package tenant

import (
	"fmt"
	"regexp"
)

// Route describes a SaaS-owned exact Topic binding. Dispatcher only
// consumes/publishes; it never declares, binds, or deletes these resources.
type Route struct {
	Exchange   string
	BindingKey string
	Queue      string
}

var taskIDPattern = regexp.MustCompile(`^[A-Za-z0-9_-]{1,128}$`)

func ControlRoute(dispatcherID string) (Route, error) {
	if err := ValidateDispatcherID(dispatcherID); err != nil {
		return Route{}, err
	}
	return exactRoute("agent-call.dispatchers.v1", "d."+dispatcherID+".control.in", "agent-call.d."+dispatcherID+".control.v1")
}

func TaskRoute(dispatcherID, taskID string) (Route, error) {
	if err := ValidateDispatcherID(dispatcherID); err != nil {
		return Route{}, err
	}
	if !taskIDPattern.MatchString(taskID) {
		return Route{}, fmt.Errorf("invalid task ID for exact MQ route")
	}
	return exactRoute("agent-call.dispatchers.v1", "d."+dispatcherID+".task."+taskID+".in", "agent-call.d."+dispatcherID+".task."+taskID+".v1")
}

func ResultRoute(dispatcherID string) (Route, error) {
	if err := ValidateDispatcherID(dispatcherID); err != nil {
		return Route{}, err
	}
	// The shared queue name is only a project-local Mock fixture. SaaS owns
	// the actual receiving queue and exact bindings for each Dispatcher.
	return exactRoute("agent-call.saas.v1", "d."+dispatcherID+".out", "agent-call.saas.events.v1")
}

func exactRoute(exchange, key, queue string) (Route, error) {
	if len(key) > 255 || len(queue) > 255 {
		return Route{}, fmt.Errorf("AMQP route exceeds 255 bytes")
	}
	return Route{Exchange: exchange, BindingKey: key, Queue: queue}, nil
}