Added main pages, print and order_pizzas, that interact with the API

README.md

@@ -1 +1,18 @@
 # Scontrini Web Client
+
+Golang simple http server that interfaces with Scontrini-Daemon
+
+## Usage
+
+Compiling
+
+```sh
+$ go build
+$ chmod +x ./Scontrini-Web-Client
+```
+
+Executing
+
+```sh
+$ ./Scontrini-Web-Client
+```

api.go

@@ -0,0 +1,106 @@
+package main
+
+import (
+	"encoding/binary"
+	"encoding/json"
+	"fmt"
+	"net"
+)
+
+var (
+	printer_server_IP   = net.ParseIP("127.0.0.1")
+	printer_server_port = 4444
+)
+
+// Commands to give to the API
+type JSONCommand interface {
+	PrintCommand | PizzaCommand | GetPizzasCommand
+}
+
+type PrintCommand struct {
+	Command string `json:"command"`
+	Text    string `json:"text"`
+}
+
+type PizzaCommand struct {
+	Command string  `json:"command"`
+	Pizzas  []Pizza `json:"pizzas"`
+}
+
+type GetPizzasCommand struct {
+	Command string `json:"command"`
+}
+
+// What to receive from the API
+type JSONReceived interface {
+	ReceivePizzas
+}
+
+type ReceivePizzas struct {
+	Pizzas []Pizza `json:"pizzas"`
+}
+
+/**
+* All messages from and to the API must have the first 4 bytes set to represent
+* the length of the message, followed by the message itself
+ */
+func sendJSONToServer[T JSONCommand](socket *net.TCPConn, json_command T) (*net.TCPConn, error) {
+	json_data, err := json.Marshal(json_command)
+
+	if err != nil {
+		return nil, err
+	}
+
+	// in case a socket doesn't already exist create a new one
+	if socket == nil {
+		socket, err = net.DialTCP("tcp4", nil, &net.TCPAddr{printer_server_IP, printer_server_port, ""})
+	}
+
+	if err != nil {
+		return nil, err
+	}
+
+	// the first 4 bytes must be the length of the message
+	to_send := make([]byte, 4)
+	binary.LittleEndian.PutUint32(to_send, uint32(len(json_data)))
+
+	to_send = append(to_send, json_data...)
+	socket.Write([]byte(to_send))
+
+	return socket, nil
+}
+
+func receiveJSONFromServer[T JSONReceived](socket *net.TCPConn, json_received *T) (*net.TCPConn, error) {
+	var err error
+
+	// in case a socket doesn't already exist create a new one
+	if socket == nil {
+		fmt.Println("nil")
+		socket, err = net.DialTCP("tcp4", nil, &net.TCPAddr{printer_server_IP, printer_server_port, ""})
+	}
+
+	if err != nil {
+		return nil, err
+	}
+
+	// the first 4 bytes are the length of the message
+	b := make([]byte, 4)
+	_, err = socket.Read(b[0:])
+
+	if err != nil {
+		return nil, err
+	}
+
+	body_length := binary.LittleEndian.Uint32(b)
+
+	body := make([]byte, body_length)
+	_, err = socket.Read(body[0:])
+
+	err = json.Unmarshal(body, json_received)
+
+	if err != nil {
+		return nil, err
+	}
+
+	return socket, nil
+}

