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/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to you 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.hazelcast.org.apache.calcite.runtime;
import com.hazelcast.com.google.common.base.Preconditions;
import com.hazelcast.com.google.common.collect.ImmutableList;
import java.util.Objects;
import java.util.Stack;
import java.util.stream.Collectors;
/** Regular expression, to be compiled into an {@link Automaton}. */
public interface Pattern {
default Automaton toAutomaton() {
return new AutomatonBuilder().add(this).build();
}
/** Creates a builder. */
static PatternBuilder builder() {
return new PatternBuilder();
}
/** Operator that constructs composite {@link Pattern} instances. */
enum Op {
/** A leaf pattern, consisting of a single symbol. */
SYMBOL(0, 0),
/** Anchor for start "^" */
ANCHOR_START(0, 0),
/** Anchor for end "$" */
ANCHOR_END(0, 0),
/** Pattern that matches one pattern followed by another. */
SEQ(2, -1),
/** Pattern that matches one pattern or another. */
OR(2, -1),
/** Pattern that matches a pattern repeated zero or more times. */
STAR(1, 1),
/** Pattern that matches a pattern repeated one or more times. */
PLUS(1, 1),
/** Pattern that matches a pattern repeated between {@code minRepeat}
* and {@code maxRepeat} times. */
REPEAT(1, 1),
/** Pattern that machtes a pattern one time or zero times */
OPTIONAL(1, 1);
private final int minArity;
private final int maxArity;
Op(int minArity, int maxArity) {
this.minArity = minArity;
this.maxArity = maxArity;
}
}
/** Builds a pattern expression. */
class PatternBuilder {
final Stack stack = new Stack<>();
private PatternBuilder() {}
private PatternBuilder push(Pattern item) {
stack.push(item);
return this;
}
/** Returns the resulting pattern. */
public Pattern build() {
if (stack.size() != 1) {
throw new AssertionError("expected stack to have one item, but was "
+ stack);
}
return stack.pop();
}
/** Returns the resulting automaton. */
public Automaton automaton() {
return new AutomatonBuilder().add(build()).build();
}
/** Creates a pattern that matches symbol,
* and pushes it onto the stack.
*
* @see SymbolPattern */
public PatternBuilder symbol(String symbolName) {
return push(new SymbolPattern(symbolName));
}
/** Creates a pattern that matches the two patterns at the top of the
* stack in sequence,
* and pushes it onto the stack. */
public PatternBuilder seq() {
final Pattern pattern1 = stack.pop();
final Pattern pattern0 = stack.pop();
return push(new OpPattern(Op.SEQ, pattern0, pattern1));
}
/** Creates a pattern that matches the patterns at the top
* of the stack zero or more times,
* and pushes it onto the stack. */
public PatternBuilder star() {
return push(new OpPattern(Op.STAR, stack.pop()));
}
/** Creates a pattern that matches the patterns at the top
* of the stack one or more times,
* and pushes it onto the stack. */
public PatternBuilder plus() {
return push(new OpPattern(Op.PLUS, stack.pop()));
}
/** Creates a pattern that matches either of the two patterns at the top
* of the stack,
* and pushes it onto the stack. */
public PatternBuilder or() {
if (stack.size() < 2) {
throw new AssertionError("Expecting stack to have at least 2 items, but has "
+ stack.size());
}
final Pattern pattern1 = stack.pop();
final Pattern pattern0 = stack.pop();
return push(new OpPattern(Op.OR, pattern0, pattern1));
}
public PatternBuilder repeat(int minRepeat, int maxRepeat) {
final Pattern pattern = stack.pop();
return push(new RepeatPattern(minRepeat, maxRepeat, pattern));
}
public PatternBuilder optional() {
final Pattern pattern = stack.pop();
return push(new OpPattern(Op.OPTIONAL, pattern));
}
}
/** Base class for implementations of {@link Pattern}. */
abstract class AbstractPattern implements Pattern {
final Op op;
AbstractPattern(Op op) {
this.op = Objects.requireNonNull(op);
}
public Automaton toAutomaton() {
return new AutomatonBuilder().add(this).build();
}
}
/** Pattern that matches a symbol. */
class SymbolPattern extends AbstractPattern {
final String name;
SymbolPattern(String name) {
super(Op.SYMBOL);
this.name = Objects.requireNonNull(name);
}
@Override public String toString() {
return name;
}
}
/** Pattern with one or more arguments. */
class OpPattern extends AbstractPattern {
final ImmutableList patterns;
OpPattern(Op op, Pattern... patterns) {
super(op);
Preconditions.checkArgument(patterns.length >= op.minArity);
Preconditions.checkArgument(op.maxArity == -1
|| patterns.length <= op.maxArity);
this.patterns = ImmutableList.copyOf(patterns);
}
@Override public String toString() {
switch (op) {
case SEQ:
return patterns.stream().map(Object::toString)
.collect(Collectors.joining(" "));
case STAR:
return "(" + patterns.get(0) + ")*";
case PLUS:
return "(" + patterns.get(0) + ")+";
case OR:
return patterns.get(0) + "|" + patterns.get(1);
case OPTIONAL:
return patterns.get(0) + "?";
default:
throw new AssertionError("unknown op " + op);
}
}
}
/** Pattern that matches a pattern repeated between {@code minRepeat}
* and {@code maxRepeat} times. */
class RepeatPattern extends OpPattern {
final int minRepeat;
final int maxRepeat;
RepeatPattern(int minRepeat, int maxRepeat, Pattern pattern) {
super(Op.REPEAT, pattern);
this.minRepeat = minRepeat;
this.maxRepeat = maxRepeat;
}
@Override public String toString() {
return "(" + patterns.get(0) + "){" + minRepeat
+ (maxRepeat == minRepeat ? "" : (", " + maxRepeat))
+ "}";
}
}
}
