package sse

import (
	"context"
	"encoding/json"
	"log/slog"

	"bj_power_mes/internal/eventbus"
	"bj_power_mes/internal/eventlog"
)

// EventBridge 将 EventBus 事件转发给 SSE 客户端，实现内部事件到前端的实时推送。
type EventBridge struct {
	sseHandler *Handler
	bus        eventbus.Bus
	sub        eventbus.Subscription
}

// NewEventBridge 创建桥接器并订阅所有 EventBus 事件。
func NewEventBridge(bus eventbus.Bus, sseHandler *Handler) *EventBridge {
	bridge := &EventBridge{
		sseHandler: sseHandler,
		bus:        bus,
	}
	bridge.sub = bus.SubscribeAll(bridge.onEvent)
	return bridge
}

// Close 取消事件订阅。
func (b *EventBridge) Close() {
	if b.sub != nil {
		b.sub.Unsubscribe()
	}
}

func (b *EventBridge) onEvent(_ context.Context, event eventbus.Event) error {
	data, err := json.Marshal(map[string]any{
		"id":            event.ID,
		"eventType":     string(event.Type),
		"sourceId":      event.Source,
		"entityType":    event.EntityType,
		"entityId":      event.EntityID,
		"entityVersion": event.EntityVersion,
		"description":   eventlog.EventDescription(event),
		"payload":       event.Payload,
		"createdAt":     event.Timestamp.Format("2006-01-02 15:04:05"),
	})
	if err != nil {
		slog.Error("eventbridge: marshal failed", "err", err)
		return nil
	}
	b.sseHandler.Emit("eventbus."+string(event.Type), string(data))
	return nil
}