go.mod

@@ -0,0 +1,3 @@
+module Scontrini-Web-Client
+
+go 1.19

main.go

@@ -0,0 +1,126 @@
+package main
+
+import (
+	"errors"
+	"fmt"
+	"html/template"
+	"net/http"
+	"os"
+	"strconv"
+)
+
+var (
+	templates = template.Must(template.ParseFiles("templates/index.html", "templates/pizza.html"))
+)
+
+type Pizza struct {
+	Name     string `json:"name"`
+	Price    int    `json:"price"`
+	Quantity int    `json:"quantity"`
+}
+
+/**
+* Handler function for "/"
+ */
+func indexHandler(w http.ResponseWriter, r *http.Request) {
+	templates.ExecuteTemplate(w, "index.html", nil)
+}
+
+/**
+* Handler function for "/print", only accepts POST requests
+*
+* Tells the API to print the text specified in its Form
+ */
+func printHandler(w http.ResponseWriter, r *http.Request) {
+	if r.Method != http.MethodPost {
+		http.Error(w, "Method not allowed", http.StatusMethodNotAllowed)
+		return
+	}
+
+	text := r.PostFormValue("text")
+
+	json_command := PrintCommand{Command: "print", Text: text}
+	_, err := sendJSONToServer(nil, json_command)
+
+	if err != nil {
+		fmt.Fprintf(w, "Error while connecting to the printer server")
+		return
+	}
+
+	http.Redirect(w, r, "/", http.StatusSeeOther)
+}
+
+/**
+* Handler function for "/pizza", only accepts POST requests
+*
+* Tells the API to print the pizza order specified in its Form
+ */
+func pizzaHandler(w http.ResponseWriter, r *http.Request) {
+	if r.Method != http.MethodPost {
+		http.Error(w, "Method not allowed", http.StatusMethodNotAllowed)
+		return
+	}
+
+	pizzas := make([]Pizza, 0)
+
+	r.ParseForm()
+	for key, _ := range r.Form {
+		// only put in the pizzas that have a quantity bigger than 0
+		if key != "submit" && r.Form[key][0] != "0" {
+			quantity, _ := strconv.ParseInt(r.Form[key][0], 10, 0)
+			pizzas = append(pizzas, Pizza{key, 0, int(quantity)})
+		}
+	}
+
+	json_command := PizzaCommand{Command: "pizza", Pizzas: pizzas}
+	_, err := sendJSONToServer(nil, json_command)
+
+	if err != nil {
+		fmt.Fprintf(w, "Error while connecting to the printer server")
+		return
+	}
+
+	http.Redirect(w, r, "/order_pizzas", http.StatusSeeOther)
+}
+
+/**
+* Handler function for "/order_pizzas"
+*
+* Asks the API for the list of all pizzas then returns a formatted HTML page
+ */
+func orderPizzasHandler(w http.ResponseWriter, r *http.Request) {
+	json_command := GetPizzasCommand{Command: "get-pizzas"}
+	socket, err := sendJSONToServer(nil, json_command)
+
+	if err != nil {
+		fmt.Fprintf(w, "Error while connecting to the printer server")
+		return
+	}
+
+	pizzas := ReceivePizzas{}
+	_, err = receiveJSONFromServer(socket, &pizzas)
+
+	if err != nil {
+		fmt.Fprintf(w, "Error while connecting to the printer server")
+		return
+	}
+
+	templates.ExecuteTemplate(w, "pizza.html", pizzas.Pizzas)
+}
+
+func main() {
+	mux := http.NewServeMux()
+
+	mux.HandleFunc("/", indexHandler)
+	mux.HandleFunc("/print", printHandler)
+	mux.HandleFunc("/pizza", pizzaHandler)
+	mux.HandleFunc("/order_pizzas", orderPizzasHandler)
+
+	err := http.ListenAndServe(":8080", mux)
+	if errors.Is(err, http.ErrServerClosed) {
+		fmt.Println("Server closed")
+	} else if err != nil {
+		fmt.Printf("Error starting server: %s\n", err)
+		os.Exit(1)
+	}
+}

templates/index.html

@@ -0,0 +1,21 @@
+<!DOCTYPE html>
+<html>
+
+<head>
+	<title>Scontrini</title>
+	<link rel="stylesheet" href="">
+</head>
+
+<body>
+	<h1>SCONTRINI</h1>
+
+	<h2>Cosa stampare:</h2>
+	<form action="/print" method="post">
+		<input name="text" id="text" type="text"></input>	
+		<input name="print" id="print" type="submit" value="STAMPA"></input>
+	</form>
+	<button><a href="/order_pizzas">Ordina le pizze</a></button>
+</body>
+
+</html> 
+

templates/pizza.html

@@ -0,0 +1,34 @@
+<!DOCTYPE html>
+<html>
+
+<head>
+	<title>Scontrini</title>
+	<link rel="stylesheet" href="">
+</head>
+
+<body>
+	<h1>PIZZE</h1>
+
+	<form action="/pizza" method="post">
+		<table id="pizzas">
+			{{ range . }}
+				<tr>
+					<td>
+						{{ .Name }}
+					</td>
+					<td>
+						{{ .Price }}
+					</td>
+					<td>
+						<input name="{{ .Name }}" type="number" value="0"></input>
+					</td>
+				</tr>
+			{{ end }}
+		</table>
+		<input name="submit" id="submit" type="submit" value="ORDINA LA PIZZA"></input>
+	</form>
+	<button><a href="/">Stampa qualcosa</a></button>
+</body>
+
+</html> 
+