// Copyright (C) 2009 The Android Open Source Project
//
// 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
//
// http://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 com.google.gerrit.server.query;
import static com.google.gerrit.server.query.Predicate.and;
import static com.google.gerrit.server.query.Predicate.not;
import static com.google.gerrit.server.query.Predicate.or;
import static com.google.gerrit.server.query.QueryParser.AND;
import static com.google.gerrit.server.query.QueryParser.DEFAULT_FIELD;
import static com.google.gerrit.server.query.QueryParser.EXACT_PHRASE;
import static com.google.gerrit.server.query.QueryParser.FIELD_NAME;
import static com.google.gerrit.server.query.QueryParser.NOT;
import static com.google.gerrit.server.query.QueryParser.OR;
import static com.google.gerrit.server.query.QueryParser.SINGLE_WORD;
import static com.google.gerrit.server.query.QueryParser.VARIABLE_ASSIGN;
import org.antlr.runtime.tree.Tree;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
/**
* Base class to support writing parsers for query languages.
* <p>
* Subclasses may document their supported query operators by declaring public
* methods that perform the query conversion into a {@link Predicate}. For
* example, to support "is:starred", "is:unread", and nothing else, a subclass
* may write:
*
* <pre>
* @Operator
* public Predicate is(final String value) {
* if ("starred".equals(value)) {
* return new StarredPredicate();
* }
* if ("unread".equals(value)) {
* return new UnreadPredicate();
* }
* throw new IllegalArgumentException();
* }
* </pre>
* <p>
* The available operator methods are discovered at runtime via reflection.
* Method names (after being converted to lowercase), correspond to operators in
* the query language, method string values correspond to the operator argument.
* Methods must be declared {@code public}, returning {@link Predicate},
* accepting one {@link String}, and annotated with the {@link Operator}
* annotation.
* <p>
* Subclasses may also declare a handler for values which appear without
* operator by overriding {@link #defaultField(String)}.
*
* @param <T> type of object the predicates can evaluate in memory.
*/
public abstract class QueryBuilder<T> {
/**
* Defines the operators known by a QueryBuilder.
*
* This class is thread-safe and may be reused or cached.
*
* @param <T> type of object the predicates can evaluate in memory.
* @param <Q> type of the query builder subclass.
*/
public static class Definition<T, Q extends QueryBuilder<T>> {
private final Map<String, OperatorFactory<T, Q>> opFactories =
new HashMap<>();
public Definition(Class<Q> clazz) {
// Guess at the supported operators by scanning methods.
//
Class<?> c = clazz;
while (c != QueryBuilder.class) {
for (final Method method : c.getDeclaredMethods()) {
if (method.getAnnotation(Operator.class) != null
&& Predicate.class.isAssignableFrom(method.getReturnType())
&& method.getParameterTypes().length == 1
&& method.getParameterTypes()[0] == String.class
&& (method.getModifiers() & Modifier.ABSTRACT) == 0
&& (method.getModifiers() & Modifier.PUBLIC) == Modifier.PUBLIC) {
final String name = method.getName().toLowerCase();
if (!opFactories.containsKey(name)) {
opFactories.put(name, new ReflectionFactory<T, Q>(name, method));
}
}
}
c = c.getSuperclass();
}
}
}
/**
* Locate a predicate in the predicate tree.
*
* @param p the predicate to find.
* @param clazz type of the predicate instance.
* @return the predicate, null if not found.
*/
@SuppressWarnings("unchecked")
public static <T, P extends Predicate<T>> P find(Predicate<T> p, Class<P> clazz) {
if (clazz.isAssignableFrom(p.getClass())) {
return (P) p;
}
for (Predicate<T> c : p.getChildren()) {
P r = find(c, clazz);
if (r != null) {
return r;
}
}
return null;
}
/**
* Locate a predicate in the predicate tree.
*
* @param p the predicate to find.
* @param clazz type of the predicate instance.
* @param name name of the operator.
* @return the predicate, null if not found.
*/
@SuppressWarnings("unchecked")
public static <T, P extends OperatorPredicate<T>> P find(Predicate<T> p,
Class<P> clazz, String name) {
if (p instanceof OperatorPredicate
&& ((OperatorPredicate<?>) p).getOperator().equals(name)
&& clazz.isAssignableFrom(p.getClass())) {
return (P) p;
}
for (Predicate<T> c : p.getChildren()) {
P r = find(c, clazz, name);
if (r != null) {
return r;
}
}
return null;
}
@SuppressWarnings("rawtypes")
private final Map<String, OperatorFactory> opFactories;
@SuppressWarnings({"unchecked", "rawtypes"})
protected QueryBuilder(Definition<T, ? extends QueryBuilder<T>> def) {
opFactories = (Map) def.opFactories;
}
/**
* Parse a user supplied query string into a predicate.
*
* @param query the query string.
* @return predicate representing the user query.
* @throws QueryParseException the query string is invalid and cannot be
* parsed by this parser. This may be due to a syntax error, may be
* due to an operator not being supported, or due to an invalid value
* being passed to a recognized operator.
