defmodule Raxol.Terminal.Parser.State.Manager do
  @moduledoc """
  Manages the state of the terminal parser, including escape sequences,
  control sequences, and parser modes.
  """

  defstruct [
    :state,
    :params,
    :intermediate,
    :ignore,
    :osc_buffer,
    :dcs_buffer,
    :apc_buffer,
    :pm_buffer,
    :sos_buffer,
    :string_buffer,
    :string_terminator,
    :string_flags,
    :string_parser_state,
    :params_buffer,
    :intermediates_buffer,
    :payload_buffer,
    :final_byte,
    :designating_gset,
    :single_shift
  ]

  @type parser_state ::
          :ground
          | :escape
          | :csi_entry
          | :csi_param
          | :csi_intermediate
          | :csi_ignore
          | :osc_string
          | :dcs_entry
          | :dcs_param
          | :dcs_intermediate
          | :dcs_passthrough
          | :apc_string
          | :pm_string
          | :sos_string
          | :string

  @type params :: [non_neg_integer()]
  @type intermediate :: [non_neg_integer()]
  @type string_flags :: %{String.t() => boolean()}

  @type t :: %__MODULE__{
          state: parser_state(),
          params: params(),
          intermediate: intermediate(),
          ignore: boolean(),
          osc_buffer: String.t(),
          dcs_buffer: String.t(),
          apc_buffer: String.t(),
          pm_buffer: String.t(),
          sos_buffer: String.t(),
          string_buffer: String.t(),
          string_terminator: non_neg_integer() | nil,
          string_flags: string_flags(),
          string_parser_state: parser_state() | nil
        }

  # Constants for character ranges
  @c0_range 0x00..0x1F
  @c1_range 0x80..0x9F
  @printable_range 0x20..0x7E
  @extended_range 0xA0..0xFF

  # Special characters
  @esc 0x1B
  @bel 0x07
  @st 0x9C
  @osc 0x9D
  @pm 0x9E
  @apc 0x9F
  @csi 0x9B
  @dcs 0x90

  # State handlers map
  defp state_handlers do
    %{
      ground: &process_ground_state/2,
      escape: &process_escape_state/2,
      csi_entry: &process_csi_entry_state/2,
      csi_param: &process_csi_param_state/2,
      csi_intermediate: &process_csi_intermediate_state/2,
      csi_ignore: &process_csi_ignore_state/2,
      osc_string: &process_osc_string_state/2,
      dcs_entry: &process_dcs_entry_state/2,
      dcs_param: &process_dcs_param_state/2,
      dcs_intermediate: &process_dcs_intermediate_state/2,
      dcs_passthrough: &process_dcs_passthrough_state/2,
      apc_string: &process_apc_string_state/2,
      pm_string: &process_pm_string_state/2,
      sos_string: &process_sos_string_state/2,
      string: &process_string_state/2
    }
  end

  @doc """
  Creates a new parser state manager instance.
  """
  def new do
    %__MODULE__{
      state: :ground,
      params: [],
      intermediate: [],
      ignore: false,
      osc_buffer: "",
      dcs_buffer: "",
      apc_buffer: "",
      pm_buffer: "",
      sos_buffer: "",
      string_buffer: "",
      string_terminator: nil,
      string_flags: %{},
      string_parser_state: nil,
      params_buffer: "",
      intermediates_buffer: "",
      payload_buffer: "",
      final_byte: nil,
      designating_gset: nil,
      single_shift: nil
    }
  end

  @doc """
  Processes a single character and updates the parser state accordingly.
  """
  def process_char(%__MODULE__{} = manager, char) when is_integer(char) do
    handler = Map.get(state_handlers(), manager.state, &process_ground_state/2)
    handler.(manager, char)
  end

