chat/internal/server.go

package chat

import (
	"bytes"
	"encoding/json"
	"fmt"
	"io/ioutil"
	"net/http"
	"os"
	"strconv"
	"sync"
	"time"
)

const DefaultCacheLength = 20

type Server struct {
	clients      map[string]*Client
	messageCache List
	Name         string `json:"name"`
	wg           sync.WaitGroup
}

type Message struct {
	Text     string `json:"text"`
	Time     int64  `json:"time"`
	User     string `json:"user"`
	ServerId string `json:"serverId"`
}

var Servers map[string]*Server

func StartServer(name string) (s Server) {
	s = Server{make(map[string]*Client), newList(DefaultCacheLength), name, sync.WaitGroup{}}
	Servers[name] = &s
	s.putServer()
	s.loadInitMessages()
	return
}

func getServer(name string) (*Server, error) {
	if name == "" {
		name = "root"
	}
	if s, ok := Servers[name]; ok {
		return s, nil
	}

	_, exists := retrieveServerFromDb(name)
	if !exists {
		return nil, fmt.Errorf("server does not exist")
	}

	server := StartServer(name)
	return &server, nil
}

func retrieveServerFromDb(name string) (s *Server, found bool) {
	res, err := http.Get(DbAddress + "/server?name=" + name)
	if err != nil {
		fmt.Fprintln(os.Stderr, "could not reach db server", err)
		return
	}
	if res.StatusCode != http.StatusOK {
		fmt.Println("server", name, "not found on db")
		return
	}
	if err := json.NewDecoder(res.Body).Decode(&s); err != nil {
		fmt.Fprintln(os.Stderr, "error retrieving server details from db", err)
		return
	}
	return s, true
}

func (s *Server) reportClients() (count int) {
	for range s.clients {
		count++
	}
	return
}

func (s *Server) sendMessage(message string) {
	mess := Message{message, time.Now().UnixMilli(), s.Name, ""}
	wm := WrappedMessage{"server", mess}
	for _, client := range s.clients {
		client.receivedMessages <- wm
	}
}

func (s *Server) broadcastMessage(mess *Message) {
	wm := WrappedMessage{"", *mess}
	for _, client := range s.clients {
		client.receivedMessages <- wm
	}
}

func (s *Server) storeMessage(mess *Message) {
	s.messageCache.add(&ListNode{nil, *mess})
	s.wg.Done()
	jsonData, ok := encodeJson(mess)
	if !ok {
		return
	}

	if res, err := http.Post(DbAddress+"/message?name="+s.Name, "application/json", bytes.NewBuffer(jsonData)); err != nil {
		fmt.Fprintln(os.Stderr, "db server post error", err.Error())
	} else {
		body, err := ioutil.ReadAll(res.Body)
		if err != nil {
			fmt.Fprintln(os.Stderr, "error reading response body:", err)
		}
		if res.StatusCode != http.StatusOK {
			fmt.Println("could not store message", string(body))
		}
	}
}

func (s *Server) loadInitMessages() {
	status, _, messages := s.loadMessages(0, DefaultCacheLength)
	if status != http.StatusOK {
		fmt.Fprintln(os.Stderr, "Could not load initial messages from db")
		return
	}
	s.messageCache.fromMessageSlice(messages)
}

func (s *Server) loadMessages(offset, count int) (status int, message string, messages []Message) {
	if res, err := http.Get(DbAddress + "/message?name=" + s.Name + "&offset=" + strconv.Itoa(offset) + "&count=" + strconv.Itoa(count)); err != nil {
		fmt.Fprintln(os.Stderr, "db server get messages error", err.Error())
	} else {
		body, err := ioutil.ReadAll(res.Body)
		if err != nil {
			fmt.Fprintln(os.Stderr, "error reading response body:", err)
		}

		if res.StatusCode != http.StatusOK {
			fmt.Println("load messages error", string(body))
			return res.StatusCode, string(body), nil
		} else {
			messages = make([]Message, 0)
			if err := json.Unmarshal(body, &messages); err != nil {
				fmt.Fprintln(os.Stderr, "Error unmarshalling messages from db", err.Error())
				return http.StatusInternalServerError, "Error unmarshalling messages from db " + err.Error(), nil
			}
		}
	}
	return http.StatusOK, "", messages
}

func (s *Server) putServer() {
	jsonData, ok := encodeJson(&s)
	if !ok {
		fmt.Fprintln(os.Stderr, "error encoding server")
		return
	}
	res, err := http.Post(DbAddress+"/server", "application/json", bytes.NewBuffer(jsonData))
	if err != nil {
		fmt.Fprintln(os.Stderr, "POST server to db error:", err.Error())
		return
	}
	if res.StatusCode == http.StatusOK {
		fmt.Println("server", s.Name, "already in db")
		var temp Server
		if err := json.NewDecoder(res.Body).Decode(&temp); err != nil {
			fmt.Println("error updating local server details with those from db")
			return
		}
		//TODO: update details which get pulled from db rather than on creation
		return
	}
	if res.StatusCode == http.StatusCreated {
		fmt.Println("server", s.Name, "added to db")
		return
	}

}