*/
public Predicate<T> parse(final String query) throws QueryParseException {
return toPredicate(QueryParser.parse(query));
}
private Predicate<T> toPredicate(final Tree r) throws QueryParseException,
IllegalArgumentException {
switch (r.getType()) {
case AND:
return and(children(r));
case OR:
return or(children(r));
case NOT:
return not(toPredicate(onlyChildOf(r)));
case DEFAULT_FIELD:
return defaultField(onlyChildOf(r));
case FIELD_NAME:
return operator(r.getText(), onlyChildOf(r));
case VARIABLE_ASSIGN: {
final String var = r.getText();
final Tree opTree = onlyChildOf(r);
if (opTree.getType() == FIELD_NAME) {
final Tree val = onlyChildOf(opTree);
if (val.getType() == SINGLE_WORD && "*".equals(val.getText())) {
final String op = opTree.getText();
final WildPatternPredicate<T> pat = new WildPatternPredicate<>(op);
return new VariablePredicate<>(var, pat);
}
}
return new VariablePredicate<>(var, toPredicate(opTree));
}
default:
throw error("Unsupported operator: " + r);
}
}
private Predicate<T> operator(final String name, final Tree val)
throws QueryParseException {
switch (val.getType()) {
// Expand multiple values, "foo:(a b c)", as though they were written
// out with the longer form, "foo:a foo:b foo:c".
//
case AND:
case OR: {
List<Predicate<T>> p = new ArrayList<>(val.getChildCount());
for (int i = 0; i < val.getChildCount(); i++) {
final Tree c = val.getChild(i);
if (c.getType() != DEFAULT_FIELD) {
throw error("Nested operator not expected: " + c);
}
p.add(operator(name, onlyChildOf(c)));
}
return val.getType() == AND ? and(p) : or(p);
}
case SINGLE_WORD:
case EXACT_PHRASE:
if (val.getChildCount() != 0) {
throw error("Expected no children under: " + val);
}
return operator(name, val.getText());
default:
throw error("Unsupported node in operator " + name + ": " + val);
}
}
@SuppressWarnings("unchecked")
private Predicate<T> operator(final String name, final String value)
throws QueryParseException {
@SuppressWarnings("rawtypes")
OperatorFactory f = opFactories.get(name);
if (f == null) {
throw error("Unsupported operator " + name + ":" + value);
}
return f.create(this, value);
}
private Predicate<T> defaultField(final Tree r) throws QueryParseException {
switch (r.getType()) {
case SINGLE_WORD:
case EXACT_PHRASE:
if (r.getChildCount() != 0) {
throw error("Expected no children under: " + r);
}
return defaultField(r.getText());
default:
throw error("Unsupported node: " + r);
}
}
/**
* Handle a value present outside of an operator.
* <p>
* This default implementation always throws an "Unsupported query: " message
* containing the input text. Subclasses may override this method to perform
* do-what-i-mean guesses based on the input string.
*
* @param value the value supplied by itself in the query.
* @return predicate representing this value.
* @throws QueryParseException the parser does not recognize this value.
*/
protected Predicate<T> defaultField(final String value)
throws QueryParseException {
throw error("Unsupported query:" + value);
}
@SuppressWarnings("unchecked")
private Predicate<T>[] children(final Tree r) throws QueryParseException,
IllegalArgumentException {
final Predicate<T>[] p = new Predicate[r.getChildCount()];
for (int i = 0; i < p.length; i++) {
p[i] = toPredicate(r.getChild(i));
}
return p;
}
private Tree onlyChildOf(final Tree r) throws QueryParseException {
if (r.getChildCount() != 1) {
throw error("Expected exactly one child: " + r);
}
return r.getChild(0);
}
protected static QueryParseException error(String msg) {
return new QueryParseException(msg);
}
protected static QueryParseException error(String msg, Throwable why) {
return new QueryParseException(msg, why);
}
/** Converts a value string passed to an operator into a {@link Predicate}. */
protected interface OperatorFactory<T, Q extends QueryBuilder<T>> {
Predicate<T> create(Q builder, String value) throws QueryParseException;
}
/** Denotes a method which is a query operator. */
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
protected @interface Operator {
}
private static class ReflectionFactory<T, Q extends QueryBuilder<T>>
implements OperatorFactory<T, Q> {
private final String name;
private final Method method;
ReflectionFactory(final String name, final Method method) {
this.name = name;
this.method = method;
}
@SuppressWarnings("unchecked")
@Override
public Predicate<T> create(Q builder, String value)
throws QueryParseException {
try {
return (Predicate<T>) method.invoke(builder, value);
} catch (RuntimeException e) {
throw error("Error in operator " + name + ":" + value, e);
} catch (IllegalAccessException e) {
throw error("Error in operator " + name + ":" + value, e);
} catch (InvocationTargetException e) {
if (e.getCause() instanceof QueryParseException) {
throw (QueryParseException) e.getCause();
}
throw error("Error in operator " + name + ":" + value, e.getCause());
}
}
}
}