realtime chat with bot using data-star

package handlers

import (
    "encoding/json"
    "fmt"
    "log"
    "net/http"

    "github.com/blinkinglight/chat-data-star/web/views/chatview"
    "github.com/delaneyj/datastar"
    "github.com/delaneyj/toolbelt"
    "github.com/delaneyj/toolbelt/embeddednats"
    "github.com/go-chi/chi/v5"
    "github.com/gorilla/sessions"
    "github.com/nats-io/nats.go"
)

func SetupChat(router chi.Router, session sessions.Store, ns *embeddednats.Server) error {

    type Message struct {
        Message string `json:"message"`
        Sender  string `json:"sender"`
    }

    nc, err := ns.Client()
    if err != nil {
        return err
    }

    nc.Subscribe("chat.>", func(msg *nats.Msg) {
        var message = Message{}
        err := json.Unmarshal(msg.Data, &message)
        if err != nil {
            log.Printf("%v", err)
            return
        }

        if message.Sender != "bot" {
            // do something with user message and send back response
            nc.Publish("chat."+message.Sender, []byte(`{"message":"hello, i am bot. You send me: `+message.Message+`", "sender":"bot"}`))
        }
    })

    _ = nc
    chatIndex := func(w http.ResponseWriter, r *http.Request) {
        _, err := upsertSessionID(session, r, w)
        if err != nil {
            http.Error(w, err.Error(), http.StatusInternalServerError)
            return
        }
        chatview.Index().Render(r.Context(), w)
    }

    chatMessage := func(w http.ResponseWriter, r *http.Request) {
        id, err := upsertSessionID(session, r, w)
        if err != nil {
            http.Error(w, err.Error(), http.StatusInternalServerError)
            return
        }

        var state = Message{}

        err = datastar.BodyUnmarshal(r, &state)
        if err != nil {
            http.Error(w, err.Error(), http.StatusBadRequest)
            return
        }

        state.Sender = id
        b, err := json.Marshal(state)
        if err != nil {
            http.Error(w, err.Error(), http.StatusInternalServerError)
            return
        }
        nc.Publish("chat."+id, b)
        sse := datastar.NewSSE(w, r)
        _ = sse
    }

    chatMessages := func(w http.ResponseWriter, r *http.Request) {

        id, err := upsertSessionID(session, r, w)
        if err != nil {
            http.Error(w, err.Error(), http.StatusInternalServerError)
            return
        }

        var ch = make(chan *nats.Msg)
        sub, err := nc.Subscribe("chat."+id, func(msg *nats.Msg) {
            ch <- msg
        })

        if err != nil {
            http.Error(w, err.Error(), http.StatusInternalServerError)
            return
        }
        defer close(ch)
        defer sub.Unsubscribe()

        sse := datastar.NewSSE(w, r)

        for {
            select {
            case <-r.Context().Done():
                return

            case msg := <-ch:
                var message = Message{}
                err := json.Unmarshal(msg.Data, &message)
                if err != nil {
                    datastar.Error(sse, err)
                    return
                }
                if message.Sender == "bot" {
                    datastar.RenderFragmentTempl(sse, chatview.Bot(message.Message), datastar.WithMergeAppend(), datastar.WithQuerySelector("#chatbox"))
                } else {
                    datastar.RenderFragmentTempl(sse, chatview.Me(message.Message), datastar.WithMergeAppend(), datastar.WithQuerySelector("#chatbox"))
                }
            }
        }
    }

    router.Get("/chat", chatIndex)
    router.Post("/chat", chatMessage)
    router.Get("/messages", chatMessages)

    return nil
}

func upsertSessionID(store sessions.Store, r *http.Request, w http.ResponseWriter) (string, error) {

    sess, err := store.Get(r, "chatters")
    if err != nil {
        return "", fmt.Errorf("failed to get session: %w", err)
    }
    id, ok := sess.Values["id"].(string)
    if !ok {
        id = toolbelt.NextEncodedID()
        sess.Values["id"] = id
        if err := sess.Save(r, w); err != nil {
            return "", fmt.Errorf("failed to save session: %w", err)
        }
    }
    return id, nil
}

package chatview

import "github.com/blinkinglight/chat-data-star/web/views/layoutview"

templ Index() {
    @layoutview.Main() {
        <!-- component -->
        <div class="fixed bottom-0 right-0 mb-4 mr-4">
            <button id="open-chat" class="bg-blue-500 text-white py-2 px-4 rounded-md hover:bg-blue-600 transition duration-300 flex items-center">
                <svg xmlns="http://www.w3.org/2000/svg" class="w-6 h-6 mr-2" fill="none" viewBox="0 0 24 24" stroke="currentColor">
                    <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M12 6v6m0 0v6m0-6h6m-6 0H6"></path>
                </svg>
                Chat with Admin Bot
            </button>
        </div>
        <div id="chat-container" class="hidden fixed bottom-16 right-4 w-96">
            <div class="bg-white shadow-md rounded-lg max-w-lg w-full">
                <div class="p-4 border-b bg-blue-500 text-white rounded-t-lg flex justify-between items-center">
                    <p class="text-lg font-semibold">Admin Bot</p>
                    <button id="close-chat" class="text-gray-300 hover:text-gray-400 focus:outline-none focus:text-gray-400">
                        <svg xmlns="http://www.w3.org/2000/svg" class="w-6 h-6" fill="none" viewBox="0 0 24 24" stroke="currentColor">
                            <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M6 18L18 6M6 6l12 12"></path>
                        </svg>
                    </button>
                </div>
                <div id="chatbox" class="p-4 h-80 overflow-y-auto" data-on-load="$$get('/messages')" data-store="{ message: '' }">
                    <!-- Chat messages will be displayed here -->
                </div>
                <div class="p-4 border-t flex">
                    <input data-model="message" id="user-input" type="text" placeholder="Type a message" class="w-full px-3 py-2 border rounded-l-md focus:outline-none focus:ring-2 focus:ring-blue-500"/>
                    <button data-on-keydown.window.key_enter="$$post('/chat'); $message=''" data-on-click="$$post('/chat'); $message=''" id="send-button" class="bg-blue-500 text-white px-4 py-2 rounded-r-md hover:bg-blue-600 transition duration-300">Send</button>
                </div>
            </div>
        </div>
        <script>
        const chatbox = document.getElementById("chatbox");
                const chatContainer = document.getElementById("chat-container");
                const userInput = document.getElementById("user-input");
                const sendButton = document.getElementById("send-button");
                const openChatButton = document.getElementById("open-chat");
                const closeChatButton = document.getElementById("close-chat");

                let isChatboxOpen = true; // Set the initial state to open

                function toggleChatbox() {
                    chatContainer.classList.toggle("hidden");
                    isChatboxOpen = !isChatboxOpen; // Toggle the state
                }

                openChatButton.addEventListener("click", toggleChatbox);

                closeChatButton.addEventListener("click", toggleChatbox);
                toggleChatbox();

        </script>
    }
}

templ Me(message string) {
    <div class="mb-2 text-right">
        <p class="bg-blue-500 text-white rounded-lg py-2 px-4 inline-block">{ message }</p>
    </div>
}

templ Bot(message string) {
    <div class="mb-2">
        <p class="bg-gray-200 text-gray-700 rounded-lg py-2 px-4 inline-block">{ message }</p>
    </div>
}