using Microsoft.Data.SqlClient;
using Shouldly;
using Xunit;

namespace ZB.MOM.WW.OtOpcUa.AdminUI.Tests;

/// <summary>
///     Pins <see cref="SqlTestDatabaseReaper"/> against the real shared SQL Server: an aged orphan is
///     dropped, a fresh sibling is not.
/// </summary>
/// <remarks>
///     A <b>pin, not a red-first test</b>. The reaper is time-gated and the behaviour it protects — "a
///     database created by a run that is long over gets dropped, one created by a run that may still be
///     going does not" — has no observable failing state to start from; what it needs is a guard against
///     someone later widening the age window, the <c>LIKE</c>, or the timestamp parse. It therefore drives
///     the internal core with an explicit cutoff rather than waiting 24 hours.
/// </remarks>
/// <remarks>
///     Joined to <see cref="AdminUiSqlServerCollection"/> deliberately, though it never touches the
///     fixture: xunit builds a collection fixture before running the collection's tests and serialises them
///     within it, which is what keeps <see cref="AdminUiSqlServerFixture"/>'s own startup reaper from
///     racing this one. Left in its own (parallel) collection, that reaper can drop the aged database this
///     test plants, between the plant and the assertion — observed as an intermittent failure.
/// </remarks>
[Collection(nameof(AdminUiSqlServerCollection))]
public sealed class SqlTestDatabaseReaperTests
{
    [SqlServerFact]
    public void Reap_drops_databases_older_than_the_cutoff_and_leaves_fresh_ones_alone()
    {
        var master = AdminUiSqlServer.ConnectionStringFor("master");

        // A name that carries a timestamp from 2025 — unambiguously older than any cutoff this suite uses.
        var aged = $"{AdminUiSqlServer.TestDatabasePrefix}20250101000000_{Guid.NewGuid():N}";
        var fresh = $"{AdminUiSqlServer.TestDatabasePrefix}{DateTime.UtcNow:yyyyMMddHHmmss}_{Guid.NewGuid():N}";

        CreateDatabase(master, aged);

        try
        {
            CreateDatabase(master, fresh);

            try
            {
                var reaped = SqlTestDatabaseReaper.ReapOrphans(
                    master,
                    AdminUiSqlServer.TestDatabasePrefix,
                    DateTime.UtcNow - TimeSpan.FromHours(24));

                reaped.ShouldContain(aged);
                DatabaseExists(master, aged).ShouldBeFalse("the aged orphan should have been reaped");

                reaped.ShouldNotContain(fresh);
                DatabaseExists(master, fresh).ShouldBeTrue("a database from a possibly-live run must survive");
            }
            finally
            {
                SqlTestDatabaseReaper.TryDropDatabase(master, fresh);
            }
        }
        finally
        {
            // No-op when the reaper already took it; belt-and-braces if an assertion failed first.
            SqlTestDatabaseReaper.TryDropDatabase(master, aged);
        }
    }

    [SqlServerFact]
    public void Reap_leaves_a_matching_name_whose_timestamp_does_not_parse_alone()
    {
        var master = AdminUiSqlServer.ConnectionStringFor("master");
        var unparseable = $"{AdminUiSqlServer.TestDatabasePrefix}notatimestamp_{Guid.NewGuid():N}";

        CreateDatabase(master, unparseable);

        try
        {
            // The cutoff stays at the production 24 hours — deliberately NOT a far-future one, which would
            // sweep away the live database of an AdminUI fixture running in parallel on this shared server.
            // It still bites: an unparseable name that fell through to default(DateTime) would read as year
            // 0001 and be dropped.
            var reaped = SqlTestDatabaseReaper.ReapOrphans(
                master,
                AdminUiSqlServer.TestDatabasePrefix,
                DateTime.UtcNow - TimeSpan.FromHours(24));

            reaped.ShouldNotContain(unparseable);
            DatabaseExists(master, unparseable)
                .ShouldBeTrue("a name this code could not have minted is never dropped");
        }
        finally
        {
            SqlTestDatabaseReaper.TryDropDatabase(master, unparseable);
        }
    }

    [SqlServerFact]
    public void Reap_leaves_an_aged_name_whose_suffix_is_not_a_guid_alone()
    {
        var master = AdminUiSqlServer.ConnectionStringFor("master");

        // Aged enough to be reaped on the timestamp alone — only the suffix check saves it. That check is
        // what bounds the character set of every candidate: without it a database named
        // "<prefix><aged timestamp>_" + arbitrary text would be fed to the drop statement, and before the
        // statement was parameterised that was a second-order injection running as sa.
        var notAGuid = $"{AdminUiSqlServer.TestDatabasePrefix}20250101000000_notaguid";

        CreateDatabase(master, notAGuid);

        try
        {
            var reaped = SqlTestDatabaseReaper.ReapOrphans(
                master,
                AdminUiSqlServer.TestDatabasePrefix,
                DateTime.UtcNow - TimeSpan.FromHours(24));

            reaped.ShouldNotContain(notAGuid);
            DatabaseExists(master, notAGuid)
                .ShouldBeTrue("only names shaped exactly as this code mints them are ever dropped");
        }
        finally
        {
            SqlTestDatabaseReaper.TryDropDatabase(master, notAGuid);
        }
    }

    private static void CreateDatabase(string masterConnectionString, string databaseName)
    {
        using var conn = new SqlConnection(masterConnectionString);
        conn.Open();

        using var cmd = conn.CreateCommand();
        cmd.CommandText = $"CREATE DATABASE [{databaseName}];";
        cmd.ExecuteNonQuery();
    }

    private static bool DatabaseExists(string masterConnectionString, string databaseName)
    {
        using var conn = new SqlConnection(masterConnectionString);
        conn.Open();

        using var cmd = conn.CreateCommand();
        cmd.CommandText = "SELECT DB_ID(@name);";
        cmd.Parameters.Add(new SqlParameter("@name", databaseName));

        return cmd.ExecuteScalar() is not (null or DBNull);
    }
}