From ba48adb470c4668ec53db96605e71636be5511f5 Mon Sep 17 00:00:00 2001
From: CMK <cirno.mainasuk@gmail.com>
Date: Thu, 8 Apr 2021 16:27:26 +0800
Subject: [PATCH] chore: make favorite and hashtag scene use next page token
 from response header

---
 ...tagTimelineViewModel+LoadOldestState.swift | 17 ++++++++--
 .../Favorite/FavoriteViewModel+State.swift    | 19 +++++++++--
 .../Response/Mastodon+Response+Content.swift  | 34 +++++++++++++++++++
 3 files changed, 64 insertions(+), 6 deletions(-)

diff --git a/Mastodon/Scene/HashtagTimeline/HashtagTimelineViewModel+LoadOldestState.swift b/Mastodon/Scene/HashtagTimeline/HashtagTimelineViewModel+LoadOldestState.swift
index d0607550e..e5c78f3d5 100644
--- a/Mastodon/Scene/HashtagTimeline/HashtagTimelineViewModel+LoadOldestState.swift
+++ b/Mastodon/Scene/HashtagTimeline/HashtagTimelineViewModel+LoadOldestState.swift
@@ -35,6 +35,8 @@ extension HashtagTimelineViewModel.LoadOldestState {
     }
     
     class Loading: HashtagTimelineViewModel.LoadOldestState {
+        var maxID: String?
+        
         override func isValidNextState(_ stateClass: AnyClass) -> Bool {
             return stateClass == Fail.self || stateClass == Idle.self || stateClass == NoMore.self
         }
@@ -54,7 +56,7 @@ extension HashtagTimelineViewModel.LoadOldestState {
             }
             
             // TODO: only set large count when using Wi-Fi
-            let maxID = last.id
+            let maxID = self.maxID ?? last.id
             viewModel.context.apiService.hashtagTimeline(
                 domain: activeMastodonAuthenticationBox.domain,
                 maxID: maxID,
@@ -71,10 +73,19 @@ extension HashtagTimelineViewModel.LoadOldestState {
                         // handle isFetchingLatestTimeline in fetch controller delegate
                         break
                     }
-                } receiveValue: { response in
+                } receiveValue: { [weak self] response in
+                    guard let self = self else { return }
+                    
                     let statuses = response.value
                     // enter no more state when no new statuses
-                    if statuses.isEmpty || (statuses.count == 1 && statuses[0].id == maxID) {
+                    
+                    let hasNextPage: Bool = {
+                        guard let link = response.link else { return true }     // assert has more when link invalid
+                        return link.maxID != nil
+                    }()
+                    self.maxID = response.link?.maxID
+                    
+                    if !hasNextPage || statuses.isEmpty || (statuses.count == 1 && statuses[0].id == maxID) {
                         stateMachine.enter(NoMore.self)
                     } else {
                         stateMachine.enter(Idle.self)
diff --git a/Mastodon/Scene/Profile/Favorite/FavoriteViewModel+State.swift b/Mastodon/Scene/Profile/Favorite/FavoriteViewModel+State.swift
index 134adb0a3..c4420e88b 100644
--- a/Mastodon/Scene/Profile/Favorite/FavoriteViewModel+State.swift
+++ b/Mastodon/Scene/Profile/Favorite/FavoriteViewModel+State.swift
@@ -92,6 +92,9 @@ extension FavoriteViewModel.State {
     }
     
     class Loading: FavoriteViewModel.State {
+        
+        var maxID: String?
+        
         override func isValidNextState(_ stateClass: AnyClass) -> Bool {
             switch stateClass {
             case is Fail.Type:
@@ -113,8 +116,11 @@ extension FavoriteViewModel.State {
                 stateMachine.enter(Fail.self)
                 return
             }
-            
-            let maxID = viewModel.statusFetchedResultsController.statusIDs.value.last
+            if previousState is Reloading {
+                maxID = nil
+            }
+            // prefer use `maxID` token in response header
+            // let maxID = viewModel.statusFetchedResultsController.statusIDs.value.last
             
             viewModel.context.apiService.favoritedStatuses(
                 maxID: maxID,
@@ -139,8 +145,15 @@ extension FavoriteViewModel.State {
                     statusIDs.append(status.id)
                     hasNewStatusesAppend = true
                 }
+                
+                self.maxID = response.link?.maxID
+                
+                let hasNextPage: Bool = {
+                    guard let link = response.link else { return true }     // assert has more when link invalid
+                    return link.maxID != nil
+                }()
 
-                if hasNewStatusesAppend {
+                if hasNewStatusesAppend && hasNextPage {
                     stateMachine.enter(Idle.self)
                 } else {
                     stateMachine.enter(NoMore.self)
diff --git a/MastodonSDK/Sources/MastodonSDK/Response/Mastodon+Response+Content.swift b/MastodonSDK/Sources/MastodonSDK/Response/Mastodon+Response+Content.swift
index a74d0fcaa..9c39615f9 100644
--- a/MastodonSDK/Sources/MastodonSDK/Response/Mastodon+Response+Content.swift
+++ b/MastodonSDK/Sources/MastodonSDK/Response/Mastodon+Response+Content.swift
@@ -18,6 +18,7 @@ extension Mastodon.Response {
         
         // application fields
         public let rateLimit: RateLimit?
+        public let link: Link?
         public let responseTime: Int?
         
         public var networkDate: Date {
@@ -33,6 +34,11 @@ extension Mastodon.Response {
             }()
             
             self.rateLimit = RateLimit(response: response)
+            self.link = {
+                guard let string = (response as? HTTPURLResponse)?.value(forHTTPHeaderField: "link") else { return nil }
+                return Link(link: string)
+            }()
+             
             self.responseTime = {
                 guard let string = (response as? HTTPURLResponse)?.value(forHTTPHeaderField: "x-response-time") else { return nil }
                 return Int(string)
@@ -43,6 +49,7 @@ extension Mastodon.Response {
             self.value = value
             self.date = old.date
             self.rateLimit = old.rateLimit
+            self.link = old.link
             self.responseTime = old.responseTime
         }
         
@@ -90,3 +97,30 @@ extension Mastodon.Response {
         
     }
 }
+
+extension Mastodon.Response {
+    public struct Link {
+        public let maxID: Mastodon.Entity.Status.ID?
+        public let minID: Mastodon.Entity.Status.ID?
+        
+        init(link: String) {
+            self.maxID = {
+                guard let regex = try? NSRegularExpression(pattern: "max_id=([[:digit:]]+)", options: []) else { return nil }
+                let results = regex.matches(in: link, options: [], range: NSRange(link.startIndex..<link.endIndex, in: link))
+                guard let match = results.first else { return nil }
+                guard let range = Range(match.range(at: 1), in: link) else { return nil }
+                let id = link[range]
+                return String(id)
+            }()
+            
+            self.minID = {
+                guard let regex = try? NSRegularExpression(pattern: "min_id=([[:digit:]]+)", options: []) else { return nil }
+                let results = regex.matches(in: link, options: [], range: NSRange(link.startIndex..<link.endIndex, in: link))
+                guard let match = results.first else { return nil }
+                guard let range = Range(match.range(at: 1), in: link) else { return nil }
+                let id = link[range]
+                return String(id)
+            }()
+        }
+    }
+}