using Microsoft.Data.SqlClient;
using Xunit;

namespace ZB.MOM.WW.OtOpcUa.Driver.Historian.SqlServer.IntegrationTests;

/// <summary>
///     Env-gated throwaway database for the SQL historian backend. <c>HISTORIAN_SQL_TEST_CONNECTION</c> absent ⇒
///     <see cref="SkipReason"/> is set, nothing connects, and every test calls <c>Assert.Skip</c>. Present ⇒
///     creates <c>OtOpcUaHistorian_T_&lt;guid&gt;</c> (never touches another database) and drops it on dispose.
///     Tests isolate from each other with <see cref="UniqueSchema"/>.
/// </summary>
public sealed class SqlHistorianFixture : IAsyncLifetime
{
    /// <summary>Env var holding a connection string with CREATE/DROP DATABASE rights.</summary>
    public const string ConnectionEnvVar = "HISTORIAN_SQL_TEST_CONNECTION";

    private string? _master;
    private string? _dbName;

    /// <summary>Why tests must skip, or null when the database is available.</summary>
    public string? SkipReason { get; private set; }

    /// <summary>Connection string targeting the throwaway database. Valid only when <see cref="SkipReason"/> is null.</summary>
    public string ConnectionString { get; private set; } = "";

    /// <summary>Skips the calling test when the gate is closed.</summary>
    public void SkipIfUnavailable()
    {
        if (SkipReason is not null) Assert.Skip(SkipReason);
    }

    /// <summary>A fresh, valid schema name (nothing exists under it yet).</summary>
    /// <returns>A schema identifier unique to this call.</returns>
    public static string UniqueSchema() => "h" + Guid.NewGuid().ToString("N")[..16];

    /// <inheritdoc/>
    public async ValueTask InitializeAsync()
    {
        var cs = Environment.GetEnvironmentVariable(ConnectionEnvVar);
        if (string.IsNullOrWhiteSpace(cs))
        {
            SkipReason = $"{ConnectionEnvVar} is not set; SQL Server historian integration tests skipped.";
            return;
        }

        var b = new SqlConnectionStringBuilder(cs) { InitialCatalog = "master" };
        _master = b.ConnectionString;
        _dbName = "OtOpcUaHistorian_T_" + Guid.NewGuid().ToString("N");
        await ExecAsync(_master, $"CREATE DATABASE [{_dbName}]").ConfigureAwait(false);
        b.InitialCatalog = _dbName;
        ConnectionString = b.ConnectionString;
    }

    /// <inheritdoc/>
    public async ValueTask DisposeAsync()
    {
        if (_master is null || _dbName is null) return;
        SqlConnection.ClearAllPools();
        await ExecAsync(_master,
            $"ALTER DATABASE [{_dbName}] SET SINGLE_USER WITH ROLLBACK IMMEDIATE; DROP DATABASE [{_dbName}]").ConfigureAwait(false);
    }

    private static async Task ExecAsync(string cs, string sql)
    {
        await using var c = new SqlConnection(cs);
        await c.OpenAsync().ConfigureAwait(false);
        await using var cmd = c.CreateCommand();
        cmd.CommandText = sql;
        await cmd.ExecuteNonQueryAsync().ConfigureAwait(false);
    }
}

/// <summary>Shares one throwaway database across the integration tests.</summary>
[CollectionDefinition(Name)]
public sealed class SqlHistorianCollection : ICollectionFixture<SqlHistorianFixture>
{
    /// <summary>Collection name.</summary>
    public const string Name = "SqlHistorian";
}