/* Copyright 2018 Martin Dosch
Licensed under the "MIT License" */

package main

import (
	"encoding/json"
	"flag"
	"log"
	"os"
	"os/user"
	"strings"
	"time"

	"github.com/chilts/sid"
	"github.com/mattn/go-xmpp"
)

// Variables defined globally as they are used by functions pingMUC
// and processStanzas.
var (
	id           string
	err          error
	pingSent     time.Time
	pingReceived bool
)

func main() {

	var configPath, configFile string

	type configuration struct {
		ServerAddress string
		BotJid        string
		Password      string
		Muc           string
		MucNick       string
		MaxArticles   int
		RefreshTime   time.Duration
		NoExcerpt     bool
		Feeds         []string
	}

	// Read path to config from command line option.
	configFilePtr := flag.String("config", "none", "path to configuration file")
	flag.Parse()

	if *configFilePtr != "none" {
		configFile = *configFilePtr
	} else {
		// Get systems user config path.
		osConfigDir := os.Getenv("$XDG_CONFIG_HOME")
		if osConfigDir != "" {
			// Create configPath if not yet existing.
			configPath = osConfigDir + "/.config/feed-to-muc/"
			if _, err := os.Stat(configPath); os.IsNotExist(err) {
				err = os.MkdirAll(configPath, 0700)
				if err != nil {
					log.Fatal("Error: Can't create config path: ", err)
				}
			}

		} else { // Get the current user.
			curUser, err := user.Current()
			if err != nil {
				log.Fatal("Error: Can't get current user: ", err)
				return
			}
			// Get home directory.
			home := curUser.HomeDir

			if home == "" {
				log.Fatal("Error: No home directory available.")
				return
			}

			// Create configPath if not yet existing.
			configPath = home + "/.config/feed-to-muc/"
			if _, err := os.Stat(configPath + "config.json"); os.IsNotExist(err) {
				err = os.MkdirAll(configPath, 0700)
				if err != nil {
					log.Fatal("Error: Can't create config path: ", err)
				}
			}

		}
		configFile = configPath + "config.json"
	}

	// Check that config file is existing.
	if _, err := os.Stat(configFile); os.IsNotExist(err) {
		log.Fatal("Error: Can't find config file: ", err)
	}

	// Read configuration file into variable config.
	file, _ := os.Open(configFile)
	defer file.Close()
	decoder := json.NewDecoder(file)
	config := configuration{}
	if err := decoder.Decode(&config); err != nil {
		log.Fatal("Error: Can't decode config: ", err)
	}

	if _, err := os.Stat(configFile); os.IsNotExist(err) {
		err = os.MkdirAll(configPath, 0700)
		if err != nil {
			log.Fatal("Error: Can't create config path: ", err)
		}
	}

	var client *xmpp.Client

	options := xmpp.Options{
		Host:     config.ServerAddress,
		User:     config.BotJid,
		Password: config.Password,
		NoTLS:    true,
		StartTLS: true,
		Debug:    false,
	}

	// Connect to server.
	client, err = options.NewClient()
	if err != nil {
		log.Fatal("Error: Can't connect to xmpp server: ", err)
	}

	// Join the MUC
	_, err := client.JoinMUCNoHistory(config.Muc, config.MucNick)
	if err != nil {
		log.Fatal("Error: Can't join MUC: ", err)
	}

	// Starting goroutine to ping the server every 30 seconds.
	go pingServer(client, config.ServerAddress, config.BotJid)

	// Starting goroutine to ping the MUC every 30 seconds.
	go pingMUC(client, config.BotJid, config.Muc, config.MucNick)

	// Starting goroutine to process received stanzas.
	go processStanzas(client, config.Muc, config.MucNick, config.Feeds)

	// Set RefreshTime to 30 seconds if not defined.
	if config.RefreshTime == 0 {
		config.RefreshTime = 30
	}

	for {
		// Check all configured feeds for new articles and send
		// new articles to configured MUC.
		for i := 0; i < len(config.Feeds); i++ {
			output, err := getArticles(config.Feeds[i], config.MaxArticles, config.NoExcerpt)
			if err != nil {
				// Exit if an error occurs checking the feeds.
				log.Fatal("Error: Can't check feeds for new articles: ", err)
			}

			if output != "" {
				_, err = client.Send(xmpp.Chat{Remote: config.Muc,
					Type: "groupchat", Text: output})
				if err != nil {
					// ToDo: Save message for resend.
					// Exit if message can not be sent.
					log.Fatal("Error: Can't send message to MUC: ", err)
				}
			}
		}
		// Wait 30 seconds before checking feeds again.
		time.Sleep(config.RefreshTime * time.Second)
	}
}

// Send a ping every 30 seconds after last successful ping to check if the MUC is still available.
func pingMUC(client *xmpp.Client, botJid string, muc string, mucNick string) {
	for {
		time.Sleep(30 * time.Second)

