objective-c-compiler/c_lexer.rb

def error(msg)
  puts "ERROR: #{msg}"
  exit 1
end

class Program
  def initialize()

  end
end

#FunctionHeader + Semicolon = FunctionPrototype
#FunctionHeader + Bracket = FunctionDeclaration
#
#Type + Identifier + [Identifier] + Semicolon = VarDecl
#Type + Identifier + Equal + Expr = VarDeclWithValue

class Construct
  def initialize(stream)
    @stream, @back = stream, []
  end

  def spit
    @stream.prepend @back.pop
  end

  def vomit
    @back.reverse.each { spit }
  end

  def bite(flavor)
    @back << @stream.shift
    #bite flavor if @back.last.type == :white
    taste_like? flavor
  end

  def bite_until(flavor)
    until bite flavor
      return if @stream.empty?
    end
  end

  def discard_until(flavor)
    null = nil
    until null == flavor
      h = @stream.shift
      break if h.nil?
      null = h.type
    end
  end

  #lick to get flavor
  def lick
    return @stream.first.type if @stream.first.type == Token
    return @stream.first.class
  end

  #lick until stopping point
  def deep_lick(stop)
    tongue = []
    @stream.each {|s|
      break if s.type == stop
      tongue << s.type if s.class == Token
      tongue << s.class if s.class != Token
    }
    return tongue
  end

  def deep_bite(stop)
    tongue = []
    @stream.each {|s|
      break if s.type == stop
      tongue << s
    }
    return tongue
  end

  def taste_like?(flavor)
    return true if flavor == :any
    return flavor.include? @back.last.class == Token ? @back.last.type : @back.last.class if flavor.class == Array
    return @back.last.type == flavor if @back.last.class == Token
    @back.last.class == flavor
  end

  #i could determine the type here
end

# int main(void) [;|{]
class FunctionHeader < Construct
  def initialize(stream)
    super
  end
  
  def undo
    @stream.prepend @back
  end

  def consume
    @back << @stream.shift
    if [:int, :void].include? @back.last.type
      @back << @stream.shift
    end

    if @back.last.type == :ident
      @back << @stream.shift
    end
    if @back.last.type == :oparn
      @back << @stream.shift
    end
    if [:int, :void].include? @back.last.type
      @back << @stream.shift
    end
    if @back.last.type == :cparn
      @back << @stream.shift
    end
    if @back.last.type == :obrac
      @back << @stream.shift
      return self
    end
    
    undo
    return
  end
end

class Token
  attr_accessor :text
  attr_accessor :type

  def initialize(text, type)
    @text, @type = text, type
  end

  def to_s
    "#{@type}: #{@text}"
  end
end

class Matcher
  def initialize(hash)
    @hash = hash
  end

  def self.match(hash, token)
    hash.each {|k, v|
      return Token.new(token, k) if token =~ v
    }

    return nil
  end

  #modify the token if its a keyword
  def self.match_token(hash, token)
    hash.each {|k,v|
      token.type = k if token.text =~ v
    }

    return token
  end 
end

class StringLiteral
  def initialize(str)
    @text = str
    @type = :string
  end

  def to_s
    "#{@type}: #{@text}"
  end
end

#this could just be a function
class StringSweeper < Construct
  def initialize(stream)
    super stream
    @string_mode = false
  end

  def create_string(stream)
    StringLiteral.new stream.map { |s| s.text }.join
  end

  def sweep
    until @stream.empty?
    bite_until [:quote, nil] #everything before string
    @back << create_string(deep_bite(:quote))
    back_up = @back.pop
    @back.pop #remove extra quote
    @back << back_up
    discard_until :quote #replace all tokens with string
    end
    puts @back
  end
end

class XMLBody < Construct
  def initialize(stream)

  end
end

class XMLClose < Construct
  def initialize(stream)

  end
end

class XMLOpen < Construct
  def initialize(stream)

  end
end

class XML < Construct
  def initialize(stream)
    super stream
  end

  def consume
    bite_until :close
    XMLOpen.new(@back)
  end
end

class Expr < Construct
  @@tokens = {
    :addop => /\+/,
    :subop => /\-/,
    :mulop => /\*/,
    :divop => /\//,
  }

  @@type = :exprn

  def self.tokens
    @@tokens
  end

  def initialize(stream)
    super(stream)
  end

  #parse the expression first
  #determine what kind of expression
  #it is after

  def consume
    #first token could be
    #ident, const, minus, oparn, func_call
    #
    
    if Lexer.keywords.include? lick
      puts "we have a variable (or function) declaration"
    elsif lick == :ident
      puts "we may have an assignment expression"
    elsif deep_lick(:semic).include? :equal
      puts "we definitely have an assignment expression"
      bite_until :semic
      puts @back
    else
      puts "we have an invalid expression"
    end
  end

end

class Lexer
  @@tokens = {
    :ident => /[a-zA-Z_]\w*\b/,
    :const => /[0-9]+\b/,
    :equal => /\=/,
    :oparn => /\(/,
    :cparn => /\)/,
    :obrac => /{/,
    :cbrac => /}/,
    :quote => /\"/,
    :semic => /;/,
    :white => /\s/,
  }.merge Expr.tokens

  @@xml_tokens = {
    :ident => /[a-zA-Z_]\w*/,
    :const => /[0-9]+/,
    :open_ => /\</,
    :close => /\>/,
    :equal => /\=/,
    :slash => /\//,
    :quote => /\"/,
    :white => /\s/,
  }

  @@keywords = {
    :int => /int\b/,
    :short => /short\b/,
    :long => /long\b/,
    :longlong => /long\ long\b/,
    :void => /void\b/,
    :return => /return\b/,
  }

  def self.keywords
    @@keywords.keys
  end

  def initialize(file)
    error "expected input file" if file.nil?
    @source = File.read file
    @xml = false
    @xml = true if File.extname(file) == ".xml"
  end

  def combine_id(tokens)
    skips = 0
    tokens.filter_map.with_index {|token, idx|
      if skips != 0
        skips -= 1
        next
      end

      next token unless token.type == :ident

      while tokens[idx += 1].type == :ident
        token.text << tokens[idx].text
        skips += 1
      end

      next token
    }
  end

  def no_whitespace(tokens)
    tokens.filter { |tok| tok.type != :white }
  end

  def match_keywords(tokens)
    tokens.map {|token|
      Matcher.match_token(@@keywords, token)
    }
  end

  def lex_xml
    tokens = @source.chars.filter_map { |char|
      Matcher.match(@@xml_tokens, char)
    }
    combine_id tokens
  end

  def lex
    return lex_xml if @xml

    tokens = @source.chars.filter_map { |char|
      Matcher.match(@@tokens, char)
    }

    #might be bad for strings with spaces in them
    no_whitespace match_keywords combine_id tokens
  end
end

lexer = Lexer.new(ARGV[0])
stream = lexer.lex
swept = StringSweeper.new(stream)
swept.sweep