using System.Collections.Concurrent;
using Npgsql;
using Xunit;

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

/// <summary>
///     Env-gated QuestDB for the historian integration tests. <c>HISTORIAN_QUESTDB_TEST_CONNECTION</c> absent ⇒
///     <see cref="SkipReason"/> is set, nothing connects and every test calls <c>Assert.Skip</c>. Present ⇒ tests isolate
///     from each other with <see cref="UniquePrefix"/>; every prefix handed out is dropped on dispose (and a test may
///     drop its own early with <see cref="DropPrefixAsync"/>). Never touches a table outside those prefixes.
/// </summary>
public sealed class QuestDbFixture : IAsyncLifetime
{
    /// <summary>Env var holding an Npgsql connection string for QuestDB's PG-wire port.</summary>
    public const string ConnectionEnvVar = "HISTORIAN_QUESTDB_TEST_CONNECTION";

    private readonly ConcurrentBag<string> _prefixes = new();

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

    /// <summary>The Npgsql connection string. 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 table prefix (<c>"t" + 12 hex + "_"</c>) that nothing uses yet; dropped on dispose.</summary>
    /// <returns>The prefix.</returns>
    public string UniquePrefix()
    {
        var p = "t" + Guid.NewGuid().ToString("N")[..12] + "_";
        _prefixes.Add(p);
        return p;
    }

    /// <summary>Options targeting this fixture's QuestDB under <paramref name="prefix"/>.</summary>
    /// <param name="prefix">Table prefix (normally from <see cref="UniquePrefix"/>).</param>
    /// <param name="retentionDays">Optional TTL.</param>
    /// <param name="autoCreate">AutoCreateSchema.</param>
    /// <returns>Valid options.</returns>
    public QuestDbHistorianOptions Options(string prefix, int? retentionDays = null, bool autoCreate = true) => new()
    {
        ConnectionString = ConnectionString,
        TablePrefix = prefix,
        RetentionDays = retentionDays,
        AutoCreateSchema = autoCreate,
    };

    /// <summary>Drops every table whose name starts with <paramref name="prefix"/> (found through <c>tables()</c>).</summary>
    /// <param name="prefix">Table prefix.</param>
    /// <returns>A task completing when they are gone.</returns>
    public async Task DropPrefixAsync(string prefix)
    {
        if (SkipReason is not null) return;
        if (!QuestDbHistorianOptions.IsValidPrefix(prefix)) throw new ArgumentException("Invalid prefix.", nameof(prefix));
        await using var ds = NpgsqlDataSource.Create(ConnectionString);
        await using var conn = await ds.OpenConnectionAsync().ConfigureAwait(false);
        var names = new List<string>();
        await using (var cmd = conn.CreateCommand())
        {
            cmd.CommandText = "SELECT table_name FROM tables() WHERE starts_with(table_name, $1)"; // never LIKE: '_' is a wildcard
            cmd.Parameters.Add(new NpgsqlParameter { NpgsqlDbType = NpgsqlTypes.NpgsqlDbType.Varchar, Value = prefix });
            await using var r = await cmd.ExecuteReaderAsync().ConfigureAwait(false);
            while (await r.ReadAsync().ConfigureAwait(false)) names.Add(r.GetString(0));
        }
        foreach (var n in names)
        {
            await using var drop = conn.CreateCommand();
            drop.CommandText = $"DROP TABLE IF EXISTS {n}";
            await drop.ExecuteNonQueryAsync().ConfigureAwait(false);
        }
    }

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

    /// <inheritdoc/>
    public async ValueTask DisposeAsync()
    {
        if (SkipReason is not null) return;
        foreach (var p in _prefixes.Distinct())
            await DropPrefixAsync(p).ConfigureAwait(false);
        NpgsqlConnection.ClearAllPools();
    }
}

/// <summary>Shares one fixture across the QuestDB integration tests.</summary>
[CollectionDefinition(Name)]
public sealed class QuestDbCollection : ICollectionFixture<QuestDbFixture>
{
    /// <summary>Collection name.</summary>
    public const string Name = "QuestDb";
}