using System;
using Microsoft.Extensions.Configuration;

namespace FinlyticCore.Models;

/// <summary>
/// Represents the network and security settings used to connect to the central MQTT broker.
/// </summary>
public class MqttConfiguration
{
    /// <summary>
    /// Gets or sets the host address or IP of the MQTT broker.
    /// </summary>
    public string Host { get; set; } = string.Empty;

    /// <summary>
    /// Gets or sets the port number for the connection. Defaults to 1883.
    /// </summary>
    public int Port { get; set; } = 1883;

    /// <summary>
    /// Gets or sets the unique client identifier used when registering with the broker.
    /// </summary>
    public string ClientId { get; set; } = string.Empty;

    /// <summary>
    /// Gets or sets the username for authentication (optional).
    /// </summary>
    public string? Username { get; set; }

    /// <summary>
    /// Gets or sets the password for authentication (optional).
    /// </summary>
    public string? Password { get; set; }

    /// <summary>
    /// Builds an <see cref="MqttConfiguration"/> from application configuration, understanding both the
    /// colon-separated key style (<c>MQTT:Host</c>, used by <c>appsettings.json</c>) and the double-underscore
    /// style (<c>MQTT__Host</c>, used by container environment variables). Every one of the eight service MQTT
    /// clients previously duplicated this lookup inline; centralizing it here means a new configuration key
    /// (e.g. authentication) only has to be wired up once.
    /// </summary>
    /// <param name="configuration">The application configuration to read MQTT settings from.</param>
    /// <param name="defaultClientId">
    /// The service-specific client ID prefix to fall back to when no <c>MQTT:ClientId</c>/<c>MQTT__ClientId</c>
    /// is configured (e.g. "FinlyticAssets"). A random suffix is always appended to the resolved client ID
    /// (whether it came from configuration or from this default) to avoid the broker rejecting a duplicate
    /// client ID when a service reconnects or runs multiple instances.
    /// </param>
    /// <returns>
    /// A populated <see cref="MqttConfiguration"/>. <see cref="Username"/> and <see cref="Password"/> are left
    /// <see langword="null"/> unless both are actually configured, so connections to brokers without
    /// authentication enabled remain anonymous and continue to work unchanged.
    /// </returns>
    /// <exception cref="ArgumentNullException">Thrown when <paramref name="configuration"/> is <see langword="null"/>.</exception>
    public static MqttConfiguration FromConfiguration(IConfiguration configuration, string defaultClientId)
    {
        ArgumentNullException.ThrowIfNull(configuration);

        var host = configuration["MQTT:Host"] ?? configuration["MQTT__Host"] ?? "localhost";
        var portRaw = configuration["MQTT:Port"] ?? configuration["MQTT__Port"] ?? "1883";
        var port = int.TryParse(portRaw, out var parsedPort) ? parsedPort : 1883;

        var configuredClientId = configuration["MQTT:ClientId"] ?? configuration["MQTT__ClientId"];
        var clientId = $"{(string.IsNullOrWhiteSpace(configuredClientId) ? defaultClientId : configuredClientId)}_{Guid.NewGuid():N}";

        // Optional authentication: only set Username/Password when the broker actually requires them.
        // The broker this system currently runs against has no authentication configured, so leaving both
        // unset here must keep the connection anonymous (see ManagedMqttClient.ConnectAsync).
        var username = configuration["MQTT:Username"] ?? configuration["MQTT__Username"];
        var password = configuration["MQTT:Password"] ?? configuration["MQTT__Password"];

        return new MqttConfiguration
        {
            Host = host,
            Port = port,
            ClientId = clientId,
            Username = string.IsNullOrWhiteSpace(username) ? null : username,
            Password = string.IsNullOrWhiteSpace(password) ? null : password
        };
    }
}