/*
go build for linux:
	env GOOS=linux go build -o /tmp/server server.go

run with docker:
	docker run -it --rm --name test -v /tmp/server:/server -p 3000:80 -p 3001:6060 alpine /server

run pprof debugger:
	go get github.com/google/pprof
	pprof --seconds 30 -http=:4444 /tmp/server http://localhost:3001/debug/pprof/profile

benchmarking with wrk:
	brew install wrk
	wrk -d 5s http://localhost:3000/
*/

package main

import (
	"encoding/json"
	"fmt"
	"log"
	"net/http"
	"os"
	"os/signal"
	"syscall"
	"time"

	_ "net/http/pprof"
)

// http routes
var routes = map[string]string{
	"/":        "apiRoot",
	"/healthz": "apiHealthz",
	"/error":   "apiError",
}

// handle route paths with methods
func routeHandler(w http.ResponseWriter, r *http.Request) error {
	route, ok := routes[r.RequestURI]
	if !ok {
		return fmt.Errorf("Route %s path does not exist", r.RequestURI)
	}

	switch route {
	case "apiRoot":
		return apiRoot(w, r)
	case "apiHealthz":
		return apiHealthz(w, r)
	case "apiError":
		return apiError(w, r)
	default:
		return fmt.Errorf("Route %s method not exist", r.RequestURI)
	}
}

// route methods
// root/index path
func apiRoot(w http.ResponseWriter, r *http.Request) error {
	data := map[string]string{"hello": "welcome"}
	return outputJSON(w, data)
}

// simple health check
func apiHealthz(w http.ResponseWriter, r *http.Request) error {
	data := map[string]interface{}{"alive": time.Now().Unix()}
	return outputJSON(w, data)
}
// simulate error with 1 second delay
func apiError(w http.ResponseWriter, r *http.Request) error {
	defer timeTrack(time.Now(), "/error endpoint bug taking too long")
	time.Sleep(1 * time.Second)
	return fmt.Errorf("some error")
}

// capture errors
func errorHandler(f func(http.ResponseWriter, *http.Request) error) http.HandlerFunc {
	return func(w http.ResponseWriter, r *http.Request) {
		startTime := time.Now()
		w.Header().Set("Content-Type", "application/json")
		err := f(w, r)
		if err != nil {
			errMsg := fmt.Sprintf("{ \"error:\": \"%s\" }", err.Error())
			http.Error(w, errMsg, http.StatusInternalServerError)
			log.Printf("[latency: %s] %d Error - Path: %s -- err: %v", time.Since(startTime), http.StatusInternalServerError, r.RequestURI, err)
			return
		}
		log.Printf("[latency: %s] %d OK - Path: %s", time.Since(startTime), http.StatusOK, r.RequestURI)
	}
}

// map to json string
func outputJSON(w http.ResponseWriter, data interface{}) error {
	jsonString, err := json.Marshal(data)
	if err != nil {
		log.Fatalf("[Internal Error] Unable to stringify map argument, err: %v", err)
		return fmt.Errorf("[Internal Error] JSON data")
	}
	fmt.Fprint(w, string(jsonString))
	return nil
}

// time track
func timeTrack(start time.Time, name string) {
	elapsed := time.Since(start)
	log.Printf("TimeTrack (%s) -> %s", elapsed, name)
}

// signal handler
func signalHandler(signal os.Signal) {
	fmt.Printf("\nCaught signal: %+v", signal)
	fmt.Println("\nWait for 1 second to finish processing")
	time.Sleep(1 * time.Second)

	switch signal {

	case syscall.SIGHUP: // kill -SIGHUP XXXX
		fmt.Println("- got hungup")

	case syscall.SIGINT: // kill -SIGINT XXXX or Ctrl+c
		fmt.Println("- got ctrl+c")

	case syscall.SIGTERM: // kill -SIGTERM XXXX
		fmt.Println("- got force stop")

	case syscall.SIGQUIT: // kill -SIGQUIT XXXX
		fmt.Println("- stop and core dump")

	default:
		fmt.Println("- unknown signal")
	}

	fmt.Println("\nFinished server cleanup")
	os.Exit(0)
}

// initialize signal handler
func initSignals() {
	var captureSignal = make(chan os.Signal, 1)
	signal.Notify(captureSignal, syscall.SIGINT, syscall.SIGTERM, syscall.SIGABRT)
	signalHandler(<-captureSignal)
}

// initialize PPROF debugger
func initPprofDebugger() {
	port := "6060" // default port
	if os.Getenv("PPROF_PORT") != "" {
		port = os.Getenv("PPROF_PORT")
	}
	log.Println("Running pprof debugger on :" + port)
	log.Println(fmt.Sprint(http.ListenAndServe(":"+port, nil).Error()))
}

// initialize server listener
func initApiServer() {
	// initialize routes
	for route, _ := range routes {
		http.HandleFunc(route, errorHandler(routeHandler))
	}

	port := "80" // default port
	if os.Getenv("SERVER_PORT") != "" {
		port = os.Getenv("SERVER_PORT")
	}
	log.Println("Running api server on port :" + port)
	err := http.ListenAndServe(":"+port, nil)
	if err != nil {
		log.Printf("[Error] ListenAndServe: %v", err)
	}
}

func main() {
	// start PPROF debugger
	go initPprofDebugger()

	// capture signals
	go initSignals()

	// start HTTP server
	initApiServer()
}