defmodule Ace.HTTP.Handler do
  @moduledoc false
  use Ace.Application

  alias Raxx.{
    Response,
    Fragment
  }
  alias Ace.HTTP1

  @packet_timeout 10_000
  @max_line_length 2048

  @bad_request """
  HTTP/1.1 400 Bad Request
  connection: close
  content-length: 0

  """ |> String.replace("\n", "\r\n")

  @start_line_too_long """
  HTTP/1.1 414 URI Too Long
  connection: close
  content-length: 0

  """ |> String.replace("\n", "\r\n")

  @request_timeout """
  HTTP/1.1 408 Request Timeout
  connection: close
  content-length: 0

  """ |> String.replace("\n", "\r\n")

  defstruct [
    :conn_info,
    :status, # request, headers, streamed_body, chunked_body
    :worker,
    :ref,
    :keep_alive
  ]

  def handle_connect(conn_info, app) do
    ref = {:http1, self(), 1}
    {:ok, pid} = HTTP1.Worker.start_link(ref, app)
    state = %__MODULE__{
      conn_info: conn_info,
      status: {:request, :response},
      worker: pid,
      ref: ref,
      keep_alive: false
    }
    {"", "", state}
  end

  defoverridable [handle_connect: 2]

  def handle_connect(info, config) do
    case super(info, config) do
      {outbound, unprocessed, state} ->
        case outbound do
          "" ->
            {:nosend, {unprocessed, state}, @packet_timeout}
          data ->
            {:send, data, {unprocessed, state}, @packet_timeout}
        end
    end
  end

  defp handle_data("", state) do
    {"", "", state}
  end

  defp handle_data(packet, state = %{status: {:request, :response}}) do
    case :erlang.decode_packet(:http_bin, packet, [line_length: @max_line_length]) do
      {:more, :undefined} ->
        {"", packet, state}
      {:ok, {:http_error, line}, rest} ->
        {:error, {:invalid_start_line, line}, rest}
        send(self(), {:exit, :normal})
        {@bad_request, rest, state}
      {:error, :invalid} ->
        send(self(), {:exit, :normal})
        {@start_line_too_long, "", state}
      {:ok, raw_request = {:http_request, _method, _http_uri, _version}, rest} ->
        partial = build_partial_request(raw_request, state.conn_info)
        new_status = {{:request_headers, partial}, :response}
        new_state = %{state | status: new_status}
        handle_data(rest, new_state)
    end
  end

  defp handle_data(packet, state = %{status: {{:request_headers, partial}, :response}}) do
    case :erlang.decode_packet(:httph_bin, packet, []) do
      {:more, :undefined} ->
        {"", packet, state}
      {:ok, {:http_header, _, key, _, value}, rest} ->
        case key do
          :Connection ->
            if value != "close" do
              IO.puts("received 'connection: #{value}', Ace will always close connection")
            end
            new_state = %{state | keep_alive: false}
            handle_data(rest, new_state)
          _other ->
            new_partial = add_header(partial, key, value)
            new_status = {{:request_headers, new_partial}, :response}
            new_state = %{state | status: new_status}
            handle_data(rest, new_state)
        end
      {:ok, {:http_error, line}, rest} ->
        {:error, {:invalid_header_line, line}, rest}
        send(self(), {:exit, :normal})
        {@bad_request, rest, state}
      {:ok, :http_eoh, rest} ->
        {transfer_encoding, partial} = pop_transfer_encoding(partial)
        {request, new_status} = cond do
          transfer_encoding == "chunked" ->
            {Raxx.set_body(partial, true), {:chunked_body, :response}}
          transfer_encoding != nil ->
            raise "Transfer encoding '#{transfer_encoding}' not supported by Ace.HTTP1 (beta)"
          content_length(partial) in [0, nil] ->
            {Raxx.set_body(partial, false), {:complete, :response}}
          (remaining = content_length(partial)) > 0 ->
            {Raxx.set_body(partial, true), {{:body, remaining}, :response}}
        end
        send(state.worker, {state.ref, request})
        new_state = %{state | status: new_status}
        handle_data(rest, new_state)
    end
  end

  defp handle_data(packet, state = %{status: {{:body, remaining}, :response}}) when byte_size(packet) >= remaining do
    <<data::binary-size(remaining), rest::binary>> = packet
    fragment = Raxx.fragment(data, true)
    send(state.worker, {state.ref, fragment})
    new_status = {:complete, :response}
    new_state = %{state | status: new_status}
    {"", rest, new_state}
  end

  defp handle_data(packet, state = %{status: {{:body, remaining}, :response}}) when byte_size(packet) < remaining do
    fragment = Raxx.fragment(packet, false)
    new_status = {{:body, remaining - byte_size(packet)}, :response}
    new_state = %{state | status: new_status}

    send(state.worker, {state.ref, fragment})

