defmodule ConcatJSON.ParseError do

  @type t :: %__MODULE__{position: integer, line: integer}

  defexception [:position, :line, :token]

  def message( %{position: position, line: line, token: token} ) do
    "Unexpected token at position #{position}, line #{line}: " <> inspect_char(token)
  end

  defp inspect_char( char ) do
    str = <<char>>
    if String.printable?(str) do
        "#{inspect char, base: :hex} ('#{str}')"
    else
        "#{inspect char, base: :hex}"
    end
  end
end



defmodule ConcatJSON do
  @moduledoc """
  Documentation for ConcatJSON.
  """
  require Logger
  alias ConcatJSON.{ParseError}

  @default_state %{pos: 0, line: 1, obj: 0, arr: 0, current: nil }

  @type state :: %{ pos: integer, line: integer, obj: integer, arr: integer, current: atom() | nil }
  @type input :: String.t() | list
  @type error :: {:error, ParseError.t() }


  @doc """
  Returns all
    iex> ConcatJSON.parse('{"ok":true}')
    {:ok, ['{"ok":true}'] }
  """
  @spec parse( input ) :: {:ok, list} | {:continue, list, String.t(), list, state } | error
  def parse( value ) do
    parse( value, [], @default_state )
  end

  @doc """

  ## Examples

    iex> ConcatJSON.parse!('[ "foo", "bar" ]')
    ['["foo","bar"]']

    iex> ConcatJSON.parse!('not valid ]')
    ** (ConcatJSON.ParseError) Unexpected token at position 10, line 1: 0x5D (']')

  """
  def parse!( value ) do
    case parse( value ) do
      {:ok, results} -> results
      {:continue, results, _input, _buffer, _state } -> results
      {:error, error} -> raise error
    end
  end

  @doc """

  """
  def parse( input, buffer, state, results \\ [] )

  def parse( input, buffer, state, results ) when is_list(input), do: parse( to_string(input), buffer, state, results )

  def parse( input, buffer, state, results ) do
    # Logger.debug("begin parse input #{String.length(input)} (#{input}) buffer (#{buffer})")
    parse_loop( input, Enum.reverse(buffer), state, results )
  end


  defp parse_loop( input, buffer, state, results ) do

    case walk_parse(input, buffer, state) do
      {:ok, _input, [], _state } ->
        {:ok, results }
      {:ok, "", value, _state } ->
          {:ok, results ++ [ Enum.reverse(value)] }
      {:ok, input, value, state} ->
        # Logger.debug(":ok parse input #{String.length(input)} (#{input}) buffer (#{buffer})")
        parse_loop( input, [], state, results ++ [Enum.reverse(value)] )

      {:continue, input, value, state } ->
        {:continue, results, input, Enum.reverse(value), state }

      other -> other
    end

  end


  @doc """

  inspiration from https://stackoverflow.com/a/29408700/2377677
  """
  def stream(enum) do
    enum
    |> Stream.transform( {}, fn(val,acc) ->
      # Logger.debug "val: (#{val})"
      # IO.puts "acc: #{Jason.encode!(acc)}"

      # call parse depending on whether we are continuing
      parse_result = case acc do
        {:continue, buffer, opts} ->
          # Logger.debug "continue with (#{val}) (#{buffer})"
          ConcatJSON.parse(val, buffer, opts)
        _ ->
          ConcatJSON.parse( val )
      end

      case parse_result do
        {:ok, results} ->
          # Logger.warn ":ok with #{length(results)} (#{results})"
          # parse came back with results, so return them
          {results,{}}
        {:continue, [], _input, buffer, opts } ->
          # Logger.warn "continue with empty results true"
          # the parse was incomplete, so store state in accum for continuing
          # on next read
          {[], {:continue, buffer, opts} }
        {:continue, results, _input, buffer, opts } ->
          # Logger.warn "continue with (#{results}) #{results == []}"
          # parse was incomplete, but came back with results, so emit
          # those results and keep the parse state in the buffer
          {results, {:continue, buffer, opts} }
          # {:error, _buffer, _input, _opts, msg } ->
            # for now we just let errors continue
          # Logger.warn "error: #{msg}"
          # {[], {:error, msg}}
      end
    end)
  end

