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package org.zwobble.couscous.interpreter;
import java.util.List;
import java.util.Optional;
import java.util.stream.Stream;
import org.zwobble.couscous.ast.ExpressionStatementNode;
import org.zwobble.couscous.ast.LocalVariableDeclarationNode;
import org.zwobble.couscous.ast.MethodNode;
import org.zwobble.couscous.ast.ReturnNode;
import org.zwobble.couscous.ast.StatementNode;
import org.zwobble.couscous.ast.VariableNode;
import org.zwobble.couscous.ast.visitors.StatementNodeVisitor;
import org.zwobble.couscous.values.InterpreterValue;
import org.zwobble.couscous.values.UnitValue;
import static org.zwobble.couscous.interpreter.Evaluator.eval;
import lombok.val;
public class Executor implements StatementNodeVisitor<Optional<InterpreterValue>> {
public static InterpreterValue callMethod(Environment environment, MethodNode method, Arguments arguments) {
val innerEnvironment = buildEnvironment(environment, method, arguments);
for (val statement : method.getBody()) {
val result = exec(innerEnvironment, statement);
if (result.isPresent()) {
return result.get();
}
}
return UnitValue.UNIT;
}
private static Environment buildEnvironment(
final Environment environment,
final MethodNode method,
Arguments arguments) {
val 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(stackFrame.build());
}
private static Stream<VariableNode> findDeclarations(List<StatementNode> body) {
return body.stream()
.flatMap(statement -> statement.accept(new StatementNodeVisitor<Stream<VariableNode>>() {
@Override
public Stream<VariableNode> visit(ReturnNode returnNode) {
return Stream.empty();
}
@Override
public Stream<VariableNode> visit(ExpressionStatementNode expressionStatement) {
return 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) {
val value = eval(environment, localVariableDeclaration.getInitialValue());
environment.put(localVariableDeclaration, value);
return Optional.empty();
}
}
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