<?php
/******************************************************************************
 * YMS - Yacht Management Software
 * Copyright (C) 2024-2026 Thomas Hooge
 * 
 * SPDX-License-Identifier: WTFPL
 ******************************************************************************

*/

function db_lock_acquire($table, $key, $userid) {
    global $pdo;
    $token = bin2hex(random_bytes(8));
    // first try new lock
    $sql = "INSERT INTO recordlock (lock_table, lock_key, token, userid) "
         . "VALUES (?, ?, ?, ?)";
    try {
        $sth = $pdo->prepare($sql);
        $sth->execute([$table, $key, $token, $userid]);
        return $token;
    } catch (PDOException $e) {
        if ($e->errorInfo[1] != 1062) {
            throw $e;
        }
    }
    // lazy locking: lock exists but is old, so we use it
    $sql = "UPDATE recordlock "
         . "SET token=?, userid=?, "
         . "created_at=CURRENT_TIMESTAMP, last_seen=CURRENT_TIMESTAMP "
         . "WHERE lock_table=? AND lock_key=? "
         . "AND last_seen<CURRENT_TIMESTAMP-INTERVAL 5 MINUTE";
    $sth = $pdo->prepare($sql);
    $sth->execute([$token, $userid, $table, $key]);
    if ($stmt->rowCount() === 1) {
        return $token;
    }
    return null;
}

function db_lock_refresh($token) {
    global $pdo;
    $sql = "UPDATE recordlock "
         . "SET last_seen=CURRENT_TIMESTAMP "
         . "WHERE token=?";
    $sth = $pdo->prepare($sql);
    $sth->execute([$token]);
    return $sth->rowCount() === 1;
}


function db_lock_release($token) {
    global $pdo;
    $sql = "DELETE FROM recordlock WHERE token=?";
    $sth = $pdo->prepare($sql);
    $sth->execute([$token]);
    return $sth->rowCount() === 1;
}