/*
* Copyright 2020 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* https://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.openrewrite;
import lombok.EqualsAndHashCode;
import org.jspecify.annotations.Nullable;
import java.util.*;
import java.util.function.Function;
import java.util.function.Predicate;
import java.util.stream.Collectors;
import java.util.stream.Stream;
import static java.util.stream.StreamSupport.stream;
/**
* A cursor is linked path of LST elements that can be used to traverse down the tree towards the root.
*/
@EqualsAndHashCode(exclude = "messages")
public class Cursor {
public static final String ROOT_VALUE = "root";
@Nullable
private final Cursor parent;
private final Object value;
@Nullable
private Map messages;
public Cursor(@Nullable Cursor parent, Object value) {
this.parent = parent;
this.value = value;
}
public Cursor getRoot() {
Cursor c = this;
while (c.parent != null) {
c = c.parent;
}
return c;
}
/**
* @return true if this cursor is the root of the tree, false otherwise
*/
final public boolean isRoot() {
return ROOT_VALUE.equals(value);
}
public Iterator getPathAsCursors() {
return new CursorPathIterator(this);
}
public Iterator getPathAsCursors(Predicate filter) {
return new CursorPathIterator(this, filter);
}
public Iterator getPath() {
return new CursorIterator(this);
}
public Iterator getPath(Predicate filter) {
return new CursorIterator(this, filter);
}
public Stream getPathAsStream() {
return stream(Spliterators.spliteratorUnknownSize(getPath(), 0), false);
}
public Stream getPathAsStream(Predicate filter) {
return stream(Spliterators.spliteratorUnknownSize(getPath(filter),
Spliterator.IMMUTABLE), false);
}
private static class CursorPathIterator implements Iterator {
private Predicate filter = c -> true;
private Cursor cursor;
private CursorPathIterator(Cursor cursor) {
this.cursor = cursor;
}
private CursorPathIterator(Cursor cursor, Predicate filter) {
this.cursor = cursor;
this.filter = filter;
}
@Override
public boolean hasNext() {
for (Cursor c = cursor; c != null; c = c.parent) {
if (filter.test(c)) {
return true;
}
}
return false;
}
@Override
public Cursor next() {
for (; cursor != null; cursor = cursor.parent) {
Cursor c = cursor;
if (filter.test(c)) {
cursor = c.parent;
return c;
}
}
throw new NoSuchElementException();
}
}
private static class CursorIterator implements Iterator {
private Cursor cursor;
private Predicate filter = v -> true;
private CursorIterator(Cursor cursor) {
this.cursor = cursor;
}
private CursorIterator(Cursor cursor, Predicate filter) {
this.cursor = cursor;
this.filter = filter;
}
@Override
public boolean hasNext() {
for (Cursor c = cursor; c != null; c = c.parent) {
if (filter.test(c.value)) {
return true;
}
}
return false;
}
@Override
public Object next() {
for (; cursor != null; cursor = cursor.parent) {
Object v = cursor.value;
if (filter.test(v)) {
cursor = cursor.parent;
return v;
}
}
throw new NoSuchElementException();
}
}
public @Nullable T firstEnclosing(Class tClass) {
CursorIterator iter = new CursorIterator(this);
while (iter.hasNext()) {
Object value = iter.next();
if (tClass.isAssignableFrom(value.getClass())) {
//noinspection unchecked
return (T) value;
}
}
return null;
}
public T firstEnclosingOrThrow(Class tClass) {
T firstEnclosing = firstEnclosing(tClass);
if (firstEnclosing == null) {
throw new IllegalStateException("Expected to find enclosing " + tClass.getSimpleName());
}
return firstEnclosing;
}
@Override
public String toString() {
return "Cursor{" +
stream(Spliterators.spliteratorUnknownSize(getPath(), 0), false)
.map(t -> t instanceof Tree ?
