defmodule DaProductApp.MercuryISO8583.Packagers do
  @moduledoc """
  Main entry point for ISO8583 packagers system.
  
  This module provides a clean interface to the packager system and
  mirrors the jPOS packager architecture while being idiomatic Elixir.
  
  ## Usage Examples
  
      # Get the ISO87B packager
      packager = Packagers.iso87b()
      
      # Pack a field
      {:ok, packed} = Packagers.pack_field(4, "000000005000", packager)
      
      # Unpack a field
      {:ok, {value, offset}} = Packagers.unpack_field(4, binary_data, 0, packager)
  """

  alias DaProductApp.MercuryISO8583.Packagers.ISO87BPackager
  alias DaProductApp.MercuryISO8583.Packagers.FieldPackagers.{
    IFB_NUMERIC,
    IFB_LLNUM,
    IFB_LLCHAR,
    IFB_LLLCHAR,
    IF_CHAR,
    IFB_BINARY,
    IFB_BITMAP
  }

  @doc """
  Get the ISO87B packager instance.
  """
  def iso87b(), do: ISO87BPackager

  @doc """
  Pack a specific field using the appropriate packager.
  
  ## Parameters
  - `field_number`: ISO8583 field number (0-128)
  - `value`: Field value to pack
  - `packager`: Packager module (default: ISO87BPackager)
  
  ## Returns
  - `{:ok, packed_binary}` on success
  - `{:error, reason}` on failure
  """
  def pack_field(field_number, value, packager \\ ISO87BPackager) do
    case packager.get_field_packager(field_number) do
      nil -> {:error, "Unknown field number: #{field_number}"}
      field_packager -> pack_with_packager(value, field_packager, field_number)
    end
  end

  @doc """
  Unpack a specific field using the appropriate packager.
  
  ## Parameters
  - `field_number`: ISO8583 field number (0-128)  
  - `binary_data`: Binary data to unpack
  - `offset`: Starting offset in the binary data
  - `packager`: Packager module (default: ISO87BPackager)
  
  ## Returns
  - `{:ok, {value, new_offset}}` on success
  - `{:error, reason}` on failure
  """
  def unpack_field(field_number, binary_data, offset, packager \\ ISO87BPackager) do
    case packager.get_field_packager(field_number) do
      nil -> {:error, "Unknown field number: #{field_number}"}
      field_packager -> unpack_with_packager(binary_data, offset, field_packager, field_number)
    end
  end

  @doc """
  Get field information for a specific field number.
  
  ## Parameters
  - `field_number`: ISO8583 field number (0-128)
  - `packager`: Packager module (default: ISO87BPackager)
  
  ## Returns
  - Map with field information or nil if field doesn't exist
  """
  def get_field_info(field_number, packager \\ ISO87BPackager) do
    case packager.get_field_packager(field_number) do
      nil -> nil
      field_packager -> %{
        field_number: field_number,
        description: get_field_description(field_packager),
        max_length: get_field_max_length(field_packager),
        type: get_field_type(field_packager)
      }
    end
  end

  @doc """
  List all available field packagers in the given packager.
  
  ## Parameters
  - `packager`: Packager module (default: ISO87BPackager)
  
  ## Returns
  - List of field information maps
  """
  def list_fields(packager \\ ISO87BPackager) do
    0..packager.max_fields()
    |> Enum.map(&get_field_info(&1, packager))
    |> Enum.reject(&is_nil/1)
  end

  # Private helper functions

  defp pack_with_packager(value, field_packager, field_number) do
    case field_packager do
      %DaProductApp.MercuryISO8583.Packagers.FieldPackagers.BaseFieldPackager{} = packager ->
        DaProductApp.MercuryISO8583.Packagers.FieldPackagers.BaseFieldPackager.pack_with_packager(value, packager)
      _ ->
        # For now, use the field packager's pack function
        # This would be expanded based on the specific field packager type
        {:error, "Unsupported field packager type"}
    end
  end

  defp unpack_with_packager(binary_data, offset, field_packager, field_number) do
    case field_packager do
      %DaProductApp.MercuryISO8583.Packagers.FieldPackagers.BaseFieldPackager{} = packager ->
        DaProductApp.MercuryISO8583.Packagers.FieldPackagers.BaseFieldPackager.unpack_with_packager(%{}, binary_data, offset, packager)
      _ ->
        # For now, handle unsupported types
        {:error, "Unsupported field packager type"}
    end
  end

  defp get_field_description(field_packager) do
    case field_packager do
      %DaProductApp.MercuryISO8583.Packagers.FieldPackagers.BaseFieldPackager{description: desc} -> desc
      _ -> "Unknown field type"
    end
  end

  defp get_field_max_length(field_packager) do
    case field_packager do
      %DaProductApp.MercuryISO8583.Packagers.FieldPackagers.BaseFieldPackager{length: len} -> len
      _ -> 0
    end
  end

  defp get_field_type(field_packager) do
    case field_packager do
      %DaProductApp.MercuryISO8583.Packagers.FieldPackagers.BaseFieldPackager{interpreter: interpreter} ->
        case interpreter do
          {:bcd_interpreter, _, _} -> :bcd_numeric
          {:ascii_interpreter} -> :ascii_text
          {:binary_interpreter} -> :binary
          _ -> :unknown
        end
      _ -> :unknown
    end
  end
end