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package org.zwobble.couscous.interpreter;
import org.zwobble.couscous.ast.*;
import org.zwobble.couscous.ast.structure.NodeStructure;
import org.zwobble.couscous.ast.visitors.NodeMapperWithDefault;
import org.zwobble.couscous.ast.visitors.StatementNodeMapper;
import org.zwobble.couscous.interpreter.values.BooleanInterpreterValue;
import org.zwobble.couscous.interpreter.values.InterpreterValue;
import org.zwobble.couscous.interpreter.values.UnitInterpreterValue;
import java.util.List;
import java.util.Optional;
import java.util.stream.Stream;
import static org.zwobble.couscous.ast.structure.NodeStructure.descendantNodesAndSelf;
import static org.zwobble.couscous.interpreter.Evaluator.eval;
public class Executor implements StatementNodeMapper<Optional<InterpreterValue>> {
public static InterpreterValue callMethod(Environment environment, CallableNode method, Optional<InterpreterValue> thisValue, PositionalArguments arguments) {
final org.zwobble.couscous.interpreter.Environment innerEnvironment = buildEnvironment(environment, method, thisValue, arguments);
for (final org.zwobble.couscous.ast.StatementNode statement : method.getBody()) {
final java.util.Optional<org.zwobble.couscous.interpreter.values.InterpreterValue> result = exec(innerEnvironment, statement);
if (result.isPresent()) {
return result.get();
}
}
return UnitInterpreterValue.UNIT;
}
private static Environment buildEnvironment(final Environment environment, final CallableNode method, Optional<InterpreterValue> thisValue, PositionalArguments arguments) {
final org.zwobble.couscous.interpreter.StackFrameBuilder stackFrame = new StackFrameBuilder();
for (int index = 0; index < method.getArguments().size(); index++) {
stackFrame.declare(method.getArguments().get(index), arguments.get(index));
}
findDeclarations(method.getBody()).forEach(declaration -> stackFrame.declare(declaration));
return environment.withStackFrame(thisValue, stackFrame.build());
}
private static Stream<VariableNode> findDeclarations(List<StatementNode> body) {
// TODO: add filter argument to descendantNodesAndSelf to allow recursion to be stopped early
return body.stream()
.flatMap(NodeStructure::descendantNodesAndSelf)
.flatMap(node -> node.accept(new NodeMapperWithDefault<Stream<VariableNode>>(Stream.empty()) {
@Override
public Stream<VariableNode> visit(LocalVariableDeclarationNode localVariableDeclaration) {
return Stream.of(localVariableDeclaration);
}
}));
}
public static Optional<InterpreterValue> exec(Environment environment, StatementNode statement) {
return statement.accept(new Executor(environment));
}
private final Environment environment;
private Executor(Environment environment) {
this.environment = environment;
}
@Override
public Optional<InterpreterValue> visit(ReturnNode returnNode) {
return Optional.of(eval(environment, returnNode.getValue()));
}
@Override
public Optional<InterpreterValue> visit(ExpressionStatementNode expressionStatement) {
eval(environment, expressionStatement.getExpression());
return Optional.empty();
}
@Override
public Optional<InterpreterValue> visit(LocalVariableDeclarationNode localVariableDeclaration) {
final org.zwobble.couscous.interpreter.values.InterpreterValue value = eval(environment, localVariableDeclaration.getInitialValue());
environment.put(localVariableDeclaration, value);
return Optional.empty();
}
@Override
public Optional<InterpreterValue> visit(IfStatementNode ifStatement) {
List<StatementNode> body = evalCondition(ifStatement.getCondition())
? ifStatement.getTrueBranch()
: ifStatement.getFalseBranch();
return exec(body);
}
@Override
public Optional<InterpreterValue> visit(WhileNode whileLoop) {
while (evalCondition(whileLoop.getCondition())) {
Optional<InterpreterValue> result = exec(whileLoop.getBody());
if (result.isPresent()) {
return result;
}
}
return Optional.empty();
}
private boolean evalCondition(ExpressionNode conditionExpression) {
BooleanInterpreterValue condition = (BooleanInterpreterValue) eval(environment, conditionExpression);
return condition.getValue();
}
private Optional<InterpreterValue> exec(List<StatementNode> statements) {
for (StatementNode statement : statements) {
Optional<InterpreterValue> result = exec(environment, statement);
if (result.isPresent()) {
return result;
}
}
return Optional.empty();
}
}
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