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/*
* Copyright 2019 Google Inc. All Rights Reserved.
*
* 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.turbine.processing;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.Iterables;
import com.google.turbine.binder.bound.TypeBoundClass;
import com.google.turbine.binder.env.CompoundEnv;
import com.google.turbine.binder.env.Env;
import com.google.turbine.binder.sym.ClassSymbol;
import com.google.turbine.diag.TurbineError;
import com.google.turbine.diag.TurbineError.ErrorKind;
import com.google.turbine.type.Type;
import com.google.turbine.type.Type.ClassTy;
import com.google.turbine.type.Type.TyKind;
import java.util.HashMap;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.Set;
/**
* A representation of the class hierarchy, with logic for performing search between subtypes and
* their supertypes.
*/
public class ClassHierarchy {
private final Map<ClassSymbol, HierarchyNode> cache = new HashMap<>();
private Env<ClassSymbol, ? extends TypeBoundClass> env;
ClassHierarchy(Env<ClassSymbol, ? extends TypeBoundClass> env) {
this.env = env;
}
public void round(CompoundEnv<ClassSymbol, TypeBoundClass> env) {
cache.clear();
this.env = env;
}
/** A linked list between two types in the hierarchy. */
private static class PathNode {
/** The class for this node. */
final ClassTy type;
/** The node corresponding to a direct super-type of this class, or {@code null}. */
final PathNode ancestor;
PathNode(ClassTy type, PathNode ancestor) {
this.type = type;
this.ancestor = ancestor;
}
}
/**
* A node in the type hierarchy, corresponding to a class symbol U. For each type V in the
* transitive supertype hierarchy of U, we save a mapping from the class symbol for V to the path
* from U to V in the type hierarchy.
*/
private class HierarchyNode {
private final ClassSymbol sym;
private final Map<ClassSymbol, PathNode> ancestors = new LinkedHashMap<>();
HierarchyNode(ClassSymbol sym) {
this.sym = sym;
}
/** Adds a child (direct supertype) of this node. */
private void add(Type type) {
if (type.tyKind() != TyKind.CLASS_TY) {
// ignore any erroneous types that ended up in the hierarchy
return;
}
ClassTy classTy = (ClassTy) type;
HierarchyNode child = get(classTy.sym());
// add a new edge to the direct supertype
PathNode existing = ancestors.putIfAbsent(child.sym, new PathNode(classTy, null));
if (existing != null) {
// if this child has already been added don't re-process its ancestors
return;
}
// copy and extend edges for the transitive supertypes
for (Map.Entry<ClassSymbol, PathNode> n : child.ancestors.entrySet()) {
ancestors.putIfAbsent(n.getKey(), new PathNode(classTy, n.getValue()));
}
}
/** The supertype closure of this node. */
private Set<ClassSymbol> closure() {
return ancestors.keySet();
}
}
private HierarchyNode compute(ClassSymbol sym) {
HierarchyNode node = new HierarchyNode(sym);
TypeBoundClass info = env.get(sym);
if (info == null) {
throw TurbineError.format(/* source= */ null, ErrorKind.SYMBOL_NOT_FOUND, sym);
}
if (info.superClassType() != null) {
node.add(info.superClassType());
}
for (Type type : info.interfaceTypes()) {
node.add(type);
}
return node;
}
private HierarchyNode get(ClassSymbol sym) {
// dont use computeIfAbsent, to support re-entrant lookups
HierarchyNode result = cache.get(sym);
if (result != null) {
return result;
}
result = compute(sym);
cache.put(sym, result);
return result;
}
/**
* Returns a list of types on the path between the given type {@code t} and a transitive
* superclass {@code s}, or an empty list if no such path exists.
*/
ImmutableList<ClassTy> search(Type t, ClassSymbol s) {
if (t.tyKind() != TyKind.CLASS_TY) {
return ImmutableList.of();
}
ClassTy classTy = (ClassTy) t;
if (classTy.sym().equals(s)) {
return ImmutableList.of(classTy);
}
HierarchyNode node = get(classTy.sym());
PathNode path = node.ancestors.get(s);
if (path == null) {
return ImmutableList.of();
}
ImmutableList.Builder<ClassTy> result = ImmutableList.builder();
result.add(classTy);
while (path != null) {
result.add(path.type);
path = path.ancestor;
}
return result.build().reverse();
}
/**
* Returns all classes in the transitive supertype hierarchy of the given class, including the
* class itself.
*
* <p>The iteration order of the results is undefined, and in particular no guarantees are made
* about the ordering of sub-types and super-types.
*/
public Iterable<ClassSymbol> transitiveSupertypes(ClassSymbol s) {
return Iterables.concat(ImmutableList.of(s), get(s).closure());
}
}
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