/*
 * Copyright (c) 2005, 2021, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
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 *
 */

package com.sun.tools.javac.model;

import java.util.Collection;
import java.util.Collections;
import java.util.EnumSet;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Set;
import java.util.stream.Collectors;

import javax.lang.model.element.*;
import javax.lang.model.type.*;

import com.sun.tools.javac.code.*;
import com.sun.tools.javac.code.Symbol.*;
import com.sun.tools.javac.util.*;
import com.sun.tools.javac.util.DefinedBy.Api;

import static com.sun.tools.javac.code.Kinds.Kind.*;

/**
 * Utility methods for operating on types.
 *
 * <p><b>This is NOT part of any supported API.
 * If you write code that depends on this, you do so at your own
 * risk.  This code and its internal interfaces are subject to change
 * or deletion without notice.</b></p>
 */
public class JavacTypes implements javax.lang.model.util.Types {

    private final Symtab syms;
    private final Types types;

    public static JavacTypes instance(Context context) {
        JavacTypes instance = context.get(JavacTypes.class);
        if (instance == null)
            instance = new JavacTypes(context);
        return instance;
    }

    @SuppressWarnings("this-escape")
    protected JavacTypes(Context context) {
        context.put(JavacTypes.class, this);
        syms = Symtab.instance(context);
        types = Types.instance(context);
    }

    @DefinedBy(Api.LANGUAGE_MODEL)
    public Element asElement(TypeMirror t) {
        switch (t.getKind()) {
            case DECLARED:
            case INTERSECTION:
            case ERROR:
            case TYPEVAR:
            case PACKAGE:
            case MODULE:
                Type type = cast(Type.class, t);
                return type.asElement();
            default:
                return null;
        }
    }

    @DefinedBy(Api.LANGUAGE_MODEL)
    public boolean isSameType(TypeMirror t1, TypeMirror t2) {
        if (t1.getKind() == TypeKind.WILDCARD || t2.getKind() == TypeKind.WILDCARD) {
            return false;
        }
        return types.isSameType((Type) t1, (Type) t2);
    }

    @DefinedBy(Api.LANGUAGE_MODEL)
    public boolean isSubtype(TypeMirror t1, TypeMirror t2) {
        validateTypeNotIn(t1, EXEC_OR_PKG_OR_MOD);
        validateTypeNotIn(t2, EXEC_OR_PKG_OR_MOD);
        return types.isSubtype((Type) t1, (Type) t2);
    }

    @DefinedBy(Api.LANGUAGE_MODEL)
    public boolean isAssignable(TypeMirror t1, TypeMirror t2) {
        validateTypeNotIn(t1, EXEC_OR_PKG_OR_MOD);
        validateTypeNotIn(t2, EXEC_OR_PKG_OR_MOD);
        return types.isAssignable((Type) t1, (Type) t2);
    }

    @DefinedBy(Api.LANGUAGE_MODEL)
    public boolean contains(TypeMirror t1, TypeMirror t2) {
        validateTypeNotIn(t1, EXEC_OR_PKG_OR_MOD);
        validateTypeNotIn(t2, EXEC_OR_PKG_OR_MOD);
        return types.containsType((Type) t1, (Type) t2);
    }

    @DefinedBy(Api.LANGUAGE_MODEL)
    public boolean isSubsignature(ExecutableType m1, ExecutableType m2) {
        return types.isSubSignature((Type) m1, (Type) m2);
    }

    @DefinedBy(Api.LANGUAGE_MODEL)
    public List<Type> directSupertypes(TypeMirror t) {
        validateTypeNotIn(t, EXEC_OR_PKG_OR_MOD);
        Type ty = (Type)t;
        return types.directSupertypes(ty).stream()
                .map(Type::stripMetadataIfNeeded)
                .toList();
    }

    @DefinedBy(Api.LANGUAGE_MODEL)
    public TypeMirror erasure(TypeMirror t) {
        TypeKind kind = t.getKind();
        if (kind == TypeKind.PACKAGE || kind == TypeKind.MODULE)
            throw new IllegalArgumentException(t.toString());
        return types.erasure((Type)t).stripMetadataIfNeeded();
    }

