From 822db3b0f22ea1e8b13c9ec7258d0695373ffa5b Mon Sep 17 00:00:00 2001
From: Kyle <kyle201817146@gmail.com>
Date: Wed, 17 May 2023 01:39:25 +0800
Subject: [PATCH] Add delete highlights

---
 .../Rendering/References/FileReference.swift   |  8 +++++++-
 .../Model/Rendering/RenderNodeTranslator.swift |  1 +
 .../Rendering/Tutorial/LineHighlighter.swift   | 18 ++++++++++++++----
 3 files changed, 22 insertions(+), 5 deletions(-)

diff --git a/Sources/SwiftDocC/Model/Rendering/References/FileReference.swift b/Sources/SwiftDocC/Model/Rendering/References/FileReference.swift
index e43a7a456a..d34668aea9 100644
--- a/Sources/SwiftDocC/Model/Rendering/References/FileReference.swift
+++ b/Sources/SwiftDocC/Model/Rendering/References/FileReference.swift
@@ -39,6 +39,9 @@ public struct FileReference: RenderReference, Equatable {
     /// The line highlights for this file.
     public var highlights: [LineHighlighter.Highlight] = []
     
+    /// The delete line highlights for this file.
+    public var deleteHighlights: [LineHighlighter.Highlight] = []
+    
     /// Creates a new file reference.
     ///
     /// - Parameters:
@@ -54,7 +57,8 @@ public struct FileReference: RenderReference, Equatable {
         fileType: String,
         syntax: String,
         content: [String],
-        highlights: [LineHighlighter.Highlight] = []
+        highlights: [LineHighlighter.Highlight] = [],
+        deleteHighlights: [LineHighlighter.Highlight] = []
     ) {
         self.identifier = identifier
         self.fileName = fileName
@@ -62,6 +66,7 @@ public struct FileReference: RenderReference, Equatable {
         self.syntax = syntax
         self.content = content
         self.highlights = highlights
+        self.deleteHighlights = deleteHighlights
     }
     
     public init(from decoder: Decoder) throws {
@@ -73,6 +78,7 @@ public struct FileReference: RenderReference, Equatable {
         syntax = try values.decode(String.self, forKey: .syntax)
         content = try values.decode([String].self, forKey: .content)
         highlights = try values.decodeIfPresent([LineHighlighter.Highlight].self, forKey: .highlights) ?? []
+        deleteHighlights = (try? values.decodeIfPresent([LineHighlighter.Highlight].self, forKey: .deleteHighlights)) ?? []
     }
 }
 
diff --git a/Sources/SwiftDocC/Model/Rendering/RenderNodeTranslator.swift b/Sources/SwiftDocC/Model/Rendering/RenderNodeTranslator.swift
index b3812146b9..f1ed3046ad 100644
--- a/Sources/SwiftDocC/Model/Rendering/RenderNodeTranslator.swift
+++ b/Sources/SwiftDocC/Model/Rendering/RenderNodeTranslator.swift
@@ -129,6 +129,7 @@ public struct RenderNodeTranslator: SemanticVisitor {
         // Add the highlights to the file references.
         for result in highlightsPerFile {
             fileReferences[result.file.path]?.highlights = result.highlights
+            fileReferences[result.file.path]?.deleteHighlights = result.deleteHighlights
         }
         
         return TutorialSectionsRenderSection.Section(title: tutorialSection.title, contentSection: introduction, stepsSection: stepsContent, anchor: urlReadableFragment(tutorialSection.title))
diff --git a/Sources/SwiftDocC/Model/Rendering/Tutorial/LineHighlighter.swift b/Sources/SwiftDocC/Model/Rendering/Tutorial/LineHighlighter.swift
index f3a6c720d2..52757164fe 100644
--- a/Sources/SwiftDocC/Model/Rendering/Tutorial/LineHighlighter.swift
+++ b/Sources/SwiftDocC/Model/Rendering/Tutorial/LineHighlighter.swift
@@ -56,6 +56,9 @@ public struct LineHighlighter {
         
         /// The highlights to apply when displaying this file.
         let highlights: [Highlight]
+        
+        /// The delete highlights to apply when displaying this file.
+        let deleteHighlights: [Highlight]
     }
     
     /**
@@ -121,7 +124,7 @@ public struct LineHighlighter {
     private func lineHighlights(old: ResourceReference, new: ResourceReference) -> Result {
         // Retrieve the contents of the current file and the file we're comparing against.
         guard let oldLines = lines(of: old), let newLines = lines(of: new) else {
-            return Result(file: new, highlights: [])
+            return Result(file: new, highlights: [], deleteHighlights: [])
         }
 
         let diff = newLines.difference(from: oldLines)
@@ -134,14 +137,21 @@ public struct LineHighlighter {
             return Highlight(line: offset + 1)
         }
         
-        return Result(file: new, highlights: highlights)
+        let deleteHighlights = diff.removals.compactMap { removal -> Highlight? in
+            guard case .remove(let offset, _, _) = removal else { return nil }
+            // Use 1-based indexing for line numbers.
+            // TODO: Collect intra-line diffs.
+            return Highlight(line: offset + 1)
+        }
+        
+        return Result(file: new, highlights: highlights, deleteHighlights: deleteHighlights)
     }
     
     /// Returns the line highlights between two ``Code`` elements.
     private func lineHighlights(old: Code?, new: Code) -> Result {
         if let previousFileOverride = new.previousFileReference {
             guard !new.shouldResetDiff else {
-                return Result(file: new.fileReference, highlights: [])
+                return Result(file: new.fileReference, highlights: [], deleteHighlights: [])
             }
             return lineHighlights(old: previousFileOverride, new: new.fileReference)
         }
@@ -149,7 +159,7 @@ public struct LineHighlighter {
         guard let old = old,
             old.fileName == new.fileName,
             !new.shouldResetDiff else {
-                return Result(file: new.fileReference, highlights: [])
+                return Result(file: new.fileReference, highlights: [], deleteHighlights: [])
         }
         
         return lineHighlights(old: old.fileReference, new: new.fileReference)