From 89bf5b7144bd752138831b5d5c7c5578a15f19fd Mon Sep 17 00:00:00 2001
From: Prince Yadav <66916296+prince-0408@users.noreply.github.com>
Date: Thu, 2 Apr 2026 01:01:41 +0530
Subject: [PATCH] feat(keyboard): show closest word suggestion on invalid
 command #640

Add didYouMeanSuggestion(for:) helper in CommandVariables that
progressively shortens the input word to find the closest prefix
match in autocomplete_lexicon (minimum 2 chars).

Update all 4 invalid command blocks in KeyboardViewController:
- Return key: translate (uses wordToTranslate global)
- Return key: conjugate (uses verbToConjugate global)
- Translate key with selected text
- Conjugate key with selected text
- Plural key with selected text

Each block shows 'Did you mean: X?' when a close match is found,
falls back to existing invalidCommandMsg when no match exists.
Existing alreadyPlural behavior is untouched.

Closes #640
---
 .../KeyboardViewController.swift              | 26 ++++++++++++++++---
 .../CommandVariables.swift                    | 22 ++++++++++++++++
 2 files changed, 44 insertions(+), 4 deletions(-)

diff --git a/Keyboards/KeyboardsBase/KeyboardViewController.swift b/Keyboards/KeyboardsBase/KeyboardViewController.swift
index 61dfee62..a2d2281c 100644
--- a/Keyboards/KeyboardsBase/KeyboardViewController.swift
+++ b/Keyboards/KeyboardsBase/KeyboardViewController.swift
@@ -2069,7 +2069,13 @@ class KeyboardViewController: UIInputViewController {
                 autoCapAtStartOfProxy()
 
                 if commandState == .invalid {
-                    commandBar.text = commandPromptSpacing + invalidCommandMsgWikidata
+                    // wordToTranslate is set by queryTranslation, verbToConjugate by triggerVerbConjugation.
+                    let failedWord = wordToTranslate.isEmpty ? verbToConjugate : wordToTranslate
+                    if let suggestion = didYouMeanSuggestion(for: failedWord) {
+                        commandBar.text = commandPromptSpacing + suggestion
+                    } else {
+                        commandBar.text = commandPromptSpacing + invalidCommandMsgWikidata
+                    }
                     commandBar.isShowingInfoButton = true
                 } else {
                     commandBar.isShowingInfoButton = false
@@ -2096,7 +2102,11 @@ class KeyboardViewController: UIInputViewController {
                     loadKeys()
                     proxy.insertText(selectedText)
                     autoCapAtStartOfProxy()
-                    commandBar.text = commandPromptSpacing + invalidCommandMsgWiktionary
+                    if let suggestion = didYouMeanSuggestion(for: selectedText) {
+                        commandBar.text = commandPromptSpacing + suggestion
+                    } else {
+                        commandBar.text = commandPromptSpacing + invalidCommandMsgWiktionary
+                    }
                     commandBar.isShowingInfoButton = true
                     commandBar.textColor = keyCharColor
                     return
@@ -2130,7 +2140,11 @@ class KeyboardViewController: UIInputViewController {
                     loadKeys()
                     proxy.insertText(selectedText)
                     autoCapAtStartOfProxy()
-                    commandBar.text = commandPromptSpacing + invalidCommandMsgWikidata
+                    if let suggestion = didYouMeanSuggestion(for: selectedText) {
+                        commandBar.text = commandPromptSpacing + suggestion
+                    } else {
+                        commandBar.text = commandPromptSpacing + invalidCommandMsgWikidata
+                    }
                     commandBar.isShowingInfoButton = true
                     commandBar.textColor = keyCharColor
                     return
@@ -2152,7 +2166,11 @@ class KeyboardViewController: UIInputViewController {
 
                     if commandState == .invalid {
                         proxy.insertText(selectedText)
-                        commandBar.text = commandPromptSpacing + invalidCommandMsgWikidata
+                        if let suggestion = didYouMeanSuggestion(for: selectedText) {
+                            commandBar.text = commandPromptSpacing + suggestion
+                        } else {
+                            commandBar.text = commandPromptSpacing + invalidCommandMsgWikidata
+                        }
                         commandBar.isShowingInfoButton = true
                     } else {
                         commandBar.isShowingInfoButton = false
diff --git a/Keyboards/KeyboardsBase/ScribeFunctionality/CommandVariables.swift b/Keyboards/KeyboardsBase/ScribeFunctionality/CommandVariables.swift
index 43778e4f..6de2e0e4 100644
--- a/Keyboards/KeyboardsBase/ScribeFunctionality/CommandVariables.swift
+++ b/Keyboards/KeyboardsBase/ScribeFunctionality/CommandVariables.swift
@@ -182,3 +182,25 @@ var alreadyPluralMsg = ""
 
 /// The message shown on the download data button when no language data has been downloaded.
 var downloadDataMsg = "Please download language data"
+
+/// Returns a "Did you mean: X?" suggestion string for an invalid command input.
+/// Progressively shortens the word to find the closest prefix match in the autocomplete lexicon.
+///
+/// - Parameter word: the word that was not found.
+/// - Returns: a suggestion string, or nil if no close match exists.
+func didYouMeanSuggestion(for word: String) -> String? {
+    guard !word.isEmpty else { return nil }
+
+    // Try progressively shorter prefixes (minimum 2 chars) to find a close match.
+    var prefix = word.lowercased()
+    while prefix.count >= 2 {
+        let suggestions = LanguageDBManager.shared.queryAutocompletions(word: prefix)
+        if let first = suggestions.first, !first.isEmpty {
+            // Only suggest if it's actually different from what was typed.
+            guard first.lowercased() != word.lowercased() else { return nil }
+            return "Did you mean: \(first)?"
+        }
+        prefix = String(prefix.dropLast())
+    }
+    return nil
+}