<?php

namespace App\Content;

use App\Domain\InvalidPage;
use Doctrine\DBAL\Connection;

/**
 * Addresses that moved or are deliberately gone. Checked before a page is answered with 404, so a
 * migrated site keeps every old link working.
 */
final class RedirectRepository
{
    public const MAX = 2000;

    public function __construct(private Connection $db)
    {
    }

    /** @return list<array{id: string, from: string, to: ?string, status: int}> */
    public function all(): array
    {
        return array_map(static fn (array $row): array => [
            'id' => $row['id'], 'from' => $row['from_path'], 'to' => $row['to_path'], 'status' => (int) $row['status'],
        ], $this->db->fetchAllAssociative('SELECT * FROM redirect WHERE website_id = ? ORDER BY from_path', ['default']));
    }

    /** @return array{to: ?string, status: int}|null */
    public function find(string $path): ?array
    {
        $row = $this->db->fetchAssociative('SELECT to_path, status FROM redirect WHERE website_id = ? AND from_path = ?', ['default', trim($path, '/')]);

        return false === $row ? null : ['to' => $row['to_path'], 'status' => (int) $row['status']];
    }

    public function save(string $from, string $to, int $status): void
    {
        $from = trim(trim($from), '/');
        $to = trim(trim($to), '/');
        if (!in_array($status, [301, 410], true)) {
            throw new InvalidPage('Erlaubt sind 301 für eine verschobene Adresse und 410 für eine entfernte.');
        }
        if (1 !== preg_match('#^[a-z0-9]+(?:[-/][a-z0-9]+)*$#D', $from) || strlen($from) > 400) {
            throw new InvalidPage('Die alte Adresse darf nur Kleinbuchstaben, Ziffern, Bindestriche und Schrägstriche enthalten.');
        }
        if (301 === $status) {
            if (1 !== preg_match('#^[a-z0-9]+(?:[-/][a-z0-9]+)*$#D', $to) || strlen($to) > 400) {
                throw new InvalidPage('Das Ziel darf nur Kleinbuchstaben, Ziffern, Bindestriche und Schrägstriche enthalten.');
            }
            if ($from === $to) {
                throw new InvalidPage('Eine Adresse kann nicht auf sich selbst weiterleiten.');
            }
            // One hop only: a chain would cost an extra round trip and can become a loop.
            $next = $this->find($to);
            if (null !== $next) {
                throw new InvalidPage(sprintf('Das Ziel /%s leitet selbst weiter. Zeige direkt auf das Endziel.', $to));
            }
        }
        if (self::MAX <= (int) $this->db->fetchOne('SELECT COUNT(*) FROM redirect WHERE website_id = ?', ['default'])
            && null === $this->find($from)) {
            throw new InvalidPage(sprintf('Mehr als %d Weiterleitungen sind nicht vorgesehen.', self::MAX));
        }

        $this->db->transactional(function () use ($from, $to, $status): void {
            $this->db->executeStatement('DELETE FROM redirect WHERE website_id = ? AND from_path = ?', ['default', $from]);
            $this->db->insert('redirect', [
                'id' => bin2hex(random_bytes(16)), 'website_id' => 'default',
                'from_path' => $from, 'to_path' => 301 === $status ? $to : null,
                'status' => $status, 'created_at' => gmdate('Y-m-d H:i:s'),
            ]);
        });
    }

    public function delete(string $id): void
    {
        $this->db->executeStatement('DELETE FROM redirect WHERE id = ? AND website_id = ?', [$id, 'default']);
    }

    /** Records that an address moved, used when a page is renamed. Never overwrites an entry. */
    public function remember(string $from, string $to): void
    {
        if ($from === $to || null !== $this->find($from)) {
            return;
        }
        try {
            $this->save($from, $to, 301);
        } catch (InvalidPage) {
            // A path the rules reject is simply not remembered; renaming must not fail for it.
        }
    }
}