<?php

declare(strict_types=1);

namespace GNexus\Synapse;

use GNexus\Synapse\Config\SynapseConfig;
use GNexus\Synapse\DTO\BatchRejection;
use GNexus\Synapse\DTO\BatchResult;
use GNexus\Synapse\DTO\Delivery;
use GNexus\Synapse\DTO\EventStatus;
use GNexus\Synapse\DTO\SentEvent;
use GNexus\Synapse\Envelope\EnvelopeBuilder;
use GNexus\Synapse\Exception\AuthException;
use GNexus\Synapse\Exception\ConfigurationException;
use GNexus\Synapse\Exception\ForbiddenException;
use GNexus\Synapse\Exception\NotFoundException;
use GNexus\Synapse\Exception\ServerException;
use GNexus\Synapse\Exception\StatusTimeoutException;
use GNexus\Synapse\Exception\SynapseException;
use GNexus\Synapse\Exception\TransportException;
use GNexus\Synapse\Exception\ValidationException;
use Psr\Http\Client\ClientExceptionInterface;
use Psr\Http\Client\ClientInterface;
use Psr\Http\Client\NetworkExceptionInterface;
use Psr\Http\Message\RequestFactoryInterface;
use Psr\Http\Message\RequestInterface;
use Psr\Http\Message\ResponseInterface;
use Psr\Http\Message\StreamFactoryInterface;
use Psr\Log\LoggerInterface;
use Psr\Log\NullLogger;

/**
 * Тонкий клиент Ingestion API v1 хаба уведомлений Gnexus Synapse.
 * Один POST на send; никаких ретраев и локальных очередей — очередь у
 * Synapse своя (приём отвечает мгновенно, 202). Транспорт инжектный
 * (PSR-18 + PSR-17), таймаут настраивает потребитель в своём http-клиенте.
 */
final class SynapseClient
{
    public const USER_AGENT = 'gnexus-synapse-php/0.1.2';
    private const API_PREFIX = '/api/v1';

    private const STATUS_ERRORS = [
        401 => AuthException::class,
        403 => ForbiddenException::class,
        404 => NotFoundException::class,
        422 => ValidationException::class,
    ];

    private LoggerInterface $logger;

    public function __construct(
        private readonly SynapseConfig $config,
        private readonly ClientInterface $httpClient,
        private readonly RequestFactoryInterface $requestFactory,
        private readonly StreamFactoryInterface $streamFactory,
        ?LoggerInterface $logger = null,
    ) {
        $this->logger = $logger ?? new NullLogger();
    }

    /**
     * POST /api/v1/events → 202. Ошибки — типизированные исключения.
     *
     * @param array<string, mixed> $payload
     */
    public function send(
        ?string $source = null,
        string $subject = '',
        string $action = '',
        string $priority = 'normal',
        array $payload = [],
        ?string $dedupKey = null,
        ?int $ttlSeconds = null,
        ?\DateTimeInterface $scheduledAt = null,
        ?string $userId = null,
    ): SentEvent {
        $envelope = $this->buildEnvelope(
            $source, $subject, $action, $priority, $payload, $dedupKey, $ttlSeconds, $scheduledAt, $userId,
        );
        if (isset($envelope['payload']) && is_array($envelope['payload'])) {
            EnvelopeBuilder::warnBadUserId($envelope['payload'], $this->logger);
        }
        return $this->parseSentEvent($this->post($envelope, self::API_PREFIX . '/events'));
    }

    /**
     * Fire-and-forget: ловит SynapseException, пишет warning, возвращает null.
     *
     * @param array<string, mixed> $payload
     */
    public function emit(
        ?string $source = null,
        string $subject = '',
        string $action = '',
        string $priority = 'normal',
        array $payload = [],
        ?string $dedupKey = null,
        ?int $ttlSeconds = null,
        ?\DateTimeInterface $scheduledAt = null,
        ?string $userId = null,
        bool $throw = false,
    ): ?SentEvent {
        try {
            return $this->send(
                $source, $subject, $action, $priority, $payload, $dedupKey, $ttlSeconds, $scheduledAt, $userId,
            );
        } catch (SynapseException $ex) {
            if ($throw) {
                throw $ex;
            }
            $this->logger->warning('synapse emit failed: ' . $ex->detail);
            return null;
        }
    }

