<?php
/*
 * usersettings.php
 *
 * Tiny SQLite-backed key/value store for per-user UI preferences.
 */

class UserSettingsStoreException extends Exception
{
}

class UserSettingsStore
{
    private $db;

    public function __construct($dbFile)
    {
        $dir = dirname($dbFile);

        if (!is_dir($dir)) {
            if (!mkdir($dir, 0700, true)) {
                throw new UserSettingsStoreException('Could not create database directory: ' . $dir);
            }
        }

        $this->db = new PDO('sqlite:' . $dbFile);
        $this->db->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
        $this->db->exec('PRAGMA journal_mode = WAL');
        $this->db->exec('PRAGMA busy_timeout = 5000');

        $this->init();
    }

    private function init()
    {
        $this->db->exec(
            'CREATE TABLE IF NOT EXISTS user_settings (
                user_id INTEGER NOT NULL,
                setting_key TEXT NOT NULL,
                setting_value TEXT NOT NULL,
                created_at INTEGER NOT NULL,
                updated_at INTEGER NOT NULL,
                PRIMARY KEY(user_id, setting_key)
            )'
        );
    }

    public function get($userId, $key, $default = null)
    {
        $stmt = $this->db->prepare(
            'SELECT setting_value
             FROM user_settings
             WHERE user_id = :user_id
               AND setting_key = :setting_key'
        );
        $stmt->execute(array(
            ':user_id' => $this->safeUserId($userId),
            ':setting_key' => $this->safeKey($key),
        ));

        $row = $stmt->fetch(PDO::FETCH_ASSOC);

        return $row ? (string)$row['setting_value'] : $default;
    }

    public function set($userId, $key, $value)
    {
        $now = time();

        $stmt = $this->db->prepare(
            'INSERT INTO user_settings
             (user_id, setting_key, setting_value, created_at, updated_at)
             VALUES
             (:user_id, :setting_key, :setting_value, :created_at, :updated_at)
             ON CONFLICT(user_id, setting_key)
             DO UPDATE SET
                setting_value = excluded.setting_value,
                updated_at = excluded.updated_at'
        );

        $stmt->execute(array(
            ':user_id' => $this->safeUserId($userId),
            ':setting_key' => $this->safeKey($key),
            ':setting_value' => (string)$value,
            ':created_at' => $now,
            ':updated_at' => $now,
        ));
    }

    private function safeUserId($userId)
    {
        $userId = (int)$userId;

        if ($userId <= 0) {
            throw new UserSettingsStoreException('Invalid user id.');
        }

        return $userId;
    }

    private function safeKey($key)
    {
        $key = trim((string)$key);

        if (!preg_match('/^[a-z0-9_.-]{1,80}$/', $key)) {
            throw new UserSettingsStoreException('Invalid setting key.');
        }

        return $key;
    }
}