<?php

declare(strict_types=1);

namespace App\Http\Controllers\Admin;

use App\Http\Controllers\Controller;
use Illuminate\Contracts\View\View;
use Illuminate\Http\RedirectResponse;
use Illuminate\Http\Request;
use Illuminate\Http\Response;
use Illuminate\Support\Facades\RateLimiter;
use Illuminate\Support\Str;
use Illuminate\Validation\ValidationException;

class AuthController extends Controller
{
    private const LOGIN_MAX_ATTEMPTS = 5;

    private const LOGIN_DECAY_SECONDS = 120;

    public function showLogin(): View
    {
        return view('admin.auth.login');
    }

    /**
     * @throws ValidationException
     */
    public function login(Request $request): RedirectResponse
    {
        $payload = $request->validate([
            'username' => ['required', 'string', 'max:100'],
            'password' => ['required', 'string', 'max:255'],
            'captcha' => ['required', 'string', 'size:5'],
        ], [
            'username.required' => '请输入后台账号。',
            'password.required' => '请输入后台密码。',
            'captcha.required' => '请输入验证码。',
            'captcha.size' => '验证码格式不正确。',
        ]);

        $rateLimiterKey = $this->loginRateLimiterKey($request, $payload['username']);

        if (RateLimiter::tooManyAttempts($rateLimiterKey, self::LOGIN_MAX_ATTEMPTS)) {
            $seconds = RateLimiter::availableIn($rateLimiterKey);

            throw ValidationException::withMessages([
                'username' => "尝试次数过多，请在 {$seconds} 秒后重试。",
            ]);
        }

        if (! $this->isCaptchaValid($request, $payload['captcha'])) {
            RateLimiter::hit($rateLimiterKey, self::LOGIN_DECAY_SECONDS);

            throw ValidationException::withMessages([
                'captcha' => '验证码错误，请重试。',
            ]);
        }

        if (! $this->isCredentialValid($payload['username'], $payload['password'])) {
            RateLimiter::hit($rateLimiterKey, self::LOGIN_DECAY_SECONDS);

            throw ValidationException::withMessages([
                'username' => '账号或密码错误。',
            ]);
        }

        RateLimiter::clear($rateLimiterKey);

        $request->session()->regenerate();
        $request->session()->put('admin_authenticated', true);
        $request->session()->put('admin_username', $payload['username']);
        $request->session()->forget('admin_captcha_hash');

        return redirect()->route('admin.dashboard');
    }

    public function logout(Request $request): RedirectResponse
    {
        $request->session()->forget(['admin_authenticated', 'admin_username', 'admin_captcha_hash']);
        $request->session()->invalidate();
        $request->session()->regenerateToken();

        return redirect()->route('admin.login')->with('status', '已安全退出后台。');
    }

    public function captcha(Request $request): Response
    {
        $captchaText = strtoupper(Str::random(5));
        $request->session()->put('admin_captcha_hash', hash('sha256', strtolower($captchaText)));

        $imageWidth = 140;
        $imageHeight = 46;

        $image = imagecreatetruecolor($imageWidth, $imageHeight);

        $background = imagecolorallocate($image, 241, 245, 249);
        $textColor = imagecolorallocate($image, 15, 23, 42);
        $lineColor = imagecolorallocate($image, 148, 163, 184);
        $noiseColor = imagecolorallocate($image, 100, 116, 139);

        imagefilledrectangle($image, 0, 0, $imageWidth, $imageHeight, $background);

        for ($index = 0; $index < 4; $index++) {
            imageline(
                $image,
                random_int(0, $imageWidth),
                random_int(0, $imageHeight),
                random_int(0, $imageWidth),
                random_int(0, $imageHeight),
                $lineColor,
            );
        }

        for ($index = 0; $index < 90; $index++) {
            imagesetpixel($image, random_int(0, $imageWidth - 1), random_int(0, $imageHeight - 1), $noiseColor);
        }

        imagestring($image, 5, 24, 14, $captchaText, $textColor);

        ob_start();
        imagepng($image);
        $binary = (string) ob_get_clean();
        imagedestroy($image);

        return response($binary, 200, [
            'Content-Type' => 'image/png',
            'Cache-Control' => 'no-store, no-cache, must-revalidate, max-age=0',
            'Pragma' => 'no-cache',
            'Expires' => '0',
        ]);
    }

    private function isCredentialValid(string $username, string $password): bool
    {
        $configuredUser = (string) config('app.admin_user', 'admin');
        $configuredPassword = (string) config('app.admin_password', 'change-me');

        return hash_equals($configuredUser, $username)
            && hash_equals($configuredPassword, $password);
    }

    private function isCaptchaValid(Request $request, string $input): bool
    {
        $storedHash = (string) $request->session()->get('admin_captcha_hash', '');

        $request->session()->forget('admin_captcha_hash');

        if ($storedHash === '') {
            return false;
        }

        return hash_equals($storedHash, hash('sha256', strtolower(trim($input))));
    }

    private function loginRateLimiterKey(Request $request, string $username): string
    {
        return Str::lower($username).'|'.$request->ip();
    }
}