From 23b8a47cad088e69be12e38790b7c6878ae76b13 Mon Sep 17 00:00:00 2001
From: Rajdeep Kwatra <rajkwatra@gmail.com>
Date: Fri, 19 Jul 2024 22:14:02 +1000
Subject: [PATCH] Added helper function to enumerate over continuous ranges of
 an attribute ignoring difference in value

---
 .../Helpers/NSAttributedString+Content.swift  | 34 +++++++++++++++++++
 .../NSAttributedStringExtensionTests.swift    | 12 +++++++
 2 files changed, 46 insertions(+)

diff --git a/Proton/Sources/Swift/Helpers/NSAttributedString+Content.swift b/Proton/Sources/Swift/Helpers/NSAttributedString+Content.swift
index 80877c6a..87e3b980 100644
--- a/Proton/Sources/Swift/Helpers/NSAttributedString+Content.swift
+++ b/Proton/Sources/Swift/Helpers/NSAttributedString+Content.swift
@@ -54,6 +54,40 @@ public extension NSAttributedString {
         }
         return string.makeNSRange(from: range)
     }
+
+    /// Enumerates over continuous ranges of text based on the presence or absence of a specified attribute.
+    /// - Parameters:
+    ///   - attributeName: The name of the attribute to check for presence or absence.
+    ///   - range: The range within the attributed string to enumerate. Defaults to the entire string.
+    ///   - using: The block to apply to continuous ranges, indicating whether the attribute was present or absent for the range.
+    func enumerateContinuousRangesByAttribute(_ attributeName: NSAttributedString.Key, in range: NSRange? = nil, using block: (_ isPresent: Bool, _ range: NSRange) -> Void) {
+        let enumerationRange = range ?? NSRange(location: 0, length: self.length)
+        var lastRange: NSRange? = nil
+        var attributeWasPresentInLastRange = false
+        
+        self.enumerateAttributes(in: enumerationRange, options: []) { attributes, currentRange, _ in
+            let attributeIsPresent = attributes[attributeName] != nil
+            if let lastRangeUnwrapped = lastRange {
+                if attributeWasPresentInLastRange != attributeIsPresent {
+                    // Process the last range if the attribute presence state changes
+                    block(attributeWasPresentInLastRange, lastRangeUnwrapped)
+                    lastRange = currentRange
+                } else {
+                    // Extend the last range efficiently if the state hasn't changed
+                    lastRange = NSRange(location: lastRangeUnwrapped.location, length: NSMaxRange(currentRange) - lastRangeUnwrapped.location)
+                }
+            } else {
+                // Initialize with the first range
+                lastRange = currentRange
+            }
+            attributeWasPresentInLastRange = attributeIsPresent
+        }
+        
+        // Process the final range after enumeration
+        if let lastRangeUnwrapped = lastRange {
+            block(attributeWasPresentInLastRange, lastRangeUnwrapped)
+        }
+    }
 }
 
 extension NSAttributedString {
diff --git a/Proton/Tests/ExtensionTests/NSAttributedStringExtensionTests.swift b/Proton/Tests/ExtensionTests/NSAttributedStringExtensionTests.swift
index 5b1668ab..801a32b3 100644
--- a/Proton/Tests/ExtensionTests/NSAttributedStringExtensionTests.swift
+++ b/Proton/Tests/ExtensionTests/NSAttributedStringExtensionTests.swift
@@ -218,4 +218,16 @@ class NSAttributedStringExtensionTests: XCTestCase {
         let range = text.reverseRange(of: "isx", startingLocation: text.length - 1)
         XCTAssertNil(range)
     }
+
+    func testEnumeratesIgnoringValue() {
+        let text = NSMutableAttributedString(string: "This is a test string", attributes: [.inlineContentType: "a"])
+        text.append(NSAttributedString(string: " Some more text", attributes: [.inlineContentType: "b"]))
+        text.append(NSAttributedString(string: " And more text", attributes: [.inlineContentType: "c"]))
+        text.append(NSAttributedString(string: "Not with attribute", attributes: [:]))
+        text.append(NSAttributedString(string: "Again with attribute", attributes: [.inlineContentType: "c"]))
+
+        text.enumerateContinuousRangesByAttribute(.inlineContentType) { isPresent, range in
+            print("\(text.substring(from: range)) - \(isPresent)")
+        }
+    }
 }