/*
Copyright © 2021 Arsen Musayelyan

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 <http://www.gnu.org/licenses/>.
*/
package cmd

import (
	"bytes"
	"crypto/tls"
	"net"
	"net/http"
	"strings"
	"time"

	"github.com/mitchellh/mapstructure"
	"github.com/rs/zerolog/log"
	"github.com/spf13/cobra"
	"github.com/spf13/viper"
	"github.com/vmihailenco/msgpack/v5"
	"go.arsenm.dev/lasso/internal/types"
)

// clientCmd represents the client command
var clientCmd = &cobra.Command{
	Use:   "client",
	Short: "Start the lasso client",
	Run: func(cmd *cobra.Command, args []string) {
		// Disable certificate verification as server uses self-signed key
		http.DefaultTransport.(*http.Transport).TLSClientConfig = &tls.Config{InsecureSkipVerify: true}

		// Perform server status check
		res, err := http.Get(url("status"))
		if err != nil {
			log.Fatal().Err(err).Msg("Server status check failed")
		}
		res.Body.Close()

		// Get node list from server
		res, err = http.Get(url("node", "list"))
		if err != nil {
			log.Fatal().Err(err).Msg("Error getting node list from server")
		}

		var resp types.Response
		// Decode server response
		err = msgpack.NewDecoder(res.Body).Decode(&resp)
		if err != nil {
			log.Fatal().Err(err).Msg("Error decoding response body")
		}
		res.Body.Close()

		var nodes map[string]types.Node
		// Decode response data as node list
		err = mapstructure.Decode(resp.Data, &nodes)
		if err != nil {
			log.Fatal().Err(err).Msg("Error decoding response")
		}

		// Get local IP
		ip, err := localIP()
		if err != nil {
			log.Fatal().Err(err).Msg("Error getting local IP")
		}

		// Attempt to get node from list
		node, ok := nodes[viper.GetString("node.name")]
		// If node does not exist
		if !ok {
			// Encode node as msgpack
			data, err := msgpack.Marshal(types.Node{IP: ip})
			if err != nil {
				log.Fatal().Err(err).Msg("Error encoding new node")
			}
			// Send node to server
			res, err = http.Post(url("node", viper.GetString("node.name")), "text/plain", bytes.NewReader(data))
			if err != nil {
				log.Fatal().Msg("Error adding new node to server")
			}
			var resp types.Response
			// Decode server response
			err = msgpack.NewDecoder(res.Body).Decode(&resp)
			if err != nil {
				log.Fatal().Msg("Error decoding server response")
			}
			// If server returned error
			if resp.Error {
				log.Fatal().Str("error", resp.Message).Msg("Error returned by server")
			}
			// Set new node IP
			node.IP = ip
			// Set node ID in viper
			viper.Set("node.id", resp.Data)
			// Attempt to write new ID to config
			if err := viper.WriteConfig(); err != nil {
				log.Fatal().Err(err).Msg("Error writing new ID to config")
			}
		}

		// If IP does not match current
		if node.IP != ip {
			// Encode new node as msgpack
			data, err := msgpack.Marshal(types.Node{
				IP: ip,
				ID: viper.GetString("node.id"),
			})
			if err != nil {
				log.Fatal().Err(err).Msg("Error encoding updated node")
			}
			// Create new PATCH request with new node as data
			req, err := http.NewRequest(
				http.MethodPatch,
				url("node", viper.GetString("node.name")),
				bytes.NewReader(data),
			)
			if err != nil {
				log.Fatal().Err(err).Msg("Error creating PATCH request")
			}
			// Perform request
			res, err := http.DefaultClient.Do(req)
			if err != nil {
				log.Fatal().Err(err).Msg("Error sending update request to server")
			}
			var resp types.Response
			// Decode server response
			err = msgpack.NewDecoder(res.Body).Decode(&resp)
			if err != nil {
				log.Fatal().Msg("Error decoding server response")
			}
			// If server returned error
			if resp.Error {
				log.Fatal().Str("error", resp.Message).Msg("Error returned by server")
			}
		}

		// Every minute
		for range time.Tick(time.Minute) {
			// Get local IP
			newIP, err := localIP()
			if err != nil {
				log.Error().Err(err).Msg("Error getting new local IP")
				continue
			}
			// If IP has changed since last check
			if newIP != ip {
				// Set IP to new IP
				ip = newIP
				// Encode new node as msgpack
				data, err := msgpack.Marshal(types.Node{
					IP: newIP,
					ID: viper.GetString("node.id"),
				})
				if err != nil {
					log.Error().Err(err).Msg("Error encoding updated node")
					continue
				}
				// Create new PATCH request with new node as data
				req, err := http.NewRequest(
					http.MethodPatch,
					url("node", viper.GetString("node.name")),
					bytes.NewReader(data),
				)
				if err != nil {
					log.Fatal().Err(err).Msg("Error creating PATCH request")
				}
				// Perform request
				res, err := http.DefaultClient.Do(req)
				if err != nil {
					log.Fatal().Err(err).Msg("Error sending update request to server")
				}
				var resp types.Response
				// Decode server response
				err = msgpack.NewDecoder(res.Body).Decode(&resp)
				if err != nil {
					log.Fatal().Msg("Error decoding server response")
				}
				// If server returned error
				if resp.Error {
					log.Fatal().Str("error", resp.Message).Msg("Error returned by server")
				}
			}
		}
	},
}

func init() {
	rootCmd.AddCommand(clientCmd)
}

// localIP returns the IP address of the default network interface
func localIP() (string, error) {
	// Make UDP "connection" to nonexistant address
	conn, err := net.Dial("udp", "255.255.255.255:65535")
	if err != nil {
		return "", err
	}
	defer conn.Close()
	// Get local address
	addr := conn.LocalAddr().String()
	// Get host from address
	host, _, _ := net.SplitHostPort(addr)
	return host, nil
}

// url generates a URL for the given path on the server
func url(path ...string) string {
	// Get server address with port
	serverAddr := net.JoinHostPort(viper.GetString("server.addr"), viper.GetString("server.port"))
	// Return HTTPS address
	return "https://" + serverAddr + "/" + strings.Join(path, "/")
}