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

This commit is contained in:
palo 2023-10-28 00:44:36 +02:00
parent d7b35ffffa
commit e7d62180fe
6 changed files with 307 additions and 0 deletions

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# 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
```

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api.go Normal file
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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
}

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go.mod Normal file
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module Scontrini-Web-Client
go 1.19

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main.go Normal file
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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)
}
}

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templates/index.html Normal file
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<!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>

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templates/pizza.html Normal file
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<!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>