    /**
     * Голый массив конвертов; сервер отвечает per-index (202 и 422 парсим
     * одинаково: rejected — не исключение, частичный успех норма). Локально
     * битые конверты не посылаются — сразу BatchRejection на своей позиции.
     * Транспортный сбой/5xx — исключение: частичный успех неизвестен.
     *
     * @param list<array<string, mixed>> $events
     */
    public function sendBatch(array $events): BatchResult
    {
        $results = [];
        $positions = [];
        $payload = [];
        foreach (array_values($events) as $i => $raw) {
            try {
                $rawSource = $raw['source'] ?? null;
                $rawDedup = $raw['dedup_key'] ?? null;
                $rawTtl = $raw['ttl_seconds'] ?? null;
                $rawScheduled = $raw['scheduled_at'] ?? null;
                $payload[] = EnvelopeBuilder::build(
                    is_string($rawSource) && $rawSource !== '' ? $rawSource : $this->resolveSource(),
                    (string) ($raw['subject'] ?? ''),
                    (string) ($raw['action'] ?? ''),
                    is_string($raw['priority'] ?? null) ? $raw['priority'] : 'normal',
                    is_array($raw['payload'] ?? null) ? $raw['payload'] : null,
                    is_string($rawDedup) ? $rawDedup : null,
                    is_int($rawTtl) ? $rawTtl : null,
                    $rawScheduled instanceof \DateTimeInterface ? $rawScheduled : null,
                );
                $positions[] = $i;
            } catch (SynapseException $ex) { // Configuration + Validation локально
                $results[$i] = new BatchRejection($i, $ex->detail);
            }
        }

        if ($payload !== []) {
            $resp = $this->post($payload, self::API_PREFIX . '/events/batch');
            $body = $this->jsonBody($resp);
            $serverResults = is_array($body['results'] ?? null) ? $body['results'] : [];
            foreach ($positions as $pos => $origIndex) {
                $item = $serverResults[$pos] ?? [];
                if (!is_array($item)) {
                    $results[$origIndex] = new BatchRejection($origIndex, 'битый элемент ответа');
                } elseif (($item['ok'] ?? null) === true) {
                    $results[$origIndex] = new SentEvent(
                        (string) ($item['id'] ?? ''),
                        (string) ($item['status'] ?? ''),
                        (bool) ($item['deduplicated'] ?? false),
                    );
                } else {
                    $results[$origIndex] = new BatchRejection(
                        $origIndex,
                        (string) ($item['detail'] ?? ''),
                    );
                }
            }
        }
        ksort($results);
        return new BatchResult(array_values($results));
    }

    public function status(string $eventId): EventStatus
    {
        $resp = $this->request('GET', self::API_PREFIX . '/events/' . rawurlencode($eventId));
        $body = $this->jsonBody($resp);
        if ($resp->getStatusCode() !== 200) {
            throw $this->errorFor($resp, $body);
        }
        $deliveries = [];
        foreach (is_array($body['deliveries'] ?? null) ? $body['deliveries'] : [] as $d) {
            $deliveries[] = new Delivery(
                (string) ($d['channel'] ?? ''),
                isset($d['target']) && $d['target'] !== null ? (string) $d['target'] : null,
                (string) ($d['status'] ?? ''),
                (int) ($d['attempts'] ?? 0),
                isset($d['error']) && $d['error'] !== null ? (string) $d['error'] : null,
                isset($d['rendered_message']) && $d['rendered_message'] !== null
                    ? (string) $d['rendered_message']
                    : null,
            );
        }
        return new EventStatus(
            (string) ($body['id'] ?? $eventId),
            (string) ($body['source'] ?? ''),
            (string) ($body['subject'] ?? ''),
            (string) ($body['action'] ?? ''),
            (string) ($body['priority'] ?? ''),
            (string) ($body['status'] ?? ''),
            new \DateTimeImmutable((string) ($body['created_at'] ?? 'now')),
            isset($body['expires_at']) && $body['expires_at'] !== null
                ? new \DateTimeImmutable((string) $body['expires_at'])
                : null,
            $deliveries,
        );
    }

    /** GET /api/healthz (без ключа) — смок/мониторинг. */
    public function health(): array
    {
        return $this->diagnostics('/api/healthz');
    }

    /** GET /api/readyz (без ключа). */
    public function ready(): array
    {
        return $this->diagnostics('/api/readyz');
    }

    /**
     * Поллинг до целевого статуса или таймаут — для приёмки/тестов, не
     * бизнес-кода. Морг транспорта не прерывает ожидание до дедлайна.
     * Не достигли → StatusTimeoutException с последним известным статусом.
     *
     * @param list<string> $statuses
     */
    public function waitForStatus(
        string $eventId,
        array $statuses = ['done', 'failed'],
        float $timeoutSeconds = 30.0,
        float $intervalSeconds = 1.0,
    ): EventStatus {
        $deadline = microtime(true) + $timeoutSeconds;
        $lastStatus = null;
        $sleepMicro = (int) round(max($intervalSeconds, 0.01) * 1_000_000);
        while (true) {
            try {
                $st = $this->status($eventId);
                $lastStatus = $st->status;
                if (in_array($st->status, $statuses, true)) {
                    return $st;
                }
            } catch (TransportException) {
                // Synapse моргнул — держим дедлайн
            }
            if (microtime(true) >= $deadline) {
                throw new StatusTimeoutException(
                    sprintf(
                        'событие %s не в [%s] за %s c (последний статус: %s)',
                        $eventId,
                        implode(', ', $statuses),
                        $timeoutSeconds,
                        $lastStatus ?? 'нет ответа',
                    ),
                );
            }
            usleep($sleepMicro);
        }
    }

