events demo

main.go

package main

/*
  // list of events
  curl localhost:8080/events

  // current state
  curl localhost:8080/state

  // increment counter
  curl -d '{"name": "increment", "data": {"n": 1}}' localhost:8080/event
  // decrement counter
  curl -d '{"name": "decrement", "data": {"n": 1}}' localhost:8080/event
  // set counter
  curl -d '{"name": "set", "data": {"n": 1}}' localhost:8080/event

  // collapse state into single event
  curl -X POST localhost:8080/collapse
*/

import (
	"encoding/json"
	"io/ioutil"
	"log"
	"net/http"
	"strconv"

	"github.com/gorilla/pat"
)

var state struct {
	Counter int `json:"counter"`
}

type event struct {
	Name string                 `json:"name"`
	Data map[string]interface{} `json:"data"`
}

var events []event

func main() {
	p := pat.New()
	p.Get("/events", eventsHandler)
	p.Post("/event", eventHandler)
	p.Get("/state", stateHandler)
	p.Post("/collapse", collapseHandler)
	log.Fatal(http.ListenAndServe(":8080", p))
}

func collapseHandler(w http.ResponseWriter, req *http.Request) {
	events = []event{
		event{"set", map[string]interface{}{"n": state.Counter}},
	}
}

func stateHandler(w http.ResponseWriter, req *http.Request) {
	b, _ := json.Marshal(state)
	w.Write(b)
}

func eventsHandler(w http.ResponseWriter, req *http.Request) {
	var since int
	s := req.URL.Query().Get("since")
	if len(s) > 0 {
		since, _ = strconv.Atoi(s)
	}

	b, _ := json.Marshal(events[since:])
	w.Write(b)
}

func eventHandler(w http.ResponseWriter, req *http.Request) {
	b, _ := ioutil.ReadAll(req.Body)
	req.Body.Close()

	var e event
	json.Unmarshal(b, &e)
	events = append(events, e)

	switch e.Name {
	case "set":
		n := e.Data["n"].(float64)
		state.Counter = int(n)
	case "increment":
		n := e.Data["n"].(float64)
		state.Counter += int(n)
	case "decrement":
		n := e.Data["n"].(float64)
		state.Counter -= int(n)
	default:
		w.WriteHeader(400)
	}
}