defmodule DaProductApp.TerminalManagement.MQTTCommandBuilder do
  @moduledoc """
  Builder module for generating device-specific MQTT command payloads.
  Handles different command structures for various device models (MF919, SR600, etc.)
  """

  require Logger

  @doc """
  Main entry point for building MQTT command payloads.
  Routes to device-specific builder based on model.
  """
  def build_command(device_model, download_params) when is_binary(device_model) do
    case String.downcase(device_model) do
      "mf919" -> build_mf919_command(download_params)
      "sr600" -> build_sr600_command(download_params)
      "kozen" -> build_kozen_command(download_params)
      _ -> build_sr600_command(download_params)  # Default to SR600 structure
    end
  end

  @doc """
  Builds MF919-specific MQTT payload.
  MF919 uses TMS command structure with specific command types.
  """
  def build_mf919_command(params) do
    command_type = Map.get(params, "command_type", "UPDATE_PARAMS")
    request_id = Map.get(params, "request_id", generate_request_id())
    download_url = Map.get(params, "url_path_from_download", "")
    
    payload = %{
      "type" => "tms_command",
      "command" => command_type,
      "requestId" => request_id,
      "downloadUrl" => download_url
    }
    |> Enum.reject(fn {_k, v} -> is_nil(v) or v == "" end)
    |> Map.new()

    Logger.info("MF919 MQTT Command: #{inspect(payload)}")
    {:ok, Jason.encode!(payload)}
  end

  @doc """
  Builds SR600-specific MQTT payload.
  SR600 uses file_download command structure with path and file metadata.
  """
  def build_sr600_command(params) do
    request_id = Map.get(params, "request_id", generate_request_id())
    
    payload = %{
      "command" => "file_download",
      "local_path_to_save" => Map.get(params, "local_path_to_save"),
      "url_path_from_download" => Map.get(params, "url_path_from_download"),
      "file_size" => Map.get(params, "file_size"),
      "file_category" => Map.get(params, "file_category"),
      "file_name" => Map.get(params, "file_name"),
      "merchant_config" => Map.get(params, "merchant_config", "true"),
      "retry_count" => Map.get(params, "retry_count", "3"),
      "request_id" => request_id
    }
    |> Enum.reject(fn {_k, v} -> is_nil(v) or v == "" end)
    |> Map.new()

    Logger.info("SR600 MQTT Command: #{inspect(payload)}")
    {:ok, Jason.encode!(payload)}
  end

  @doc """
  Builds Kozen-specific MQTT payload.
  Currently uses SR600 structure as baseline.
  """
  def build_kozen_command(params) do
    build_sr600_command(params)
  end

  @doc """
  Generates a unique request ID for MQTT commands.
  Format: req-{timestamp}-{random}
  """
  def generate_request_id do
    timestamp = System.os_time(:second)
    random_id = :rand.uniform(1_000_000) |> Integer.to_string()
    "req-#{timestamp}-#{random_id}"
  end

  @doc """
  Returns available file categories for a specific device model.
  """
  def get_file_categories("mf919") do
    [
      {"params", "📦 Parameters (params.zip)"},
      {"l3config", "⚙️ L3 Config (l3config.zip)"},
      {"keys", "🔑 Keys (keys.json)"}
    ]
  end

  def get_file_categories("sr600") do
    [
      {"firmware", "🔧 Firmware"},
      {"application", "📱 Application"},
      {"config", "⚙️ Configuration"},
      {"logo_image", "🖼️ Logo Image"}
    ]
  end

  def get_file_categories("kozen") do
    # Kozen might have its own categories - add here as needed
    get_file_categories("sr600")
  end

  def get_file_categories(_), do: get_file_categories("sr600")

  @doc """
  Returns available command types for a specific device model.
  """
  def get_command_types("mf919") do
    [
      {"UPDATE_PARAMS", "Update Parameters"},
      {"UPDATE_L3_CONFIG", "Update L3 Config"},
      {"LOAD_KEYS", "Load Keys"}
    ]
  end

  def get_command_types("sr600") do
    [
      {"file_download", "File Download"}
    ]
  end

  def get_command_types(_), do: get_command_types("sr600")

  @doc """
  Returns the URL pattern/hint for a specific device model and file category.
  """
  def get_url_hint("mf919", category) do
    case category do
      "params" -> "http://demo.ctrmv.com/ota/mf919/params.zip"
      "l3config" -> "http://demo.ctrmv.com/ota/mf919/l3config.zip"
      "keys" -> "http://demo.ctrmv.com/ota/mf919/keys.json"
      _ -> "http://demo.ctrmv.com/ota/mf919/"
    end
  end

  def get_url_hint("sr600", _category) do
    "http://demo.ctrmv.com/ota/sr600/"
  end

  def get_url_hint(_, category) do
    get_url_hint("sr600", category)
  end

  @doc """
  Validates parameters based on device model requirements.
  """
  def validate_device_params("mf919", params) do
    required = ["command_type", "url_path_from_download"]
    
    case Enum.find(required, fn field -> is_nil(params[field]) or params[field] == "" end) do
      nil -> {:ok, params}
      missing -> {:error, "Missing required field for MF919: #{missing}"}
    end
  end

  def validate_device_params("sr600", params) do
    required = ["local_path_to_save", "url_path_from_download", "file_name"]
    
    case Enum.find(required, fn field -> is_nil(params[field]) or params[field] == "" end) do
      nil -> {:ok, params}
      missing -> {:error, "Missing required field for SR600: #{missing}"}
    end
  end

  def validate_device_params(_model, params) do
    validate_device_params("sr600", params)
  end
end