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package org.zwobble.couscous.interpreter;
import org.zwobble.couscous.ast.*;
import org.zwobble.couscous.ast.visitors.NodeMapperWithDefault;
import org.zwobble.couscous.ast.visitors.StatementNodeMapper;
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;
import static org.zwobble.couscous.interpreter.Evaluator.evalCondition;
public class Executor implements StatementNodeMapper<Optional<InterpreterValue>> {
public static InterpreterValue callMethod(
Environment environment,
MethodNode method,
Optional<InterpreterValue> thisValue,
PositionalArguments actualArguments)
{
List<StatementNode> body = method.getBody().orElseThrow(() -> new RuntimeException("Cannot call abstract method"));
return callMethod(environment, method.getArguments(), body, thisValue, actualArguments);
}
public static InterpreterValue callConstructor(
Environment environment,
ConstructorNode constructor,
Optional<InterpreterValue> thisValue,
PositionalArguments actualArguments)
{
return callMethod(environment, constructor.getArguments(), constructor.getBody(), thisValue, actualArguments);
}
private static InterpreterValue callMethod(
Environment environment,
List<FormalArgumentNode> formalArguments,
List<StatementNode> statements,
Optional<InterpreterValue> thisValue,
PositionalArguments actualArguments)
{
Environment innerEnvironment = buildEnvironment(environment, formalArguments, statements, thisValue, actualArguments);
return exec(innerEnvironment, statements)
.orElse(UnitInterpreterValue.UNIT);
}
private static Environment buildEnvironment(
Environment environment,
List<FormalArgumentNode> formalArguments,
List<StatementNode> statements,
Optional<InterpreterValue> thisValue,
PositionalArguments arguments)
{
// TODO use map with multiple iterables
final org.zwobble.couscous.interpreter.StackFrameBuilder stackFrame = new StackFrameBuilder();
for (int index = 0; index < formalArguments.size(); index++) {
stackFrame.declare(formalArguments.get(index), arguments.get(index));
}
findDeclarations(statements).forEach(declaration -> stackFrame.declare(declaration));
return environment.withStackFrame(thisValue, stackFrame.build());
}
private static Stream<VariableNode> findDeclarations(List<StatementNode> body) {
return body.stream()
.flatMap(statement -> descendantNodesAndSelf(statement, node -> node instanceof StatementNode))
.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, Iterable<StatementNode> statements) {
for (StatementNode statement : statements) {
Optional<InterpreterValue> result = exec(environment, statement);
if (result.isPresent()) {
return result;
}
}
return Optional.empty();
}
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(environment, ifStatement.getCondition())
? ifStatement.getTrueBranch()
: ifStatement.getFalseBranch();
return exec(body);
}
@Override
public Optional<InterpreterValue> visit(WhileNode whileLoop) {
while (evalCondition(environment, whileLoop.getCondition())) {
Optional<InterpreterValue> result = exec(whileLoop.getBody());
if (result.isPresent()) {
return result;
}
}
return Optional.empty();
}
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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