From da17ddb7314b79d1164ae7eed6a0762700d249ec Mon Sep 17 00:00:00 2001
From: Abhimanyu Singh <superhit0@gmail.com>
Date: Sun, 1 Jul 2018 14:53:33 +0530
Subject: [PATCH] Fix cursor Issue#205

---
 __tests__/utils.test.js           | 26 ++++++++++++++++++++
 src/components/IntlTelInputApp.js | 16 +++++++++++--
 src/components/TelInput.js        | 18 +++++++++++++-
 src/components/utils.js           | 40 +++++++++++++++++++++++++++++++
 4 files changed, 97 insertions(+), 3 deletions(-)

diff --git a/__tests__/utils.test.js b/__tests__/utils.test.js
index bb001f085..3bcfbe23a 100644
--- a/__tests__/utils.test.js
+++ b/__tests__/utils.test.js
@@ -173,4 +173,30 @@ describe('utils', () => {
 
     expect(utils.findIndex(array, predicate)).toEqual(-1);
   });
+
+  it('getCursorPositionAfterFormating', () => {
+    let previousStringBeforeCursor = '9123';
+    let previousString = '912345';
+    let nextString = '912345';
+
+    expect(utils.getCursorPositionAfterFormating(previousStringBeforeCursor, previousString, nextString)).toEqual(4);
+
+    previousStringBeforeCursor = '0912 345';
+    previousString = '0912 345 678';
+    nextString = '91234678';
+
+    expect(utils.getCursorPositionAfterFormating(previousStringBeforeCursor, previousString, nextString)).toEqual(5);
+
+    previousStringBeforeCursor = '91234';
+    previousString = '91234678';
+    nextString = '0912 345 678';
+
+    expect(utils.getCursorPositionAfterFormating(previousStringBeforeCursor, previousString, nextString)).toEqual(7);
+
+    previousStringBeforeCursor = '(201) 5';
+    previousString = '(201) 55-01';
+    nextString = '201-5501';
+
+    expect(utils.getCursorPositionAfterFormating(previousStringBeforeCursor, previousString, nextString)).toEqual(5);
+  });
 });
diff --git a/src/components/IntlTelInputApp.js b/src/components/IntlTelInputApp.js
index ad0e893f3..e91e1649f 100644
--- a/src/components/IntlTelInputApp.js
+++ b/src/components/IntlTelInputApp.js
@@ -61,6 +61,7 @@ class IntlTelInputApp extends Component {
       title: '',
       countryCode: 'us',
       dialCode: '',
+      cursorPosition: (props.value || props.defaultValue).length,
     };
 
     this.selectedCountryData = {};
@@ -1055,14 +1056,24 @@ class IntlTelInputApp extends Component {
   // Either notify phoneNumber changed if component is controlled
   // or udpate the state and notify change if component is uncontrolled
   handleInputChange(e) {
+    let cursorPosition = e.target.selectionStart;
+    const previousValue = e.target.value;
+    const previousStringBeforeCursor = previousValue === '' ? previousValue : previousValue.substring(0, cursorPosition);
     const value = this.props.format ? this.formatNumber(e.target.value) : e.target.value;
 
+    cursorPosition = utils.getCursorPositionAfterFormating(previousStringBeforeCursor, previousValue, value);
+
     if (this.props.value !== undefined) {
-      this.updateFlagFromNumber(value);
-      this.notifyPhoneNumberChange(value);
+      this.setState({
+        cursorPosition,
+      }, () => {
+        this.updateFlagFromNumber(value);
+        this.notifyPhoneNumberChange(value);
+      });
     } else {
       this.setState({
         value,
+        cursorPosition,
       }, () => {
         this.updateFlagFromNumber(value);
         this.notifyPhoneNumberChange(value);
@@ -1170,6 +1181,7 @@ class IntlTelInputApp extends Component {
           autoFocus={ this.props.autoFocus }
           autoComplete={ this.props.autoComplete }
           inputProps={ this.props.telInputProps }
+          cursorPosition={ this.state.cursorPosition }
         />
       </div>
     );
diff --git a/src/components/TelInput.js b/src/components/TelInput.js
index 152cc9185..bfbfab783 100644
--- a/src/components/TelInput.js
+++ b/src/components/TelInput.js
@@ -2,11 +2,26 @@ import React, { Component } from 'react';
 import PropTypes from 'prop-types';
 
 class TelInput extends Component {
+  constructor(props) {
+    super(props);
+
+    this.refHandler = this.refHandler.bind(this);
+  }
+
+  componentDidUpdate() {
+    this.tel.setSelectionRange(this.props.cursorPosition, this.props.cursorPosition);
+  }
+
+  refHandler(element) {
+    this.tel = element;
+    this.props.refCallback(element);
+  }
+
   render() {
     return (
       <input
         { ...this.props.inputProps }
-        ref={ this.props.refCallback }
+        ref={ this.refHandler }
         type="tel"
         autoComplete={ this.props.autoComplete }
         className={ this.props.className }
@@ -38,6 +53,7 @@ TelInput.propTypes = {
   autoComplete: PropTypes.string,
   inputProps: PropTypes.object, // eslint-disable-line react/forbid-prop-types
   refCallback: PropTypes.func.isRequired,
+  cursorPosition: PropTypes.number,
 };
 
 export default TelInput;
diff --git a/src/components/utils.js b/src/components/utils.js
index b07b33fce..c22f21aba 100644
--- a/src/components/utils.js
+++ b/src/components/utils.js
@@ -195,4 +195,44 @@ export default {
 
     return index;
   },
+
+  // Get the location of cursor after formatting is done on the phone number
+  getCursorPositionAfterFormating(prevBeforeCursor, prev, next) {
+    if (prev === next) {
+      return prevBeforeCursor.length;
+    }
+    let cursorShift = 0;
+
+    if (prev.length > next.length) {
+      for (let i = 0, j = 0; i < prevBeforeCursor.length && j < next.length; i += 1) {
+        if (prevBeforeCursor[i] !== next[j]) {
+          if (isNaN(next[j]) && !isNaN(prevBeforeCursor[i])) {
+            i -= 1;
+            j += 1;
+            cursorShift += 1;
+          } else {
+            cursorShift -= 1;
+          }
+        } else {
+          j += 1;
+        }
+      }
+    } else {
+      for (let i = 0, j = 0; i < prevBeforeCursor.length && j < next.length; j += 1) {
+        if (prevBeforeCursor[i] !== next[j]) {
+          if (isNaN(prevBeforeCursor[i]) && !isNaN(next[j])) {
+            j -= 1;
+            i += 1;
+            cursorShift -= 1;
+          } else {
+            cursorShift += 1;
+          }
+        } else {
+          i += 1;
+        }
+      }
+    }
+
+    return prevBeforeCursor.length + cursorShift;
+  }
 };