/*
 * Copyright (C) 2016 ScyllaDB
 */

/*
 * This file is part of Scylla.
 *
 * Scylla is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * Scylla 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with Scylla.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <boost/range/algorithm/heap_algorithm.hpp>

#include "partition_version.hh"

static void remove_or_mark_as_unique_owner(partition_version* current)
{
    while (current && !current->is_referenced()) {
        auto next = current->next();
        current_allocator().destroy(current);
        current = next;
    }
    if (current) {
        current->back_reference().mark_as_unique_owner();
    }
}

partition_version::partition_version(partition_version&& pv) noexcept
    : anchorless_list_base_hook(std::move(pv))
    , _backref(pv._backref)
    , _partition(std::move(pv._partition))
{
    if (_backref) {
        _backref->_version = this;
    }
    pv._backref = nullptr;
}

partition_version& partition_version::operator=(partition_version&& pv) noexcept
{
    if (this != &pv) {
        this->~partition_version();
        new (this) partition_version(std::move(pv));
    }
    return *this;
}

partition_version::~partition_version()
{
    if (_backref) {
        _backref->_version = nullptr;
    }
}

partition_snapshot::~partition_snapshot() {
    if (_version && _version.is_unique_owner()) {
        auto v = &*_version;
        _version = {};
        remove_or_mark_as_unique_owner(v);
    } else if (_entry) {
        _entry->_snapshot = nullptr;
    }
}

void partition_snapshot::merge_partition_versions() {
    if (_version && !_version.is_unique_owner()) {
        auto v = &*_version;
        _version = { };
        auto first_used = v;
        while (first_used->prev() && !first_used->is_referenced()) {
            first_used = first_used->prev();
        }

        auto current = first_used->next();
        while (current && !current->is_referenced()) {
            auto next = current->next();
            try {
                first_used->partition().apply(*_schema, std::move(current->partition()));
                current_allocator().destroy(current);
            } catch (...) {
                // Set _version so that the merge can be retried.
                _version = partition_version_ref(*current);
                throw;
            }
            current = next;
        }
    }
}

unsigned partition_snapshot::version_count()
{
    unsigned count = 0;
    for (auto&& v : versions()) {
        (void)v;
        count++;
    }
    return count;
}

partition_entry::partition_entry(mutation_partition mp)
{
    auto new_version = current_allocator().construct<partition_version>(std::move(mp));
    _version = partition_version_ref(*new_version);
}

partition_entry::~partition_entry() {
    if (!_version) {
        return;
    }
    if (_snapshot) {
        _snapshot->_version = std::move(_version);
        _snapshot->_version.mark_as_unique_owner();
        _snapshot->_entry = nullptr;
    } else {
        auto v = &*_version;
        _version = { };
        remove_or_mark_as_unique_owner(v);
    }
}

void partition_entry::set_version(partition_version* new_version)
{
    if (_snapshot) {
        _snapshot->_version = std::move(_version);
        _snapshot->_entry = nullptr;
    }

    _snapshot = nullptr;
    _version = partition_version_ref(*new_version);
}

void partition_entry::apply(const schema& s, partition_version* pv, const schema& pv_schema)
{
    if (!_snapshot) {
        _version->partition().apply(s, std::move(pv->partition()), pv_schema);
        current_allocator().destroy(pv);
    } else {
        if (s.version() != pv_schema.version()) {
            pv->partition().upgrade(pv_schema, s);
        }
        pv->insert_before(*_version);
        set_version(pv);
    }
}

void partition_entry::apply(const schema& s, const mutation_partition& mp, const schema& mp_schema)
{
    if (!_snapshot) {
        _version->partition().apply(s, mp, mp_schema);
    } else {
        mutation_partition mp1 = mp;
        if (s.version() != mp_schema.version()) {
            mp1.upgrade(mp_schema, s);
        }
        auto new_version = current_allocator().construct<partition_version>(std::move(mp1));
        new_version->insert_before(*_version);

        set_version(new_version);
    }
}

void partition_entry::apply(const schema& s, mutation_partition&& mp, const schema& mp_schema)
{
    if (!_snapshot) {
        _version->partition().apply(s, std::move(mp), mp_schema);
    } else {
        if (s.version() != mp_schema.version()) {
            apply(s, mp, mp_schema);
        } else {
            auto new_version = current_allocator().construct<partition_version>(std::move(mp));
            new_version->insert_before(*_version);

            set_version(new_version);
        }
    }
}

void partition_entry::apply(const schema& s, mutation_partition_view mpv, const schema& mp_schema)
{
    if (!_snapshot) {
        _version->partition().apply(s, mpv, mp_schema);
    } else {
        mutation_partition mp(s.shared_from_this());
        mp.apply(s, mpv, mp_schema);
        auto new_version = current_allocator().construct<partition_version>(std::move(mp));
        new_version->insert_before(*_version);

        set_version(new_version);
    }
}

void partition_entry::apply(const schema& s, partition_entry&& pe, const schema& mp_schema)
{
    auto begin = &*pe._version;
    auto snapshot = pe._snapshot;
    if (pe._snapshot) {
        pe._snapshot->_version = std::move(pe._version);
        pe._snapshot->_entry = nullptr;
        pe._snapshot = nullptr;
    }
    pe._version = { };

    auto current = begin;
    if (!current->next() && !current->is_referenced()) {
        try {
            apply(s, current, mp_schema);
        } catch (...) {
            pe._version = partition_version_ref(*current);
            throw;
        }
        return;
    }

    try {
        while (current && !current->is_referenced()) {
            auto next = current->next();
            apply(s, std::move(current->partition()), mp_schema);
            // Leave current->partition() valid (albeit empty) in case we throw later.
            current->partition() = mutation_partition(mp_schema.shared_from_this());
            current = next;
        }
        while (current) {
            auto next = current->next();
            apply(s, current->partition(), mp_schema);
            current = next;
        }
    } catch (...) {
        if (snapshot) {
            pe._snapshot = snapshot;
            snapshot->_entry = &pe;
            pe._version = std::move(snapshot->_version);
        } else {
            pe._version = partition_version_ref(*begin);
        }
        throw;
    }

    current = begin;
    while (current && !current->is_referenced()) {
        auto next = current->next();
        current_allocator().destroy(current);
        current = next;
    }
    if (current) {
        current->back_reference().mark_as_unique_owner();
    }
}

mutation_partition partition_entry::squashed(schema_ptr from, schema_ptr to)
{
    mutation_partition mp(to);
    for (auto&& v : _version->all_elements()) {
        mp.apply(*to, v.partition(), *from);
    }
    return mp;
}

void partition_entry::upgrade(schema_ptr from, schema_ptr to)
{
    auto new_version = current_allocator().construct<partition_version>(mutation_partition(to));
    try {
        for (auto&& v : _version->all_elements()) {
            new_version->partition().apply(*to, v.partition(), *from);
        }
    } catch (...) {
        current_allocator().destroy(new_version);
        throw;
    }

    auto old_version = &*_version;
    set_version(new_version);
    remove_or_mark_as_unique_owner(old_version);
}

lw_shared_ptr<partition_snapshot> partition_entry::read(schema_ptr entry_schema)
{
    if (_snapshot) {
        return _snapshot->shared_from_this();
    } else {
        auto snp = make_lw_shared<partition_snapshot>(entry_schema, this);
        _snapshot = snp.get();
        return snp;
    }
}