  @doc """
  Takes an enumeration and parses all of the values
  """
  def reduce(enum) do
    { result, _acc } = Enum.reduce(enum, { [], {} }, fn value, { result, acc } ->
      parse_result = case acc do
        {:continue, buffer, opts } ->
          ConcatJSON.parse(value, buffer, opts)
        _ -> ConcatJSON.parse(value)
      end

      case parse_result do
        {:ok, results} ->
          { result ++ results, {} }
        {:continue, [], _input, buffer, opts } ->
          {result, {:continue, buffer, opts} }
        {:continue, results, _input, buffer, opts } ->
          {result ++ results, {:continue, buffer, opts} }
      end
    end)
    result
  end

  defp walk_parse(binary, acc, state)

    defp walk_parse(binary, acc, state) when is_list(binary) do
      walk_parse(to_string(binary), acc, state)
    end

    defp walk_parse(binary, acc, state) when binary == "" do
      # Logger.debug "walk_parse 4 - binary end (#{binary}) (#{acc})"
      # raise "STAHP"
      {:ok, binary, acc, state}
    end

  # defp walk_parse(binary, acc, state) do
  #   walk_parse(binary, Enum.reverse(to_charlist(acc)), state)
  # end

  defp walk_parse(<<"#", rest::binary>>, acc, %{pos: position} = state) do
    case walk_parse_comment(rest, acc, %{state | pos: position + 1, current: :comment}) do
      {:ok, rest, acc, state} -> walk_parse(rest, acc, state)
      {:continue, rest, acc, state} -> {:continue, rest, acc, state}
    end
  end

  defp walk_parse(<<"//", rest::binary>>, acc, %{pos: position} = state) do
    case walk_parse_comment(rest, acc, %{state | pos: position + 2, current: :comment}) do
      {:ok, rest, acc, state} ->
        # Logger.debug "walk_parse 5 // :ok - (#{rest}) (#{acc})"
        walk_parse(rest, acc, state)
      {:continue, rest, acc, state} ->
        # Logger.debug "walk_parse 5 // :continue"
        {:continue, rest, acc, state}
    end
  end

  defp walk_parse(<<"[", rest::binary>>, acc, %{pos: pos} = state) do
    # Logger.debug("> walk_parse 6 '#{acc}' '[#{rest}'")

    case walk_parse_array(rest, '[' ++ acc, %{state | pos: pos + 1, arr: 1, current: :array}) do
      {:ok, rest, acc, state} -> {:ok, rest, acc, %{state|current: nil}}
      {:continue, rest, acc, state} -> {:continue, rest, acc, state}
    end
  end

  defp walk_parse(<<"{", rest::binary>>, acc, %{pos: pos} = state) do
    # Logger.debug("walk_parse 7 (#{'{' ++ acc}) ({#{rest})")

    case walk_parse_obj(rest, '{' ++ acc, %{state | pos: pos + 1, obj: 1, current: :obj}) do
      {:ok, rest, acc, state} -> {:ok, rest, acc, %{state|current: nil}}
      {:continue, rest, acc, state} -> {:continue, rest, acc, state}
    end
  end

  # continues a partial parse of an obj, array, or string
  defp walk_parse(<<rest::binary>>, acc, %{pos: pos, obj: obj, arr: arr, current: current} = state)
       when obj > 0 or arr > 0 or current == :string or current == :value do

    acc = Enum.reverse(acc)
    # Logger.debug("> walk_parse 7a (#{to_string(acc) <> rest})")

    case walk_parse(to_string(acc) <> rest, [], %{
           state
           | pos: pos - length(acc),
             obj: 0,
             arr: 0,
             current: nil
         }) do
      {:ok, rest, acc, state} -> {:ok, rest, acc, state}
      {:continue, rest, acc, state} -> {:continue, rest, acc, state}
    end
  end

