1 files changed, 209 insertions, 0 deletions
diff --git a/dice-lang/src/main/java/bjc/dicelang/old/ast/optimization/DiceASTOptimizer.java b/dice-lang/src/main/java/bjc/dicelang/old/ast/optimization/DiceASTOptimizer.java
new file mode 100644
index 0000000..dead812
--- /dev/null
+++ b/dice-lang/src/main/java/bjc/dicelang/old/ast/optimization/DiceASTOptimizer.java
@@ -0,0 +1,209 @@
+package bjc.dicelang.old.ast.optimization;
+
+import static bjc.dicelang.old.ast.nodes.DiceASTType.*;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.function.BiFunction;
+import java.util.function.BinaryOperator;
+
+import bjc.dicelang.IDiceExpression;
+import bjc.dicelang.old.ast.nodes.DiceASTType;
+import bjc.dicelang.old.ast.nodes.IDiceASTNode;
+import bjc.dicelang.old.ast.nodes.LiteralDiceNode;
+import bjc.dicelang.old.ast.nodes.OperatorDiceNode;
+import bjc.utils.parserutils.AST;
+
+/**
+ * Optimize an AST
+ * 
+ * @author ben
+ *
+ */
+public class DiceASTOptimizer {
+	private static final class NestedArithmeticOperationCollapser
+			implements BinaryOperator<AST<IDiceASTNode>> {
+		private IDiceASTNode							type;
+		private BiFunction<Integer, Integer, Integer>	valueCollapser;
+
+		public NestedArithmeticOperationCollapser(IDiceASTNode type,
+				BiFunction<Integer, Integer, Integer> valueCollapser) {
+			this.type = type;
+			this.valueCollapser = valueCollapser;
+		}
+
+		@Override
+		public AST<IDiceASTNode> apply(AST<IDiceASTNode> leftAST,
+				AST<IDiceASTNode> rightAST) {
+			AST<IDiceASTNode> rightBranchOfLeftAST = leftAST
+					.applyToRight((rightSideAST) -> rightSideAST);
+			AST<IDiceASTNode> leftBranchOfLeftAST = leftAST
+					.applyToRight((rightSideAST) -> rightSideAST);
+
+			boolean leftContainsNestedConstant = DiceASTOptimizer
+					.checkNodeType(rightBranchOfLeftAST, LITERAL)
+					&& DiceASTOptimizer.isNodeConstant(leftAST);
+
+			boolean isRightConstant = DiceASTOptimizer
+					.checkNodeType(rightAST, LITERAL)
+					&& DiceASTOptimizer.isNodeConstant(leftAST);
+
+			if (leftContainsNestedConstant && isRightConstant) {
+				int combinedValue = valueCollapser.apply(
+						getNodeValue(rightBranchOfLeftAST),
+						getNodeValue(rightAST));
+
+				AST<IDiceASTNode> newRightBranch = new AST<>(
+						new LiteralDiceNode(combinedValue));
+
+				return new AST<>(type, leftBranchOfLeftAST,
+						newRightBranch);
+			}
+
+			return new AST<>(type, leftAST, rightAST);
+		}
+	}
+
+	private static final class ArithmeticOperationCollapser
+			implements BinaryOperator<AST<IDiceASTNode>> {
+		private IDiceASTNode							type;
+		private BiFunction<Integer, Integer, Integer>	valueCollapser;
+		private boolean									doSwap;
+
+		public ArithmeticOperationCollapser(IDiceASTNode type,
+				BiFunction<Integer, Integer, Integer> valueCollapser,
+				boolean doSwap) {
+			this.type = type;
+			this.valueCollapser = valueCollapser;
+			this.doSwap = doSwap;
+		}
+
+		@Override
+		public AST<IDiceASTNode> apply(AST<IDiceASTNode> leftAST,
+				AST<IDiceASTNode> rightAST) {
+			boolean isLeftConstant = DiceASTOptimizer
+					.checkNodeType(leftAST, LITERAL)
+					&& DiceASTOptimizer.isNodeConstant(leftAST);
+
+			boolean isRightConstant = DiceASTOptimizer
+					.checkNodeType(rightAST, LITERAL)
+					&& DiceASTOptimizer.isNodeConstant(leftAST);
+
+			if (isLeftConstant) {
+				if (isRightConstant) {
+					int combinedValue = valueCollapser.apply(
+							getNodeValue(leftAST), getNodeValue(rightAST));
+
+					return new AST<>(new LiteralDiceNode(combinedValue));
+				}
+
+				if (doSwap) {