    @DefinedBy(Api.LANGUAGE_MODEL)
    public TypeElement boxedClass(PrimitiveType p) {
        return types.boxedClass((Type) p);
    }

    @DefinedBy(Api.LANGUAGE_MODEL)
    public PrimitiveType unboxedType(TypeMirror t) {
        if (t.getKind() != TypeKind.DECLARED)
            throw new IllegalArgumentException(t.toString());
        Type unboxed = types.unboxedType((Type) t);
        if (! unboxed.isPrimitive())    // only true primitives, not void
            throw new IllegalArgumentException(t.toString());
        return (PrimitiveType)unboxed;
    }

    @DefinedBy(Api.LANGUAGE_MODEL)
    public TypeMirror capture(TypeMirror t) {
        validateTypeNotIn(t, EXEC_OR_PKG_OR_MOD);
        return types.capture((Type)t).stripMetadataIfNeeded();
    }

    @DefinedBy(Api.LANGUAGE_MODEL)
    public PrimitiveType getPrimitiveType(TypeKind kind) {
        switch (kind) {
        case BOOLEAN:   return syms.booleanType;
        case BYTE:      return syms.byteType;
        case SHORT:     return syms.shortType;
        case INT:       return syms.intType;
        case LONG:      return syms.longType;
        case CHAR:      return syms.charType;
        case FLOAT:     return syms.floatType;
        case DOUBLE:    return syms.doubleType;
        default:
            throw new IllegalArgumentException("Not a primitive type: " + kind);
        }
    }

    @DefinedBy(Api.LANGUAGE_MODEL)
    public NullType getNullType() {
        return (NullType) syms.botType;
    }

    @DefinedBy(Api.LANGUAGE_MODEL)
    public NoType getNoType(TypeKind kind) {
        switch (kind) {
        case VOID:      return syms.voidType;
        case NONE:      return Type.noType;
        default:
            throw new IllegalArgumentException(kind.toString());
        }
    }

    @DefinedBy(Api.LANGUAGE_MODEL)
    public ArrayType getArrayType(TypeMirror componentType) {
        switch (componentType.getKind()) {
        case VOID:
        case EXECUTABLE:
        case WILDCARD:  // heh!
        case PACKAGE:
        case MODULE:
            throw new IllegalArgumentException(componentType.toString());
        }
        return new Type.ArrayType((Type) componentType, syms.arrayClass);
    }

    @DefinedBy(Api.LANGUAGE_MODEL)
    public WildcardType getWildcardType(TypeMirror extendsBound,
                                        TypeMirror superBound) {
        BoundKind bkind;
        Type bound;
        if (extendsBound == null && superBound == null) {
            bkind = BoundKind.UNBOUND;
            bound = syms.objectType;
        } else if (superBound == null) {
            bkind = BoundKind.EXTENDS;
            bound = (Type) extendsBound;
        } else if (extendsBound == null) {
            bkind = BoundKind.SUPER;
            bound = (Type) superBound;
        } else {
            throw new IllegalArgumentException(
                    "Extends and super bounds cannot both be provided");
        }
        switch (bound.getKind()) {
        case ARRAY:
        case DECLARED:
        case ERROR:
        case TYPEVAR:
            return new Type.WildcardType(bound, bkind, syms.boundClass);
        default:
            throw new IllegalArgumentException(bound.toString());
        }
    }

    @DefinedBy(Api.LANGUAGE_MODEL)
    public DeclaredType getDeclaredType(TypeElement typeElem,
                                        TypeMirror... typeArgs) {
        ClassSymbol sym = (ClassSymbol) typeElem;

        if (typeArgs.length == 0)
            return (DeclaredType) sym.erasure(types);
        if (sym.type.getEnclosingType().isParameterized())
            throw new IllegalArgumentException(sym.toString());

        return getDeclaredType0(sym.type.getEnclosingType(), sym, typeArgs);
    }

    @DefinedBy(Api.LANGUAGE_MODEL)
    public DeclaredType getDeclaredType(DeclaredType enclosing,
                                        TypeElement typeElem,
                                        TypeMirror... typeArgs) {
        if (enclosing == null)
            return getDeclaredType(typeElem, typeArgs);

