<?php
require_once 'db/config.php';

header('Content-Type: application/json');

$url = $_POST['url'] ?? null;

if (!$url || !filter_var($url, FILTER_VALIDATE_URL)) {
    echo json_encode(['error' => 'Please provide a valid URL.']);
    exit;
}

function generateShortCode($length = 6) {
    return substr(str_shuffle('0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ'), 0, $length);
}

$short_code = generateShortCode();

// Ensure the short code is unique
$pdoconnection = db();
$stmt = $pdoconnection->prepare("SELECT id FROM links WHERE short_code = ?");
$stmt->execute([$short_code]);

while ($stmt->fetch()) {
    $short_code = generateShortCode();
    $stmt->execute([$short_code]);
}

$stmt = $pdoconnection->prepare("INSERT INTO links (original_url, short_code) VALUES (?, ?)");

if ($stmt->execute([$url, $short_code])) {
    $protocol = isset($_SERVER['HTTPS']) && $_SERVER['HTTPS'] === 'on' ? "https" : "http";
    $host = $_SERVER['HTTP_HOST'];
    $short_url = "$protocol://$host/$short_code";
    echo json_encode(['short_url' => $short_url]);
} else {
    echo json_encode(['error' => 'Could not create short link.']);
}