package seatlist

import (
	"encoding/json"
	"fmt"
	"strings"

	"github.com/nats-io/nats.go/jetstream"

	"git.novox.be/novox/mesh-sdk/go/seatdef"
)

// EventHandlers is where a process registers the handler of a subject on the module's one pull of its durable consumer
// (process.EventHub). Register every handler, then start the hub.
type EventHandlers interface {
	Handle(pattern string, handle func(jetstream.Msg)) error
}

type processBus struct {
	call func(string, any) (json.RawMessage, error)
	hub  EventHandlers
}

// ProcessBus is the bus of a process on its own credential: a verb of the seat is called through its connection
// (process.Conn.Call), and the seat's events are heard as handlers of the module's event hub, on the seat's own subject
// (`mesh.seat.<seat>.event.<event>`). The process starts the hub after the reader is started, so every handler is registered.
func ProcessBus(call func(string, any) (json.RawMessage, error), hub EventHandlers) Bus {
	return processBus{call: call, hub: hub}
}

func (b processBus) Ask(key string, body any) (json.RawMessage, error) { return b.call(key, body) }

func (b processBus) Subscribe(pattern string, handle func(key string, body json.RawMessage) error) error {
	seat, event, ok := strings.Cut(pattern, ".")
	if !ok || seat == "" || event == "" {
		return fmt.Errorf("%q is no seat event's pattern, <seat>.<event>", pattern)
	}
	return b.hub.Handle(seatdef.EventSubject(seat, event), func(m jetstream.Msg) {
		// A reader that could not take the event says so in its status and reads again at the next event or by hand
		// (Reload): the message is not delivered again for it.
		_ = handle(pattern, m.Data())
		_ = m.Ack()
	})
}