using Xunit;

namespace ScadaLink.ConfigurationDatabase.Tests.Migrations;

/// <summary>
/// SourceNode-stamping (#23) integration tests for the
/// <c>AddNotificationSourceNode</c> migration: applies the EF migrations to a
/// freshly-created MSSQL test database on the running infra/mssql container and
/// asserts that the central <c>Notifications</c> table carries the new
/// <c>SourceNode varchar(64) NULL</c> column. No index — Notification Outbox KPIs
/// are per-site, not per-node, so the column is never a query predicate on this
/// table; it's only echoed onto NotifyDeliver audit rows (#23) for cross-row
/// correlation.
/// </summary>
/// <remarks>
/// <c>Notifications</c> is non-partitioned (operational state, not audit), so this
/// is a plain metadata-only <c>ALTER TABLE … ADD</c> with no index.
/// </remarks>
public class AddNotificationSourceNodeMigrationTests : IClassFixture<MsSqlMigrationFixture>
{
    private readonly MsSqlMigrationFixture _fixture;

    public AddNotificationSourceNodeMigrationTests(MsSqlMigrationFixture fixture)
    {
        _fixture = fixture;
    }

    [SkippableFact]
    public async Task AppliesMigration_AddsSourceNodeColumn_ToNotifications()
    {
        Skip.IfNot(_fixture.Available, _fixture.SkipReason);

        var present = await ScalarAsync<int>(
            "SELECT COUNT(*) FROM INFORMATION_SCHEMA.COLUMNS " +
            "WHERE TABLE_NAME = 'Notifications' AND COLUMN_NAME = 'SourceNode' " +
            "AND TABLE_SCHEMA = 'dbo';");
        Assert.Equal(1, present);
    }

    [SkippableFact]
    public async Task SourceNodeColumn_IsNullableVarchar64()
    {
        Skip.IfNot(_fixture.Available, _fixture.SkipReason);

        // varchar(64), not nvarchar — SourceNode is ASCII (`node-a`, `central-a` etc.).
        var dataType = await ScalarAsync<string?>(
            "SELECT DATA_TYPE FROM INFORMATION_SCHEMA.COLUMNS " +
            "WHERE TABLE_NAME = 'Notifications' AND COLUMN_NAME = 'SourceNode';");
        Assert.Equal("varchar", dataType);

        var maxLength = await ScalarAsync<int>(
            "SELECT CHARACTER_MAXIMUM_LENGTH FROM INFORMATION_SCHEMA.COLUMNS " +
            "WHERE TABLE_NAME = 'Notifications' AND COLUMN_NAME = 'SourceNode';");
        Assert.Equal(64, maxLength);

        var isNullable = await ScalarAsync<string?>(
            "SELECT IS_NULLABLE FROM INFORMATION_SCHEMA.COLUMNS " +
            "WHERE TABLE_NAME = 'Notifications' AND COLUMN_NAME = 'SourceNode';");
        Assert.Equal("YES", isNullable);
    }

    // --- helpers ------------------------------------------------------------

    private async Task<T> ScalarAsync<T>(string sql)
    {
        await using var conn = _fixture.OpenConnection();
        await using var cmd = conn.CreateCommand();
        cmd.CommandText = sql;
        var result = await cmd.ExecuteScalarAsync();
        if (result is null || result is DBNull)
        {
            return default!;
        }
        return (T)Convert.ChangeType(result, typeof(T) == typeof(string) ? typeof(string) : Nullable.GetUnderlyingType(typeof(T)) ?? typeof(T))!;
    }
}