From d56d8ae854515dff7a7ebc02d8c9cbd93146b708 Mon Sep 17 00:00:00 2001
From: Maas Lalani <maas@lalani.dev>
Date: Mon, 13 Jun 2022 09:39:01 -0400
Subject: [PATCH] Example: Credit Card Input Form (#338)

* feat(cc): Add Credit Card Input Form Example and `ValidatorFuncs` to ensure credit cards are valid
---
 examples/credit-card-form/main.go | 203 ++++++++++++++++++++++++++++++
 examples/go.mod                   |   2 +-
 examples/go.sum                   |   2 +
 3 files changed, 206 insertions(+), 1 deletion(-)
 create mode 100644 examples/credit-card-form/main.go

diff --git a/examples/credit-card-form/main.go b/examples/credit-card-form/main.go
new file mode 100644
index 0000000000..f4a9293654
--- /dev/null
+++ b/examples/credit-card-form/main.go
@@ -0,0 +1,203 @@
+package main
+
+import (
+	"fmt"
+	"log"
+	"strconv"
+	"strings"
+
+	"github.com/charmbracelet/bubbles/textinput"
+	tea "github.com/charmbracelet/bubbletea"
+	"github.com/charmbracelet/lipgloss"
+)
+
+func main() {
+	p := tea.NewProgram(initialModel())
+
+	if err := p.Start(); err != nil {
+		log.Fatal(err)
+	}
+}
+
+type tickMsg struct{}
+type errMsg error
+
+const (
+	ccn = iota
+	exp
+	cvv
+)
+
+const (
+	hotPink  = lipgloss.Color("#FF06B7")
+	darkGray = lipgloss.Color("#767676")
+)
+
+var (
+	inputStyle    = lipgloss.NewStyle().Foreground(hotPink)
+	continueStyle = lipgloss.NewStyle().Foreground(darkGray)
+)
+
+type model struct {
+	inputs  []textinput.Model
+	focused int
+	err     error
+}
+
+// Validator functions to ensure valid input
+func ccnValidator(s string) error {
+	// Credit Card Number should a string less than 20 digits
+	// It should include 16 integers and 3 spaces
+	if len(s) > 16+3 {
+		return fmt.Errorf("CCN is too long")
+	}
+
+	// The last digit should be a number unless it is a multiple of 4 in which
+	// case it should be a space
+	if len(s)%5 == 0 && s[len(s)-1] != ' ' {
+		return fmt.Errorf("CCN must separate groups with spaces")
+	}
+	if len(s)%5 != 0 && (s[len(s)-1] < '0' || s[len(s)-1] > '9') {
+		return fmt.Errorf("CCN is invalid")
+	}
+
+	// The remaining digits should be integers
+	c := strings.ReplaceAll(s, " ", "")
+	_, err := strconv.ParseInt(c, 10, 64)
+
+	return err
+}
+
+func expValidator(s string) error {
+	// The 3 character should be a slash (/)
+	// The rest thould be numbers
+	e := strings.ReplaceAll(s, "/", "")
+	_, err := strconv.ParseInt(e, 10, 64)
+	if err != nil {
+		return fmt.Errorf("EXP is invalid")
+	}
+
+	// There should be only one slash and it should be in the 2nd index (3rd character)
+	if len(s) >= 3 && (strings.Index(s, "/") != 2 || strings.LastIndex(s, "/") != 2) {
+		return fmt.Errorf("EXP is invalid")
+	}
+
+	return nil
+}
+
+func cvvValidator(s string) error {
+	// The CVV should be a number of 3 digits
+	// Since the input will already ensure that the CVV is a string of length 3,
+	// All we need to do is check that it is a number
+	_, err := strconv.ParseInt(s, 10, 64)
+	return err
+}
+
+func initialModel() model {
+	var inputs []textinput.Model = make([]textinput.Model, 3)
+	inputs[ccn] = textinput.New()
+	inputs[ccn].Placeholder = "4505 **** **** 1234"
+	inputs[ccn].Focus()
+	inputs[ccn].CharLimit = 20
+	inputs[ccn].Width = 30
+	inputs[ccn].Prompt = ""
+	inputs[ccn].Validate = ccnValidator
+
+	inputs[exp] = textinput.New()
+	inputs[exp].Placeholder = "MM/YY "
+	inputs[exp].CharLimit = 5
+	inputs[exp].Width = 5
+	inputs[exp].Prompt = ""
+	inputs[exp].Validate = expValidator
+
+	inputs[cvv] = textinput.New()
+	inputs[cvv].Placeholder = "XXX"
+	inputs[cvv].CharLimit = 3
+	inputs[cvv].Width = 5
+	inputs[cvv].Prompt = ""
+	inputs[cvv].Validate = cvvValidator
+
+	return model{
+		inputs:  inputs,
+		focused: 0,
+		err:     nil,
+	}
+}
+
+func (m model) Init() tea.Cmd {
+	return textinput.Blink
+}
+
+func (m model) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
+	var (
+		cmds []tea.Cmd = make([]tea.Cmd, len(m.inputs))
+	)
+
+	switch msg := msg.(type) {
+	case tea.KeyMsg:
+		switch msg.Type {
+		case tea.KeyEnter:
+			if m.focused == len(m.inputs)-1 {
+				return m, tea.Quit
+			} else {
+				m.nextInput()
+			}
+		case tea.KeyCtrlC, tea.KeyEsc:
+			return m, tea.Quit
+		case tea.KeyShiftTab, tea.KeyCtrlP:
+			m.prevInput()
+		case tea.KeyTab, tea.KeyCtrlN:
+			m.nextInput()
+		}
+		for i := range m.inputs {
+			m.inputs[i].Blur()
+		}
+		m.inputs[m.focused].Focus()
+
+	// We handle errors just like any other message
+	case errMsg:
+		m.err = msg
+		return m, nil
+	}
+
+	for i := range m.inputs {
+		m.inputs[i], cmds[i] = m.inputs[i].Update(msg)
+	}
+	return m, tea.Batch(cmds...)
+}
+
+func (m model) View() string {
+	return fmt.Sprintf(
+		` Total: $21.50:
+
+ %s
+ %s
+ 
+ %s  %s
+ %s  %s
+
+ %s
+`,
+		inputStyle.Width(30).Render("Card Number"),
+		m.inputs[ccn].View(),
+		inputStyle.Width(6).Render("EXP"),
+		inputStyle.Width(6).Render("CVV"),
+		m.inputs[exp].View(),
+		m.inputs[cvv].View(),
+		continueStyle.Render("Continue ->"),
+	) + "\n"
+}
+
+// nextInput focuses the next input field
+func (m *model) nextInput() {
+	m.focused = (m.focused + 1) % len(m.inputs)
+}
+
+// prevInput focuses the previous input field
+func (m *model) prevInput() {
+	m.focused--
+	// Wrap around
+	if m.focused < 0 {
+		m.focused = len(m.inputs) - 1
+	}
+}
diff --git a/examples/go.mod b/examples/go.mod
index 7851f35f21..54d3cc6a7e 100644
--- a/examples/go.mod
+++ b/examples/go.mod
@@ -3,7 +3,7 @@ module examples
 go 1.13
 
