Parser + boilerplate for Among Us

1 files changed, 48 insertions, 0 deletions

diff --git a/src/among_us/parser.cr b/src/among_us/parser.cr
new file mode 100644
index 0000000..84894bd
--- /dev/null
+++ b/src/among_us/parser.cr
@@ -0,0 +1,48 @@
+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
+