    // -- internal --------------------------------------------------------

    /**
     * @return array<string, mixed>
     */
    private function diagnostics(string $path): array
    {
        $resp = $this->request('GET', $path);
        $body = $this->jsonBody($resp);
        if ($resp->getStatusCode() !== 200) {
            throw $this->errorFor($resp, $body);
        }
        return $body;
    }

    /**
     * @param  array<string, mixed>|null $payload
     * @return array<string, mixed>
     */
    private function buildEnvelope(
        ?string $source,
        string $subject,
        string $action,
        string $priority,
        ?array $payload,
        ?string $dedupKey,
        ?int $ttlSeconds,
        ?\DateTimeInterface $scheduledAt,
        ?string $userId = null,
    ): array {
        // user_id — first-class конвенция «о ком событие» (docs/05):
        // явный параметр перебивает payload["user_id"], если тот был
        if ($userId !== null && $userId !== '') {
            $payload = [...($payload ?? []), 'user_id' => $userId];
        }
        return EnvelopeBuilder::build(
            $this->resolveSource($source),
            $subject,
            $action,
            $priority,
            $payload !== null && $payload !== [] ? $payload : null,
            $dedupKey,
            $ttlSeconds,
            $scheduledAt,
        );
    }

    private function resolveSource(?string $source = null): string
    {
        $source = $source ?? $this->config->source();
        if ($source === '') {
            throw new ConfigurationException(
                'не задан source: передайте source или SYNAPSE_DEFAULT_SOURCE (' .
                SynapseConfig::ENV_DEFAULT_SOURCE . ')',
            );
        }
        return $source;
    }

    /**
     * @param array<string, mixed>|list<array<string, mixed>> $body
     */
    private function post(array $body, string $path): ResponseInterface
    {
        if ($this->config->apiKey === null) {
            throw new ConfigurationException(
                'не задан api_key: передайте ключ или ' . SynapseConfig::ENV_API_KEY,
            );
        }
        return $this->request('POST', $path, json_encode($body, JSON_THROW_ON_ERROR));
    }

    private function request(string $method, string $path, ?string $json = null): ResponseInterface
    {
        $request = $this->requestFactory->createRequest($method, $this->config->url($path))
            ->withHeader('Content-Type', 'application/json')
            ->withHeader('User-Agent', self::USER_AGENT);
        if ($this->config->apiKey !== null) {
            $request = $request->withHeader('Authorization', 'Bearer ' . $this->config->apiKey);
        }
        if ($json !== null) {
            $request = $request->withBody($this->streamFactory->createStream($json));
        }
        try {
            return $this->httpClient->sendRequest($request);
        } catch (NetworkExceptionInterface $ex) {
            throw new TransportException('Synapse недоступен: ' . $ex->getMessage(), $ex);
        } catch (ClientExceptionInterface $ex) {
            throw new TransportException('Транспортная ошибка: ' . $ex->getMessage(), $ex);
        }
    }

    /**
     * @return array<string, mixed>
     */
    private function jsonBody(ResponseInterface $resp): array
    {
        $raw = (string) $resp->getBody();
        if ($raw === '') {
            return [];
        }
        try {
            $decoded = json_decode($raw, true, 512, JSON_THROW_ON_ERROR);
        } catch (\JsonException) {
            return [];
        }
        return is_array($decoded) ? $decoded : [];
    }

    private function errorFor(ResponseInterface $resp, array $body): SynapseException
    {
        $code = $resp->getStatusCode();
        if (isset($body['detail']) && is_scalar($body['detail'])) {
            $detail = (string) $body['detail'];
        } else {
            $detail = sprintf('HTTP %d: %s', $code, substr((string) $resp->getBody(), 0, 300));
        }
        if ($code >= 500) {
            return new ServerException($detail, $code);
        }
        $cls = self::STATUS_ERRORS[$code] ?? SynapseException::class;
        return new $cls($detail, $code);
    }

    private function parseSentEvent(ResponseInterface $resp): SentEvent
    {
        $body = $this->jsonBody($resp);
        if ($resp->getStatusCode() !== 202) {
            throw $this->errorFor($resp, $body);
        }
        return new SentEvent(
            (string) ($body['id'] ?? ''),
            (string) ($body['status'] ?? ''),
            (bool) ($body['deduplicated'] ?? false),
        );
    }
}