main.go

package main

import (
	"encoding/json"
	"github.com/go-chi/chi"
	uuid "github.com/satori/go.uuid"
	"log"
	"math/rand"
	"net/http"
	"time"
)

const (
	_ = iota
	StatusWorking
	StatusDone
	StatusCanceled
)

type handler struct {
	tickets map[string]*ticket
}

type ticket struct {
	ID     string `json:"id"`
	Status int    `json:"status"`

	done chan struct{}
}

func init() {
	rand.Seed(time.Now().UnixNano())
}

func main() {
	h := handler{tickets: make(map[string]*ticket)}

	r := chi.NewRouter()
	r.Post("/import", h.handleFileImporting)
	r.Get("/import/{ID}", h.printStatus)
	r.Post("/import/{ID}/cancel", h.cancelFileImporting)

	log.Println("server is listening on port :8080")
	err := http.ListenAndServe(":8080", r)
	if err != nil {
		log.Panic(err)
	}
}

func (h *handler) handleFileImporting(w http.ResponseWriter, _ *http.Request) {
	w.Header().Set("Content-Type", "application/json")

	t := &ticket{
		ID:     uuid.NewV4().String(),
		Status: StatusWorking,
		done:   make(chan struct{}),
	}
	h.tickets[t.ID] = t

	go func(t *ticket) {
		defer func() {
			if t.Status != StatusCanceled {
				t.Status = StatusDone
			}

			close(t.done)
		}()

		// simulate importing too many records data to database
		for i := 0; i < 10; i++ {
			time.Sleep(time.Second * time.Duration(rand.Intn(10)))
			select {
			case <-t.done:
				t.Status = StatusCanceled
				log.Printf("[%s] canceled\n", t.ID)
				return
			default:
				log.Printf("[%s] importing data...\n", t.ID)
			}
		}
		
		log.Printf("[%s] finished", t.ID)
	}(t)

	data, _ := json.Marshal(t)
	_, _ = w.Write(data)
}

func (h *handler) printStatus(w http.ResponseWriter, r *http.Request) {
	id := chi.URLParam(r, "ID")

	t, ok := h.tickets[id]
	if !ok {
		w.WriteHeader(http.StatusNotFound)
		return
	}

	data, _ := json.Marshal(t)

	w.Header().Set("Content-Type", "application/json")
	_, _ = w.Write(data)
}

func (h *handler) cancelFileImporting(w http.ResponseWriter, r *http.Request) {
	id := chi.URLParam(r, "ID")

	t, ok := h.tickets[id]
	if !ok {
		w.WriteHeader(http.StatusNotFound)
		return
	}

	if t.Status != StatusWorking {
		w.WriteHeader(http.StatusNotAcceptable)
		return
	}

	log.Printf("[%s] cancelling...", t.ID)
	t.done <- struct{}{}

	w.WriteHeader(http.StatusAccepted)
	_, _ = w.Write([]byte("OK"))
}