  # continues a partial parse of a comment
  defp walk_parse(<<rest::binary>>, acc, %{pos: pos, current: current} = state)
       when current == :comment do
    acc = Enum.reverse(acc)
    # Logger.debug("> walk_parse 7b '#{to_string(acc) <> rest}'")

    case walk_parse(to_string(acc) <> "#" <> rest, [], %{
           state
           | pos: pos - length(acc),
             current: nil
         }) do
      {:ok, rest, acc, state} -> {:ok, rest, acc, state}
      {:continue, rest, acc, state} -> {:continue, rest, acc, state}
    end
  end

  defp walk_parse(<<ch, _rest::binary>>, _acc, %{pos: pos, line: line})
       when ch == ?] or ch == ?} do
     {:error, %ParseError{position: pos, line: line, token: ch}}
  end

  # begin parsing quote
  defp walk_parse(<<"\"", rest::binary>>, acc, %{pos: pos} = state) do
    case walk_parse_quote(rest, '\"' ++ acc, %{state | pos: pos + 1, current: :string}) do
      {:ok, rest, acc, state} -> {:ok, rest, acc, %{state|current: nil}}
      {code, rest, acc, state} -> {code, rest, acc, state}
    end
  end

  # newline - inc line number
  defp walk_parse(<<"\n", rest::binary>>, acc, %{line: line} = state) do
    # Logger.debug "walk_parse 5 (#{acc}) rest:(#{rest})"
    walk_parse(rest, acc, %{state | pos: 0, line: line + 1})
  end

  defp walk_parse(<<" ", rest::binary>>, acc, %{pos: pos} = state) do
    # Logger.debug "walk_parse space #{acc}"
    walk_parse(rest, acc, %{state | pos: pos + 1})
  end

  # pass everything
  defp walk_parse(<<char, rest::binary>>, acc, %{pos: pos} = state) do
    # Logger.debug "walk_parse char:(#{to_string([char])})"
    case walk_parse_value(rest, [char] ++ acc, %{state| pos: pos + 1, current: :value}) do
      {:ok, rest, acc, state} -> {:ok, rest, acc, %{state|current: nil}}
      {code, rest, acc, state} -> {code, rest, acc, state}
    end
    # walk_parse(rest, [char] ++ acc, %{state | pos: pos + 1})
  end

  defp walk_parse_comment(<<"\n", rest::binary>>, acc, %{line: line} = state) do
    # Logger.debug("walk_parse_comment 1 - :ok")
    {:ok, rest, acc, %{state | line: line + 1, pos: 0, current: nil}}
  end

  defp walk_parse_comment(<<_char, rest::binary>>, acc, %{pos: pos} = state) do
    # Logger.debug("walk_parse_comment 2 ")
    walk_parse_comment(rest, acc, %{state | pos: pos + 1})
  end

  defp walk_parse_comment(binary, acc, state) when binary == "" do
    # Logger.debug("walk_parse_comment 3 - :ok")
    {:continue, binary, acc, state}
  end

  defp walk_parse_quote(<<(~s(\\")), rest::binary>>, acc, %{pos: pos} = state) do
    # Logger.debug("walk_parse_quote 1 #{acc} char:(#{~s(\\")})")
    walk_parse_quote(rest, '\"' ++ acc, %{state | pos: pos + 1})
  end

  defp walk_parse_quote(<<(~s(")), rest::binary>>, acc, %{pos: pos} = state) do
    # Logger.debug("walk_parse_quote 2 #{acc} - fin")
    {:ok, rest, '"' ++ acc, %{state | pos: pos + 1}}
  end

  defp walk_parse_quote(<<char, rest::binary>>, acc, %{pos: pos} = state) do
    # Logger.debug("walk_parse_quote 3 (#{acc}) ++ (#{[char]})")
    walk_parse_quote(rest, [char] ++ acc, %{state | pos: pos + 1})
  end

  defp walk_parse_quote(binary, acc, state) when binary == "" do
    # Logger.debug("walk_parse_quote 4 (#{acc}) (#{binary})")
    {:continue, binary, acc, state}
  end


