Add unvote feature for posts and comments

Implement the ability to unvote posts and comments within the 1-hour window
that Hacker News allows. The unvote option appears automatically when an
unvote link is available from the server.

Changes:
- Add unvote methods to VoteUseCase protocol
- Implement unvote in PostRepository for posts and comments
- Update VotingState to track unvote availability with canUnvote property
- Add unvote to VotingStateProvider protocol and DefaultVotingStateProvider
- Update VotingViewModel with unvote methods and optimistic UI updates
- Update VoteButton to enable interaction when unvote is available
- Add unvote options to VotingContextMenuItems for posts and comments
- Update PostDisplayView to support unvote with toggle between upvote/unvote
- Add unvote swipe actions and context menus in FeedView
- Add unvote swipe actions and context menus in CommentsView for posts and comments

The feature includes:
- Optimistic UI updates with automatic rollback on error
- Swipe actions (orange arrow.uturn.down icon for unvote)
- Context menu options
- Proper accessibility labels and hints
- Automatic detection of unvote availability based on server response

Author: claude

Data/Sources/Data/PostRepository+Voting.swift

@@ -37,7 +37,23 @@ extension PostRepository {
         if containsLoginForm { throw HackersKitError.unauthenticated }
     }
 
-    // Unvote functionality removed
+    public func unvote(post: Post) async throws {
+        guard let voteLinks = post.voteLinks else { throw HackersKitError.unauthenticated }
+        guard let unvoteURL = voteLinks.unvote else {
+            throw HackersKitError.scraperError
+        }
+
+        let fullURLString = unvoteURL.absoluteString.hasPrefix("http")
+            ? unvoteURL.absoluteString
+            : urlBase + "/" + unvoteURL.absoluteString
+        guard let realURL = URL(string: fullURLString) else { throw HackersKitError.scraperError }
+
+        let response = try await networkManager.get(url: realURL)
+        let containsLoginForm =
+            response.contains("<form action=\"/login") ||
+            response.contains("You have to be logged in")
+        if containsLoginForm { throw HackersKitError.unauthenticated }
+    }
 
     public func upvote(comment: Domain.Comment, for _: Post) async throws {
         guard let voteLinks = comment.voteLinks else { throw HackersKitError.unauthenticated }
@@ -58,7 +74,23 @@ extension PostRepository {
         await MainActor.run { comment.upvoted = true }
     }
 
-    // Unvote functionality removed
+    public func unvote(comment: Domain.Comment, for _: Post) async throws {
+        guard let voteLinks = comment.voteLinks else { throw HackersKitError.unauthenticated }
+        guard let unvoteURL = voteLinks.unvote else {
+            throw HackersKitError.scraperError
+        }
+
+        let fullURLString = unvoteURL.absoluteString.hasPrefix("http")
+            ? unvoteURL.absoluteString
+            : urlBase + "/" + unvoteURL.absoluteString
+        guard let realURL = URL(string: fullURLString) else { throw HackersKitError.scraperError }
+
+        let response = try await networkManager.get(url: realURL)
+        let containsLoginForm = response.contains("<form action=\"/login")
+        if containsLoginForm { throw HackersKitError.unauthenticated }
+
+        await MainActor.run { comment.upvoted = false }
+    }
 
     // MARK: - Vote link extraction
 

DesignSystem/Sources/DesignSystem/Components/PostDisplayView.swift

@@ -16,6 +16,7 @@ public struct PostDisplayView: View {
     let showThumbnails: Bool
     let onThumbnailTap: (() -> Void)?
     let onUpvoteTap: (() async -> Bool)?
+    let onUnvoteTap: (() async -> Bool)?
     let onBookmarkTap: (() async -> Bool)?
     let onCommentsTap: (() -> Void)?
 
@@ -33,6 +34,7 @@ public struct PostDisplayView: View {
         showThumbnails: Bool = true,
         onThumbnailTap: (() -> Void)? = nil,
         onUpvoteTap: (() async -> Bool)? = nil,
+        onUnvoteTap: (() async -> Bool)? = nil,
         onBookmarkTap: (() async -> Bool)? = nil,
         onCommentsTap: (() -> Void)? = nil
     ) {
@@ -42,6 +44,7 @@ public struct PostDisplayView: View {
         self.showThumbnails = showThumbnails
         self.onThumbnailTap = onThumbnailTap
         self.onUpvoteTap = onUpvoteTap
+        self.onUnvoteTap = onUnvoteTap
         self.onBookmarkTap = onBookmarkTap
         self.onCommentsTap = onCommentsTap
         _displayedScore = State(initialValue: post.score)
@@ -125,7 +128,8 @@ public struct PostDisplayView: View {
         let isUpvoted = displayedUpvoted
         let isLoading = isSubmittingUpvote
         let canVote = post.voteLinks?.upvote != nil
-        let canInteract = canVote && !isUpvoted && !isLoading
+        let canUnvote = post.voteLinks?.unvote != nil
+        let canInteract = ((canVote && !isUpvoted) || (canUnvote && isUpvoted)) && !isLoading
         // Avoid keeping a disabled Button so the upvoted state retains the bright tint
         let (backgroundColor, textColor): (Color, Color) = {
             let style = AppColors.PillStyle.upvote(isActive: isUpvoted)
@@ -135,12 +139,19 @@ public struct PostDisplayView: View {
         }()
         let iconName = isUpvoted ? "arrow.up.circle.fill" : "arrow.up"
         let accessibilityLabel: String
+        let accessibilityHint: String
         if isLoading {
             accessibilityLabel = "Submitting vote"
+            accessibilityHint = ""
+        } else if isUpvoted && canUnvote {
+            accessibilityLabel = "\(score) points, upvoted"
+            accessibilityHint = "Double tap to unvote"
         } else if isUpvoted {
             accessibilityLabel = "\(score) points, upvoted"
+            accessibilityHint = ""
         } else {
             accessibilityLabel = "\(score) points"
+            accessibilityHint = "Double tap to upvote"
         }
 
