/*
    Copyright © 2015-2016 by The qTox Project Contributors

    This file is part of qTox, a Qt-based graphical interface for Tox.

    qTox is libre software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    qTox 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 qTox.  If not, see <http://www.gnu.org/licenses/>.
*/

#include <QDebug>
#include <cassert>

#include "history.h"
#include "profile.h"
#include "settings.h"
#include "db/rawdatabase.h"

/**
 * @class History
 * @brief Interacts with the profile database to save the chat history.
 *
 * @var QHash<QString, int64_t> History::peers
 * @brief Maps friend public keys to unique IDs by index.
 * Caches mappings to speed up message saving.
 */

/**
 * @brief Prepares the database to work with the history.
 * @param db This database will be prepared for use with the history.
 */
History::History(std::shared_ptr<RawDatabase> db)
    : db(db)
{
    if (!isValid()) {
        qWarning() << "Database not open, init failed";
        return;
    }

    db->execLater(
        "CREATE TABLE IF NOT EXISTS peers (id INTEGER PRIMARY KEY, public_key TEXT NOT NULL "
        "UNIQUE);"
        "CREATE TABLE IF NOT EXISTS aliases (id INTEGER PRIMARY KEY, owner INTEGER,"
        "display_name BLOB NOT NULL, UNIQUE(owner, display_name));"
        "CREATE TABLE IF NOT EXISTS history (id INTEGER PRIMARY KEY, timestamp INTEGER NOT NULL, "
        "chat_id INTEGER NOT NULL, sender_alias INTEGER NOT NULL, "
        "message BLOB NOT NULL);"
        "CREATE TABLE IF NOT EXISTS faux_offline_pending (id INTEGER PRIMARY KEY);");

    // Cache our current peers
    db->execLater(RawDatabase::Query{"SELECT public_key, id FROM peers;",
                                     [this](const QVector<QVariant>& row) {
                                         peers[row[0].toString()] = row[1].toInt();
                                     }});
}

History::~History()
{
    if (!isValid()) {
        return;
    }

    // We could have execLater requests pending with a lambda attached,
    // so clear the pending transactions first
    db->sync();
}

/**
 * @brief Checks if the database was opened successfully
 * @return True if database if opened, false otherwise.
 */
bool History::isValid()
{
    return db && db->isOpen();
}

/**
 * @brief Erases all the chat history from the database.
 */
void History::eraseHistory()
{
    if (!isValid()) {
        return;
    }

    db->execNow("DELETE FROM faux_offline_pending;"
                "DELETE FROM history;"
                "DELETE FROM aliases;"
                "DELETE FROM peers;"
                "VACUUM;");
}

/**
 * @brief Erases the chat history with one friend.
 * @param friendPk Friend public key to erase.
 */
void History::removeFriendHistory(const QString& friendPk)
{
    if (!isValid()) {
        return;
    }

    if (!peers.contains(friendPk)) {
        return;
    }

    int64_t id = peers[friendPk];

    QString queryText = QString("DELETE FROM faux_offline_pending "
                                "WHERE faux_offline_pending.id IN ( "
                                "    SELECT faux_offline_pending.id FROM faux_offline_pending "
                                "    LEFT JOIN history ON faux_offline_pending.id = history.id "
                                "    WHERE chat_id=%1 "
                                "); "
                                "DELETE FROM history WHERE chat_id=%1; "
                                "DELETE FROM aliases WHERE owner=%1; "
                                "DELETE FROM peers WHERE id=%1; "
                                "VACUUM;")
                            .arg(id);

    if (db->execNow(queryText)) {
        peers.remove(friendPk);
    } else {
        qWarning() << "Failed to remove friend's history";
    }
}

