//  SPDX-FileCopyrightText: 2023 Yury Gubich <blue@macaw.me>
//  SPDX-License-Identifier: GPL-3.0-or-later

#include "mysql.h"

#include <fstream>
#include <iostream>

#include "mysqld_error.h"

#include "statement.h"

constexpr const char* updateQuery = "UPDATE system SET `value` = ? WHERE `key` = 'version'";

static const std::filesystem::path buildSQLPath = "database";

struct ResDeleter {
    void operator () (MYSQL_RES* res) {
        mysql_free_result(res);
    }
};

MySQL::MySQL():
    DBInterface(Type::mysql),
    connection(),
    login(),
    password(),
    database()
{
    mysql_init(&connection);
}

MySQL::~MySQL() {
    mysql_close(&connection);
}


void MySQL::connect(const std::string& path) {
    if (state != State::disconnected)
        return;

    MYSQL* con = &connection;
    MYSQL* res = mysql_real_connect(
        con,
        NULL,
        login.c_str(),
        password.c_str(),
        database.empty() ? NULL : database.c_str(),
        0,
        path.c_str(),
        0
    );

    if (res != con)
        throw std::runtime_error(std::string("Error changing connecting: ") + mysql_error(con));

    state = State::connected;
}

void MySQL::setCredentials(const std::string& login, const std::string& password) {
    if (MySQL::login == login && MySQL::password == password)
        return;

    MySQL::login = login;
    MySQL::password = password;

    if (state == State::disconnected)
        return;

    MYSQL* con = &connection;
    int result = mysql_change_user(
        con,
        login.c_str(),
        password.c_str(),
        database.empty() ? NULL : database.c_str()
    );

    if (result != 0)
        throw std::runtime_error(std::string("Error changing credetials: ") + mysql_error(con));
}

void MySQL::setDatabase(const std::string& database) {
    if (MySQL::database == database)
        return;

    MySQL::database = database;

    if (state == State::disconnected)
        return;

    MYSQL* con = &connection;
    int result = mysql_select_db(con, database.c_str());

    if (result != 0)
        throw std::runtime_error(std::string("Error changing db: ") + mysql_error(con));
}

void MySQL::disconnect() {
    if (state == State::disconnected)
        return;

    MYSQL* con = &connection;
    mysql_close(con);
    mysql_init(con);            //this is ridiculous!
}

void MySQL::executeFile(const std::filesystem::path& relativePath) {
    MYSQL* con = &connection;
    std::filesystem::path path = sharedPath() / relativePath;
    if (!std::filesystem::exists(path))
        throw std::runtime_error("Error executing file "
            + std::filesystem::absolute(path).string()
            + ": file doesn't exist");

    std::cout << "Executing file " << path << std::endl;
    std::ifstream inputFile(path);
    std::string query;
    while (std::getline(inputFile, query, ';')) {
        int result = mysql_query(con, query.c_str());
        if (result != 0) {
            int errcode = mysql_errno(con);
            if (errcode == ER_EMPTY_QUERY)
                continue;

            throw std::runtime_error("Error executing file " + path.string() + ": " + mysql_error(con));
        }

    }
}

uint8_t MySQL::getVersion() {
    MYSQL* con = &connection;
    int result = mysql_query(con, "SELECT value FROM system WHERE `key` = 'version'");

    if (result != 0) {
        unsigned int errcode = mysql_errno(con);
        if (errcode == ER_NO_SUCH_TABLE)
            return 0;

        throw std::runtime_error(std::string("Error executing retreiving version: ") + mysql_error(con));
    }

    std::unique_ptr<MYSQL_RES, ResDeleter> res(mysql_store_result(con));
    if (!res)
        throw std::runtime_error(std::string("Querying version returned no result: ") + mysql_error(con));

    MYSQL_ROW row = mysql_fetch_row(res.get());
    if (row)
        return std::stoi(row[0]);
    else
        return 0;
}

void MySQL::setVersion(uint8_t version) {
    std::string strVersion = std::to_string(version);
    Statement statement(&connection, updateQuery);
    statement.bind(strVersion.data(), MYSQL_TYPE_VAR_STRING);
    statement.execute();
}

void MySQL::migrate(uint8_t targetVersion) {
    uint8_t currentVersion = getVersion();

    while (currentVersion < targetVersion) {
        std::string fileName = "migrations/m" + std::to_string(currentVersion) + ".sql";
        std::cout << "Performing migration "
            << std::to_string(currentVersion)
            << " -> "
            << std::to_string(++currentVersion)
        << std::endl;
        executeFile(fileName);
        setVersion(currentVersion);
    }

    std::cout << "Database is now on actual version " << std::to_string(targetVersion) << std::endl;
}