1 files changed, 201 insertions, 0 deletions
diff --git a/dice-lang/src/bjc/dicelang/ast/DiceASTReferenceSanitizer.java b/dice-lang/src/bjc/dicelang/ast/DiceASTReferenceSanitizer.java
new file mode 100644
index 0000000..d8f658e
--- /dev/null
+++ b/dice-lang/src/bjc/dicelang/ast/DiceASTReferenceSanitizer.java
@@ -0,0 +1,201 @@
+package bjc.dicelang.ast;
+
+import bjc.utils.data.IHolder;
+import bjc.utils.data.Identity;
+import bjc.utils.funcdata.IMap;
+import bjc.utils.funcdata.ITree;
+import bjc.utils.funcdata.TopDownTransformResult;
+import bjc.utils.funcdata.Tree;
+
+import bjc.dicelang.ast.nodes.IDiceASTNode;
+import bjc.dicelang.ast.nodes.OperatorDiceNode;
+import bjc.dicelang.ast.nodes.VariableDiceNode;
+
+/**
+ * Sanitize the references in an AST so that a variable that refers to
+ * itself in its definition has the occurance of it replaced with its
+ * previous definition
+ * 
+ * @author ben
+ *
+ */
+public class DiceASTReferenceSanitizer {
+	private static ITree<IDiceASTNode> doSanitize(ITree<IDiceASTNode> ast,
+			IMap<String, ITree<IDiceASTNode>> enviroment) {
+		if (ast.getChildrenCount() != 2) {
+			throw new UnsupportedOperationException(
+					"Assignment must have two arguments.");
+		}
+
+		ITree<IDiceASTNode> nameTree = ast.getChild(0);
+		ITree<IDiceASTNode> valueTree = ast.getChild(1);
+
+		if (!DiceASTUtils.containsSimpleVariable(nameTree)) {
+			if (nameTree.getHead() == OperatorDiceNode.ARRAY) {
+				IHolder<Boolean> allSimpleVariables = new Identity<>(true);
+
+				nameTree.doForChildren((child) -> {
+					if (allSimpleVariables.getValue()) {
+						boolean isSimple = DiceASTUtils
+								.containsSimpleVariable(child);
+
+						allSimpleVariables.replace(isSimple);
+					}
+				});
+
+				if (!allSimpleVariables.getValue()) {
+					throw new UnsupportedOperationException(
+							"Array assignment must be between variables and"
+									+ " a expression/array of expressions");
+				}
+
+				if (valueTree.getHead() == OperatorDiceNode.ARRAY) {
+					if (nameTree.getChildrenCount() != valueTree
+							.getChildrenCount()) {
+						throw new UnsupportedOperationException(
+								"Array assignment between arrays must be"
+										+ " between two arrays of equal length");
+					}
+				}
+			} else {
+				throw new UnsupportedOperationException(
+						"Assignment must be between a variable and a expression");
+			}
+		}
+
+		if (nameTree.getHead() == OperatorDiceNode.ARRAY) {
+			if (valueTree.getHead() == OperatorDiceNode.ARRAY) {
+				IHolder<Integer> childCounter = new Identity<>(0);
+
+				ITree<IDiceASTNode> returnTree = new Tree<>(
+						OperatorDiceNode.ARRAY);
+
+				nameTree.doForChildren((child) -> {
+					String variableName = child.transformHead((node) -> {
+						return ((VariableDiceNode) node).getVariable();
+					});
+
+					ITree<IDiceASTNode> currentValue = valueTree
+							.getChild(childCounter.getValue());
+
+					ITree<IDiceASTNode> sanitizedSubtree = doSingleSanitize(
+							ast, enviroment, child, currentValue,
+							variableName);
+
+					if (sanitizedSubtree == null) {
+						ITree<IDiceASTNode> oldTree = new Tree<>(
+								ast.getHead(), child, currentValue);
+
+						returnTree.addChild(oldTree);
+					} else {
+						returnTree.addChild(sanitizedSubtree);
+					}
+
+					childCounter.transform((count) -> count + 1);
+				});
+
+				return returnTree;
+			}
+
+			ITree<IDiceASTNode> returnTree = new Tree<>(
+					OperatorDiceNode.ARRAY);
+
+			nameTree.doForChildren((child) -> {
+				String variableName = child.transformHead(
+						(node) -> ((VariableDiceNode) node).getVariable());
+
+				ITree<IDiceASTNode> sanitizedChild = doSingleSanitize(ast,
+						enviroment, child, valueTree, variableName);
+				if (sanitizedChild == null) {
+					ITree<IDiceASTNode> oldTree = new Tree<>(ast.getHead(),
+							child, valueTree);
+
+					returnTree.addChild(oldTree);
+				} else {
+					returnTree.addChild(sanitizedChild);
+				}
+			});
+
+			return returnTree;
+		}
+
+		String variableName = nameTree.transformHead(
+				(node) -> ((VariableDiceNode) node).getVariable());
+
+		ITree<IDiceASTNode> sanitizedTree = doSingleSanitize(ast,
+				enviroment, nameTree, valueTree, variableName);
+
+		if (sanitizedTree == null) {
+			return ast;
+		}
+
+		return sanitizedTree;
+	}
+
+	private static ITree<IDiceASTNode> doSingleSanitize(
+			ITree<IDiceASTNode> ast,
+			IMap<String, ITree<IDiceASTNode>> enviroment,
+			ITree<IDiceASTNode> nameTree, ITree<IDiceASTNode> valueTree,
+			String variableName) {
+		if (enviroment.containsKey(variableName)) {
+			// @ is a meta-variable standing for the left side of an
+			// assignment
+			ITree<IDiceASTNode> oldVal = enviroment.put("@",
+					enviroment.get(variableName));
+
+			// We should always inline out references to last, because it
+			// will always change
+			ITree<IDiceASTNode> inlinedValue = DiceASTInliner
+					.selectiveInline(valueTree, enviroment, variableName,
+							"last", "@");
+
+			if (oldVal != null) {
+				enviroment.put("@", oldVal);
+			} else {
+				enviroment.remove("@");
+			}
+
+			return new Tree<>(ast.getHead(), nameTree, inlinedValue);
+		}
+
+		return null;
+	}
+
+	/**
+	 * Sanitize the references in an AST
+	 * 
+	 * @param ast
+	 * @param enviroment
+	 * @return The sanitized AST
+	 */
+	public static ITree<IDiceASTNode> sanitize(ITree<IDiceASTNode> ast,
+			IMap<String, ITree<IDiceASTNode>> enviroment) {
+		return ast.topDownTransform(
+				DiceASTReferenceSanitizer::shouldSanitize, (subTree) -> {
+					return doSanitize(subTree, enviroment);
+				});
+	}
+
+	private static TopDownTransformResult shouldSanitize(
+			IDiceASTNode node) {
+		if (!node.isOperator()) {
+			return TopDownTransformResult.SKIP;
+		}
+
+		switch (((OperatorDiceNode) node)) {
+			case ASSIGN:
+				return TopDownTransformResult.TRANSFORM;
+			case ARRAY:
+			case LET:
+				return TopDownTransformResult.PASSTHROUGH;
+			case ADD:
+			case COMPOUND:
+			case DIVIDE:
+			case GROUP:
+			case MULTIPLY:
+			case SUBTRACT:
+			default:
+				return TopDownTransformResult.SKIP;
+		}
+	}
+}