t.getClass().getSimpleName() :
t.toString())
.collect(Collectors.joining("->")) +
"}";
}
public Cursor dropParentUntil(Predicate valuePredicate) {
Cursor cursor = parent;
while (cursor != null && !valuePredicate.test(cursor.value)) {
cursor = cursor.parent;
}
if (cursor == null) {
throw new IllegalStateException("Expected to find a matching parent for " + this);
}
return cursor;
}
public Cursor dropParentWhile(Predicate valuePredicate) {
Cursor cursor = parent;
while (cursor != null && valuePredicate.test(cursor.value)) {
cursor = cursor.parent;
}
if (cursor == null) {
throw new IllegalStateException("Expected to find a matching parent for " + this);
}
return cursor;
}
public @Nullable Cursor getParent(int levels) {
Cursor cursor = this;
for (int i = 0; i < levels && cursor != null; i++) {
cursor = cursor.parent;
}
return cursor;
}
public @Nullable Cursor getParent() {
return getParent(1);
}
public Cursor getParentOrThrow(int levels) {
Cursor parent = getParent(levels);
if (parent == null) {
throw new IllegalStateException("Expected to find a parent for " + this);
}
return parent;
}
public Cursor getParentOrThrow() {
return getParentOrThrow(1);
}
/**
* Return the first parent of the current cursor which points to an AST element, or the root cursor if the current
* cursor already points to the root AST element. This skips over non-tree Padding elements.
* T getValue() {
return (T) value;
}
public boolean isScopeInPath(Tree scope) {
return value instanceof Tree && ((Tree) value).getId().equals(scope.getId()) ||
getPathAsStream().anyMatch(p -> p instanceof Tree && ((Tree) p).getId().equals(scope.getId()));
}
public void putMessageOnFirstEnclosing(Class enclosing, String key, Object value) {
if (enclosing.isInstance(this.getValue())) {
putMessage(key, value);
} else if (parent != null) {
parent.putMessageOnFirstEnclosing(enclosing, key, value);
}
}
public void putMessage(String key, Object value) {
if (messages == null) {
messages = new HashMap<>();
}
messages.put(key, value);
}
public T computeMessageIfAbsent(String key, Function mappingFunction) {
if (messages == null) {
messages = new HashMap<>();
}
//noinspection unchecked
return (T) messages.computeIfAbsent(key, mappingFunction);
}
/**
* Finds the closest message matching the provided key, leaving it in the message map for further access.
*
* @param key The message key to find.
* @param The expected value of the message.
* @return The closest message matching the provided key in the cursor stack, or null if none.
*/
public @Nullable T getNearestMessage(String key) {
@SuppressWarnings("unchecked") T t = messages == null ? null : (T) messages.get(key);
return t == null && parent != null ? parent.getNearestMessage(key) : t;
}
public T getNearestMessage(String key, T defaultValue) {
@SuppressWarnings("unchecked") T t = messages == null ? null : (T) messages.get(key);
if (t == null) {
if (parent != null) {
return parent.getNearestMessage(key, defaultValue);
}
return defaultValue;
}
return t;
}
/**
* Finds the closest message matching the provided key, removing it from the message map.
*
* @param key The message key to find.
* @param The expected value of the message.
* @return The closest message matching the provided key in the cursor stack, or null if none.
*/
public @Nullable T pollNearestMessage(String key) {
@SuppressWarnings("unchecked") T t = messages == null ? null : (T) messages.remove(key);
return t == null && parent != null ? parent.pollNearestMessage(key) : t;
}
/**
* Finds the closest message matching the provided key, leaving it in the message map for further access.
*
* @param key The message key to find.
* @param The expected value of the message.
* @return The message matching the provided key, or null if none.
*/
public @Nullable T getMessage(String key) {
//noinspection unchecked
return messages == null ? null : (T) messages.get(key);
}
public T getMessage(String key, T defaultValue) {
//noinspection unchecked
return messages == null ? defaultValue : (T) messages.getOrDefault(key, defaultValue);
}
/**
* Finds the message matching the provided key, removing it from the message map.
*
* @param key The message key to find.
* @param The expected value of the message.
* @return The message matching the provided key, or null if none.
*/
public @Nullable T pollMessage(String key) {
//noinspection unchecked
return messages == null ? null : (T) messages.remove(key);
}
public void clearMessages() {
if (messages != null) {
messages.clear();
messages = null;
}
}
/**
* Creates a cursor at the same position, but with its own messages that can't influence
* the messages of the cursor that was forked.
*
* @return A new cursor with the same position but an initially clear set of messages.
*/
public Cursor fork() {
return new Cursor(parent == null ? null : parent.fork(), value);
}
}
