package org.checkerframework.javacutil;

import com.sun.source.tree.ClassTree;
import com.sun.source.util.JavacTask;
import com.sun.source.util.TaskEvent;
import com.sun.source.util.TaskListener;
import com.sun.source.util.TreePath;
import com.sun.source.util.Trees;
import com.sun.tools.javac.comp.CompileStates.CompileState;
import com.sun.tools.javac.main.JavaCompiler;
import com.sun.tools.javac.processing.JavacProcessingEnvironment;
import com.sun.tools.javac.util.Context;
import com.sun.tools.javac.util.Log;
import java.util.HashSet;
import java.util.Set;
import javax.annotation.processing.AbstractProcessor;
import javax.annotation.processing.ProcessingEnvironment;
import javax.annotation.processing.Processor;
import javax.annotation.processing.RoundEnvironment;
import javax.lang.model.element.Name;
import javax.lang.model.element.TypeElement;
import javax.lang.model.util.ElementFilter;

/**
 * This class is an abstract annotation processor designed to be a convenient superclass for
 * concrete "type processors", processors that require the type information in the processed source.
 *
 * <p>Type processing occurs in one round after the tool (e.g. Java compiler) analyzes the source
 * (all sources taken as input to the tool and sources generated by other annotation processors).
 *
 * <p>The tool infrastructure will interact with classes extending this abstract class as follows.
 *
 * <p>1-3 are identical to the {@link Processor} life cycle. 4-5 are unique to {@code
 * AbstractTypeProcessor} subclasses.
 *
 * <ol>
 *   <li>If an existing {@code Processor} object is not being used, to create an instance of a
 *       processor the tool calls the no-arg constructor of the processor class.
 *   <li>Next, the tool calls the {@link #init init} method with an appropriate {@code
 *       ProcessingEnvironment}.
 *   <li>Afterwards, the tool calls {@link #getSupportedAnnotationTypes
 *       getSupportedAnnotationTypes}, {@link #getSupportedOptions getSupportedOptions}, and {@link
 *       #getSupportedSourceVersion getSupportedSourceVersion}. These methods are only called once
 *       per run, not on each round.
 *   <li>For each class containing a supported annotation, the tool calls {@link
 *       #typeProcess(TypeElement, TreePath) typeProcess} method on the {@code Processor}. The class
 *       is guaranteed to be type-checked Java code and all the tree type and symbol information is
 *       resolved.
 *   <li>Finally, the tools calls the {@link #typeProcessingOver() typeProcessingOver} method on the
 *       {@code Processor}.
 * </ol>
 *
 * <p>The tool is permitted to ask type processors to process a class once it is analyzed before the
 * rest of classes are analyzed. The tool is also permitted to stop type processing immediately if
 * any errors are raised, without invoking {@code typeProcessingOver}
 *
 * <p>A subclass may override any of the methods in this class, as long as the general {@link
 * javax.annotation.processing.Processor Processor} contract is obeyed, with one notable exception.
 * {@link #process(Set, RoundEnvironment)} may not be overridden, as it is called during the
 * declaration annotation phase before classes are analyzed.
 */
public abstract class AbstractTypeProcessor extends AbstractProcessor {
    /**
     * The set of fully-qualified element names that should be type-checked. We store the names of
     * the elements, in order to prevent possible confusion between different Element
     * instantiations.
     */
    private final Set<Name> elements = new HashSet<>();

    /**
     * Method {@link #typeProcessingStart()} must be invoked exactly once, before any invocation of
     * {@link #typeProcess(TypeElement, TreePath)}.
     */
    private boolean hasInvokedTypeProcessingStart = false;

    /**
     * Method {@link #typeProcessingOver()} must be invoked exactly once, after the last invocation
     * of {@link #typeProcess(TypeElement, TreePath)}.
     */
    private static boolean hasInvokedTypeProcessingOver = false;

    /** The TaskListener registered for completion of attribution. */
    private final AttributionTaskListener listener = new AttributionTaskListener();

    /** Constructor for subclasses to call. */
    protected AbstractTypeProcessor() {}

    /**
     * {@inheritDoc}
     *
     * <p>Register a TaskListener that will get called after FLOW.
     */
    @Override
    public synchronized void init(ProcessingEnvironment env) {
        super.init(env);
        JavacTask.instance(env).addTaskListener(listener);
        Context ctx = ((JavacProcessingEnvironment) processingEnv).getContext();
        JavaCompiler compiler = JavaCompiler.instance(ctx);
        compiler.shouldStopPolicyIfNoError =
                CompileState.max(compiler.shouldStopPolicyIfNoError, CompileState.FLOW);
        compiler.shouldStopPolicyIfError =
                CompileState.max(compiler.shouldStopPolicyIfError, CompileState.FLOW);
    }

    /**
     * The use of this method is obsolete in type processors. The method is called during
     * declaration annotation processing phase only. It registers the names of elements to process.
     */
    @Override
    public final boolean process(
            Set<? extends TypeElement> annotations, RoundEnvironment roundEnv) {
        for (TypeElement elem : ElementFilter.typesIn(roundEnv.getRootElements())) {
            elements.add(elem.getQualifiedName());
        }
        return false;
    }

    /**
     * A method to be called once before the first call to typeProcess.
     *
     * <p>Subclasses may override this method to do any initialization work.
     */
    public void typeProcessingStart() {}

    /**
     * Processes a fully-analyzed class that contains a supported annotation (see {@link
     * #getSupportedAnnotationTypes()}).
     *
     * <p>The passed class is always valid type-checked Java code.
     *
     * @param element element of the analyzed class
     * @param tree the tree path to the element, with the leaf being a {@link ClassTree}
     */
    public abstract void typeProcess(TypeElement element, TreePath tree);

    /**
     * A method to be called once all the classes are processed and no error is reported.
     *
     * <p>Subclasses may override this method to do any aggregate analysis (e.g. generate report,
     * persistence) or resource deallocation.
     *
     * <p>If an error (a Java error or a processor error) is reported, this method is not guaranteed
     * to be invoked.
     */
    public void typeProcessingOver() {}

    /** A task listener that invokes the processor whenever a class is fully analyzed. */
    private final class AttributionTaskListener implements TaskListener {

        @Override
        public void finished(TaskEvent e) {
            if (e.getKind() != TaskEvent.Kind.ANALYZE) {
                return;
            }

            if (!hasInvokedTypeProcessingStart) {
                typeProcessingStart();
                hasInvokedTypeProcessingStart = true;
            }

            Log log = Log.instance(((JavacProcessingEnvironment) processingEnv).getContext());

            if (!hasInvokedTypeProcessingOver && elements.isEmpty() && log.nerrors == 0) {
                typeProcessingOver();
                hasInvokedTypeProcessingOver = true;
            }

            if (e.getTypeElement() == null) {
                throw new BugInCF("event task without a type element");
            }
            if (e.getCompilationUnit() == null) {
                throw new BugInCF("event task without compilation unit");
            }

            if (!elements.remove(e.getTypeElement().getQualifiedName())) {
                return;
            }

            TypeElement elem = e.getTypeElement();
            TreePath p = Trees.instance(processingEnv).getPath(elem);

            typeProcess(elem, p);

            if (!hasInvokedTypeProcessingOver && elements.isEmpty() && log.nerrors == 0) {
                typeProcessingOver();
                hasInvokedTypeProcessingOver = true;
            }
        }

        @Override
        public void started(TaskEvent e) {}
    }
}
