1 files changed, 152 insertions, 0 deletions
diff --git a/dice-lang/src/main/java/bjc/dicelang/DiceExpressionParser.java b/dice-lang/src/main/java/bjc/dicelang/DiceExpressionParser.java
new file mode 100644
index 0000000..9f96835
--- /dev/null
+++ b/dice-lang/src/main/java/bjc/dicelang/DiceExpressionParser.java
@@ -0,0 +1,152 @@
+package bjc.dicelang;
+
+import java.util.Map;
+import java.util.Stack;
+
+import org.apache.commons.lang3.StringUtils;
+
+import bjc.utils.funcdata.FunctionalList;
+import bjc.utils.funcdata.FunctionalStringTokenizer;
+import bjc.utils.parserutils.ShuntingYard;
+
+/**
+ * Parse a dice expression from a string
+ * 
+ * @author ben
+ *
+ */
+public class DiceExpressionParser {
+	/**
+	 * Parse a dice expression from a string
+	 * 
+	 * @param exp
+	 *            The string to parse an expression from
+	 * @param env
+	 *            The enviroment to use when parsing expressions
+	 * @return The parsed dice expression
+	 */
+	public IDiceExpression parse(String exp,
+			Map<String, IDiceExpression> env) {
+		/*
+		 * Create a tokenizer over the strings
+		 */
+		FunctionalStringTokenizer fst = new FunctionalStringTokenizer(exp);
+
+		/*
+		 * Create a shunter to rewrite the expression
+		 */
+		ShuntingYard<String> yard = new ShuntingYard<>();
+
+		/*
+		 * Add our custom operators to the yard
+		 */
+		yard.addOp("d", 5); // dice operator: use for creating variable
+							// size dice groups
+		yard.addOp("c", 6); // compound operator: use for creating compound
+							// dice from expressions
+		yard.addOp(":=", 0); // binding operator: Bind a name to a variable
+								// expression
+
+		/*
+		 * Shunt the expression to postfix form
+		 */
+		FunctionalList<String> ls =
+				yard.postfix(fst.toList(s -> s), s -> s);
+
+		/*
+		 * Create a stack for building an expression from parts
+		 */
+		Stack<IDiceExpression> dexps = new Stack<>();
+
+		/*
+		 * Create the expression from parts
+		 */
+		ls.forEach((tok) -> {
+			/*
+			 * Handle compound dice
+			 */
+			if (StringUtils.countMatches(tok, 'c') == 1
+					&& !tok.equalsIgnoreCase("c")) {
+				String[] strangs = tok.split("c");
+
+				dexps.push(new CompoundDice(strangs));
+			} else if (StringUtils.countMatches(tok, 'd') == 1
+					&& !tok.equalsIgnoreCase("d")) {
+				/*
+				 * Handle dice groups
+				 */
+				dexps.push(ComplexDice.fromString(tok));
+			} else {
+				try {
+					/*
+					 * Handle scalar numbers
+					 */
+					dexps.push(new ScalarDie(Integer.parseInt(tok)));
+				} catch (NumberFormatException nfex) {
+
+					if (dexps.size() >= 2) {
+						/*
+						 * Apply an operation to two dice
+						 */
+						IDiceExpression r = dexps.pop();
+						IDiceExpression l = dexps.pop();
+						switch (tok) {
+							case ":=":
+								dexps.push(new BindingDiceExpression(l, r,
+										env));
+								break;
+							case "+":
+								dexps.push(new CompoundDiceExpression(r, l,
+										DiceExpressionType.ADD));
+								break;
+							case "-":
+								dexps.push(new CompoundDiceExpression(r, l,
+										DiceExpressionType.SUBTRACT));
+								break;
+							case "*":
+								dexps.push(new CompoundDiceExpression(r, l,
+										DiceExpressionType.MULTIPLY));
+								break;
+							case "/":
+								dexps.push(new CompoundDiceExpression(r, l,
+										DiceExpressionType.DIVIDE));
+								break;
+							case "c":
+								dexps.push(new CompoundDice(l, r));
+								break;
+							case "d":
+								dexps.push(new ComplexDice(l, r));
+								break;
+							default:
+								/*
+								 * Parse it as a variable reference
+								 * 
+								 * Make sure to restore popped variables
+								 */
+								dexps.push(l);
+								dexps.push(r);
+
+								dexps.push(new ReferenceDiceExpression(tok,
+										env));
+						}
+					} else {
+						/*
+						 * Parse it as a variable reference
+						 */
+						dexps.push(new ReferenceDiceExpression(tok, env));
+					}
+				}
+			}
+		});
+
+		if (dexps.size() != 1) {
+			System.err.println(
+					"WARNING: Leftovers found on dice expression stack. Remember, := is assignment.");
+		}
+
+		/*
+		 * Return the built expression
+		 */
+		return dexps.pop();
+	}
+}