// 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"
	"strings"
	"time"

	"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, Highlighting: go3270.Underscore},
	{Row: 4, Col: 40, Autoskip: true}, // field "stop" character
	{Row: 5, Col: 0, Content: "Last Name . . . ."},
	{Row: 5, Col: 19, Name: "lname", Write: true, Highlighting: go3270.Underscore},
	{Row: 5, Col: 40, Autoskip: true}, // field "stop" character
	{Row: 6, Col: 0, Content: "Password  . . . ."},
	{Row: 6, Col: 19, Name: "password", Write: true, Hidden: true},
	{Row: 6, Col: 40}, // field "stop" character
	{Row: 7, Col: 0, Content: "Employee ID . . ."},
	{Row: 7, Col: 19, Name: "employeeID", Write: true, Highlighting: go3270.Underscore, NumericOnly: true},
	{Row: 7, Col: 40}, // field "stop" character
	{Row: 8, Col: 0, Content: "Press"},
	{Row: 8, Col: 6, Intense: true, Content: "enter"},
	{Row: 8, Col: 12, Content: "to submit your name."},
	{Row: 10, Col: 0, Intense: true, Color: go3270.Red, Name: "errormsg"}, // a blank field for error messages

	// Demonstrate the AttributeOnly property:
	{Row: 12, Col: 0, Content: "Demonstration of AttributeOnly to change format without a new field:"},
	{Row: 13, Col: 1, AttributeOnly: true, Color: go3270.Green, Content: "████"},
	{Row: 13, Col: 5, AttributeOnly: true, Color: go3270.Yellow, Content: "████"},
	{Row: 13, Col: 9, AttributeOnly: true, Color: go3270.Red, Content: "████"},
	{Row: 13, Col: 13, AttributeOnly: true, Color: go3270.Red, Highlighting: go3270.Blink, Content: "████"},
	// When using extended attributes, need to explicitly reset to defaults, the next field won't necessarily clear the attributes out.
	{Row: 13, Col: 17, AttributeOnly: true, Color: go3270.DefaultColor, Highlighting: go3270.DefaultHighlight},

	{Row: 15, Col: 0, Content: "Detected code page:"},
	{Row: 15, Col: 20, Name: "codepage"},
	{Row: 16, Col: 0, Content: "The following should be left and right square brackets: [ ]"},
	{Row: 17, Col: 0, Content: "Graphic escape support:"},
	{Row: 17, Col: 24, Name: "gesupport"},

	// Can use PositionOnly attribute to place text beginning at a specific
	// position without introducing a new attribute byte.
	{Row: 19, Col: 0, PositionOnly: true, Content: "This text starts in first column"},

	{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: 6, Col: 0, Content: "And your employeed ID is"},
	{Row: 6, Col: 22, Name: "employeeID"}, // We're giving this field a name to replace its value at runtime
	{Row: 7, Col: 0, Name: "passwordOutput"},
	{Row: 9, Col: 0, Content: "Press"},
	{Row: 9, Col: 6, Intense: true, Content: "enter"},
	{Row: 9, Col: 12, Content: "to enter your name again, or"},
	{Row: 9, Col: 41, Intense: true, Content: "PF3"},
	{Row: 9, Col: 45, Content: "to quit and disconnect."},
	{Row: 12, Col: 0, Color: go3270.Turquoise, Highlighting: go3270.ReverseVideo, Content: "Here is a field with extended attributes."},
	{Row: 12, Col: 42},                  // remember to "stop" fields with a regular field, to clear the reverse video for example
	{Row: 14, Col: 0, Name: "position"}, // will be filled when displaying
	{Row: 22, Col: 0, Content: "PF3 Exit"},
}

var goodbyeScreen = go3270.Screen{
	{Row: 0, Col: 27, Intense: true, Content: "3270 Example Application"},
	{Row: 2, Col: 0, Content: "Thank you using this application. Goodbye."},
}

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
	devinfo, err := go3270.NegotiateTelnet(conn)
	if err != nil {
		fmt.Printf("ERROR: %v\n", err)
		return
	}

	fieldValues := make(map[string]string)

	var response go3270.Response

	// We will loop forever until the user quits with PF3
mainLoop:
	for {

		// Need to set the codepage display field value each time through the
		// loop so it persists between screen1->screen2->screen1 navigation.
		if devinfo.Codepage() == nil {
			fieldValues["codepage"] = "(unknown)"
		} else {
			fieldValues["codepage"] = devinfo.Codepage().ID()
		}
		fieldValues["gesupport"] = fmt.Sprintf("%v", devinfo.SupportsGE())

	screen1Loop:
		for {
			// loop until the user passes input validation, or quits

			// Always reset password input to blank each time through the loop
			fieldValues["password"] = ""

			// 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.ShowScreenOpts(screen1, fieldValues, conn,
				go3270.ScreenOpts{
					Codepage:  devinfo.Codepage(),
					CursorRow: 4,
					CursorCol: 20,
				})
			if err != nil {
				fmt.Println(err)
				return
			}

			// If the user pressed PF3, exit
			if response.AID == go3270.AIDPF3 {
				go3270.ShowScreenOpts(goodbyeScreen, nil, conn,
					go3270.ScreenOpts{
						Codepage:   devinfo.Codepage(),
						NoResponse: true,
					})
				time.Sleep(2 * time.Second)
				break mainLoop
			}

			// If anything OTHER than "Enter", restart the loop
			if response.AID != go3270.AIDEnter {
				continue screen1Loop
			}

			// User must have pressed "Enter", so let's check the input.
			fieldValues = response.Values
			if strings.TrimSpace(fieldValues["fname"]) == "" &&
				strings.TrimSpace(fieldValues["lname"]) == "" {
				fieldValues["errormsg"] =
					"First and Last Name fields are required."
				continue screen1Loop
			}
			if strings.TrimSpace(fieldValues["fname"]) == "" {
				fieldValues["errormsg"] = "First Name field is required."
				continue screen1Loop
			}
			if strings.TrimSpace(fieldValues["lname"]) == "" {
				fieldValues["errormsg"] = "Last Name field is required."
				continue screen1Loop
			}

			// At this point, we know the user provided both fields and had
			// hit enter, so we are going to reset the error message for the
			// next time through the loop, and break out of this loop so we
			// move on to screen 2.
			fieldValues["errormsg"] = ""
			break screen1Loop
		}

		// Now we're ready to display screen2
		passwordLength := len(strings.TrimSpace(fieldValues["password"]))
		passwordPlural := "s"
		if passwordLength == 1 {
			passwordPlural = ""
		}
		fieldValues["passwordOutput"] = fmt.Sprintf(
			"Your password was %d character%s long",
			passwordLength, passwordPlural)
		fieldValues["position"] = fmt.Sprintf(
			"When you pressed enter the cursor was at row %d column %d.",
			response.Row+1, response.Col+1)
		response, err := go3270.ShowScreenOpts(screen2, fieldValues, conn,
			go3270.ScreenOpts{Codepage: devinfo.Codepage()})
		if err != nil {
			fmt.Println(err)
			return
		}

		// If the user pressed PF3, exit
		if response.AID == go3270.AIDPF3 {
			go3270.ShowScreenOpts(goodbyeScreen, nil, conn,
				go3270.ScreenOpts{
					Codepage:   devinfo.Codepage(),
					NoResponse: true,
				})
			time.Sleep(2 * time.Second)
			break
		}

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

	fmt.Println("Connection closed")
}