/*
	httpprocwatchd provides HTTP interface to a list of process' statuses
	formatted as JSON.
	Copyright (c) 2021 Alexander "Arav" Andreev <me@arav.top>

	This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program.  If not, see <https://www.gnu.org/licenses/>.
*/

package main

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

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

	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) func(http.ResponseWriter, *http.Request) {
	return func(w http.ResponseWriter, r *http.Request) {
		if r.Method == http.MethodGet {
			proclist := NewProcessList()

			for _, proc := range *processes {
				isup, _, _ := IsProcessUp(proc)
				proclist.AddProcess(proc, isup)
			}

			if hdr := r.Header.Get("Accept"); hdr == "application/xml" {
				w.Header().Add("Content-Type", "application/xml")
				enc := xml.NewEncoder(w)
				enc.Indent("", "\t")
				enc.Encode(proclist)
			} else {
				w.Header().Add("Content-Type", "application/json")
				enc := json.NewEncoder(w)
				enc.SetIndent("", "\t")
				enc.Encode(proclist)
			}
		} else {
			w.WriteHeader(http.StatusMethodNotAllowed)
			w.Header().Add("Allow", "GET")
		}
	}
}