/**
 * @brief Generate query to insert new message in database
 * @param friendPk Friend publick key to save.
 * @param message Message to save.
 * @param sender Sender to save.
 * @param time Time of message sending.
 * @param isSent True if message was already sent.
 * @param dispName Name, which should be displayed.
 * @param insertIdCallback Function, called after query execution.
 */
QVector<RawDatabase::Query>
History::generateNewMessageQueries(const QString& friendPk, const QString& message,
                                   const QString& sender, const QDateTime& time, bool isSent,
                                   QString dispName, std::function<void(int64_t)> insertIdCallback)
{
    QVector<RawDatabase::Query> queries;

    // Get the db id of the peer we're chatting with
    int64_t peerId;
    if (peers.contains(friendPk)) {
        peerId = peers[friendPk];
    } else {
        if (peers.isEmpty()) {
            peerId = 0;
        } else {
            peerId = *std::max_element(peers.begin(), peers.end()) + 1;
        }

        peers[friendPk] = peerId;
        queries += RawDatabase::Query(("INSERT INTO peers (id, public_key) "
                                       "VALUES (%1, '"
                                       + friendPk + "');")
                                          .arg(peerId));
    }

    // Get the db id of the sender of the message
    int64_t senderId;
    if (peers.contains(sender)) {
        senderId = peers[sender];
    } else {
        if (peers.isEmpty()) {
            senderId = 0;
        } else {
            senderId = *std::max_element(peers.begin(), peers.end()) + 1;
        }

        peers[sender] = senderId;
        queries += RawDatabase::Query{("INSERT INTO peers (id, public_key) "
                                       "VALUES (%1, '"
                                       + sender + "');")
                                          .arg(senderId)};
    }

    queries += RawDatabase::Query(
        QString("INSERT OR IGNORE INTO aliases (owner, display_name) VALUES (%1, ?);").arg(senderId),
        {dispName.toUtf8()});

    // If the alias already existed, the insert will ignore the conflict and last_insert_rowid()
    // will return garbage,
    // so we have to check changes() and manually fetch the row ID in this case
    queries +=
        RawDatabase::Query(QString(
                               "INSERT INTO history (timestamp, chat_id, message, sender_alias) "
                               "VALUES (%1, %2, ?, ("
                               "  CASE WHEN changes() IS 0 THEN ("
                               "    SELECT id FROM aliases WHERE owner=%3 AND display_name=?)"
                               "  ELSE last_insert_rowid() END"
                               "));")
                               .arg(time.toMSecsSinceEpoch())
                               .arg(peerId)
                               .arg(senderId),
                           {message.toUtf8(), dispName.toUtf8()}, insertIdCallback);

    if (!isSent) {
        queries += RawDatabase::Query{"INSERT INTO faux_offline_pending (id) VALUES ("
                                      "    last_insert_rowid()"
                                      ");"};
    }

    return queries;
}

/**
 * @brief Saves a chat message in the database.
 * @param friendPk Friend publick key to save.
 * @param message Message to save.
 * @param sender Sender to save.
 * @param time Time of message sending.
 * @param isSent True if message was already sent.
 * @param dispName Name, which should be displayed.
 * @param insertIdCallback Function, called after query execution.
 */
void History::addNewMessage(const QString& friendPk, const QString& message, const QString& sender,
                            const QDateTime& time, bool isSent, QString dispName,
                            const std::function<void(int64_t)>& insertIdCallback)
{
    if (!isValid()) {
        return;
    }

    db->execLater(generateNewMessageQueries(friendPk, message, sender, time, isSent, dispName,
                                            insertIdCallback));
}

/**
 * @brief Fetches chat messages from the database.
 * @param friendPk Friend publick key to fetch.
 * @param from Start of period to fetch.
 * @param to End of period to fetch.
 * @return List of messages.
 */
QList<History::HistMessage> History::getChatHistory(const QString& friendPk, const QDateTime& from,
                                                    const QDateTime& to)
{
    if (!isValid()) {
        return {};
    }

