src/among_us/parser.cr


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require "../util.cr"
require "./among_us.cr"

struct AmongUs::Parser
  def initialize(code_io : IO)
    @raw_code = code_io.gets_to_end
    code_io.close
  end

  def parse : Array(Instruction)
    tokens = @raw_code.split
    instructions = [] of Instruction
    color_seen = false
    sus_safe = false

    tokens.each do |token|
      case token.upcase
      when "WHO?"
        instructions << Command::WHO
      when "WHERE?"
        instructions << Command::WHERE
      else
        i = parse_instruction(token)
        if i.nil?
          raise Util::ParserError.new("Failed to parse command/color '#{token}'")
        end
        instructions << i
      end

      color_seen = true if instructions[-1].is_a?(Color)
      if instructions[-1] == Command::SUS && !sus_safe
        unless color_seen
          raise Util::ParserError.new("Provided program uses SUS command, but no colors are provided before first SUS")
        end
        sus_safe = true
      end
    end

    return instructions
  end

  private def parse_instruction(str : String) : Instruction?
    i = Command.parse?(str)
    return i unless i.nil?
    Color.parse?(str)
  end
end