1 files changed, 173 insertions, 0 deletions
diff --git a/dice-lang/src/bjc/dicelang/v1/DiceExpressionParser.java b/dice-lang/src/bjc/dicelang/v1/DiceExpressionParser.java
new file mode 100644
index 0000000..fd8f37b
--- /dev/null
+++ b/dice-lang/src/bjc/dicelang/v1/DiceExpressionParser.java
@@ -0,0 +1,173 @@
+package bjc.dicelang.v1;
+
+import java.util.Map;
+import java.util.Stack;
+
+import bjc.utils.funcdata.FunctionalStringTokenizer;
+import bjc.utils.funcdata.IList;
+import bjc.utils.parserutils.ShuntingYard;
+
+import org.apache.commons.lang3.StringUtils;
+
+/**
+ * Parse a dice expression from a string
+ * 
+ * @author ben
+ *
+ */
+public class DiceExpressionParser {
+	/**
+	 * Parse a dice expression from a string
+	 * 
+	 * @param expression
+	 *            The string to parse an expression from
+	 * @param enviroment
+	 *            The enviroment to use when parsing expressions
+	 * @return The parsed dice expression
+	 */
+	public static IDiceExpression parse(String expression,
+			Map<String, IDiceExpression> enviroment) {
+		/*
+		 * Create a tokenizer over the strings
+		 */
+		FunctionalStringTokenizer tokenizer = new FunctionalStringTokenizer(
+				expression);
+
+		/*
+		 * Create a shunter to rewrite the expression
+		 */
+		ShuntingYard<String> yard = new ShuntingYard<>(true);
+
+		/*
+		 * 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
+		 */
+		IList<String> list = yard.postfix(tokenizer.toList(), s -> s);
+
+		/*
+		 * Create a stack for building an expression from parts
+		 */
+		Stack<IDiceExpression> expressions = new Stack<>();
+
+		/*
+		 * Create the expression from parts
+		 */
+		list.forEach((expressionPart) -> {
+			/*
+			 * Handle compound dice
+			 */
+			if (StringUtils.countMatches(expressionPart, 'c') == 1
+					&& !expressionPart.equalsIgnoreCase("c")) {
+				String[] strangs = expressionPart.split("c");
+
+				expressions.push(new CompoundDice(strangs));
+			} else if (StringUtils.countMatches(expressionPart, 'd') == 1
+					&& !expressionPart.equalsIgnoreCase("d")) {
+				/*
+				 * Handle dice groups
+				 */
+				expressions.push(ComplexDice.fromString(expressionPart));
+			} else {
+				try {
+					/*
+					 * Handle scalar numbers
+					 */
+					expressions.push(new ScalarDie(
+							Integer.parseInt(expressionPart)));
+				} catch (NumberFormatException nfex) {
+					// We don't care about details, just that it failed
+					if (expressions.size() >= 2) {
+						/*
+						 * Apply an operation to two dice
+						 */
+						IDiceExpression right = expressions
+								.pop();
+						IDiceExpression left = expressions.pop();
+
+						switch (expressionPart) {
+							case ":=":
+								expressions.push(new BindingDiceExpression(
+										left, right,
+										enviroment));
+								break;
+							case "+":
+								expressions
+										.push(new OperatorDiceExpression(
+												right,
+												left,
+												DiceExpressionType.ADD));
+								break;
+							case "-":
+								expressions
+										.push(new OperatorDiceExpression(
+												right,
+												left,
+												DiceExpressionType.SUBTRACT));
+								break;
+							case "*":
+								expressions
+										.push(new OperatorDiceExpression(
+												right,
+												left,
+												DiceExpressionType.MULTIPLY));
+								break;
+							case "/":
+								expressions
+										.push(new OperatorDiceExpression(
+												right,
+												left,
+												DiceExpressionType.DIVIDE));
+								break;
+							case "c":
+								expressions.push(new CompoundDice(
+										left, right));
+								break;
+							case "d":
+								expressions.push(new ComplexDice(
+										left, right));
+								break;
+							default:
+								/*
+								 * Parse it as a variable reference
+								 * 
+								 * Make sure to restore popped variables
+								 */
+								expressions.push(left);
+								expressions.push(right);
+
+								expressions
+										.push(new ReferenceDiceExpression(
+												expressionPart,
+												enviroment));
+						}
+					} else {
+						/*
+						 * Parse it as a variable reference
+						 */
+						expressions.push(new ReferenceDiceExpression(
+								expressionPart, enviroment));
+					}
+				}
+			}
+		});
+
+		if (expressions.size() != 1) {
+			System.err.println(
+					"WARNING: Leftovers found on dice expression stack. Remember, := is assignment.");
+		}
+
+		/*
+		 * Return the built expression
+		 */
+		return expressions.pop();
+	}
+}