using Deal.Grpc.Telegram;
using Deal.Infrastructure.Integrations.Options;
using Grpc.Core;
using Grpc.Net.Client;

namespace Deal.Infrastructure.Integrations.Models;

/// <summary>
/// Транспорт gRPC-клиента telegram-service
/// </summary>
public sealed class TelegramGrpcConnection : IDisposable
{
    /// <summary>
    /// Env-ключ ожидаемого service-token.
    /// </summary>
    public const string ServiceTokenEnvKey = "DEAL_SERVICE_TOKEN";

    /// <summary>
    /// Ключ gRPC-metadata с tenant-id.
    /// </summary>
    public const string TenantIdMetadataKey = "tenant-id";

    /// <summary>
    /// Ключ gRPC-metadata с service-token.
    /// </summary>
    public const string ServiceTokenMetadataKey = "service-token";

    private readonly GrpcChannel _channel;
    private readonly string _serviceToken;

    /// <summary>
    /// Создаёт транспорт telegram-service по конфигурации и env-токену
    /// </summary>
    /// <param name="options">Конфигурация секции <c>Services:Telegram</c> (endpoint).</param>
    /// <param name="mtlsCertificates">Сертификаты mTLS: null — plaintext-канал (dev, флаг выключен).</param>
    /// <exception cref="InvalidOperationException">Пустой endpoint или пустой DEAL_SERVICE_TOKEN.</exception>
    public TelegramGrpcConnection(TelegramServiceOptions options, MtlsCertificates? mtlsCertificates = null)
    {
        ArgumentNullException.ThrowIfNull(options);
        if (string.IsNullOrWhiteSpace(options.Endpoint))
        {
            throw new InvalidOperationException(
                $"TelegramGrpcConnection: не задан endpoint telegram-service (секция \"{TelegramServiceOptions.SectionName}:Endpoint\").");
        }

        _serviceToken = Environment.GetEnvironmentVariable(ServiceTokenEnvKey) ?? string.Empty;
        if (_serviceToken.Length == 0)
        {
            throw new InvalidOperationException(
                $"TelegramGrpcConnection: не задан env {ServiceTokenEnvKey} — telegram-service отвергнет вызовы (fail-closed, Ruling 1).");
        }

        GrpcChannelOptions channelOptions = new() { MaxRetryAttempts = 0 };
        if (mtlsCertificates is not null)
        {
            channelOptions.HttpHandler = mtlsCertificates.CreateClientHttpHandler();
        }

        _channel = GrpcChannel.ForAddress(options.Endpoint, channelOptions);
    }

    /// <summary>
    /// Создаёт клиент RPC TelegramService поверх общего канала
    /// </summary>
    /// <returns>Клиент сервиса Telegram (команды ядра наружу).</returns>
    public TelegramService.TelegramServiceClient CreateClient() => new(_channel);

    /// <summary>
    /// Собирает обязательные metadata вызова
    /// </summary>
    /// <param name="tenantId">Id тенанта (строка, формат N — как в сессиях telegram-service).</param>
    /// <returns>Metadata для CallOptions вызова.</returns>
    public Metadata CreateMetadata(string tenantId)
    {
        var metadata = new Metadata
        {
            { TenantIdMetadataKey, tenantId },
            { ServiceTokenMetadataKey, _serviceToken },
        };
        return metadata;
    }

    /// <inheritdoc />
    public void Dispose() => _channel.Dispose();
}