  # close array - finish if count ends, continue otherwise
  defp walk_parse_array(<<"]", rest::binary>>, acc, %{pos: pos, arr: arr} = state) do
    # Logger.debug("walk_parse_array 2 #{acc} arr:#{arr}")
    acc = ']' ++ acc
    state = %{state | pos: pos + 1, arr: arr - 1}

    case arr do
      1 -> {:ok, rest, acc, state}
      _ -> walk_parse_array(rest, acc, state)
    end
  end

  defp walk_parse_array(<<"[", rest::binary>>, acc, %{pos: pos, arr: arr} = state) do
    # Logger.debug("walk_parse_array 4 #{acc} arr: #{arr + 1}")
    walk_parse_array(rest, '[' ++ acc, %{state | pos: pos + 1, arr: arr + 1})
  end

  defp walk_parse_array(<<"\"", rest::binary>>, acc, %{pos: pos} = state) do
    # Logger.debug("walk_parse_array 5 #{acc}")

    case walk_parse_quote(rest, '"' ++ acc, %{state | pos: pos + 1, current: :string}) do
      {:ok, rest, acc, state} -> walk_parse_array(rest, acc, %{state| current: :array})
      {:continue, rest, acc, state} -> {:continue, rest, acc, state}
    end
  end

  defp walk_parse_array(<<"#", rest::binary>>, acc, %{pos: pos} = state) do
    case walk_parse_comment(rest, acc, %{state | pos: pos + 1, current: :comment}) do
      {:ok, rest, acc, state} -> walk_parse_array(rest, acc, %{state|current: :array})
      {:continue, rest, acc, state} -> {:continue, rest, acc, state}
    end
  end

  defp walk_parse_array(<<"//", rest::binary>>, acc, %{pos: position} = state) do
    case walk_parse_comment(rest, acc, %{state | pos: position + 2, current: :comment}) do
      {:ok, rest, acc, state} -> walk_parse_array(rest, acc, %{state|current: :array})
      {:continue, rest, acc, state} -> {:continue, rest, acc, state}
    end
  end

  defp walk_parse_array(<<"\n", rest::binary>>, acc, %{line: line} = state) do
    # Logger.debug("walk_parse_array 6 #{acc}")
    walk_parse_array(rest, acc, %{state | pos: 0, line: line + 1})
  end

  defp walk_parse_array(<<" ", rest::binary>>, acc, %{pos: pos} = state) do
    # Logger.debug "parse space #{acc}"
    walk_parse_array(rest, acc, %{state | pos: pos + 1})
  end

  # everything else
  defp walk_parse_array(<<char, rest::binary>>, acc, %{pos: pos, arr: _arr} = state) do
    # Logger.debug("walk_parse_array 7 (#{acc}) '#{to_string([char])}' arr:#{arr}")
    walk_parse_array(rest, [char] ++ acc, %{state | pos: pos + 1})
  end

  # end of input
  defp walk_parse_array(binary, acc, state) when binary == "" do
    # Logger.debug("walk_parse_array 8 #{acc}")
    {:continue, binary, acc, state}
  end

  defp walk_parse_obj(<<"}", rest::binary>>, acc, %{pos: pos, obj: obj} = state) when obj == 1 do
    acc = '}' ++ acc
    # Logger.debug("walk_parse_obj 2 (#{acc}) obj:#{obj} - :ok")
    {:ok, rest, acc, %{state | pos: pos + 1, obj: obj - 1}}
  end

  defp walk_parse_obj(<<"}", rest::binary>>, acc, %{pos: pos, obj: obj} = state) do
    # Logger.debug("walk_parse_obj 3 #{acc} obj:#{obj}")
    walk_parse_obj(rest, '}' ++ acc, %{state | pos: pos + 1, obj: obj - 1})
  end

