/*
 * Copyright (C) 2004-2022 Apple Inc. All rights reserved.
 * Copyright (C) 2010 Patrick Gansterer <paroga@paroga.com>
 * Copyright (C) 2012 Google Inc. All rights reserved.
 * Copyright (C) 2015 Yusuke Suzuki<utatane.tea@gmail.com>. All rights reserved.
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Library General Public License for more details.
 *
 * You should have received a copy of the GNU Library General Public License
 * along with this library; see the file COPYING.LIB.  If not, write to
 * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
 * Boston, MA 02110-1301, USA.
 *
 */

#include "config.h"
#include <wtf/text/AtomStringImpl.h>

#include <wtf/Threading.h>
#include <wtf/text/ASCIIFastPath.h>
#include <wtf/text/AtomStringTable.h>
#include <wtf/text/WTFString.h>

#if USE(WEB_THREAD)
#include <wtf/Lock.h>
#endif

namespace WTF {

using namespace Unicode;

IGNORE_CLANG_WARNINGS_BEGIN("missing-noreturn")
// Always destroyed via StringImpl::destroy().
AtomStringImpl::~AtomStringImpl()
{
    RELEASE_ASSERT_NOT_REACHED();
}
IGNORE_CLANG_WARNINGS_END

#if USE(WEB_THREAD)

class AtomStringTableLocker : public Locker<Lock> {
    WTF_MAKE_NONCOPYABLE(AtomStringTableLocker);

    static Lock s_stringTableLock;
public:
    AtomStringTableLocker()
        : Locker<Lock>(s_stringTableLock)
    {
    }
};

Lock AtomStringTableLocker::s_stringTableLock;

#else

class AtomStringTableLocker {
    WTF_MAKE_NONCOPYABLE(AtomStringTableLocker);
public:
    AtomStringTableLocker() { }
};

#endif // USE(WEB_THREAD)

using StringTableImpl = AtomStringTable::StringTableImpl;

static ALWAYS_INLINE StringTableImpl& stringTable()
{
    return Thread::currentSingleton().atomStringTable()->table();
}

template<typename T, typename HashTranslator>
static inline Ref<AtomStringImpl> addToStringTable(AtomStringTableLocker&, StringTableImpl& atomStringTable, const T& value)
{
    auto addResult = atomStringTable.add<HashTranslator>(value);

    // If the string is newly-translated, then we need to adopt it.
    // The boolean in the pair tells us if that is so.
    if (addResult.isNewEntry)
        return adoptRef(uncheckedDowncast<AtomStringImpl>(*addResult.iterator->get()));
    return *uncheckedDowncast<AtomStringImpl>(addResult.iterator->get());
}

template<typename T, typename HashTranslator>
static inline Ref<AtomStringImpl> addToStringTable(const T& value)
{
    AtomStringTableLocker locker;
    return addToStringTable<T, HashTranslator>(locker, stringTable(), value);
}

using UTF16Buffer = HashTranslatorCharBuffer<char16_t>;
struct UTF16BufferTranslator {
    static unsigned NODELETE hash(const UTF16Buffer& buf)
    {
        return buf.hash;
    }

    static bool equal(AtomStringTable::StringEntry const& str, const UTF16Buffer& buf)
    {
        return WTF::equal(str.get(), buf.characters);
    }

    static void translate(AtomStringTable::StringEntry& location, const UTF16Buffer& buf, unsigned hash)
    {
        Ref stringImpl = StringImpl::create8BitIfPossible(buf.characters);
        stringImpl->setHash(hash);
        stringImpl->setIsAtom(true);
        location = &stringImpl.leakRef();
    }
};

RefPtr<AtomStringImpl> AtomStringImpl::add(std::span<const char16_t> characters)
{
    if (!characters.data())
        return nullptr;

    if (characters.empty())
        return uncheckedDowncast<AtomStringImpl>(StringImpl::empty());

    UTF16Buffer buffer { characters };
    return addToStringTable<UTF16Buffer, UTF16BufferTranslator>(buffer);
}

