// This file is part of https://github.com/racingmars/go3270/
// Copyright 2020 by Matthew R. Wilson, licensed under the MIT license. See
// LICENSE in the project root for license information.

package main

import (
	"fmt"
	"net"
	"os"

	"github.com/racingmars/go3270"
)

func init() {
	// put the go3270 library in debug mode
	go3270.Debug = os.Stderr
}

// A Screen is an array of go3270.Field structs. We will build two screens,
// a query screen and a result screen:

var screen1 = go3270.Screen{
	{Row: 0, Col: 27, Intense: true, Content: "3270 Example Application"},
	{Row: 2, Col: 0, Content: "Welcome to the go3270 example application. Please enter your name."},
	{Row: 4, Col: 0, Content: "First Name  . . ."},
	{Row: 4, Col: 19, Name: "fname", Write: true},
	{Row: 4, Col: 40}, // field "stop" character
	{Row: 5, Col: 0, Content: "Last Name . . . ."},
	{Row: 5, Col: 19, Name: "lname", Write: true},
	{Row: 5, Col: 40}, // field "stop" character,
	{Row: 7, Col: 0, Content: "Press"},
	{Row: 7, Col: 6, Intense: true, Content: "enter"},
	{Row: 7, Col: 12, Content: "to submit your name."},
	{Row: 22, Col: 0, Content: "PF3 Exit"},
}

var screen2 = go3270.Screen{
	{Row: 0, Col: 27, Intense: true, Content: "3270 Example Application"},
	{Row: 2, Col: 0, Content: "Thank you for submitting your name. Here's what I know:"},
	{Row: 4, Col: 0, Content: "Your first name is"},
	{Row: 4, Col: 19, Name: "fname"}, // We're giving this field a name to replace its value at runtime
	{Row: 5, Col: 0, Content: "And your last name is"},
	{Row: 5, Col: 22, Name: "lname"}, // We're giving this field a name to replace its value at runtime
	{Row: 7, Col: 0, Content: "Press"},
	{Row: 7, Col: 6, Intense: true, Content: "enter"},
	{Row: 7, Col: 12, Content: "to enter your name again, or"},
	{Row: 7, Col: 41, Intense: true, Content: "PF3"},
	{Row: 7, Col: 45, Content: "to quit and disconnect."},
	{Row: 22, Col: 0, Content: "PF3 Exit"},
}

func main() {
	ln, err := net.Listen("tcp", ":3270")
	if err != nil {
		panic(err)
	}
	fmt.Println("LISTENING ON PORT 3270 FOR CONNECTIONS")
	fmt.Println("Press Ctrl-C to end server.")
	for {
		conn, err := ln.Accept()
		if err != nil {
			panic(err)
		}
		go handle(conn)
	}
}

// handle is the handler for individual user connections.
func handle(conn net.Conn) {
	defer conn.Close()

	// Always begin new connection by negotiating the telnet options
	go3270.NegotiateTelnet(conn)

	// We will loop forever until the user quits with PF3
	var fieldValues map[string]string
	for {
		// Show the first screen, and wait to get a client response. Place
		// the cursor at the beginning of the first input field.
		// We're passing in the fieldValues map to carry values over from
		// the previous submission. We could pass nil, instead, if always want
		// the fields to start out blank.
		response, err := go3270.ShowScreen(screen1, fieldValues, 4, 20, conn)
		if err != nil {
			fmt.Println(err)
			return
		}

		// If the user pressed PF3, exit
		if response.AID == go3270.AIDPF3 {
			break
		}

		// If anything OTHER than "Enter", restart the loop
		if response.AID != go3270.AIDEnter {
			continue
		}

		// User must have pressed "Enter", so let's display the second screen,
		// echoing their responses back to them.
		fieldValues = response.Values
		response, err = go3270.ShowScreen(screen2, fieldValues, 0, 0, conn)
		if err != nil {
			fmt.Println(err)
			return
		}

		// If the user pressed PF3, exit
		if response.AID == go3270.AIDPF3 {
			break
		}

		// If they pressed anything else, just let the loop continue...
		continue
	}

	fmt.Println("Connection closed")
}