/*
 * Copyright (C) 2008-2021 Apple Inc. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1.  Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 * 2.  Redistributions in binary form must reproduce the above copyright
 *     notice, this list of conditions and the following disclaimer in the
 *     documentation and/or other materials provided with the distribution.
 * 3.  Neither the name of Apple Inc. ("Apple") nor the names of
 *     its contributors may be used to endorse or promote products derived
 *     from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#pragma once

#include <JavaScriptCore/DirectEvalExecutable.h>
#include <wtf/HashMap.h>
#include <wtf/RefPtr.h>
#include <wtf/text/StringHash.h>

namespace JSC {

    class SlotVisitor;

    class DirectEvalCodeCache {
    public:
        enum class RopeSuffix : uint8_t {
            None,
            FunctionCall
        };

        class CacheLookupKey;

        class CacheKey {
            friend class CacheLookupKey;
        public:
            CacheKey(StringImpl* source, BytecodeIndex bytecodeIndex, RopeSuffix ropeSuffix)
                : m_source(source)
                , m_bytecodeIndex(bytecodeIndex)
                , m_ropeSuffix(ropeSuffix)
            {
            }

            CacheKey(WTF::HashTableDeletedValueType)
                : m_source(WTF::HashTableDeletedValue)
            {
            }

            CacheKey() = default;

            unsigned hash() const { return m_source->hash() + m_bytecodeIndex.asBits() + enumToUnderlyingType(m_ropeSuffix); }

            bool isEmptyValue() const { return !m_source; }

            bool operator==(const CacheKey& other) const
            {
                return m_bytecodeIndex == other.m_bytecodeIndex && m_ropeSuffix == other.m_ropeSuffix && WTF::equal(m_source.get(), other.m_source.get());
            }

            bool isHashTableDeletedValue() const { return m_source.isHashTableDeletedValue(); }

            typedef SimpleClassHashTraits<CacheKey> HashTraits;

        private:
            RefPtr<StringImpl> m_source;
            BytecodeIndex m_bytecodeIndex;
            RopeSuffix m_ropeSuffix;
        };

        class CacheLookupKey {
            void* operator new(size_t) = delete;

        public:
            CacheLookupKey(StringImpl* source, BytecodeIndex bytecodeIndex, RopeSuffix ropeSuffix)
                : m_source(source)
                , m_bytecodeIndex(bytecodeIndex)
                , m_ropeSuffix(ropeSuffix)
            {
            }

            CacheLookupKey() = default;

            unsigned hash() const { return m_source->hash() + m_bytecodeIndex.asBits() + enumToUnderlyingType(m_ropeSuffix); }

            bool operator==(const CacheKey& other) const
            {
                return m_bytecodeIndex == other.m_bytecodeIndex && m_ropeSuffix == other.m_ropeSuffix && WTF::equal(m_source, other.m_source.get());
            }

            operator CacheKey() const
            {
                return CacheKey(m_source, m_bytecodeIndex, m_ropeSuffix);
            }

        private:
            SUPPRESS_UNCOUNTED_MEMBER StringImpl* m_source;
            BytecodeIndex m_bytecodeIndex;
            RopeSuffix m_ropeSuffix;
        };

        struct CacheLookupKeyHashTranslator {
            static unsigned hash(const CacheLookupKey& key)
            {
                return key.hash();
            }

            static bool equal(const CacheKey& a, const CacheLookupKey& b)
            {
                return b == a;
            }
        };

        DirectEvalExecutable* get(const CacheLookupKey& cacheKey)
        {
            return m_cacheMap.inlineGet<CacheLookupKeyHashTranslator>(cacheKey).get();
        }
        
        void set(JSGlobalObject* globalObject, JSCell* owner, const CacheLookupKey& cacheKey, DirectEvalExecutable* evalExecutable)
        {
            if (m_cacheMap.size() < maxCacheEntries)
                setSlow(globalObject, owner, cacheKey, evalExecutable);
        }

        bool isEmpty() const { return m_cacheMap.isEmpty(); }

        DECLARE_VISIT_AGGREGATE;

        void clear();

    private:
        static constexpr int maxCacheEntries = 64;

        void setSlow(JSGlobalObject*, JSCell* owner, const CacheLookupKey& cacheKey, DirectEvalExecutable*);

        typedef UncheckedKeyHashMap<CacheKey, WriteBarrier<DirectEvalExecutable>, DefaultHash<CacheKey>, CacheKey::HashTraits> EvalCacheMap;
        EvalCacheMap m_cacheMap;
        Lock m_lock;
    };

} // namespace JSC