RefPtr<AtomStringImpl> AtomStringImpl::add(HashTranslatorCharBuffer<char16_t>& buffer)
{
    if (!buffer.characters.data())
        return nullptr;

    if (buffer.characters.empty())
        return uncheckedDowncast<AtomStringImpl>(StringImpl::empty());

    return addToStringTable<UTF16Buffer, UTF16BufferTranslator>(buffer);
}

struct SubstringLocation {
    SUPPRESS_UNCOUNTED_MEMBER StringImpl* baseString;
    unsigned start;
    unsigned length;
};

struct SubstringTranslator {
    static void translate(AtomStringTable::StringEntry& location, const SubstringLocation& buffer, unsigned hash)
    {
        SUPPRESS_UNCOUNTED_ARG Ref stringImpl = StringImpl::createSubstringSharingImpl(*buffer.baseString, buffer.start, buffer.length);
        stringImpl->setHash(hash);
        stringImpl->setIsAtom(true);
        location = &stringImpl.leakRef();
    }
};

struct SubstringTranslator8 : SubstringTranslator {
    static unsigned hash(const SubstringLocation& buffer)
    {
        return StringHasher::computeHashAndMaskTop8Bits(buffer.baseString->span8().subspan(buffer.start, buffer.length));
    }

    static bool equal(AtomStringTable::StringEntry const& string, const SubstringLocation& buffer)
    {
        return WTF::equal(string.get(), buffer.baseString->span8().subspan(buffer.start, buffer.length));
    }
};

struct SubstringTranslator16 : SubstringTranslator {
    static unsigned hash(const SubstringLocation& buffer)
    {
        return StringHasher::computeHashAndMaskTop8Bits(buffer.baseString->span16().subspan(buffer.start, buffer.length));
    }

    static bool equal(AtomStringTable::StringEntry const& string, const SubstringLocation& buffer)
    {
        return WTF::equal(string.get(), buffer.baseString->span16().subspan(buffer.start, buffer.length));
    }
};

RefPtr<AtomStringImpl> AtomStringImpl::add(StringImpl* baseString, unsigned start, unsigned length)
{
    if (!baseString)
        return nullptr;

    if (!length || start >= baseString->length())
        return uncheckedDowncast<AtomStringImpl>(StringImpl::empty());

    unsigned maxLength = baseString->length() - start;
    if (length >= maxLength) {
        if (!start)
            return add(baseString);
        length = maxLength;
    }

    SubstringLocation buffer = { baseString, start, length };
    if (baseString->is8Bit())
        return addToStringTable<SubstringLocation, SubstringTranslator8>(buffer);
    return addToStringTable<SubstringLocation, SubstringTranslator16>(buffer);
}
    
using Latin1Buffer = HashTranslatorCharBuffer<Latin1Character>;
struct Latin1BufferTranslator {
    static unsigned NODELETE hash(const Latin1Buffer& buf)
    {
        return buf.hash;
    }

    static bool equal(AtomStringTable::StringEntry const& str, const Latin1Buffer& buf)
    {
        return WTF::equal(str.get(), buf.characters);
    }

    static void translate(AtomStringTable::StringEntry& location, const Latin1Buffer& buf, unsigned hash)
    {
        Ref stringImpl = StringImpl::create(buf.characters);
        stringImpl->setHash(hash);
        stringImpl->setIsAtom(true);
        location = &stringImpl.leakRef();
    }
};

template<typename CharType>
struct BufferFromStaticDataTranslator {
    using Buffer = HashTranslatorCharBuffer<CharType>;
    static unsigned NODELETE hash(const Buffer& buf)
    {
        return buf.hash;
    }

    static bool equal(AtomStringTable::StringEntry const& str, const Buffer& buf)
    {
        return WTF::equal(str.get(), buf.characters);
    }

    static void translate(AtomStringTable::StringEntry& location, const Buffer& buf, unsigned hash)
    {
        Ref stringImpl = StringImpl::createWithoutCopying(buf.characters);
        stringImpl->setHash(hash);
        stringImpl->setIsAtom(true);
        location = &stringImpl.leakRef();
    }
};

template<typename CharType>
struct StaticStringAtomBuffer {
    SUPPRESS_UNCOUNTED_MEMBER const StringImpl& staticImpl;
    std::span<const CharType> characters;
    unsigned hash;
};

// Translator that stores a StaticStringImpl directly in the atom table without
// heap-allocating a copy. The StaticStringImpl must have been constructed with
// StringImpl::StringAtom so that isAtom() returns true. This enables global
// atom strings that share the same StringImpl* across all threads.
template<typename CharType>
struct StaticStringAtomTranslator {
    using Buffer = StaticStringAtomBuffer<CharType>;

    static unsigned NODELETE hash(const Buffer& buf)
    {
        return buf.hash;
    }

    static bool equal(AtomStringTable::StringEntry const& str, const Buffer& buf)
    {
        return WTF::equal(str.get(), buf.characters);
    }

    static void translate(AtomStringTable::StringEntry& location, const Buffer& buf, unsigned)
    {
        location = const_cast<StringImpl*>(&buf.staticImpl);
    }
};

