goweb/cqrs/registry.go

package cqrs

type CommandMiddleware func(next CommandHandler) CommandHandler
type QueryMiddleware func(next QueryHandler) QueryHandler

type Registry struct {
	commands []*commandHandler
	queries  []*queryHandler
}

type commandHandler struct {
	Match       MatchFunc
	Handler     CommandHandler
	Middlewares []CommandMiddleware
}

type queryHandler struct {
	Match       MatchFunc
	Handler     QueryHandler
	Middlewares []QueryMiddleware
}

func (r *Registry) MatchCommand(cmd Command) (CommandHandler, []CommandMiddleware, error) {
	// TODO cache matching to avoid unnecessary ops
	for _, reg := range r.commands {
		matches, err := reg.Match(cmd)
		if err != nil {
			return nil, nil, err
		}

		if matches {
			return reg.Handler, reg.Middlewares, nil
		}
	}

	return nil, nil, ErrHandlerNotFound
}

func (r *Registry) MatchQuery(qry Query) (QueryHandler, []QueryMiddleware, error) {
	// TODO cache matching to avoid unnecessary ops
	for _, reg := range r.queries {
		matches, err := reg.Match(qry)
		if err != nil {
			return nil, nil, err
		}

		if matches {
			return reg.Handler, reg.Middlewares, nil
		}
	}

	return nil, nil, ErrHandlerNotFound
}

func (r *Registry) RegisterCommand(match MatchFunc, hdlr CommandHandler, mdlwrs ...CommandMiddleware) {
	r.commands = append(r.commands, &commandHandler{match, hdlr, mdlwrs})
}

func (r *Registry) RegisterQuery(match MatchFunc, hdlr QueryHandler, mdlwrs ...QueryMiddleware) {
	r.queries = append(r.queries, &queryHandler{match, hdlr, mdlwrs})
}

func NewRegistry() *Registry {
	return &Registry{
		commands: make([]*commandHandler, 0),
		queries:  make([]*queryHandler, 0),
	}
}