  # State processing functions

  defp process_ground_state(manager, char) when char in @c0_range,
    do: handle_c0_control(manager, char)

  defp process_ground_state(manager, char) when char in @c1_range,
    do: handle_c1_control(manager, char)

  defp process_ground_state(manager, char) when char in @printable_range,
    do: handle_printable(manager, char)

  defp process_ground_state(manager, char) when char in @extended_range,
    do: handle_extended(manager, char)

  defp process_ground_state(manager, _char), do: manager

  defp process_escape_state(manager, char) when char in @c0_range,
    do: handle_c0_control(manager, char)

  defp process_escape_state(manager, char) when char in @c1_range,
    do: handle_c1_control(manager, char)

  defp process_escape_state(manager, char) when char in @printable_range,
    do: handle_escape_printable(manager, char)

  defp process_escape_state(manager, char) when char in @extended_range,
    do: handle_escape_extended(manager, char)

  defp process_escape_state(manager, _char), do: manager

  defp process_csi_entry_state(manager, char) when char in 0x30..0x3F//1,
    do: set_state(manager, :csi_param)

  defp process_csi_entry_state(manager, char) when char in 0x20..0x2F//1,
    do: set_state(manager, :csi_intermediate)

  defp process_csi_entry_state(manager, char) when char in 0x40..0x7E//1,
    do: set_state(manager, :ground)

  defp process_csi_entry_state(manager, _char),
    do: set_state(manager, :csi_ignore)

  defp process_csi_param_state(manager, char) when char in 0x30..0x3F//1,
    do: manager

  defp process_csi_param_state(manager, char) when char in 0x20..0x2F//1,
    do: set_state(manager, :csi_intermediate)

  defp process_csi_param_state(manager, char) when char in 0x40..0x7E//1,
    do: set_state(manager, :ground)

  defp process_csi_param_state(manager, _char),
    do: set_state(manager, :csi_ignore)

  defp process_csi_intermediate_state(manager, char) when char in 0x20..0x2F//1,
    do: manager

  defp process_csi_intermediate_state(manager, char) when char in 0x40..0x7E//1,
    do: set_state(manager, :ground)

  defp process_csi_intermediate_state(manager, _char),
    do: set_state(manager, :csi_ignore)

  defp process_csi_ignore_state(manager, char) when char in 0x40..0x7E//1,
    do: set_state(manager, :ground)

  defp process_csi_ignore_state(manager, _char), do: manager

  defp process_osc_string_state(manager, @bel),
    do: set_state(manager, :ground)

  defp process_osc_string_state(manager, @st),
    do: set_state(manager, :ground)

  defp process_osc_string_state(manager, char),
    do: set_osc_buffer(manager, manager.osc_buffer <> <<char>>)

  defp process_dcs_entry_state(manager, char) when char in 0x30..0x3F//1,
    do: set_state(manager, :dcs_param)

  defp process_dcs_entry_state(manager, char) when char in 0x20..0x2F//1,
    do: set_state(manager, :dcs_intermediate)

  defp process_dcs_entry_state(manager, char) when char in 0x40..0x7E//1,
    do: set_state(manager, :dcs_passthrough)

  defp process_dcs_entry_state(manager, _char),
    do: set_state(manager, :ground)

  defp process_dcs_param_state(manager, char) when char in 0x30..0x3F//1,
    do: manager

  defp process_dcs_param_state(manager, char) when char in 0x20..0x2F//1,
    do: set_state(manager, :dcs_intermediate)

  defp process_dcs_param_state(manager, char) when char in 0x40..0x7E//1,
    do: set_state(manager, :dcs_passthrough)

  defp process_dcs_param_state(manager, _char),
    do: set_state(manager, :ground)

  defp process_dcs_intermediate_state(manager, char) when char in 0x20..0x2F//1,
    do: manager

  defp process_dcs_intermediate_state(manager, char) when char in 0x40..0x7E//1,
    do: set_state(manager, :dcs_passthrough)

  defp process_dcs_intermediate_state(manager, _char),
    do: set_state(manager, :ground)

  defp process_dcs_passthrough_state(manager, @st),
    do: set_state(manager, :ground)

  defp process_dcs_passthrough_state(manager, char),
    do: set_dcs_buffer(manager, manager.dcs_buffer <> <<char>>)

  defp process_apc_string_state(manager, @bel),
    do: set_state(manager, :ground)