         return pillView(
@@ -149,7 +160,7 @@ public struct PostDisplayView: View {
             textColor: textColor,
             backgroundColor: backgroundColor,
             accessibilityLabel: accessibilityLabel,
-            accessibilityHint: "Double tap to upvote",
+            accessibilityHint: accessibilityHint,
             isHighlighted: isUpvoted,
             isLoading: isLoading,
             isEnabled: canInteract,
@@ -202,22 +213,47 @@ public struct PostDisplayView: View {
     }
 
     private func makeUpvoteAction() -> (() -> Void)? {
-        guard let onUpvoteTap else { return nil }
         return {
             guard !isSubmittingUpvote else { return }
-            isSubmittingUpvote = true
-            let previousScore = displayedScore
-            let previousUpvoted = displayedUpvoted
-            displayedUpvoted = true
-            displayedScore += 1
-            Task {
-                let success = await onUpvoteTap()
-                await MainActor.run {
-                    if !success {
-                        displayedScore = previousScore
-                        displayedUpvoted = previousUpvoted
+
+            let isCurrentlyUpvoted = displayedUpvoted
+            let canUnvote = post.voteLinks?.unvote != nil
+
+            // If already upvoted and can unvote, perform unvote
+            if isCurrentlyUpvoted && canUnvote {
+                guard let onUnvoteTap else { return }
+                isSubmittingUpvote = true
+                let previousScore = displayedScore
+                let previousUpvoted = displayedUpvoted
+                displayedUpvoted = false
+                displayedScore -= 1
+                Task {
+                    let success = await onUnvoteTap()
+                    await MainActor.run {
+                        if !success {
+                            displayedScore = previousScore
+                            displayedUpvoted = previousUpvoted
+                        }
+                        isSubmittingUpvote = false
+                    }
+                }
+            } else {
+                // Perform upvote
+                guard let onUpvoteTap else { return }
+                isSubmittingUpvote = true
+                let previousScore = displayedScore
+                let previousUpvoted = displayedUpvoted
+                displayedUpvoted = true
+                displayedScore += 1
+                Task {
+                    let success = await onUpvoteTap()
+                    await MainActor.run {
+                        if !success {
+                            displayedScore = previousScore
+                            displayedUpvoted = previousUpvoted
+                        }
+                        isSubmittingUpvote = false
                     }
-                    isSubmittingUpvote = false
                 }
             }
         }
@@ -298,31 +334,42 @@ public struct PostDisplayView: View {
 public struct PostContextMenu: View {
     let post: Post
     let onVote: () -> Void
+    let onUnvote: () -> Void
     let onOpenLink: () -> Void
     let onShare: () -> Void
 
     public init(
         post: Post,
         onVote: @escaping () -> Void,
+        onUnvote: @escaping () -> Void = {},
         onOpenLink: @escaping () -> Void,
         onShare: @escaping () -> Void,
     ) {
         self.post = post
         self.onVote = onVote
+        self.onUnvote = onUnvote
         self.onOpenLink = onOpenLink
         self.onShare = onShare
     }
 
     public var body: some View {
         Group {
-            if post.voteLinks?.upvote != nil {
+            if post.voteLinks?.upvote != nil, !post.upvoted {
                 Button {
                     onVote()
                 } label: {
                     Label("Upvote", systemImage: "arrow.up")
                 }
             }
 
+            if post.voteLinks?.unvote != nil, post.upvoted {
+                Button {
+                    onUnvote()
+                } label: {
+                    Label("Unvote", systemImage: "arrow.uturn.down")
+                }
+            }
+
             Divider()
 
