Class: DParse::Parsers::JSON

Inherits:
DParse::Parser show all
Defined in:
lib/d-parse/parsers/highlevel/json.rb

Class Method Summary collapse

Instance Method Summary collapse

Methods inherited from DParse::Parser

#apply, #bind, #capture, #compact, #expectation_message, #first, #flatten, #ignore, #inspect, #map, #match?, #read, #second, #select_even, #select_odd, #to_s

Constructor Details

#initialize ⇒ JSON

Returns a new instance of JSON.

Raises:

  • (ArgumentError) 


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# File 'lib/d-parse/parsers/highlevel/json.rb', line 232

def initialize(*)
  raise ArgumentError, "#{self.class} is not supposed to be initialized"
end

Class Method Details

.new ⇒ Object 



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# File 'lib/d-parse/parsers/highlevel/json.rb', line 4

def self.new
  extend DParse::DSL

  json_value = nil # Undefined for now

  whitespace =
    repeat(
      alt(
        char(' '),
        char("\t"),
        char("\r"),
        char("\n"),
      ),
    )

  # String

  json_digit_hex =
    alt(
      char_in('0'..'9'),
      char_in('a'..'f'),
      char_in('A'..'F'),
    )

  json_string =
    seq(
      char('"').ignore,
      repeat(
        alt(
          char_not_in(%w(" \\ )).capture,
          seq(
            char('\\').ignore,
            alt(
              char_in(%w(" \\ / b f n r t)).capture,
              seq(
                char('u').capture,
                seq(
                  json_digit_hex,
                  json_digit_hex,
                  json_digit_hex,
                  json_digit_hex,
                ).capture,
              ),
            ),
          ).compact,
        ),
      ),
      char('"').ignore,
    ).compact.first.map do |d, _, _|
      new_chars =
        d.map do |char|
          case char
          when ::String
            char
          when ::Array
            case char[0]
            when '"'
              '"'
            when '\\'
              '\\'
            when '/'
              '/'
            when 'b'
              "\b"
            when 'f'
              "\f"
            when 'n'
              "\n"
            when 'r'
              "\r"
            when 't'
              "\t"
            else
              if char[0].is_a?(Array) && char[0][0] == 'u'
                char[0][1].to_i(16).chr(Encoding::UTF_8)
              else
                raise "Unexpected escape sequence #{char[0].inspect}"
              end
            end
          else
            raise "??? #{char.inspect} (#{char.class})"
          end
        end

      new_chars.join('')
    end

  # Array

  json_elements =
    intersperse(
      lazy { json_value },
      seq(
        whitespace,
        char(','),
        whitespace,
      ).ignore,
    ).compact

  json_array =
    seq(
      char('[').ignore,
      whitespace.ignore,
      json_elements,
      whitespace.ignore,
      char(']').ignore,
    ).compact.first

  # Misc

  json_true =
    string('true').map { true }

  json_false =
    string('false').map { false }

  json_null =
    string('null').map { nil }

  # Number

  json_digit =
    char_in('0'..'9')

  json_number =
    seq(
      opt(char('-')).capture,
      alt(
        char('0'),
        seq(
          char_in('1'..'9'),
          repeat(json_digit),
        ),
      ).capture,
      opt(
        seq(
          char('.').ignore,
          repeat(json_digit).capture,
        ).compact,
      ),
      opt(
        seq(
          alt(char('e'), char('E')),
          alt(char('+'), char('-'), succeed).capture,
          repeat(json_digit).capture,
        ).compact,
      ),
    ).map do |d, _, _|
      sign_char          = d[0]
      digits_before_dot  = d[1]
      digits_after_dot   = d[2]
      sci_data           = d[3]

      base =
        if digits_after_dot
          [sign_char, digits_before_dot, '.', digits_after_dot].join('').to_f
        else
          [sign_char, digits_before_dot].join('').to_i(10)
        end

      factor =
        if sci_data
          sign_char = sci_data[0]
          exponent  = sci_data[1]

          unsigned_factor = exponent.to_i(10)

          case sign_char
          when '+', ''
            10**unsigned_factor
          when '-'
            - 10**unsigned_factor
          end
        else
          1
        end

      base * factor
    end

  # Object

  json_pair =
    seq(
      json_string,
      whitespace.ignore,
      char(':').ignore,
      whitespace.ignore,
      lazy { json_value },
    ).compact

  json_pairs =
    intersperse(
      json_pair,
      seq(
        whitespace,
        char(','),
        whitespace,
      ).ignore,
    ).compact.map { |d| Hash[d] }

  json_object =
    seq(
      char('{').ignore,
      whitespace.ignore,
      json_pairs,
      whitespace.ignore,
      char('}').ignore,
    ).compact.first

  # Value

  json_value =
    alt(
      json_string,
      json_number,
      json_object,
      json_array,
      json_true,
      json_false,
      json_null,
    )

  # All

  json_object
end