  defp process_apc_string_state(manager, @st),
    do: set_state(manager, :ground)

  defp process_apc_string_state(manager, char),
    do: set_apc_buffer(manager, manager.apc_buffer <> <<char>>)

  defp process_pm_string_state(manager, @bel),
    do: set_state(manager, :ground)

  defp process_pm_string_state(manager, @st),
    do: set_state(manager, :ground)

  defp process_pm_string_state(manager, char),
    do: set_pm_buffer(manager, manager.pm_buffer <> <<char>>)

  defp process_sos_string_state(manager, @bel),
    do: set_state(manager, :ground)

  defp process_sos_string_state(manager, @st),
    do: set_state(manager, :ground)

  defp process_sos_string_state(manager, char),
    do: set_sos_buffer(manager, manager.sos_buffer <> <<char>>)

  defp process_string_state(manager, char) do
    case char do
      c when c == manager.string_terminator -> set_state(manager, :ground)
      c -> set_string_buffer(manager, manager.string_buffer <> <<c>>)
    end
  end

  # Helper functions for handling different character types

  defp handle_c0_control(manager, char) do
    case char do
      @esc -> set_state(manager, :escape)
      @bel -> manager
      @st -> manager
      _ -> manager
    end
  end

  defp handle_c1_control(manager, char) do
    case char do
      @osc -> set_state(manager, :osc_string)
      @pm -> set_state(manager, :pm_string)
      @apc -> set_state(manager, :apc_string)
      @csi -> set_state(manager, :csi_entry)
      @dcs -> set_state(manager, :dcs_entry)
      _ -> manager
    end
  end

  defp handle_printable(manager, _char) do
    manager
  end

  defp handle_extended(manager, _char) do
    manager
  end

  defp handle_escape_printable(manager, char) do
    case char do
      _ when char in 0x30..0x7E//1 -> set_state(manager, :ground)
      _ -> manager
    end
  end

  defp handle_escape_extended(manager, _char) do
    set_state(manager, :ground)
  end

  @doc """
  Gets the current parser state.
  """
  def get_state(%__MODULE__{} = manager) do
    manager.state
  end

  @doc """
  Sets the parser state.
  """
  def set_state(%__MODULE__{} = manager, state)
      when state in [
             :ground,
             :escape,
             :csi_entry,
             :csi_param,
             :csi_intermediate,
             :csi_ignore,
             :osc_string,
             :dcs_entry,
             :dcs_param,
             :dcs_intermediate,
             :dcs_passthrough,
             :apc_string,
             :pm_string,
             :sos_string,
             :string
           ] do
    %{manager | state: state}
  end

  @doc """
  Gets the current parameters.
  """
  def get_params(%__MODULE__{} = manager) do
    manager.params
  end

  @doc """
  Sets the parameters.
  """
  def set_params(%__MODULE__{} = manager, params) when is_list(params) do
    %{manager | params: params}
  end

  @doc """
  Gets the current intermediate characters.
  """
  def get_intermediate(%__MODULE__{} = manager) do
    manager.intermediate
  end

  @doc """
  Sets the intermediate characters.
  """
  def set_intermediate(%__MODULE__{} = manager, intermediate)
      when is_list(intermediate) do
    %{manager | intermediate: intermediate}
  end

  @doc """
  Checks if the parser is in ignore mode.
  """
  def ignore?(%__MODULE__{} = manager) do
    manager.ignore
  end

  @doc """
  Sets the ignore mode.
  """
  def set_ignore(%__MODULE__{} = manager, ignore) when is_boolean(ignore) do
    %{manager | ignore: ignore}
  end

  @doc """
  Gets the OSC buffer content.
  """
  def get_osc_buffer(%__MODULE__{} = manager) do
    manager.osc_buffer
  end

  @doc """
  Sets the OSC buffer content.
  """
  def set_osc_buffer(%__MODULE__{} = manager, content)
      when is_binary(content) do
    %{manager | osc_buffer: content}
  end

