package main

import (
	"context"
	"encoding/json"
	"encoding/xml"
	"log"
	"net/http"
	"strings"
	"time"
)

func CreateAndStartHTTPServer(conf *Configuration) *http.Server {
	router := http.NewServeMux()
	router.HandleFunc("/processes", AreProcessesUp(&conf.Processes, conf.IndentedOutput))

	srv := &http.Server{
		Addr:         conf.ListenAddress,
		Handler:      router,
		ReadTimeout:  5 * time.Second,
		WriteTimeout: 5 * time.Second,
		IdleTimeout:  10 * time.Second,
	}

	go func() {
		if err := srv.ListenAndServe(); err != nil && err != http.ErrServerClosed {
			log.Fatalf("ListenAndServe: %s\n", err)
		}
	}()

	return srv
}

func ShutdownHTTPServer(srv *http.Server) {
	ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
	defer cancel()

	srv.SetKeepAlivesEnabled(false)
	if err := srv.Shutdown(ctx); err != nil {
		log.Fatalf("%s\n", err)
	}
}

// AreProcessesUp handles a GET /processes request and sends back status of given
// processes.
func AreProcessesUp(processes *[]string, indented bool) func(http.ResponseWriter, *http.Request) {
	return func(w http.ResponseWriter, r *http.Request) {
		if r.Method == http.MethodGet {
			proclist := make(ProcessList)

			for _, proc := range *processes {
				pids, err := GetProcessPIDs(proc)
				proclist[proc] = err == nil && len(pids) > 0
			}

			switch r.Header.Get("Accept") {
			case "application/xml":
				w.Header().Add("Content-Type", "application/xml")
				enc := xml.NewEncoder(w)
				if indented {
					enc.Indent("", "\t")
				}
				enc.Encode(proclist)
			case "text/plain":
				w.Header().Add("Content-Type", "text/plain")
				var s []string
				for k, v := range proclist {
					if v {
						s = append(s, k)
					}
				}
				w.Write([]byte(strings.Join(s, ",")))
			default:
				w.Header().Add("Content-Type", "application/json")
				enc := json.NewEncoder(w)
				if indented {
					enc.SetIndent("", "\t")
				}
				enc.Encode(proclist)
			}
		} else {
			w.WriteHeader(http.StatusMethodNotAllowed)
			w.Header().Add("Allow", "GET")
		}
	}
}