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package org.zwobble.couscous.interpreter;
import java.util.List;
import java.util.Map;
import java.util.Optional;
import java.util.stream.IntStream;
import org.zwobble.couscous.Project;
import org.zwobble.couscous.ast.Assignment;
import org.zwobble.couscous.ast.ExpressionNode;
import org.zwobble.couscous.ast.ExpressionStatementNode;
import org.zwobble.couscous.ast.LiteralNode;
import org.zwobble.couscous.ast.MethodNode;
import org.zwobble.couscous.ast.ReturnNode;
import org.zwobble.couscous.ast.VariableReferenceNode;
import org.zwobble.couscous.ast.visitors.ExpressionNodeVisitor;
import org.zwobble.couscous.ast.visitors.StatementNodeVisitor;
import org.zwobble.couscous.values.InterpreterValue;
import static com.google.common.collect.Iterables.find;
import static java.util.stream.Collectors.toMap;
import static org.zwobble.couscous.values.UnitValue.UNIT;
import lombok.val;
public class Interpreter {
private Project project;
public Interpreter(Project project) {
this.project = project;
}
public InterpreterValue run(String className, String methodName, List<InterpreterValue> arguments) {
val clazz = project.findClass(className);
val method = find(clazz.getMethods(),
method -> method.getName().equals(methodName));
val stackFrame = buildStackFrame(method, arguments);
for (val statement : method.getBody()) {
val result = statement.accept(new Executor(new Evaluator(stackFrame)));
if (result.isPresent()) {
return result.get();
}
}
return UNIT;
}
private Map<Integer, InterpreterValue> buildStackFrame(
final MethodNode method,
List<InterpreterValue> arguments) {
if (method.getArguments().size() != arguments.size()) {
throw new WrongNumberOfArguments(method.getArguments().size(), arguments.size());
}
return IntStream.range(0, method.getArguments().size())
.boxed()
.collect(toMap(
index -> method.getArguments().get(index).getId(),
index -> arguments.get(index)));
}
private class Executor implements StatementNodeVisitor<Optional<InterpreterValue>> {
private Evaluator evaluator;
public Executor(Evaluator evaluator) {
this.evaluator = evaluator;
}
@Override
public Optional<InterpreterValue> visit(ReturnNode returnNode) {
return Optional.of(evaluator.eval(returnNode.getValue()));
}
@Override
public Optional<InterpreterValue> visit(ExpressionStatementNode expressionStatement) {
evaluator.eval(expressionStatement.getExpression());
return Optional.empty();
}
}
private class Evaluator implements ExpressionNodeVisitor<InterpreterValue> {
private final Map<Integer, InterpreterValue> stackFrame;
public Evaluator(Map<Integer, InterpreterValue> stackFrame) {
this.stackFrame = stackFrame;
}
public InterpreterValue eval(ExpressionNode expression) {
return expression.accept(this);
}
@Override
public InterpreterValue visit(LiteralNode literal) {
return literal.getValue();
}
@Override
public InterpreterValue visit(VariableReferenceNode variableReference) {
return stackFrame.get(variableReference.getReferentId());
}
@Override
public InterpreterValue visit(Assignment assignment) {
val value = eval(assignment.getValue());
stackFrame.put(assignment.getTarget().getReferentId(), value);
return value;
}
}
}
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