		// Send ping to own MUC participant to check we are still joined.
		id, err = client.RawInformation(botJid, muc+"/"+mucNick, sid.Id(),
			"get", "<ping xmlns='urn:xmpp:ping'/>")
		if err != nil {
			log.Fatal("Error: Can't send MUC self ping: ", err)
		}

		pingSent = time.Now()
		pingReceived = false

		// Check for result IQ as long as there was no reply yet.
		for (time.Since(pingSent).Seconds() < 10.0) && (pingReceived == false) {
			time.Sleep(1 * time.Second)
			if pingReceived == true {
				break
			}

		}
		// Quit if no ping reply was received.
		if pingReceived == false {
			log.Fatal("MUC not available.")
		}
	}
}

// Send a ping to the server every 30 seconds to check if the connection is still alive.
func pingServer(client *xmpp.Client, server string, botJid string) {
	for {
		time.Sleep(30 * time.Second)

		// Send ping to server to check if connection still exists.
		err := client.PingC2S(botJid, strings.Split(server, ":")[0])
		if err != nil {
			log.Fatal("Error: Client2Server ping failed:", err)
		}
	}
}

func processStanzas(client *xmpp.Client, muc string, mucNick string, feeds []string) {
	for { // Receive stanzas. ToDo: Receive stanzas continiously without 30s delay.
		stanza, err := client.Recv()
		if err != nil {
			log.Fatal("Error: Failed receiving Stanzas:", err)
		}

		// Check stanzas, maybe we want to reply.
		switch v := stanza.(type) {
		// Reply to requests for source and feeds.
		case xmpp.Chat:
			// Get first word of the message and transform it to lower case.
			var mention string
			mention = strings.ToLower(strings.Split(v.Text, " ")[0])

			// If it is not the bots nick remove one trailing character as
			// a lot of clients append `:` or `,` to mentions.
			if mention != strings.ToLower(mucNick) {
				mentionLength := len(mention)
				// Leave if mentionLength is <= 0
				if mentionLength <= 0 {
					break
				}
				mention = mention[:mentionLength-1]
				// Leave if the message is not addressed to the bot.
				if mention != strings.ToLower(mucNick) {
					break
				}
			}

			// Check for the second word (command).
			switch strings.ToLower(strings.Split(v.Text, " ")[1]) {

			// Reply with a short summary of available commands for `help`.
			case "help":
				_, err = client.Send(xmpp.Chat{Remote: muc,
					Type: "groupchat", Text: strings.Split(v.Remote, "/")[1] +
						": The following commands are available:\n" +
						"\"feeds\": List feeds I'm following.\n" +
						"\"source\": Show source code URL."})
				if err != nil {
					log.Fatal("Error: Failed sending message to MUC:", err)
				}
			// Reply with repo address for `source`.
			case "source":
				_, err = client.Send(xmpp.Chat{Remote: muc,
					Type: "groupchat", Text: strings.Split(v.Remote, "/")[1] +
						": My source can be found at " +
						"https://salsa.debian.org/mdosch-guest/feed-to-muc"})
				if err != nil {
					log.Fatal("Error: Failed sending message to MUC:", err)
				}
			// Reply with the list of monitored feeds for `feeds`.
			case "feeds":
				var feedList string
				for _, feed := range feeds {
					// Add next feed element and a newline.
					feedList = feedList + feed + "\n"
				}

				_, err = client.Send(xmpp.Chat{Remote: muc,
					Type: "groupchat", Text: strings.Split(v.Remote, "/")[1] +
						": Feeds I'm following:\n" + feedList})
				if err != nil {
					log.Fatal("Error: Failed sending message to MUC:", err)
				}

			}

		// Reply to pings and disco queries.
		case xmpp.IQ:
			if (v.Type == "error") && (v.ID == id) {
				log.Fatal("MUC not available.")
			}

			if (v.Type == "result") && (v.ID == id) {
				pingReceived = true
			}

			if v.Type == "get" {
				// Reply to disco#info requests according to https://xmpp.org/extensions/xep-0030.html.
				if strings.Contains(string(v.Query),
					"<query xmlns='http://jabber.org/protocol/disco#info'/>") == true {
					_, err := client.RawInformation(client.JID(), v.From, v.ID,
						"result", "<query xmlns='http://jabber.org/protocol/disco#info'>"+
							"<identity category='client' type='bot' name='feedbot'/>"+
							"<feature var='http://jabber.org/protocol/disco#info'/></query>")
					if err != nil {
						log.Fatal("Error: Failed to reply to disco#info:", err)
					}
				} else if strings.Contains(string(v.Query), "<ping xmlns='urn:xmpp:ping'/>") == true {
					// Reply to pings.
					_, err := client.RawInformation(client.JID(), v.From, v.ID, "result", "")
					if err != nil {
						log.Fatal("Error: Failed to reply to ping:", err)
					}
				} else {
					// Send error replies for all other IQs.
					_, err := client.RawInformation(client.JID(), v.From, v.ID, "error",
						"<error type='cancel'><service-unavailable "+
							"xmlns='urn:ietf:params:xml:ns:xmpp-stanzas'/></error>")
					if err != nil {
						log.Fatal("Error: Failed to send error IQ:", err)
					}
				}
			}

		default:
			break
		}
	}
}