matemat/uncanny/server.go

package uncanny

import (
	"log"
	"fmt"
	"net/http"
	"path"
	"strconv"
)

const (
	// highest slot number (range: 0..maxSlot)
	maxSlot = 4
)

type Server struct {
	*http.ServeMux
	can *Can
}

func NewServer(can *Can) *Server {
	ret := &Server{
		ServeMux: http.NewServeMux(),
		can:      can,
	}
	ret.registerHandlers()
	return ret
}

func (s *Server) registerHandlers() {
	s.HandleFunc("/", http.NotFound)
	s.HandleFunc("/dispense/", func(rw http.ResponseWriter, r *http.Request) {
		if matched, _ := path.Match("/dispense/[0-9]?[0-9]*", r.URL.Path); matched {
			slot, err := strconv.ParseUint(path.Base(r.URL.Path), 10, 32)
			if err != nil {
				log.Printf("Error decoding slot number: %v", err)
				http.Error(rw, http.StatusText(http.StatusBadRequest), http.StatusBadRequest)
			} else if slot < 0 || slot > maxSlot {
				log.Printf("Invalid slot number: %u", slot)
				http.Error(rw, http.StatusText(http.StatusBadRequest), http.StatusBadRequest)
			} else {
				err = s.can.Dispense(int(slot))
				if err != nil {
					log.Printf("Error sending dispense command: %v", err)
					rw.Header().Set("Content-Type", "text/plain")
					rw.WriteHeader(http.StatusServiceUnavailable)
					fmt.Fprintf(rw, "%u error", slot)
				} else {
					rw.Header().Set("Content-Type", "text/plain")
					rw.WriteHeader(http.StatusOK)
					fmt.Fprintf(rw, "%u dispense", slot)
				}
			}
		} else {
			http.Error(rw, http.StatusText(http.StatusBadRequest), http.StatusBadRequest)
		}
	})
	s.HandleFunc("/stop", func(rw http.ResponseWriter, r *http.Request) {
		err := s.can.Cancel()
		if err != nil {
			log.Printf("Error sending stop command: %v", err)
			rw.Header().Set("Content-Type", "text/plain")
			rw.WriteHeader(http.StatusServiceUnavailable)
			fmt.Fprintf(rw, "error")
		} else {
			rw.Header().Set("Content-Type", "text/plain")
			rw.WriteHeader(http.StatusOK)
			fmt.Fprintf(rw, "stopped")
		}
	})
	s.HandleFunc("/level/", func(rw http.ResponseWriter, r *http.Request) {
		if matched, _ := path.Match("/level/[0-9]?[0-9]*", r.URL.Path); matched {
			slot, err := strconv.ParseUint(path.Base(r.URL.Path), 10, 32)
			if err != nil {
				log.Printf("Error decoding slot number: %v", err)
				http.Error(rw, http.StatusText(http.StatusBadRequest), http.StatusBadRequest)
			} else if slot < 0 || slot > maxSlot {
				log.Printf("Invalid slot number: %u", slot)
				http.Error(rw, http.StatusText(http.StatusBadRequest), http.StatusBadRequest)
			} else {
				rw.Header().Set("Content-Type", "text/plain")
				rw.WriteHeader(http.StatusOK)
				if s.can.IsEmpty(int(slot)) {
					fmt.Fprintf(rw, "%u empty", slot)
				} else {
					fmt.Fprintf(rw, "%u full", slot)
				}
			}
		} else {
			http.Error(rw, http.StatusText(http.StatusBadRequest), http.StatusBadRequest)
		}
	})
	s.HandleFunc("/active/", func(rw http.ResponseWriter, r *http.Request) {
		if matched, _ := path.Match("/active/[0-9]?[0-9]*", r.URL.Path); matched {
			slot, err := strconv.ParseUint(path.Base(r.URL.Path), 10, 32)
			if err != nil {
				log.Printf("Error decoding slot number: %v", err)
				http.Error(rw, http.StatusText(http.StatusBadRequest), http.StatusBadRequest)
			} else if slot < 0 || slot > maxSlot {
				log.Printf("Invalid slot number: %u", slot)
				http.Error(rw, http.StatusText(http.StatusBadRequest), http.StatusBadRequest)
			} else {
				rw.Header().Set("Content-Type", "text/plain")
				rw.WriteHeader(http.StatusOK)
				if s.can.IsDispensing(int(slot)) {
					fmt.Fprintf(rw, "%u dispensing", slot)
				} else {
					fmt.Fprintf(rw, "%u off", slot)
				}
			}
		} else {
			http.Error(rw, http.StatusText(http.StatusBadRequest), http.StatusBadRequest)
		}
	})
}

func (s *Server) ListenAndServe(addr string) error {
	return http.ListenAndServe(addr, s)
}