Class: JGrep::Parser

Inherits:
Object
  • Object
show all
Defined in:
lib/parser/parser.rb

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(args) ⇒ Parser

Returns a new instance of Parser.



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# File 'lib/parser/parser.rb', line 5

def initialize(args)
  @scanner = Scanner.new(args)
  @execution_stack = []

  parse
end

Instance Attribute Details

#execution_stack ⇒ Object (readonly)

Returns the value of attribute execution_stack.



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# File 'lib/parser/parser.rb', line 3

def execution_stack
  @execution_stack
end

#scanner ⇒ Object (readonly)

Returns the value of attribute scanner.



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# File 'lib/parser/parser.rb', line 3

def scanner
  @scanner
end

Instance Method Details

#parse(substatement = nil, token_index = 0) ⇒ Object

Parse the input string, one token at a time a contruct the call stack



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# File 'lib/parser/parser.rb', line 13

def parse(substatement = nil, token_index = 0)
  p_token = nil

  if substatement
    c_token, c_token_value = substatement[token_index]
  else
    c_token, c_token_value = @scanner.get_token
  end

  parenth = 0

  until c_token.nil?
    if substatement
      token_index += 1
      n_token, n_token_value = substatement[token_index]
    else
      @scanner.token_index += 1
      n_token, n_token_value = @scanner.get_token
    end

    next if n_token == " "
    case c_token

    when "and"
      unless (n_token =~ /not|statement|\(|\+|-/) || (scanner.token_index == scanner.arguments.size)
        raise "Error at column #{scanner.token_index}. \nExpected 'not', 'statement' or '('. Found '#{n_token_value}'"
      end

      raise "Error at column #{scanner.token_index}. \n Expression cannot start with 'and'" if p_token.nil?
      raise "Error at column #{scanner.token_index}. \n #{p_token} cannot be followed by 'and'" if %w[and or].include?(p_token)

    when "or"
      unless (n_token =~ /not|statement|\(|\+|-/) || (scanner.token_index == scanner.arguments.size)
        raise "Error at column #{scanner.token_index}. \nExpected 'not', 'statement', '('. Found '#{n_token_value}'"
      end

      raise "Error at column #{scanner.token_index}. \n Expression cannot start with 'or'" if p_token.nil?
      raise "Error at column #{scanner.token_index}. \n #{p_token} cannot be followed by 'or'" if %w[and or].include?(p_token)

    when "not"
      unless n_token =~ /statement|\(|not|\+|-/
        raise "Error at column #{scanner.token_index}. \nExpected 'statement' or '('. Found '#{n_token_value}'"
      end

    when "statement"
      if c_token_value.is_a? Array
        raise "Error at column #{scanner.token_index}\nError, cannot define '[' in a '[...]' block." if substatement

        parse(c_token_value, 0)
      end

      if c_token_value.is_a?(String) && c_token_value =~ /!=/
        c_token_value = c_token_value.gsub("!=", "=")
        @execution_stack << {"not" => "not"}
      end

      if !n_token.nil? && !n_token.match(/and|or|\)/)
        raise "Error at column #{scanner.token_index}. \nExpected 'and', 'or', ')'. Found '#{n_token_value}'"
      end

    when "+"
      if !n_token.nil? && !n_token.match(/and|or|\)/)
        raise "Error at column #{scanner.token_index}. \nExpected 'and', 'or', ')'. Found '#{n_token_value}'"
      end

    when "-"
      if !n_token.nil? && !n_token.match(/and|or|\)/)
        raise "Error at column #{scanner.token_index}. \nExpected 'and', 'or', ')'. Found '#{n_token_value}'"
      end

    when ")"
      if !n_token.nil? && n_token !~ /|and|or|not|\(/
        raise "Error at column #{scanner.token_index}. \nExpected 'and', 'or', 'not' or '('. Found '#{n_token_value}'"
      end

      parenth += 1

    when "("
      unless n_token =~ /statement|not|\(|\+|-/
        raise "Error at column #{scanner.token_index}. \nExpected 'statement', '(',  not. Found '#{n_token_value}'"
      end

      parenth -= 1

    else
      raise "Unexpected token found at column #{scanner.token_index}. '#{c_token_value}'"
    end

    unless n_token == " " || substatement
      @execution_stack << {c_token => c_token_value}
    end

    p_token = c_token
    c_token = n_token
    c_token_value = n_token_value
  end

  return if substatement

  raise "Error. Missing parentheses ')'." if parenth < 0
  raise "Error. Missing parentheses '('." if parenth > 0
end