<?php

declare(strict_types=1);

namespace App\Controllers;

use App\Libraries\BookApi;
use App\Libraries\Captcha;
use App\Libraries\Mongo;
use App\Libraries\PdfAccess;

/**
 * Access gate: captcha + countdown before viewing/downloading a book's PDF.
 */
class Download extends BaseController
{
    private BookApi $api;

    public function __construct()
    {
        $this->api = new BookApi();
        helper(['text', 'form']);
    }

    /**
     * Reader route /doc/{id}: captcha gate first, then the reading page.
     */
    public function page(string $id)
    {
        $book = $this->api->book($id);
        if (! $book) {
            throw \CodeIgniter\Exceptions\PageNotFoundException::forPageNotFound();
        }

        $error = null;

        if ($this->request->getPost('download')) {
            if (Captcha::verify($this->request->getPost('captcha'))) {
                PdfAccess::grant($id);
                return redirect()->to(site_url('doc/' . $id));
            }
            $error = 'Mã captcha không đúng hoặc đã hết hạn. Vui lòng thử lại.';
        }

        // access granted → reading page with viewer
        if (PdfAccess::has($id)) {
            return view('books/read', ['book' => $book]);
        }

        // otherwise → captcha gate
        return view('books/download', [
            'book'      => $book,
            'error'     => $error,
            'countdown' => (int) env('download.countdown', 15),
        ]);
    }

    public function captcha()
    {
        Captcha::render(Captcha::issue());
    }

    /**
     * Token-gated actual download. Requires an active PDF access grant.
     */
    public function fetch(string $id, string $token)
    {
        if (! PdfAccess::has($id)) {
            return view('pages/error_api', ['message' => 'Phiên truy cập đã hết hạn. Vui lòng xác nhận captcha lại để tải xuống.']);
        }

        if (! $this->consumeToken($id, $token)) {
            return view('pages/error_api', ['message' => 'Liên kết tải về không hợp lệ hoặc đã hết hạn. Vui lòng thực hiện lại quy trình tải xuống.']);
        }

        $book = $this->api->book($id);
        if (! $book) {
            throw \CodeIgniter\Exceptions\PageNotFoundException::forPageNotFound();
        }

        // stats
        $stats = Mongo::col('stats');
        $stats->updateOne(['_id' => 'book:' . $id], ['$inc' => ['downloads' => 1]], ['upsert' => true]);
        $stats->updateOne(['_id' => 'global'], ['$inc' => ['downloads' => 1]], ['upsert' => true]);

        $safeName = preg_replace('/[^\p{L}\p{N} _.-]/u', '_', $book['title']) . '.pdf';

        $this->response->setHeader('Content-Type', 'application/pdf');
        $this->api->stream($book['pdfEndpoint'], $safeName);
        exit;
    }

    /**
     * Issue a one-time download token (requires access grant).
     */
    public function token(string $id)
    {
        if (! $this->request->isAJAX() && strtolower($this->request->getMethod()) !== 'post') {
            return $this->response->setStatusCode(405);
        }

        if (! PdfAccess::has($id)) {
            return $this->response->setStatusCode(403)->setJSON(['ok' => false, 'error' => 'expired']);
        }

        $token = bin2hex(random_bytes(16));
        Mongo::col('download_tokens')->insertOne([
            '_id'       => $token,
            'bookId'    => $id,
            'session'   => session_id(),
            'expiresAt' => new \MongoDB\BSON\UTCDateTime((time() + 300) * 1000),
            'used'      => false,
        ]);

        return $this->response->setJSON(['ok' => true, 'url' => site_url("tai-ve/{$id}/{$token}")]);
    }

    private function consumeToken(string $id, string $token): bool
    {
        $col   = Mongo::col('download_tokens');
        $doc   = $col->findOne(['_id' => $token, 'bookId' => $id, 'used' => false]);
        if (! $doc) {
            return false;
        }
        if ($doc['expiresAt']->toDateTime()->getTimestamp() < time()) {
            $col->deleteOne(['_id' => $token]);
            return false;
        }
        $col->updateOne(['_id' => $token], ['$set' => ['used' => true]]);
        return true;
    }
}