YesChef/src/backend/YesChef.Api.IntegrationTests/Infrastructure/PostgresFixture.cs

using Npgsql;
using Testcontainers.PostgreSql;
using TUnit.Core.Interfaces;
using YesChef.Api.Data;

namespace YesChef.Api.IntegrationTests.Infrastructure;

/// <summary>
/// One Postgres container per test session. A migrated "template" database is
/// created once; each test asks the fixture for a fresh DB cloned from the
/// template via <c>CREATE DATABASE … TEMPLATE …</c>, which is far cheaper than
/// replaying migrations.
/// </summary>
public sealed class PostgresFixture : IAsyncInitializer, IAsyncDisposable
{
    private const string TemplateDbName = "yeschef_template";

    private readonly PostgreSqlContainer _container = new PostgreSqlBuilder("postgres:17")
        .WithDatabase("postgres")
        .WithUsername("postgres")
        .WithPassword("postgres")
        .Build();

    private string _adminConnectionString = null!;

    public async Task InitializeAsync()
    {
        await _container.StartAsync();
        _adminConnectionString = _container.GetConnectionString();

        await CreateTemplateAsync();
    }

    private async Task CreateTemplateAsync()
    {
        await ExecuteOnPostgresAsync($"""CREATE DATABASE "{TemplateDbName}";""");

        var templateConnectionString = BuildConnectionString(TemplateDbName);
        var options = new DbContextOptionsBuilder<YesChefDb>()
            .UseNpgsql(templateConnectionString)
            .Options;
        await using (var db = new YesChefDb(options))
        {
            await db.Database.MigrateAsync();
        }

        // Postgres holds idle pooled connections to the template; close them so
        // the template is free to be used as a CREATE DATABASE source.
        NpgsqlConnection.ClearAllPools();
    }

    public async Task<TestDatabase> CreateDatabaseAsync()
    {
        var name = $"yeschef_test_{Guid.NewGuid():N}";
        await ExecuteOnPostgresAsync($"""CREATE DATABASE "{name}" TEMPLATE "{TemplateDbName}";""");
        return new TestDatabase(name, BuildConnectionString(name), this);
    }

    internal async Task DropDatabaseAsync(string name)
    {
        NpgsqlConnection.ClearAllPools();
        await ExecuteOnPostgresAsync($"""DROP DATABASE IF EXISTS "{name}" WITH (FORCE);""");
    }

    private async Task ExecuteOnPostgresAsync(string sql)
    {
        await using var conn = new NpgsqlConnection(_adminConnectionString);
        await conn.OpenAsync();
        await using var cmd = new NpgsqlCommand(sql, conn);
        await cmd.ExecuteNonQueryAsync();
    }

    private string BuildConnectionString(string database)
    {
        var builder = new NpgsqlConnectionStringBuilder(_adminConnectionString)
        {
            Database = database,
            // Per-test apps open a small number of connections; the high default
            // pool keeps the cluster from being flooded under heavy parallelism.
            MaxPoolSize = 10,
            Timeout = 60,
        };
        return builder.ConnectionString;
    }

    public async ValueTask DisposeAsync()
    {
        NpgsqlConnection.ClearAllPools();
        await _container.DisposeAsync();
    }
}

/// <summary>Handle to a per-test database. Disposing drops it.</summary>
public sealed class TestDatabase(string name, string connectionString, PostgresFixture fixture) : IAsyncDisposable
{
    public string Name { get; } = name;
    public string ConnectionString { get; } = connectionString;

    public async ValueTask DisposeAsync() => await fixture.DropDatabaseAsync(Name);
}