  defp walk_parse_obj(<<"#", rest::binary>>, acc, %{pos: pos} = state) do
    case walk_parse_comment(rest, acc, %{state | pos: pos + 1, current: :comment}) do
      {:ok, rest, acc, state} -> walk_parse_obj(rest, acc, state)
      {:continue, rest, acc, state} -> {:continue, rest, acc, state}
    end
  end

  defp walk_parse_obj(<<"//", rest::binary>>, acc, %{pos: position} = state) do
    case walk_parse_comment(rest, acc, %{state | pos: position + 2, current: :comment}) do
      {:ok, rest, acc, state} -> walk_parse_obj(rest, acc, state)
      {:continue, rest, acc, state} -> {:continue, rest, acc, state}
    end
  end

  defp walk_parse_obj(<<"{", rest::binary>>, acc, %{pos: pos, obj: obj} = state) do
    # Logger.debug("walk_parse_obj 4 #{acc} obj: #{obj + 1}")
    walk_parse_obj(rest, '{' ++ acc, %{state | pos: pos + 1, obj: obj + 1})
  end

  defp walk_parse_obj(<<"\"", rest::binary>>, acc, %{pos: pos} = state) do
    # Logger.debug("walk_parse_obj 5 (#{acc})")

    case walk_parse_quote(rest, '"' ++ acc, %{state | pos: pos + 1, current: :string}) do
      {:ok, rest, acc, state} -> walk_parse_obj(rest, acc, state)
      {:continue, rest, acc, state} -> {:continue, rest, acc, state}
    end
  end

  defp walk_parse_obj(<<"\n", rest::binary>>, acc, %{line: line} = state) do
    # Logger.debug("walk_parse_obj 6 #{acc}")
    walk_parse_obj(rest, acc, %{state | pos: 0, line: line + 1})
  end

  defp walk_parse_obj(<<" ", rest::binary>>, acc, %{pos: pos} = state) do
    # Logger.debug "parse space #{acc}"
    walk_parse_obj(rest, acc, %{state | pos: pos + 1})
  end

  defp walk_parse_obj(<<char, rest::binary>>, acc, %{pos: pos, obj: _obj } = state) do
    # Logger.debug("walk_parse_obj 7 (#{acc}) '#{to_string([char])}' obj:#{obj}")
    walk_parse_obj(rest, [char] ++ acc, %{state | pos: pos + 1})
  end

  defp walk_parse_obj("", acc, state) do
    # Logger.debug("walk_parse_obj 8 #{acc}")
    {:continue, "", acc, state}
  end

  defp walk_parse_value("", acc, state) do
    # Logger.debug("walk_parse_value :continue")
    {:continue, "", acc, state}
  end

  # end of input
  defp walk_parse_value(<<char, rest::binary>>, acc, %{pos: pos} = state) when char == ?\n or char == 32 do
    # Logger.debug "walk_parse_value newline/space :ok"
    {:ok, rest, acc, %{state | pos: pos + 1}}
  end

  # space indicates end of value
  # defp walk_parse_value(<<" ", rest::binary>>, acc, %{pos: pos} = state) do
  #   # Logger.debug "walk_parse_value :ok"
  #   {:ok, rest, acc, %{state | pos: pos + 1}}
  # end

  # regular character
  defp walk_parse_value(<<char, rest::binary>>, acc, %{pos: pos} = state) do
    # Logger.debug "walk_parse_value char:(#{to_string([char])})"
    walk_parse_value(rest, [char] ++ acc, %{state | pos: pos + 1})
  end

  # def finish_ok(acc, rest, state) do
  #   # IO.inspect( acc )
  #   {:ok, to_string(Enum.reverse(acc)), to_string(rest), state}
  # end

  # def finish_continue(acc, rest, state) do
  #   {:continue, to_string(Enum.reverse(acc)), to_string(rest), state}
  # end

end