package main

import (
	"flag"
	"fmt"
	"github.com/gorilla/mux"
	"log"
	"net/http"
	"strconv"
)

var (
	metrics map[string]float64
)

func metricsHandler(w http.ResponseWriter, r *http.Request) {

	// if the request method is GET, return all metrics
	if r.Method == "GET" {

		// if the length of the metrics map is zero, return some information on how to add metrics
		if len(metrics) == 0 {
			returnString := "Add metrics by making a post request to this endpoint\n" +
				"curl -X POST --data = \"\" <url>:<port>/meetrics"

			_, _ = fmt.Fprintf(w, returnString)

		} else {
			// return all the metrics
			for key, value := range metrics {
				_, _ = fmt.Fprintf(w, "%s %f\n", key, value)
			}

		}

		// if the request method is POST, add the posted metrics to the metrics map
	} else if r.Method == "POST" {

		// parse the POST form
		errParseForm := r.ParseForm()
		if errParseForm != nil {
			panic(errParseForm)
		}

		// parse the parameters
		key := r.Form.Get("key")
		value, parseFloatErr := strconv.ParseFloat(r.Form.Get("value"), 64)
		if parseFloatErr != nil {
			log.Printf("Error parsing %v", value)
		}

		// if the metrics var does not exist yet, create it
		if metrics == nil {
			metrics = map[string]float64{}
		}

		// assign the value to the key
		metrics[key] = value

		_, _ = fmt.Fprintf(w, "added the metrics")

		// return an error
	} else {
		log.Println("Error, the handler was neither accessed using a GET or a POST request!")

	}
}

func main() {

	// parse some command line flags
	var port string
	flag.StringVar(&port, "p", "8080", "port used to host the service")
	flag.Parse()
	log.Println("[ ] Done loading the flags")

	// setup a new router and define routes
	r := mux.NewRouter()
	r.HandleFunc("/metrics", metricsHandler).Methods("GET", "POST")

	// start the http server
	log.Printf("Starting the http server on port %s", port)
	log.Fatal(http.ListenAndServe(fmt.Sprintf(":%s", port), r))
}