/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
/*
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/.
 */

#include <orcus/string_pool.hpp>
#include <orcus/exception.hpp>

#include <iostream>
#include <unordered_set>
#include <vector>
#include <memory>
#include <cassert>
#include <algorithm>
#include <string_view>

#include <boost/pool/object_pool.hpp>

namespace orcus {

using std::cout;
using std::endl;

using string_set_type = std::unordered_set<std::string_view>;
using string_store_type = boost::object_pool<std::string>;
using string_stores_type = std::vector<std::unique_ptr<string_store_type>>;

struct string_pool::impl
{
    string_stores_type m_stores;
    string_set_type m_set;

    impl()
    {
        // first element is the active store used for the current instance.
        m_stores.push_back(std::make_unique<string_store_type>(256, 0));
    }
};

string_pool::string_pool() : mp_impl(std::make_unique<impl>()) {}

string_pool::string_pool(string_pool&& other) : mp_impl(std::move(other.mp_impl)) {}

string_pool::~string_pool() = default;

std::pair<std::string_view, bool> string_pool::intern(std::string_view str)
{
    if (str.empty())
        return std::pair<std::string_view, bool>(std::string_view(), false);

    string_set_type::const_iterator itr = mp_impl->m_set.find(str);
    if (itr == mp_impl->m_set.end())
    {
        // This string has not been interned.  Intern it.
        string_store_type& store = *mp_impl->m_stores[0];
        std::string* p = store.construct(str);
        if (!p)
            throw general_error("failed to intern a new string instance.");

        std::pair<string_set_type::iterator,bool> r =
            mp_impl->m_set.emplace(p->data(), p->size());
        if (!r.second)
            throw general_error("failed to intern a new string instance.");

        std::string_view ps = *r.first;
        assert(ps == str);

        return std::pair<std::string_view, bool>(ps, true);
    }

    // This string has already been interned.

    std::string_view stored_str = *itr;
    assert(stored_str == str);
    return std::pair<std::string_view, bool>(stored_str, false);
}

std::vector<std::string_view> string_pool::get_interned_strings() const
{
    std::vector<std::string_view> sorted;
    sorted.reserve(mp_impl->m_set.size());

    for (std::string_view ps : mp_impl->m_set)
        sorted.push_back(ps);

    std::sort(sorted.begin(), sorted.end());

    return sorted;
}

void string_pool::dump() const
{
    auto sorted = get_interned_strings();

    cout << "interned string count: " << sorted.size() << endl;

    // Dump them all to stdout.
    size_t counter = 0;
    for (std::string_view s : sorted)
        cout << counter++ << ": '" << s << "'" << endl;
}

void string_pool::clear()
{
    mp_impl = std::make_unique<impl>();
}

size_t string_pool::size() const
{
    return mp_impl->m_set.size();
}

void string_pool::swap(string_pool& other)
{
    std::swap(mp_impl, other.mp_impl);
}

void string_pool::merge(string_pool& other)
{
    while (!other.mp_impl->m_stores.empty())
    {
        mp_impl->m_stores.push_back(
            std::move(other.mp_impl->m_stores.back()));
        other.mp_impl->m_stores.pop_back();
    }

    for (std::string_view p : other.mp_impl->m_set)
        mp_impl->m_set.insert(p);

    other.mp_impl->m_set.clear();
}

}

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