  @doc """
  Gets the DCS buffer content.
  """
  def get_dcs_buffer(%__MODULE__{} = manager) do
    manager.dcs_buffer
  end

  @doc """
  Sets the DCS buffer content.
  """
  def set_dcs_buffer(%__MODULE__{} = manager, content)
      when is_binary(content) do
    %{manager | dcs_buffer: content}
  end

  @doc """
  Gets the APC buffer content.
  """
  def get_apc_buffer(%__MODULE__{} = manager) do
    manager.apc_buffer
  end

  @doc """
  Sets the APC buffer content.
  """
  def set_apc_buffer(%__MODULE__{} = manager, content)
      when is_binary(content) do
    %{manager | apc_buffer: content}
  end

  @doc """
  Gets the PM buffer content.
  """
  def get_pm_buffer(%__MODULE__{} = manager) do
    manager.pm_buffer
  end

  @doc """
  Sets the PM buffer content.
  """
  def set_pm_buffer(%__MODULE__{} = manager, content) when is_binary(content) do
    %{manager | pm_buffer: content}
  end

  @doc """
  Gets the SOS buffer content.
  """
  def get_sos_buffer(%__MODULE__{} = manager) do
    manager.sos_buffer
  end

  @doc """
  Sets the SOS buffer content.
  """
  def set_sos_buffer(%__MODULE__{} = manager, content)
      when is_binary(content) do
    %{manager | sos_buffer: content}
  end

  @doc """
  Gets the string buffer content.
  """
  def get_string_buffer(%__MODULE__{} = manager) do
    manager.string_buffer
  end

  @doc """
  Sets the string buffer content.
  """
  def set_string_buffer(%__MODULE__{} = manager, content)
      when is_binary(content) do
    %{manager | string_buffer: content}
  end

  @doc """
  Gets the string terminator.
  """
  def get_string_terminator(%__MODULE__{} = manager) do
    manager.string_terminator
  end

  @doc """
  Sets the string terminator.
  """
  def set_string_terminator(%__MODULE__{} = manager, terminator)
      when is_integer(terminator) do
    %{manager | string_terminator: terminator}
  end

  @doc """
  Gets the string flags.
  """
  def get_string_flags(%__MODULE__{} = manager) do
    manager.string_flags
  end

  @doc """
  Sets the string flags.
  """
  def set_string_flags(%__MODULE__{} = manager, flags) when is_map(flags) do
    %{manager | string_flags: flags}
  end

  @doc """
  Gets the string parser state.
  """
  def get_string_parser_state(%__MODULE__{} = manager) do
    manager.string_parser_state
  end

  @doc """
  Sets the string parser state.
  """
  def set_string_parser_state(%__MODULE__{} = manager, state)
      when state in [
             :ground,
             :escape,
             :csi_entry,
             :csi_param,
             :csi_intermediate,
             :csi_ignore,
             :osc_string,
             :dcs_entry,
             :dcs_param,
             :dcs_intermediate,
             :dcs_passthrough,
             :apc_string,
             :pm_string,
             :sos_string,
             :string
           ] do
    %{manager | string_parser_state: state}
  end

  @doc """
  Clears all string buffers.
  """
  def clear_string_buffers(%__MODULE__{} = manager) do
    %{
      manager
      | osc_buffer: "",
        dcs_buffer: "",
        apc_buffer: "",
        pm_buffer: "",
        sos_buffer: "",
        string_buffer: "",
        string_terminator: nil,
        string_flags: %{},
        string_parser_state: nil
    }
  end

  @doc """
  Resets the parser state manager to its initial state.
  """
  def reset(%__MODULE__{} = _manager) do
    new()
  end