    QList<HistMessage> messages;

    auto rowCallback = [&messages](const QVector<QVariant>& row) {
        // dispName and message could have null bytes, QString::fromUtf8
        // truncates on null bytes so we strip them
        messages += {row[0].toLongLong(),
                     row[1].isNull(),
                     QDateTime::fromMSecsSinceEpoch(row[2].toLongLong()),
                     row[3].toString(),
                     QString::fromUtf8(row[4].toByteArray().replace('\0', "")),
                     row[5].toString(),
                     QString::fromUtf8(row[6].toByteArray().replace('\0', ""))};
    };

    // Don't forget to update the rowCallback if you change the selected columns!
    QString queryText =
        QString("SELECT history.id, faux_offline_pending.id, timestamp, "
                "chat.public_key, aliases.display_name, sender.public_key, "
                "message FROM history "
                "LEFT JOIN faux_offline_pending ON history.id = faux_offline_pending.id "
                "JOIN peers chat ON chat_id = chat.id "
                "JOIN aliases ON sender_alias = aliases.id "
                "JOIN peers sender ON aliases.owner = sender.id "
                "WHERE timestamp BETWEEN %1 AND %2 AND chat.public_key='%3';")
            .arg(from.toMSecsSinceEpoch())
            .arg(to.toMSecsSinceEpoch())
            .arg(friendPk);

    db->execNow({queryText, rowCallback});

    return messages;
}

/**
 * @brief Fetches chat messages counts for each day from the database.
 * @param friendPk Friend public key to fetch.
 * @param from Start of period to fetch.
 * @param to End of period to fetch.
 * @return List of structs containing days offset and message count for that day.
 */
QList<History::DateMessages> History::getChatHistoryCounts(const ToxPk& friendPk, const QDate& from,
                                                           const QDate& to)
{
    if (!isValid()) {
        return {};
    }
    QDateTime fromTime(from);
    QDateTime toTime(to);

    QList<DateMessages> counts;

    auto rowCallback = [&counts](const QVector<QVariant>& row) {
        DateMessages app;
        app.count = row[0].toUInt();
        app.offsetDays = row[1].toUInt();
        counts.append(app);
    };

    QString queryText =
        QString("SELECT COUNT(history.id), ((timestamp / 1000 / 60 / 60 / 24) - %4 ) AS day "
                "FROM history "
                "JOIN peers chat ON chat_id = chat.id "
                "WHERE timestamp BETWEEN %1 AND %2 AND chat.public_key='%3'"
                "GROUP BY day;")
            .arg(fromTime.toMSecsSinceEpoch())
            .arg(toTime.toMSecsSinceEpoch())
            .arg(friendPk.toString())
            .arg(QDateTime::fromMSecsSinceEpoch(0).daysTo(fromTime));

    db->execNow({queryText, rowCallback});

    return counts;
}

QDateTime History::getDateWhereFindPhrase(const QString& friendPk, const QDateTime& from, const QString& phrase)
{
    QList<QDateTime> counts;
    auto rowCallback = [&counts](const QVector<QVariant>& row) {
        counts.append(QDateTime::fromMSecsSinceEpoch(row[0].toLongLong()));
    };

    QString queryText =
        QString("SELECT timestamp "
                "FROM history "
                "LEFT JOIN faux_offline_pending ON history.id = faux_offline_pending.id "
                "JOIN peers chat ON chat_id = chat.id "
                "WHERE chat.public_key='%1' "
                "AND message LIKE '%%2%' "
                "AND timestamp < '%3' ORDER BY timestamp DESC LIMIT 1;")
            .arg(friendPk)
            .arg(phrase)
            .arg(from.toMSecsSinceEpoch());


    db->execNow({queryText, rowCallback});

    if (!counts.isEmpty()) {
        return counts[0];
    }

    return QDateTime();
}

/**
 * @brief Marks a message as sent.
 * Removing message from the faux-offline pending messages list.
 *
 * @param id Message ID.
 */
void History::markAsSent(qint64 messageId)
{
    if (!isValid()) {
        return;
    }

    db->execLater(QString("DELETE FROM faux_offline_pending WHERE id=%1;").arg(messageId));
}