From 9a138c98a1ec65d57f593f8f091f1cf3768db716 Mon Sep 17 00:00:00 2001
From: Nikita Barsukov <nikita.s.barsukov@gmail.com>
Date: Mon, 17 Jun 2024 18:29:42 +0300
Subject: [PATCH] fix(kit): move caret after attempt to erase fixed character
 in a mask with `Placeholder`

---
 .../tests/recipes/placeholder/us-phone.cy.ts  | 53 +++++++++++++++++++
 .../src/lib/processors/with-placeholder.ts    | 30 ++++++++---
 2 files changed, 75 insertions(+), 8 deletions(-)

diff --git a/projects/demo-integrations/src/tests/recipes/placeholder/us-phone.cy.ts b/projects/demo-integrations/src/tests/recipes/placeholder/us-phone.cy.ts
index c90ebc3ca..2a355527a 100644
--- a/projects/demo-integrations/src/tests/recipes/placeholder/us-phone.cy.ts
+++ b/projects/demo-integrations/src/tests/recipes/placeholder/us-phone.cy.ts
@@ -79,4 +79,57 @@ describe('Placeholder | US phone', () => {
             .blur()
             .should('have.value', '');
     });
+
+    describe('caret navigation on attempt to erase fixed character', () => {
+        beforeEach(() => {
+            cy.get('@input')
+                .type('2125552')
+                .should('have.value', '+1 (212) 555-2___')
+                .should('have.prop', 'selectionStart', '+1 (212) 555-2'.length)
+                .should('have.prop', 'selectionEnd', '+1 (212) 555-2'.length);
+        });
+
+        it('+1 (212) 555-|2___ => Backspace => +1 (212) 555|-2___', () => {
+            cy.get('@input')
+                .type('{leftArrow}{backspace}')
+                .should('have.value', '+1 (212) 555-2___')
+                .should('have.prop', 'selectionStart', '+1 (212) 555'.length)
+                .should('have.prop', 'selectionEnd', '+1 (212) 555'.length);
+        });
+
+        it('+1 (212) 555|-2___ => Delete => +1 (212) 555-|2___', () => {
+            cy.get('@input')
+                .type('{leftArrow}'.repeat(2))
+                .should('have.prop', 'selectionStart', '+1 (212) 555'.length)
+                .should('have.prop', 'selectionEnd', '+1 (212) 555'.length)
+                .type('{del}')
+                .should('have.value', '+1 (212) 555-2___')
+                .should('have.prop', 'selectionStart', '+1 (212) 555-'.length)
+                .should('have.prop', 'selectionEnd', '+1 (212) 555-'.length);
+        });
+
+        it('+1 (212) |555-2___ => Backspace x2 => +1 (212|) 555-2___', () => {
+            cy.get('@input')
+                .type('{leftArrow}'.repeat('555-2'.length))
+                .type('{backspace}')
+                .should('have.value', '+1 (212) 555-2___')
+                .should('have.prop', 'selectionStart', '+1 (212)'.length)
+                .should('have.prop', 'selectionEnd', '+1 (212)'.length)
+                .type('{backspace}')
+                .should('have.value', '+1 (212) 555-2___')
+                .should('have.prop', 'selectionStart', '+1 (212'.length)
+                .should('have.prop', 'selectionEnd', '+1 (212'.length);
+        });
+
+        it('+1 (212|) 555-2___ => Delete => +1 (212) |555-2___', () => {
+            cy.get('@input')
+                .type('{leftArrow}'.repeat(') 555-2'.length))
+                .should('have.prop', 'selectionStart', '+1 (212'.length)
+                .should('have.prop', 'selectionEnd', '+1 (212'.length)
+                .type('{del}')
+                .should('have.value', '+1 (212) 555-2___')
+                .should('have.prop', 'selectionStart', '+1 (212) '.length)
+                .should('have.prop', 'selectionEnd', '+1 (212) '.length);
+        });
+    });
 });
diff --git a/projects/kit/src/lib/processors/with-placeholder.ts b/projects/kit/src/lib/processors/with-placeholder.ts
index 2c2dd6845..8829420ab 100644
--- a/projects/kit/src/lib/processors/with-placeholder.ts
+++ b/projects/kit/src/lib/processors/with-placeholder.ts
@@ -1,4 +1,4 @@
-import type {MaskitoOptions} from '@maskito/core';
+import type {MaskitoOptions, MaskitoPreprocessor} from '@maskito/core';
 import {maskitoUpdateElement} from '@maskito/core';
 
 import {maskitoCaretGuard, maskitoEventHandler} from '../plugins';
@@ -10,6 +10,7 @@ export function maskitoWithPlaceholder(
     removePlaceholder: (value: string) => string;
 } {
     let lastClearValue = '';
+    let action: Parameters<MaskitoPreprocessor>[1] = 'validation';
     const removePlaceholder = (value: string): string => {
         for (let i = value.length - 1; i >= lastClearValue.length; i--) {
             if (value[i] !== placeholder[i]) {
@@ -52,7 +53,8 @@ export function maskitoWithPlaceholder(
         plugins,
         removePlaceholder,
         preprocessors: [
-            ({elementState, data}) => {
+            ({elementState, data}, actionType) => {
+                action = actionType;
                 const {value, selection} = elementState;
 
                 return {
@@ -76,12 +78,24 @@ export function maskitoWithPlaceholder(
                  * For example, developer wants to remove manually placeholder (+ do something else with value) on blur.
                  * Without this condition, placeholder will be unexpectedly added again.
                  */
-                return value !== initialElementState.value && (focused || !focusedOnly)
-                    ? {
-                          value: value + placeholder.slice(value.length),
-                          selection,
-                      }
-                    : {value, selection};
+                const newValue =
+                    value !== initialElementState.value && (focused || !focusedOnly)
+                        ? value + placeholder.slice(value.length)
+                        : value;
+
+                if (
+                    newValue === initialElementState.value &&
+                    action === 'deleteBackward'
+                ) {
+                    const [caretIndex] = initialElementState.selection;
+
+                    return {
+                        value: newValue,
+                        selection: [caretIndex, caretIndex],
+                    };
+                }
+
+                return {value: newValue, selection};
             },
         ],
     };