        ClassSymbol sym = (ClassSymbol) typeElem;
        Type outer = (Type) enclosing;

        if (outer.tsym != sym.owner.enclClass())
            throw new IllegalArgumentException(enclosing.toString());
        if (!outer.isParameterized())
            return getDeclaredType(typeElem, typeArgs);

        return getDeclaredType0(outer, sym, typeArgs);
    }
    // where
        private DeclaredType getDeclaredType0(Type outer,
                                              ClassSymbol sym,
                                              TypeMirror... typeArgs) {
            if (typeArgs.length != sym.type.getTypeArguments().length())
                throw new IllegalArgumentException(
                "Incorrect number of type arguments");

            ListBuffer<Type> targs = new ListBuffer<>();
            for (TypeMirror t : typeArgs) {
                if (!(t instanceof ReferenceType || t instanceof WildcardType))
                    throw new IllegalArgumentException(t.toString());
                targs.append((Type) t);
            }
            // TODO: Would like a way to check that type args match formals.

            return (DeclaredType) new Type.ClassType(outer, targs.toList(), sym);
        }

    /**
     * Returns the type of an element when that element is viewed as
     * a member of, or otherwise directly contained by, a given type.
     * For example,
     * when viewed as a member of the parameterized type {@code Set<String>},
     * the {@code Set.add} method is an {@code ExecutableType}
     * whose parameter is of type {@code String}.
     *
     * @param containing  the containing type
     * @param element     the element
     * @return the type of the element as viewed from the containing type
     * @throws IllegalArgumentException if the element is not a valid one
     *          for the given type
     */
    @DefinedBy(Api.LANGUAGE_MODEL)
    public TypeMirror asMemberOf(DeclaredType containing, Element element) {
        Type site = (Type)containing;
        Symbol sym = (Symbol)element;
        if (types.asSuper(site, sym.getEnclosingElement()) == null)
            throw new IllegalArgumentException(sym + "@" + site);
        return types.memberType(site, sym);
    }


    private static final Set<TypeKind> EXEC_OR_PKG_OR_MOD =
        EnumSet.of(TypeKind.EXECUTABLE, TypeKind.PACKAGE, TypeKind.MODULE);

    /**
     * Throws an IllegalArgumentException if a type's kind is one of a set.
     */
    private void validateTypeNotIn(TypeMirror t, Set<TypeKind> invalidKinds) {
        if (invalidKinds.contains(t.getKind()))
            throw new IllegalArgumentException(t.toString());
    }

    /**
     * Returns an object cast to the specified type.
     * @throws NullPointerException if the object is {@code null}
     * @throws IllegalArgumentException if the object is of the wrong type
     */
    private static <T> T cast(Class<T> clazz, Object o) {
        if (! clazz.isInstance(o))
            throw new IllegalArgumentException(o.toString());
        return clazz.cast(o);
    }

    public Set<MethodSymbol> getOverriddenMethods(Element elem) {
        if (elem.getKind() != ElementKind.METHOD
                || elem.getModifiers().contains(Modifier.STATIC)
                || elem.getModifiers().contains(Modifier.PRIVATE))
            return Collections.emptySet();

        if (!(elem instanceof MethodSymbol methodSymbol))
            throw new IllegalArgumentException();

        ClassSymbol origin = (ClassSymbol) methodSymbol.owner;

        Set<MethodSymbol> results = new LinkedHashSet<>();
        for (Type t : types.closure(origin.type)) {
            if (t != origin.type) {
                ClassSymbol c = (ClassSymbol) t.tsym;
                for (Symbol sym : c.members().getSymbolsByName(methodSymbol.name)) {
                    if (sym.kind == MTH && methodSymbol.overrides(sym, origin, types, true)) {
                        results.add((MethodSymbol) sym);
                    }
                }
            }
        }

        return results;
    }
}
