<?php

declare(strict_types=1);

namespace App\Services\Adsense;

use App\Models\AdsenseConnection;
use App\Services\Adsense\Exceptions\AdsenseAuthorizationException;
use App\Services\Adsense\Exceptions\AdsenseOAuthException;
use Illuminate\Http\Client\ConnectionException;
use Illuminate\Http\Request;
use Illuminate\Support\Facades\Cache;
use Illuminate\Support\Facades\Http;
use Illuminate\Support\Facades\Log;
use Illuminate\Support\Str;

final class AdsenseOAuthService
{
    public const SESSION_STATE_KEY = 'adsense.oauth_state';

    public const SESSION_PENDING_ACCOUNTS_KEY = 'adsense.pending_accounts';

    public function isConfigured(): bool
    {
        return $this->clientId() !== '' && $this->clientSecret() !== '' && $this->redirectUri() !== '';
    }

    public function authorizationUrl(Request $request, bool $promptConsent = true): string
    {
        if (! $this->isConfigured()) {
            throw new AdsenseOAuthException('Google AdSense OAuth is not configured.');
        }

        $state = bin2hex(random_bytes(32));
        $request->session()->put(self::SESSION_STATE_KEY, $state);

        $query = [
            'client_id' => $this->clientId(),
            'redirect_uri' => $this->redirectUri(),
            'response_type' => 'code',
            'scope' => (string) config('adsense.scope'),
            'access_type' => 'offline',
            'include_granted_scopes' => 'true',
            'state' => $state,
        ];

        if ($promptConsent) {
            $query['prompt'] = 'consent';
        }

        return (string) config('adsense.oauth_authorize_url').'?'.http_build_query($query);
    }

    /**
     * @return array{access_token: string, refresh_token: ?string, expires_in: int}
     */
    public function exchangeAuthorizationCode(string $code): array
    {
        return $this->requestToken([
            'grant_type' => 'authorization_code',
            'code' => $code,
            'redirect_uri' => $this->redirectUri(),
            'client_id' => $this->clientId(),
            'client_secret' => $this->clientSecret(),
        ]);
    }

    /**
     * @return array{access_token: string, refresh_token: ?string, expires_in: int}
     */
    public function refreshAccessToken(string $refreshToken): array
    {
        try {
            return $this->requestToken([
                'grant_type' => 'refresh_token',
                'refresh_token' => $refreshToken,
                'client_id' => $this->clientId(),
                'client_secret' => $this->clientSecret(),
            ]);
        } catch (AdsenseOAuthException $exception) {
            if ($this->isInvalidGrant($exception)) {
                throw new AdsenseAuthorizationException(
                    'AdSense authorization expired or was revoked.',
                    0,
                    $exception,
                );
            }

            throw $exception;
        }
    }

    public function persistTokens(AdsenseConnection $connection, array $tokens, ?int $userId = null): void
    {
        $refreshToken = $tokens['refresh_token'] ?? null;
        if (is_string($refreshToken) && $refreshToken !== '') {
            $connection->encrypted_refresh_token = $refreshToken;
        }

        if (! $connection->hasRefreshToken()) {
            throw new AdsenseOAuthException('Google did not return a refresh token. Reconnect with consent.');
        }

        if ($userId !== null) {
            $connection->connected_by_user_id = $userId;
        }

        if ($connection->connected_at === null) {
            $connection->connected_at = now();
        }

        if ($connection->status === AdsenseConnection::STATUS_DISCONNECTED) {
            $connection->status = AdsenseConnection::STATUS_PENDING;
        }

        $connection->last_error = null;
        $connection->save();

        if (isset($tokens['access_token']) && is_string($tokens['access_token']) && $tokens['access_token'] !== '') {
            $this->cacheAccessToken(
                (int) $connection->id,
                $tokens['access_token'],
                (int) ($tokens['expires_in'] ?? 3600),
            );
        }
    }

    public function accessToken(AdsenseConnection $connection, bool $forceRefresh = false): string
    {
        if (! $connection->hasRefreshToken()) {
            $this->markReconnectRequired($connection, 'AdSense authorization expired or was revoked.');

            throw new AdsenseAuthorizationException('AdSense authorization expired or was revoked.');
        }

        $cacheKey = $this->cacheKey((int) $connection->id);

        if (! $forceRefresh) {
            $cached = Cache::get($cacheKey);
            if (is_string($cached) && $cached !== '') {
                return $cached;
            }
        }

        try {
            $tokens = $this->refreshAccessToken((string) $connection->encrypted_refresh_token);
        } catch (AdsenseAuthorizationException $exception) {
            $this->forgetAccessToken((int) $connection->id);
            $this->markReconnectRequired($connection, $exception->getMessage());

            throw $exception;
        }

        $accessToken = (string) ($tokens['access_token'] ?? '');
        if ($accessToken === '') {
            throw new AdsenseOAuthException('Google did not return an access token.');
        }

        if (isset($tokens['refresh_token']) && is_string($tokens['refresh_token']) && $tokens['refresh_token'] !== '') {
            $connection->encrypted_refresh_token = $tokens['refresh_token'];
            $connection->save();
        }

