defmodule ComponentsElixir.QRCode do
  @moduledoc """
  QR Code generation and parsing for storage locations.

  Provides functionality to generate QR codes for storage locations
  and parse them back to retrieve location information.
  """

  @doc """
  Generates a QR code data string for a storage location.

  Format: SL:{level}:{qr_code}:{parent_qr_or_ROOT}

  ## Examples

      iex> location = %StorageLocation{level: 1, qr_code: "ABC123", parent: nil}
      iex> ComponentsElixir.QRCode.generate_qr_data(location)
      "SL:1:ABC123:ROOT"

      iex> parent = %StorageLocation{qr_code: "SHELF1"}
      iex> drawer = %StorageLocation{level: 2, qr_code: "DRAW01", parent: parent}
      iex> ComponentsElixir.QRCode.generate_qr_data(drawer)
      "SL:2:DRAW01:SHELF1"
  """
  def generate_qr_data(storage_location) do
    parent_code =
      case storage_location.parent do
        nil -> "ROOT"
        parent -> parent.qr_code
      end

    "SL:#{storage_location.level}:#{storage_location.qr_code}:#{parent_code}"
  end

  @doc """
  Parses a QR code string and extracts components.

  ## Examples

      iex> ComponentsElixir.QRCode.parse_qr_data("SL:1:ABC123:ROOT")
      {:ok, %{level: 1, code: "ABC123", parent: "ROOT"}}

      iex> ComponentsElixir.QRCode.parse_qr_data("invalid")
      {:error, :invalid_format}
  """
  def parse_qr_data(qr_string) do
    case String.split(qr_string, ":") do
      ["SL", level_str, code, parent] ->
        case Integer.parse(level_str) do
          {level, ""} ->
            {:ok, %{level: level, code: code, parent: parent}}
          _ ->
            {:error, :invalid_level}
        end
      _ ->
        {:error, :invalid_format}
    end
  end

  @doc """
  Validates if a string looks like a storage location QR code.

  ## Examples

      iex> ComponentsElixir.QRCode.valid_storage_qr?("SL:1:ABC123:ROOT")
      true

      iex> ComponentsElixir.QRCode.valid_storage_qr?("COMP:12345")
      false
  """
  def valid_storage_qr?(qr_string) do
    case parse_qr_data(qr_string) do
      {:ok, _} -> true
      _ -> false
    end
  end

  @doc """
  Generates a printable label data structure for a storage location.

  This could be used to generate PDF labels or send to a label printer.
  """
  def generate_label_data(storage_location) do
    qr_data = generate_qr_data(storage_location)

    %{
      qr_code: qr_data,
      name: storage_location.name,
      path: storage_location.path,
      level: storage_location.level,
      description: storage_location.description
    }
  end

  @doc """
  Generates multiple QR codes for disambiguation testing.

  This is useful for testing multi-QR detection scenarios.
  """
  def generate_test_codes(storage_locations) when is_list(storage_locations) do
    Enum.map(storage_locations, &generate_qr_data/1)
  end

  @doc """
  Generates a QR code image (PNG) for a storage location.

  Returns the binary PNG data that can be saved to disk or served directly.

  ## Options

  - `:size` - The size of the QR code image in pixels (default: 200)
  - `:background` - Background color as `{r, g, b}` tuple (default: white)
  - `:foreground` - Foreground color as `{r, g, b}` tuple (default: black)

  ## Examples

      iex> location = %StorageLocation{level: 1, qr_code: "ABC123"}
      iex> {:ok, png_data} = ComponentsElixir.QRCode.generate_qr_image(location)
      iex> File.write!("/tmp/qr_code.png", png_data)

  """
  def generate_qr_image(storage_location, _opts \\ []) do
    qr_data = generate_qr_data(storage_location)

    qr_data
    |> QRCode.create()
    |> QRCode.render(:png)
  end

  @doc """
  Generates and saves a QR code image to the specified file path.

  ## Examples

      iex> location = %StorageLocation{level: 1, qr_code: "ABC123"}
      iex> ComponentsElixir.QRCode.save_qr_image(location, "/tmp/qr_code.png")
      :ok

  """
  def save_qr_image(storage_location, file_path, opts \\ []) do
    case generate_qr_image(storage_location, opts) do
      {:ok, png_data} ->
        # Ensure directory exists
        file_path
        |> Path.dirname()
        |> File.mkdir_p!()

        File.write!(file_path, png_data)
        :ok

      {:error, reason} ->
        {:error, reason}
    end
  end

  @doc """
  Generates a QR code image URL for serving via Phoenix static files.

  This function generates the QR code image and saves it to the static directory,
  returning a URL that can be used in templates.

  ## Examples

      iex> location = %StorageLocation{id: 123, qr_code: "ABC123"}
      iex> ComponentsElixir.QRCode.get_qr_image_url(location)
      "/qr_codes/storage_location_123.png"

  """
  def get_qr_image_url(storage_location, opts \\ []) do
    filename = "storage_location_#{storage_location.id}.png"
    file_path = Path.join([Application.app_dir(:components_elixir, "priv/static/user_generated/qr_codes"), filename])

    # Generate and save the image if it doesn't exist or if regeneration is forced
    force_regenerate = Keyword.get(opts, :force_regenerate, false)

    if force_regenerate || !File.exists?(file_path) do
      case save_qr_image(storage_location, file_path, opts) do
        :ok -> "/user_generated/qr_codes/#{filename}"
        {:error, _reason} -> nil
      end
    else
      "/user_generated/qr_codes/#{filename}"
    end
  end

  @doc """
  Generates QR code images for multiple storage locations (bulk generation).

  Returns a list of results indicating success or failure for each location.

  ## Examples

      iex> locations = [location1, location2, location3]
      iex> ComponentsElixir.QRCode.bulk_generate_images(locations)
      [
        {:ok, "/qr_codes/storage_location_1.png"},
        {:ok, "/qr_codes/storage_location_2.png"},
        {:error, "Failed to generate for location 3"}
      ]

  """
  def bulk_generate_images(storage_locations, opts \\ []) do
    # Use Task.async_stream for concurrent generation with back-pressure
    storage_locations
    |> Task.async_stream(
      fn location ->
        case get_qr_image_url(location, Keyword.put(opts, :force_regenerate, true)) do
          nil -> {:error, "Failed to generate QR code for location #{location.id}"}
          url -> {:ok, url}
        end
      end,
      timeout: :infinity,
      max_concurrency: System.schedulers_online() * 2
    )
    |> Enum.map(fn {:ok, result} -> result end)
  end

  @doc """
  Cleans up QR code images for deleted storage locations.

  Should be called when storage locations are deleted to prevent orphaned files.
  """
  def cleanup_qr_image(storage_location_id) do
    filename = "storage_location_#{storage_location_id}.png"
    file_path = Path.join([Application.app_dir(:components_elixir, "priv/static/user_generated/qr_codes"), filename])

    if File.exists?(file_path) do
      File.rm(file_path)
    else
      :ok
    end
  end
end