+					return new AST<>(type, rightAST, leftAST);
+				}
+			}
+
+			return new AST<>(type, leftAST, rightAST);
+		}
+	}
+
+	private static Map<IDiceASTNode, BinaryOperator<AST<IDiceASTNode>>> buildConstantCollapsers() {
+		Map<IDiceASTNode, BinaryOperator<AST<IDiceASTNode>>> operatorCollapsers = new HashMap<>();
+
+		operatorCollapsers.put(OperatorDiceNode.ADD,
+				new ArithmeticOperationCollapser(OperatorDiceNode.ADD,
+						(leftVal, rightVal) -> leftVal + rightVal, true));
+
+		operatorCollapsers.put(OperatorDiceNode.MULTIPLY,
+				new ArithmeticOperationCollapser(OperatorDiceNode.MULTIPLY,
+						(leftVal, rightVal) -> leftVal * rightVal, true));
+
+		operatorCollapsers.put(OperatorDiceNode.SUBTRACT,
+				new ArithmeticOperationCollapser(OperatorDiceNode.SUBTRACT,
+						(leftVal, rightVal) -> leftVal - rightVal, false));
+
+		operatorCollapsers.put(OperatorDiceNode.DIVIDE,
+				new ArithmeticOperationCollapser(OperatorDiceNode.DIVIDE,
+						(leftVal, rightVal) -> leftVal / rightVal, false));
+
+		return operatorCollapsers;
+	}
+
+	private static Map<IDiceASTNode, BinaryOperator<AST<IDiceASTNode>>> buildNestedConstantCollapsers() {
+		Map<IDiceASTNode, BinaryOperator<AST<IDiceASTNode>>> operatorCollapsers = new HashMap<>();
+
+		operatorCollapsers.put(OperatorDiceNode.ADD,
+				new NestedArithmeticOperationCollapser(
+						OperatorDiceNode.ADD,
+						(leftVal, rightVal) -> leftVal + rightVal));
+
+		operatorCollapsers.put(OperatorDiceNode.MULTIPLY,
+				new NestedArithmeticOperationCollapser(
+						OperatorDiceNode.MULTIPLY,
+						(leftVal, rightVal) -> leftVal * rightVal));
+
+		return operatorCollapsers;
+	}
+
+	private static AST<IDiceASTNode> collapseLeaf(IDiceASTNode leaf) {
+		// Can't optimize a simple reference
+		if (leaf.getType() == VARIABLE) {
+			return new AST<>(leaf);
+		} else if (leaf.getType() == LITERAL) {
+			LiteralDiceNode node = (LiteralDiceNode) leaf;
+
+			return new AST<>(optimizeLiteral(node, node.toExpression()));
+		} else {
+			throw new UnsupportedOperationException(
+					"Found leaf operator. This isn't supported");
+		}
+	}
+
+	private static IDiceASTNode optimizeLiteral(LiteralDiceNode node,
+			IDiceExpression leaf) {
+		if (leaf.canOptimize()) {
+			return new LiteralDiceNode(Integer.toString(leaf.optimize()));
+		}
+
+		return node;
+	}
+
+	private static AST<IDiceASTNode> finishTree(AST<IDiceASTNode> tree) {
+		return tree;
+	}
+
+	/**
+	 * Optimize a tree of expressions into a simpler form
+	 * 
+	 * @param tree
+	 *            The tree to optimize
+	 * @return The optimized tree
+	 */
+	public static AST<IDiceASTNode> optimizeTree(AST<IDiceASTNode> tree) {
+		AST<IDiceASTNode> astWithConstantsFolded = tree.collapse(
+				DiceASTOptimizer::collapseLeaf,
+				buildConstantCollapsers()::get,
+				DiceASTOptimizer::finishTree);
+
+		AST<IDiceASTNode> astWithNestedConstantsFolded = astWithConstantsFolded
+				.collapse(DiceASTOptimizer::collapseLeaf,
+						buildNestedConstantCollapsers()::get,
+						DiceASTOptimizer::finishTree);
+
+		return astWithNestedConstantsFolded;
+	}
+
+	private static boolean checkNodeType(AST<IDiceASTNode> ast,
+			DiceASTType type) {
+		return ast.applyToHead((node) -> node.getType()) == type;
+	}
+
+	private static boolean isNodeConstant(AST<IDiceASTNode> ast) {
+		return ast.applyToHead(
+				(node) -> ((LiteralDiceNode) node).isConstant());
+	}
+
+	private static int getNodeValue(AST<IDiceASTNode> ast) {
+		return ast.applyToHead(
+				(node) -> ((LiteralDiceNode) node).toConstant());
+	}
+}