empty((await CleanupAsync(dir, dryRun: false, retentionDays: 0, now: farFuture)).Items);
        Assert.Empty((await CleanupAsync(dir, dryRun: false, retentionDays: 400, now: monthEnd.AddDays(399))).Items);

        var result = await CleanupAsync(dir, dryRun: false, retentionDays: 400, now: farFuture);

        var expired = Assert.Single(result.Items);
        Assert.Equal((purged.Name, AuditArchiveCleanupAction.DeletedExpired), (expired.Name, expired.Action));
        Assert.False(File.Exists(ManifestPath(dir, purged)));
        Assert.True(File.Exists(ManifestPath(dir, live)));
    }

    /// <summary>Deletion uses the archive name's own three files — never a path from the manifest.</summary>
    /// <returns>A task that represents the asynchronous operation.</returns>
    [SkippableFact]
    public async Task Deletion_NeverFollowsAManifestPath_OutOfTheArchiveFolder()
    {
        Skip.IfNot(_fixture.Available, _fixture.SkipReason);
        var dir = Dir("paths");
        var month = Month(2027, 7);
        await InsertAsync([NewEvent(month.AddDays(1))]);
        var manifest = await ArchiveAsync(dir, month);
        await using (var ctx = CreateContext())
        {
            await Archive(ctx, dir).PurgeArchivedPartitionAsync(manifest);
        }

        var outside = Path.Combine(_root.FullName, "outside.parquet");
        await File.WriteAllTextAsync(outside, "not an archive");
        var path = ManifestPath(dir, manifest);
        var tampered = JsonSerializer.Deserialize<AuditArchiveManifest>(await File.ReadAllTextAsync(path), Json)! with
        {
            DataFile = "../../outside.parquet",
            TombstoneFile = "../../outside.parquet",
        };
        await File.WriteAllTextAsync(path, JsonSerializer.Serialize(tampered, Json));

        var result = await CleanupAsync(dir, dryRun: false, retentionDays: 30, now: month.AddYears(5));

        Assert.Equal(AuditArchiveCleanupAction.DeletedExpired, Assert.Single(result.Items).Action);
        Assert.True(File.Exists(outside));
        Assert.Empty(Directory.EnumerateFiles(Path.Combine(dir, "2027")));
    }

    private static readonly JsonSerializerOptions Json = new() { PropertyNamingPolicy = JsonNamingPolicy.CamelCase };

    private sealed class FixedClock(DateTime now) : TimeProvider
    {
        public override DateTimeOffset GetUtcNow() => new(DateTime.SpecifyKind(now, DateTimeKind.Utc));
    }

    private string Dir(string name) => Directory.CreateDirectory(Path.Combine(_root.FullName, name)).FullName;

    private static string ManifestPath(string dir, AuditArchiveManifest m) => Path.Combine(dir, m.Partition[..4], m.Name + ".manifest.json");

    private static async Task SetStatusAsync(string dir, AuditArchiveManifest manifest, AuditArchiveStatus status)
    {
        var path = ManifestPath(dir, manifest);
        var current = JsonSerializer.Deserialize<AuditArchiveManifest>(await File.ReadAllTextAsync(path), Json)!;
        await File.WriteAllTextAsync(path, JsonSerializer.Serialize(current with { Status = status, PurgedAtUtc = null }, Json));
    }

    private static AuditLogPartitionArchive Archive(
        ScadaBridgeDbContext ctx, string dir, int retentionDays = 0, DateTime? now = null) => new(ctx, new AuditLogArchiveOptions
        {
            Enabled = true,
            Directory = dir,
            RowGroupSize = 1_000,
            RetentionDays = retentionDays,
        }, time: now is null ? null : new FixedClock(now.Value));

    private async Task<AuditArchiveManifest> ArchiveAsync(string dir, DateTime month)
    {
        await using var ctx = CreateContext();
        var manifest = await Archive(ctx, dir).ArchivePartitionAsync(month);
        await Task.Delay(5); // distinct millisecond archive names
        return manifest;
    }

    private async Task<AuditArchiveCleanupResult> CleanupAsync(string dir, bool dryRun, int retentionDays = 0, DateTime? now = null)
    {
        await using var ctx = CreateContext();
        return await Archive(ctx, dir, retentionDays, now).CleanupAsync(dryRun);
    }

    private async Task InsertAsync(IEnumerable<AuditEvent> events)
    {
        await using var ctx = CreateContext();
        var repo = new AuditLogRepository(ctx);
        foreach (var e in events)
        {
            await repo.InsertIfNotExistsAsync(e);
        }
    }

    private async Task DrainAsync()
    {
        await using var ctx = CreateContext();
        var chain = new AuditLogHashChain(ctx);
        for (var i = 0; i < 1000; i++)
        {
            var r = await chain.ChainPendingAsync(500);
            if (r.RowsChained == 0 && !r.LockBusy)
            {
                return;
            }
        }

        throw new InvalidOperationException("Chain did not drain.");
    }

    private static DateTime Month(int year, int month) => new(year, month, 1, 0, 0, 0, DateTimeKind.Utc);

    private ScadaBridgeDbContext CreateContext()
        => new(new DbContextOptionsBuilder<ScadaBridgeDbContext>().UseSqlServer(_fixture.ConnectionString).Options);

    private static AuditEvent NewEvent(DateTime occurredAtUtc, AuditChannel channel = AuditChannel.ApiOutbound) =>
        ScadaBridgeAuditEventFactory.Create(
            channel: channel,
            kind: channel == AuditChannel.DbOutbound ? AuditKind.DbWrite : AuditKind.ApiCall,
            status: AuditStatus.Delivered,
            occurredAtUtc: occurredAtUtc,
            actor: "cleanup-test",
            target: "erp",
            sourceNode: "central-a",
            sourceSiteId: "cleanup-test",
            correlationId: Guid.NewGuid());
}