    {"", "", new_state}
  end

  defp handle_data(packet, state = %{status: {:chunked_body, :response}}) do
    {chunk, rest} = HTTP1.pop_chunk(packet)
    case chunk do
      nil ->
        {"", rest, state}
      "" ->
        send(state.worker, {state.ref, Raxx.trailer([])})
        {"", rest, state}
      chunk ->
        fragment = Raxx.fragment(chunk, false)
        send(state.worker, {state.ref, fragment})
        {"", rest, state}
    end
  end

  def handle_packet("", x) do
    {:nosend, x}
  end
  def handle_packet(data, {buffer, state}) do
    case handle_data(buffer <> data, state) do
      {outbound, unprocessed, state} ->
        case outbound do
          "" ->
            {:nosend, {unprocessed, state}, @packet_timeout}
          iodata when is_binary(iodata) or is_list(iodata) ->
            {:send, iodata, {unprocessed, state}, @packet_timeout}
        end
    end
  end

  def handle_info({ref = {:http1, _, _}, part}, {buffer, state}) do
    ^ref = state.ref
    {outbound, new_state} = case send_part(part, state) do
      {outbound, :stop} ->
        send(self(), {:exit, :normal})
        {outbound, state}
      {outbound, new_state} ->
        {outbound, new_state}
    end
    {:send, outbound, {buffer, new_state}}
  end
  def handle_info(:timeout, {buffer, state}) do
    send(self(), {:exit, :normal})
    {:send, @request_timeout, {buffer, state}}
  end
  def handle_info({:exit, reason}, _state) do
    exit(reason)
  end

  defp send_part(response = %Response{body: true}, state = %{status: {up, :response}}) do
    case content_length(response) do
      nil ->
        headers = [{"connection", "close"}, {"transfer-encoding", "chunked"} | response.headers]
        new_status = {up, :chunked_body}
        new_state = %{state | status: new_status}
        {HTTP1.serialize_response(response.status, headers, ""), new_state}
      content_length when content_length > 0 ->
        headers = [{"connection", "close"} | response.headers]
        new_status = {up, {:body, content_length}}
        new_state = %{state | status: new_status}
        {HTTP1.serialize_response(response.status, headers, ""), new_state}
    end
  end
  defp send_part(response = %Response{body: false}, state = %{status: {up, :response}}) do
    case content_length(response) do
      nil ->
        headers = [{"connection", "close"}, {"content-length", "0"} | response.headers]
        new_status = {up, :complete}
        new_state = %{state | status: new_status}
        new_state # Not used
        {HTTP1.serialize_response(response.status, headers, ""), :stop}
    end
  end
  defp send_part(response = %Response{body: body}, state = %{status: {up, :response}}) when is_binary(body) do
    case content_length(response) do
      nil ->
        content_length = :erlang.iolist_size(body) |> to_string
        headers = [{"connection", "close"}, {"content-length", content_length} | response.headers]
        new_status = {up, :complete}
        new_state = %{state | status: new_status}
        new_state # Not used
        {HTTP1.serialize_response(response.status, headers, response.body), :stop}
      _content_length ->
        headers = [{"connection", "close"} | response.headers]
        new_status = {up, :complete}
        new_state = %{state | status: new_status}
        new_state # Not used
        {HTTP1.serialize_response(response.status, headers, response.body), :stop}
    end
  end
  defp send_part(fragment = %Fragment{}, state = %{status: {up, {:body, remaining}}}) do
    remaining = remaining - :erlang.iolist_size(fragment.data)
    new_status = {up, {:body, remaining}}
    new_state = %{state | status: new_status}
    {[fragment.data], new_state}
  end
  defp send_part(fragment = %Fragment{end_stream: false}, state = %{status: {_up, :chunked_body}}) do
    chunk = HTTP1.serialize_chunk(fragment.data)
    {[chunk], state}
  end
  defp send_part(fragment = %Fragment{end_stream: true}, %{status: {_up, :chunked_body}}) do
    chunk = HTTP1.serialize_chunk(fragment.data)

    {[chunk, HTTP1.serialize_chunk("")], :stop}
  end

  def handle_disconnect(_reason, _) do
    :ok
  end

  defp build_partial_request({:http_request, method, http_uri, _version}, conn_info) do
    path_string = case http_uri do
      {:abs_path, path_string} ->
        path_string
      {:absoluteURI, _scheme, _host, _port, path_string} ->
        # Throw away the rest of the absolute URI since we are not proxying
        path_string
    end
    %{path: path, query: query_string} = URI.parse(path_string)
    # DEBT in case of path '//' then parsing returns path of nil.
    # e.g. localhost:8080//
    path = path || "/"
    {:ok, query} = URI2.Query.decode(query_string || "")
    path = Raxx.split_path(path)
    scheme = case conn_info.transport do
      :tcp ->
        :http
      :tls ->
        :https
    end
    %Raxx.Request{
      scheme: scheme,
      method: method,
      path: path,
      query: query,
      headers: [],
      body: false
    }
  end

  defp pop_transfer_encoding(request = %{headers: headers}) do
    case :proplists.get_value("transfer-encoding", headers) do
      :undefined ->
        {nil, request}
      binary ->
        headers = :proplists.delete("transfer-encoding", headers)
        {binary, %{request | headers: headers}}
    end
  end
  defp content_length(%{headers: headers}) do
    case :proplists.get_value("content-length", headers) do
      :undefined ->
        nil
      binary ->
        {content_length, ""} = Integer.parse(binary)
      content_length
    end
  end

  defp add_header(request = %{headers: headers}, :Host, location) do
    %{request | headers: headers, authority: location}
  end
  defp add_header(request = %{headers: headers}, key, value) do
    key = String.downcase("#{key}")
    headers = headers ++ [{key, value}]
    %{request | headers: headers}
  end

end