package com.baiyue.eventbridge.service;

import com.baiyue.common.event.EventEnvelope;
import com.baiyue.common.event.EventPayloadCanonicalizer;
import com.baiyue.common.event.EventPayloadHash;
import com.baiyue.eventbridge.domain.BridgeInbox;
import com.baiyue.eventbridge.dto.EventReceiveResult;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.dao.DuplicateKeyException;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

import java.time.LocalDateTime;

/**
 * 入站事件校验与幂等落库服务。
 */
@Service
public class EventInboxService {
    private final InboxStore inboxStore;
    private final ObjectMapper objectMapper;
    private final String localRegion;

    public EventInboxService(InboxStore inboxStore, ObjectMapper objectMapper,
                             @Value("${baiyue.region:CN}") String localRegion) {
        this.inboxStore = inboxStore;
        this.objectMapper = objectMapper;
        this.localRegion = localRegion;
    }

    @Transactional
    public EventReceiveResult receive(EventEnvelope envelope) {
        envelope.requireValid();
        if (!envelope.targetRegion().name().equalsIgnoreCase(localRegion)) {
            throw new IllegalArgumentException("事件目标区域与当前事件桥区域不一致");
        }
        if (!EventPayloadHash.matches(EventPayloadCanonicalizer.canonicalize(envelope.payload()), envelope.payloadHash())) {
            throw new IllegalArgumentException("payloadHash 与规范化事件负载不一致");
        }
        BridgeInbox existing = inboxStore.findByEventId(envelope.eventId());
        if (existing != null) {
            return duplicateOrConflict(existing, envelope);
        }
        BridgeInbox inbox = toInbox(envelope);
        try {
            inboxStore.insert(inbox);
            return new EventReceiveResult(envelope.eventId(), "已接收", inbox.getReceivedAt());
        } catch (DuplicateKeyException exception) {
            BridgeInbox concurrent = inboxStore.findByEventId(envelope.eventId());
            if (concurrent == null) {
                throw exception;
            }
            return duplicateOrConflict(concurrent, envelope);
        }
    }

    private EventReceiveResult duplicateOrConflict(BridgeInbox existing, EventEnvelope envelope) {
        if (!existing.getPayloadHash().equalsIgnoreCase(envelope.payloadHash())) {
            throw new IllegalArgumentException("相同 eventId 对应的 payloadHash 不一致，拒绝覆盖既有事件");
        }
        return new EventReceiveResult(envelope.eventId(), "重复", existing.getReceivedAt());
    }

    private BridgeInbox toInbox(EventEnvelope envelope) {
        BridgeInbox inbox = new BridgeInbox();
        inbox.setEventId(envelope.eventId());
        inbox.setIdempotencyKey(envelope.sourceRegion() + ":" + envelope.eventId());
        inbox.setEventType(envelope.eventType());
        inbox.setEventVersion(envelope.eventVersion());
        inbox.setSourceRegion(envelope.sourceRegion().name());
        inbox.setTargetRegion(envelope.targetRegion().name());
        inbox.setTenantId(envelope.tenantId());
        inbox.setAggregateType(envelope.aggregateType());
        inbox.setAggregateId(envelope.aggregateId());
        inbox.setAggregateVersion(envelope.aggregateVersion());
        inbox.setHandoverVersion(envelope.handoverVersion());
        inbox.setTraceId(envelope.traceId());
        inbox.setCorrelationId(envelope.correlationId());
        inbox.setCausationId(envelope.causationId());
        inbox.setOccurredAt(envelope.occurredAt());
        inbox.setPayloadHash(envelope.payloadHash().toLowerCase(java.util.Locale.ROOT));
        try {
            inbox.setPayloadJson(objectMapper.writeValueAsString(envelope.payload()));
        } catch (JsonProcessingException exception) {
            throw new IllegalArgumentException("事件负载无法序列化", exception);
        }
        inbox.setStatus("RECEIVED");
        inbox.setReceivedAt(LocalDateTime.now());
        return inbox;
    }
}