  # Functions expected by tests
  def get_current_state(manager) do
    manager
  end

  def transition_to(manager, :csi_entry) do
    %{
      manager
      | state: :csi_entry,
        params_buffer: "",
        intermediates_buffer: ""
    }
  end

  def transition_to(manager, :osc_string) do
    %{manager | state: :osc_string, payload_buffer: ""}
  end

  def transition_to(manager, :dcs_entry) do
    %{
      manager
      | state: :dcs_entry,
        params_buffer: "",
        intermediates_buffer: "",
        payload_buffer: ""
    }
  end

  def transition_to(manager, _) do
    %{manager | state: :ground}
  end

  def append_param(manager, param) do
    %{manager | params_buffer: manager.params_buffer <> param}
  end

  def append_intermediate(manager, intermediate) do
    append = convert_intermediate_to_string(intermediate)
    %{manager | intermediates_buffer: manager.intermediates_buffer <> append}
  end

  defp convert_intermediate_to_string(intermediate)
       when is_integer(intermediate) do
    <<intermediate>>
  end

  defp convert_intermediate_to_string(intermediate)
       when is_binary(intermediate) do
    intermediate
  end

  defp convert_intermediate_to_string([single]) when is_integer(single) do
    <<single>>
  end

  defp convert_intermediate_to_string(intermediate)
       when is_list(intermediate) do
    to_string(intermediate)
  end

  defp convert_intermediate_to_string(_) do
    ""
  end

  def append_payload(manager, payload) do
    %{manager | payload_buffer: manager.payload_buffer <> payload}
  end

  def set_final_byte(manager, byte) do
    %{manager | final_byte: byte}
  end

  def set_designating_gset(manager, gset) do
    %{manager | designating_gset: gset}
  end

  def process_input(emulator, state, input) do
    handler =
      Map.get(state_handlers_input(), state.state, &handle_default_state/3)

    handler.(emulator, state, input)
  end

  defp handle_default_state(emulator, state, input) do
    {:continue, emulator, %{state | state: :ground}, input}
  end

  defp state_handlers_input do
    %{
      ground: &handle_ground_state/3,
      escape: &handle_escape_state/3
    }
  end

  defp handle_ground_state(emulator, state, input) do
    case detect_single_shift(input) do
      {:ss2, next} -> handle_single_shift(emulator, state, :ss2, next)
      {:ss3, next} -> handle_single_shift(emulator, state, :ss3, next)
      :none -> handle_single_shift_consumption(emulator, state, input)
    end
  end

  defp handle_escape_state(emulator, state, input) do
    case input do
      <<"N", rest::binary>> ->
        # ESC N (SS2) - Single Shift 2
        {:continue, emulator, %{state | state: :ground, single_shift: :ss2}, rest}

      <<"O", rest::binary>> ->
        # ESC O (SS3) - Single Shift 3
        {:continue, emulator, %{state | state: :ground, single_shift: :ss3}, rest}

      <<"[", rest::binary>> ->
        # ESC [ - CSI entry
        {:continue, emulator, %{state | state: :csi_entry}, rest}

      _ ->
        # Default: transition to ground state
        {:continue, emulator, %{state | state: :ground}, input}
    end
  end

  defp detect_single_shift(<<142, next::binary>>), do: {:ss2, next}
  defp detect_single_shift(<<143, next::binary>>), do: {:ss3, next}
  defp detect_single_shift(_), do: :none

  defp handle_single_shift(emulator, state, shift_type, <<char, rest::binary>>) do
    # When there's a character after SS2/SS3, set the shift and then process the character
    # This matches the expected behavior: SS2/SS3 affects the next character only
    state_with_shift = %{state | single_shift: shift_type}

    handle_single_shift_consumption(
      emulator,
      state_with_shift,
      <<char, rest::binary>>
    )
  end

  defp handle_single_shift(emulator, state, shift_type, _) do
    # When SS2/SS3 is at the end of input, set the shift for the next character
    {:continue, emulator, %{state | single_shift: shift_type}, ""}
  end

  defp handle_single_shift_consumption(emulator, state, input) do
    case {state.single_shift, input} do
      {nil, _} ->
        {:continue, emulator, state, input}

      {_shift, <<>>} ->
        # No input to process, keep the shift
        {:continue, emulator, state, input}

      {_shift, <<_byte, rest::binary>>} ->
        # Process the first byte, clear the shift, reset state to :ground, and return the rest
        {:continue, emulator, %{state | single_shift: nil, state: :ground}, rest}
    end
  end
end