        $this->cacheAccessToken((int) $connection->id, $accessToken, (int) ($tokens['expires_in'] ?? 3600));

        return $accessToken;
    }

    public function cacheAccessToken(int $connectionId, string $accessToken, int $expiresIn): void
    {
        $ttl = max(30, $expiresIn - (int) config('adsense.access_token_skew_seconds', 60));
        Cache::put($this->cacheKey($connectionId), $accessToken, $ttl);
    }

    public function forgetAccessToken(int $connectionId): void
    {
        Cache::forget($this->cacheKey($connectionId));
    }

    public function markReconnectRequired(AdsenseConnection $connection, string $message): void
    {
        $connection->status = AdsenseConnection::STATUS_RECONNECT_REQUIRED;
        $connection->last_error = $message;
        $connection->save();
    }

    public function disconnect(AdsenseConnection $connection): void
    {
        $refreshToken = $connection->encrypted_refresh_token;
        $this->forgetAccessToken((int) $connection->id);

        if (is_string($refreshToken) && $refreshToken !== '') {
            $this->revokeToken($refreshToken);
        }

        $connection->encrypted_refresh_token = null;
        $connection->status = AdsenseConnection::STATUS_DISCONNECTED;
        $connection->last_error = null;
        $connection->save();
    }

    public function revokeToken(string $token): void
    {
        try {
            Http::asForm()
                ->timeout((int) config('adsense.timeout', 20))
                ->connectTimeout((int) config('adsense.connect_timeout', 5))
                ->post((string) config('adsense.oauth_revoke_url'), [
                    'token' => $token,
                ]);
        } catch (\Throwable $exception) {
            Log::warning('AdSense token revocation failed.', AdsenseLogSanitizer::context([
                'message' => $exception->getMessage(),
            ]));
        }
    }

    public function assertValidCallback(Request $request): string
    {
        $error = trim((string) $request->query('error', ''));
        if ($error !== '') {
            $description = trim((string) $request->query('error_description', ''));
            $request->session()->forget(self::SESSION_STATE_KEY);

            throw new AdsenseOAuthException(
                $description !== ''
                    ? 'Google AdSense authorization was denied: '.$description
                    : 'Google AdSense authorization was denied.'
            );
        }

        $expected = (string) $request->session()->pull(self::SESSION_STATE_KEY, '');
        $provided = (string) $request->query('state', '');

        if ($expected === '' || $provided === '' || ! hash_equals($expected, $provided)) {
            throw new AdsenseOAuthException('Invalid OAuth state.');
        }

        $code = trim((string) $request->query('code', ''));
        if ($code === '') {
            throw new AdsenseOAuthException('Missing authorization code.');
        }

        return $code;
    }

    /**
     * @param  array<string, string>  $payload
     * @return array{access_token: string, refresh_token: ?string, expires_in: int}
     */
    private function requestToken(array $payload): array
    {
        try {
            $response = Http::asForm()
                ->acceptJson()
                ->timeout((int) config('adsense.timeout', 20))
                ->connectTimeout((int) config('adsense.connect_timeout', 5))
                ->post((string) config('adsense.oauth_token_url'), $payload);
        } catch (ConnectionException $exception) {
            Log::warning('AdSense OAuth token request failed.', AdsenseLogSanitizer::context([
                'message' => $exception->getMessage(),
            ]));

            throw new AdsenseOAuthException('Unable to contact Google OAuth.', 0, $exception);
        }

        $json = $response->json();
        $json = is_array($json) ? $json : [];

        if ($response->failed()) {
            $error = $json['error'] ?? 'oauth_error';
            if (is_array($error)) {
                $error = (string) ($error['message'] ?? $error['status'] ?? 'oauth_error');
            } else {
                $error = (string) $error;
            }
            Log::warning('AdSense OAuth token request rejected.', AdsenseLogSanitizer::context([
                'status' => $response->status(),
                'error' => $error,
            ]));

            throw new AdsenseOAuthException($error, $response->status());
        }

        $accessToken = (string) ($json['access_token'] ?? '');
        if ($accessToken === '') {
            throw new AdsenseOAuthException('Google did not return an access token.');
        }

        $refreshToken = $json['refresh_token'] ?? null;

        return [
            'access_token' => $accessToken,
            'refresh_token' => is_string($refreshToken) && $refreshToken !== '' ? $refreshToken : null,
            'expires_in' => (int) ($json['expires_in'] ?? 3600),
        ];
    }

    private function isInvalidGrant(AdsenseOAuthException $exception): bool
    {
        $message = Str::lower($exception->getMessage());

        return str_contains($message, 'invalid_grant')
            || str_contains($message, 'revoked')
            || str_contains($message, 'invalid_token');
    }

    private function cacheKey(int $connectionId): string
    {
        return (string) config('adsense.access_token_cache_prefix', 'adsense.access_token.').$connectionId;
    }

    private function clientId(): string
    {
        return trim((string) config('adsense.client_id'));
    }

    private function clientSecret(): string
    {
        return trim((string) config('adsense.client_secret'));
    }

    public function redirectUri(): string
    {
        return trim((string) config('adsense.redirect_uri'));
    }
}