 require (
-	github.com/charmbracelet/bubbles v0.11.0
+	github.com/charmbracelet/bubbles v0.11.1-0.20220610161724-e57fd292cc68
 	github.com/charmbracelet/bubbletea v0.21.0
 	github.com/charmbracelet/glamour v0.5.0
 	github.com/charmbracelet/lipgloss v0.5.0
diff --git a/examples/go.sum b/examples/go.sum
index 19af6250a3..b5de6a0084 100644
--- a/examples/go.sum
+++ b/examples/go.sum
@@ -6,6 +6,8 @@ github.com/aymerick/douceur v0.2.0 h1:Mv+mAeH1Q+n9Fr+oyamOlAkUNPWPlA8PPGR0QAaYuP
 github.com/aymerick/douceur v0.2.0/go.mod h1:wlT5vV2O3h55X9m7iVYN0TBM0NH/MmbLnd30/FjWUq4=
 github.com/charmbracelet/bubbles v0.11.0 h1:fBLyY0PvJnd56Vlu5L84JJH6f4axhgIJ9P3NET78f0Q=
 github.com/charmbracelet/bubbles v0.11.0/go.mod h1:bbeTiXwPww4M031aGi8UK2HT9RDWoiNibae+1yCMtcc=
+github.com/charmbracelet/bubbles v0.11.1-0.20220610161724-e57fd292cc68 h1:oDxdCcM/JreVa7RTt2NQLdp06PwkApSL3huTwrOl/ww=
+github.com/charmbracelet/bubbles v0.11.1-0.20220610161724-e57fd292cc68/go.mod h1:bbeTiXwPww4M031aGi8UK2HT9RDWoiNibae+1yCMtcc=
 github.com/charmbracelet/glamour v0.5.0 h1:wu15ykPdB7X6chxugG/NNfDUbyyrCLV9XBalj5wdu3g=
 github.com/charmbracelet/glamour v0.5.0/go.mod h1:9ZRtG19AUIzcTm7FGLGbq3D5WKQ5UyZBbQsMQN0XIqc=
 github.com/charmbracelet/harmonica v0.2.0 h1:8NxJWRWg/bzKqqEaaeFNipOu77YR5t8aSwG4pgaUBiQ=