<?php

namespace App\Http\Controllers;

use App\Http\Resources\MessageResource;
use App\Services\ChatService;
use Illuminate\Http\Request;
use Illuminate\Http\Response;
use Illuminate\Support\Facades\Redis;
use Symfony\Component\HttpFoundation\StreamedResponse;

class ChatSessionSseController extends Controller
{
    public function __construct(private readonly ChatService $service)
    {
    }

    public function stream(Request $request, string $sessionId): Response|StreamedResponse
    {
        $this->service->getSession($sessionId); // ensure exists

        $lastEventId = $request->header('Last-Event-ID');
        $afterSeq = is_numeric($lastEventId) ? (int) $lastEventId : (int) $request->query('after_seq', 0);
        $limit = (int) $request->query('limit', 200);
        $limit = $limit > 0 && $limit <= 500 ? $limit : 200;

        $useBacklogOnly = app()->runningUnitTests()
            || app()->environment('testing')
            || defined('PHPUNIT_COMPOSER_INSTALL')
            || ! class_exists(\Redis::class);

        if ($useBacklogOnly) {
            $lastSentSeq = $afterSeq;
            ob_start();
            $this->sendBacklog($sessionId, $lastSentSeq, $limit, false);
            $content = ob_get_clean() ?: '';

            return response($content, 200, [
                'Content-Type' => 'text/event-stream',
                'Cache-Control' => 'no-cache',
                'X-Accel-Buffering' => 'no',
            ]);
        }

        $response = new StreamedResponse(function () use ($sessionId, $afterSeq, $limit) {
            $lastSentSeq = $afterSeq;

            $this->sendBacklog($sessionId, $lastSentSeq, $limit);

            try {
                $redis = Redis::connection()->client();
                if (method_exists($redis, 'setOption')) {
                    $redis->setOption(\Redis::OPT_READ_TIMEOUT, 5);
                }

                $channel = "session:{$sessionId}:messages";
                $lastPing = time();
                logger()->info('sse open');
                if (method_exists($redis, 'pubSubLoop')) {
                    $pubSub = $redis->pubSubLoop();
                    $pubSub->subscribe($channel);

                    foreach ($pubSub as $message) {
                        if ($message->kind === 'subscribe') {
                            continue;
                        }

                        if (connection_aborted()) {
                            $pubSub->unsubscribe();
                            break;
                        }

                        $payloadId = $message->payload ?? null;
                        if ($payloadId) {
                            $msg = $this->service->getMessage($sessionId, $payloadId);
                            if ($msg && $msg->seq > $lastSentSeq) {
                                $this->emitMessage($msg);
                                $lastSentSeq = $msg->seq;
                            }
                        }

                        if (time() - $lastPing >= 180) {
                            logger()->info('ping: sent'.$sessionId);
                            echo ": ping\n\n";
                            @ob_flush();
                            @flush();
                            $lastPing = time();
                        }
                    }
                    logger()->info('close: sent'.$sessionId);
                    unset($pubSub);
                } else {
                    // Fallback for Redis drivers without pubSubLoop (older phpredis)
                    $redis->subscribe([$channel], function ($redisInstance, $chan, $payload) use (&$lastSentSeq, $sessionId) {
                        if (connection_aborted()) {
                            $redisInstance->unsubscribe([$chan]);
                            return;
                        }

                        if (! $payload) {
                            return;
                        }

                        $msg = $this->service->getMessage($sessionId, $payload);
                        if ($msg && $msg->seq > $lastSentSeq) {
                            $this->emitMessage($msg);
                            $lastSentSeq = $msg->seq;
                        }
                    });
                }
            } catch (\RedisException $exception) {
                logger()->warning('SSE redis subscription failed', [
                    'session_id' => $sessionId,
                    'message' => $exception->getMessage(),
                ]);
                echo ": redis-error\n\n";
                @ob_flush();
                @flush();
            }
        });

        $response->headers->set('Content-Type', 'text/event-stream');
        $response->headers->set('Cache-Control', 'no-cache');
        $response->headers->set('X-Accel-Buffering', 'no');

        return $response;
    }

    private function sendBacklog(string $sessionId, int &$lastSentSeq, int $limit, bool $flush = true): void
    {
        $backlog = $this->service->listMessagesBySeq($sessionId, $lastSentSeq, $limit);
        foreach ($backlog as $message) {
            $this->emitMessage($message, $flush);
            $lastSentSeq = $message->seq;
        }
    }

    private function emitMessage($message, bool $flush = true): void
    {
        $payload = (new MessageResource($message))->resolve();
        echo 'id: '.$message->seq."\n";
        echo "event: message\n";
        echo 'data: '.json_encode($payload, JSON_UNESCAPED_UNICODE)."\n\n";
        if ($flush) {
            @ob_flush();
            @flush();
        }
    }
}