fix(macOS): unify find/replace match scanning with highlight logic

macOS/SynapseNotes/EditorView.swift

@@ -2655,21 +2655,33 @@ class LinkAwareTextView: NSTextView {
         }
     }
 
-    private func applySearchHighlights(query: String, focusIndex: Int) {
-        guard let storage = textStorage, !query.isEmpty else {
-            clearSearchHighlights()
-            return
-        }
-        let content = storage.string
-        let needle = query.lowercased()
+    /// Non-overlapping UTF-16 `NSRange`s of `query` in `content` using a single case-folding
+    /// strategy (`.caseInsensitive`). Shared by find highlights, Replace All, and next-match so
+    /// the UI never disagrees with what replace operations will touch.
+    internal static func caseInsensitiveNonOverlappingMatchRanges(
+        in content: String,
+        query: String,
+        maxCount: Int? = nil
+    ) -> [NSRange] {
+        guard !query.isEmpty else { return [] }
         var matches: [NSRange] = []
         var searchStart = content.startIndex
         while searchStart < content.endIndex,
-              let range = content.range(of: needle, options: .caseInsensitive, range: searchStart..<content.endIndex) {
+              let range = content.range(of: query, options: .caseInsensitive, range: searchStart..<content.endIndex) {
             matches.append(NSRange(range, in: content))
             searchStart = range.upperBound
-            if matches.count > 2000 { break }
+            if let maxCount, matches.count >= maxCount { break }
         }
+        return matches
+    }
+
+    private func applySearchHighlights(query: String, focusIndex: Int) {
+        guard let storage = textStorage, !query.isEmpty else {
+            clearSearchHighlights()
+            return
+        }
+        let content = storage.string
+        let matches = Self.caseInsensitiveNonOverlappingMatchRanges(in: content, query: query, maxCount: 2000)
 
         let dimHighlight = NSColor.yellow.withAlphaComponent(0.30)
         let focusHighlight = NSColor.yellow
@@ -2740,13 +2752,7 @@ class LinkAwareTextView: NSTextView {
     private func replaceAllMatches(query: String, replacement: String) {
         guard !query.isEmpty, let storage = textStorage else { return }
         let content = storage.string
-        var matches: [NSRange] = []
-        var searchStart = content.startIndex
-        while searchStart < content.endIndex,
-              let r = content.range(of: query, options: .caseInsensitive, range: searchStart..<content.endIndex) {
-            matches.append(NSRange(r, in: content))
-            searchStart = r.upperBound
-        }
+        let matches = Self.caseInsensitiveNonOverlappingMatchRanges(in: content, query: query, maxCount: nil)
         guard !matches.isEmpty else { return }
 
         // Build the post-replace string in one shot, then ask the delegate to permit a
@@ -2773,14 +2779,7 @@ class LinkAwareTextView: NSTextView {
     private func nextMatchIndex(forQuery query: String, after location: Int) -> Int {
         guard let storage = textStorage else { return 0 }
         let content = storage.string
-        var matches: [NSRange] = []
-        var searchStart = content.startIndex
-        while searchStart < content.endIndex,
-              let r = content.range(of: query, options: .caseInsensitive, range: searchStart..<content.endIndex) {
-            matches.append(NSRange(r, in: content))
-            searchStart = r.upperBound
-            if matches.count > 2000 { break }
-        }
+        let matches = Self.caseInsensitiveNonOverlappingMatchRanges(in: content, query: query, maxCount: 2000)
         if matches.isEmpty { return 0 }
         if let idx = matches.firstIndex(where: { $0.location >= location }) {
             return idx

macOS/SynapseNotesTests/LinkAwareTextViewFindMatchRangesTests.swift

@@ -0,0 +1,34 @@
+import XCTest
+@testable import Synapse
+
+/// `LinkAwareTextView.caseInsensitiveNonOverlappingMatchRanges` must stay aligned with find
+/// highlights and replace-all so ranges never disagree for the same query and body text.
+final class LinkAwareTextViewFindMatchRangesTests: XCTestCase {
+
+    func test_emptyQuery_returnsNoRanges() {
+        let ranges = LinkAwareTextView.caseInsensitiveNonOverlappingMatchRanges(
+            in: "hello world",
+            query: "",
+            maxCount: nil
+        )
+        XCTAssertTrue(ranges.isEmpty)
+    }
+
+    func test_caseInsensitive_findsAllNonOverlapping() {
+        let ranges = LinkAwareTextView.caseInsensitiveNonOverlappingMatchRanges(
+            in: "Aa aa AA",
+            query: "aA",
+            maxCount: nil
+        )
+        XCTAssertEqual(ranges.count, 3)
+    }
+
+    func test_maxCount_stopsAfterFirst() {
+        let ranges = LinkAwareTextView.caseInsensitiveNonOverlappingMatchRanges(
+            in: "foo Foo FOO",
+            query: "foo",
+            maxCount: 1
+        )
+        XCTAssertEqual(ranges.count, 1)
+    }
+}