RefPtr<AtomStringImpl> AtomStringImpl::add(HashTranslatorCharBuffer<Latin1Character>& buffer)
{
    if (!buffer.characters.data())
        return nullptr;

    if (buffer.characters.empty())
        return uncheckedDowncast<AtomStringImpl>(StringImpl::empty());

    return addToStringTable<Latin1Buffer, Latin1BufferTranslator>(buffer);
}

RefPtr<AtomStringImpl> AtomStringImpl::add(std::span<const Latin1Character> characters)
{
    if (!characters.data())
        return nullptr;

    if (characters.empty())
        return uncheckedDowncast<AtomStringImpl>(StringImpl::empty());

    Latin1Buffer buffer { characters };
    return addToStringTable<Latin1Buffer, Latin1BufferTranslator>(buffer);
}

Ref<AtomStringImpl> AtomStringImpl::addLiteral(std::span<const Latin1Character> characters)
{
    ASSERT(characters.data());
    ASSERT(!characters.empty());

    Latin1Buffer buffer { characters };
    return addToStringTable<Latin1Buffer, BufferFromStaticDataTranslator<Latin1Character>>(buffer);
}

static Ref<AtomStringImpl> addSymbol(AtomStringTableLocker& locker, StringTableImpl& atomStringTable, StringImpl& base)
{
    ASSERT(base.length());
    ASSERT(base.isSymbol());

    SubstringLocation buffer = { &base, 0, base.length() };
    if (base.is8Bit())
        return addToStringTable<SubstringLocation, SubstringTranslator8>(locker, atomStringTable, buffer);
    return addToStringTable<SubstringLocation, SubstringTranslator16>(locker, atomStringTable, buffer);
}

static inline Ref<AtomStringImpl> addSymbol(StringImpl& base)
{
    AtomStringTableLocker locker;
    return addSymbol(locker, stringTable(), base);
}

static Ref<AtomStringImpl> addStatic(AtomStringTableLocker& locker, StringTableImpl& atomStringTable, const StringImpl& base)
{
    ASSERT(base.length());
    ASSERT(base.isStatic());

    // StaticStringImpl with StringAtom: store the static pointer directly in the
    // atom table with no heap allocation. The isAtom() flag is already set at
    // construction time, enabling uncheckedDowncast<AtomStringImpl> and the
    // dynamicDowncast fast path in add(StringImpl&). All threads that register
    // the same StaticStringImpl share the same StringImpl pointer.
    if (base.isAtom()) {
        if (base.is8Bit()) {
            StaticStringAtomBuffer<Latin1Character> buffer { base, base.span8(), base.hash() };
            return addToStringTable<StaticStringAtomBuffer<Latin1Character>, StaticStringAtomTranslator<Latin1Character>>(locker, atomStringTable, buffer);
        }
        StaticStringAtomBuffer<char16_t> buffer { base, base.span16(), base.hash() };
        return addToStringTable<StaticStringAtomBuffer<char16_t>, StaticStringAtomTranslator<char16_t>>(locker, atomStringTable, buffer);
    }

    if (base.is8Bit()) {
        Latin1Buffer buffer { base.span8(), base.hash() };
        return addToStringTable<Latin1Buffer, BufferFromStaticDataTranslator<Latin1Character>>(locker, atomStringTable, buffer);
    }
    UTF16Buffer buffer { base.span16(), base.hash() };
    return addToStringTable<UTF16Buffer, BufferFromStaticDataTranslator<char16_t>>(locker, atomStringTable, buffer);
}

static inline Ref<AtomStringImpl> addStatic(const StringImpl& base)
{
    AtomStringTableLocker locker;
    return addStatic(locker, stringTable(), base);
}

RefPtr<AtomStringImpl> AtomStringImpl::add(const StaticStringImpl& string)
{
    ASSERT(static_cast<const StringImpl&>(string).isStatic());
    SUPPRESS_UNCOUNTED_ARG return addStatic(static_cast<const StringImpl&>(string));
}

Ref<AtomStringImpl> AtomStringImpl::addSlowCase(StringImpl& string)
{
    // This check is necessary for null symbols.
    // Their length is zero, but they are not AtomStringImpl.
    if (!string.length())
        return *uncheckedDowncast<AtomStringImpl>(StringImpl::empty());

    if (string.isStatic())
        return addStatic(string);

    if (string.isSymbol())
        return addSymbol(string);

    ASSERT_WITH_MESSAGE(!string.isAtom(), "AtomStringImpl should not hit the slow case if the string is already an atom.");

    AtomStringTableLocker locker;
    auto addResult = stringTable().add(&string);

    if (addResult.isNewEntry) {
        ASSERT(addResult.iterator->get() == &string);
        string.setIsAtom(true);
    }

    return *uncheckedDowncast<AtomStringImpl>(addResult.iterator->get());
}

Ref<AtomStringImpl> AtomStringImpl::addSlowCase(Ref<StringImpl>&& string)
{
    // This check is necessary for null symbols.
    // Their length is zero, but they are not AtomStringImpl.
    if (!string->length())
        return *uncheckedDowncast<AtomStringImpl>(StringImpl::empty());

    if (string->isStatic())
        return addStatic(WTF::move(string));

    if (string->isSymbol())
        return addSymbol(WTF::move(string));