             if !isHackerNewsItemURL(post.url) {

DesignSystem/Sources/DesignSystem/Components/VoteButton.swift

@@ -44,11 +44,11 @@ public struct VoteButton: View {
                 }
             }
         }
-        .disabled(!votingState.canVote || votingState.isVoting)
+        .disabled((!votingState.canVote && !votingState.canUnvote) || votingState.isVoting)
         .scaleEffect(votingState.isVoting ? 0.95 : 1.0)
         .animation(.easeInOut(duration: 0.1), value: votingState.isVoting)
-        .accessibilityLabel(votingState.isUpvoted ? "Upvoted" : "Upvote")
-        .accessibilityHint(votingState.isUpvoted ? "Already upvoted" : (votingState.canVote ? "Double-tap to upvote" : "Voting unavailable"))
+        .accessibilityLabel(votingState.isUpvoted && votingState.canUnvote ? "Unvote" : (votingState.isUpvoted ? "Upvoted" : "Upvote"))
+        .accessibilityHint(votingState.isUpvoted && votingState.canUnvote ? "Double-tap to unvote" : (votingState.isUpvoted ? "Already upvoted" : (votingState.canVote ? "Double-tap to upvote" : "Voting unavailable")))
         .accessibilityValue({ () -> String in
             if let score = votingState.score { return "\(score) points" }
             return ""

DesignSystem/Sources/DesignSystem/Components/VotingContextMenuItems.swift

@@ -15,15 +15,24 @@ public enum VotingContextMenuItems {
     public static func postVotingMenuItems(
         for post: Post,
         onVote: @escaping @Sendable () -> Void,
+        onUnvote: @escaping @Sendable () -> Void = {},
     ) -> some View {
-        // Only show upvote if available and not already upvoted
+        // Show upvote if available and not already upvoted
         if post.voteLinks?.upvote != nil, !post.upvoted {
             Button {
                 onVote()
             } label: {
                 Label("Upvote", systemImage: "arrow.up")
             }
         }
+        // Show unvote if available and already upvoted
+        if post.voteLinks?.unvote != nil, post.upvoted {
+            Button {
+                onUnvote()
+            } label: {
+                Label("Unvote", systemImage: "arrow.uturn.down")
+            }
+        }
     }
 
     // MARK: - Comment Voting Menu Items
@@ -32,15 +41,24 @@ public enum VotingContextMenuItems {
     public static func commentVotingMenuItems(
         for comment: Comment,
         onVote: @escaping @Sendable () -> Void,
+        onUnvote: @escaping @Sendable () -> Void = {},
     ) -> some View {
-        // Only show upvote if available and not already upvoted
+        // Show upvote if available and not already upvoted
         if comment.voteLinks?.upvote != nil, !comment.upvoted {
             Button {
                 onVote()
             } label: {
                 Label("Upvote", systemImage: "arrow.up")
             }
         }
+        // Show unvote if available and already upvoted
+        if comment.voteLinks?.unvote != nil, comment.upvoted {
+            Button {
+                onUnvote()
+            } label: {
+                Label("Unvote", systemImage: "arrow.uturn.down")
+            }
+        }
     }
 
     // MARK: - Generic Votable Menu Items
@@ -49,15 +67,24 @@ public enum VotingContextMenuItems {
     public static func votingMenuItems(
         for item: some Votable,
         onVote: @escaping @Sendable () -> Void,
+        onUnvote: @escaping @Sendable () -> Void = {},
     ) -> some View {
-        // Only show upvote if available and not already upvoted
+        // Show upvote if available and not already upvoted
         if item.voteLinks?.upvote != nil, !item.upvoted {
             Button {
                 onVote()
             } label: {
                 Label("Upvote", systemImage: "arrow.up")
             }
         }
+        // Show unvote if available and already upvoted
+        if item.voteLinks?.unvote != nil, item.upvoted {
+            Button {
+                onUnvote()
+            } label: {
+                Label("Unvote", systemImage: "arrow.uturn.down")
+            }
+        }
     }
 }
 
@@ -90,10 +117,11 @@ public extension View {
     func votingContextMenu(
         for item: some Votable,
         onVote: @escaping @Sendable () -> Void,
+        onUnvote: @escaping @Sendable () -> Void = {},
         additionalItems: @escaping () -> some View = { EmptyView() },
     ) -> some View {
         contextMenu {
-            VotingContextMenuItems.votingMenuItems(for: item, onVote: onVote)
+            VotingContextMenuItems.votingMenuItems(for: item, onVote: onVote, onUnvote: onUnvote)
             additionalItems()
         }
     }

Domain/Sources/Domain/Models.swift

@@ -14,19 +14,22 @@ public struct VotingState: Sendable {
     public let isUpvoted: Bool
     public let score: Int?
     public let canVote: Bool
+    public let canUnvote: Bool
     public let isVoting: Bool
     public let error: Error?
 
     public init(
         isUpvoted: Bool,
         score: Int? = nil,
         canVote: Bool,
+        canUnvote: Bool = false,
         isVoting: Bool = false,
         error: Error? = nil,
     ) {
         self.isUpvoted = isUpvoted
         self.score = score
         self.canVote = canVote
+        self.canUnvote = canUnvote
         self.isVoting = isVoting
         self.error = error
     }

Domain/Sources/Domain/VoteUseCase.swift

@@ -10,4 +10,6 @@ import Foundation
 public protocol VoteUseCase: Sendable {
     func upvote(post: Post) async throws
     func upvote(comment: Comment, for post: Post) async throws
+    func unvote(post: Post) async throws
+    func unvote(comment: Comment, for post: Post) async throws
 }