package order

import (
	"context"
	"encoding/json"
	"fmt"

	"git.k6n.net/mats/go-cart-actor/pkg/flow"
)

// Publisher is the minimal seam the amqp_emit hook needs. cmd/order supplies a
// RabbitMQ-backed implementation; tests pass a fake. Keeping it an interface
// keeps pkg/order free of an AMQP dependency.
type Publisher interface {
	Publish(exchange, routingKey string, body []byte) error
}

// RegisterEmitHook registers the "amqp_emit" flow hook, which publishes a flow
// event to a message broker — the bridge from a saga step to other services
// (loyalty, ERP sync, notifications) without coupling the flow to them. It is
// the commerce analogue of the CMS event listeners. Params (optional):
//
//	{"exchange": "", "routingKey": "order-events"}
//
// The body is {step, phase, id, error, vars}. With a nil publisher the hook is
// still registered (so the editor lists it) but errors at run time — and since
// hook errors never abort a flow, that failure is logged, not fatal.
func RegisterEmitHook(reg *flow.Registry, pub Publisher) {
	reg.Hook("amqp_emit", func(_ context.Context, st *flow.State, info flow.HookInfo, params json.RawMessage) error {
		if pub == nil {
			return fmt.Errorf("amqp_emit: no publisher configured")
		}
		var p struct {
			Exchange   string `json:"exchange"`
			RoutingKey string `json:"routingKey"`
		}
		if len(params) > 0 {
			if err := json.Unmarshal(params, &p); err != nil {
				return fmt.Errorf("amqp_emit: bad params: %w", err)
			}
		}
		if p.RoutingKey == "" {
			p.RoutingKey = "order-events"
		}
		errStr := ""
		if info.Err != nil {
			errStr = info.Err.Error()
		}
		body, _ := json.Marshal(map[string]any{
			"step":  info.Step,
			"phase": info.Phase,
			"id":    st.ID,
			"error": errStr,
			"vars":  st.Vars,
		})
		return pub.Publish(p.Exchange, p.RoutingKey, body)
	})
}