    ASSERT_WITH_MESSAGE(!string->isAtom(), "AtomStringImpl should not hit the slow case if the string is already an atom.");

    AtomStringTableLocker locker;
    auto addResult = stringTable().add(string.ptr());

    if (addResult.isNewEntry) {
        ASSERT(addResult.iterator->get() == string.ptr());
        string->setIsAtom(true);
        return uncheckedDowncast<AtomStringImpl>(WTF::move(string));
    }

    return *uncheckedDowncast<AtomStringImpl>(addResult.iterator->get());
}

Ref<AtomStringImpl> AtomStringImpl::addSlowCase(AtomStringTable& stringTable, StringImpl& string)
{
    // This check is necessary for null symbols.
    // Their length is zero, but they are not AtomStringImpl.
    if (!string.length())
        return *uncheckedDowncast<AtomStringImpl>(StringImpl::empty());

    if (string.isStatic()) {
        AtomStringTableLocker locker;
        return addStatic(locker, stringTable.table(), string);
    }

    if (string.isSymbol()) {
        AtomStringTableLocker locker;
        return addSymbol(locker, stringTable.table(), string);
    }

    ASSERT_WITH_MESSAGE(!string.isAtom(), "AtomStringImpl should not hit the slow case if the string is already an atom.");

    AtomStringTableLocker locker;
    auto addResult = stringTable.table().add(&string);

    if (addResult.isNewEntry) {
        ASSERT(addResult.iterator->get() == &string);
        string.setIsAtom(true);
    }

    return *uncheckedDowncast<AtomStringImpl>(addResult.iterator->get());
}

// When removing a string from the table, we know it's already the one in the table, so no need for a string equality check.
struct AtomStringTableRemovalHashTranslator {
    static unsigned hash(const AtomStringImpl* string) { return string->hash(); }
    static bool equal(const AtomStringTable::StringEntry& a, const AtomStringImpl* b) { return a == b; }
};

void AtomStringImpl::remove(AtomStringImpl* string)
{
    ASSERT(string->isAtom());
    AtomStringTableLocker locker;
    auto& atomStringTable = stringTable();
    auto iterator = atomStringTable.find<AtomStringTableRemovalHashTranslator>(string);
    bool wasRemoved = atomStringTable.remove(iterator);
    RELEASE_ASSERT(wasRemoved, "The string being removed is an atom in the string table of an other thread!");
}

RefPtr<AtomStringImpl> AtomStringImpl::lookUpSlowCase(StringImpl& string)
{
    ASSERT_WITH_MESSAGE(!string.isAtom(), "AtomStringImpl objects should return from the fast case.");

    if (!string.length())
        return uncheckedDowncast<AtomStringImpl>(StringImpl::empty());

    AtomStringTableLocker locker;
    auto& atomStringTable = stringTable();
    auto iterator = atomStringTable.find(&string);
    if (iterator != atomStringTable.end())
        return uncheckedDowncast<AtomStringImpl>(iterator->get());
    return nullptr;
}

RefPtr<AtomStringImpl> AtomStringImpl::add(std::span<const char8_t> characters)
{
    if (charactersAreAllASCII(characters))
        return add(byteCast<Latin1Character>(characters));
    auto string = String::fromUTF8(characters);
    if (string.isNull())
        return nullptr;
    return add(string.releaseImpl());
}

RefPtr<AtomStringImpl> AtomStringImpl::lookUp(std::span<const Latin1Character> characters)
{
    AtomStringTableLocker locker;
    auto& table = stringTable();

    Latin1Buffer buffer { characters };
    auto iterator = table.find<Latin1BufferTranslator>(buffer);
    if (iterator != table.end())
        return uncheckedDowncast<AtomStringImpl>(iterator->get());
    return nullptr;
}

RefPtr<AtomStringImpl> AtomStringImpl::lookUp(std::span<const char16_t> characters)
{
    AtomStringTableLocker locker;
    auto& table = stringTable();

    UTF16Buffer buffer { characters };
    auto iterator = table.find<UTF16BufferTranslator>(buffer);
    if (iterator != table.end())
        return uncheckedDowncast<AtomStringImpl>(iterator->get());
    return nullptr;
}

#if ASSERT_ENABLED
bool AtomStringImpl::isInAtomStringTable(StringImpl* string)
{
    AtomStringTableLocker locker;
    return stringTable().contains(string);
}
#endif

} // namespace WTF
