filters: generalize ContentFilter

This simplifies our content filters so that it is a bit more flexible
for future additions.

Fixes: 0957cc896cc8 ("Add "Do not show #nsfw tagged posts" setting")

damus/ContentView.swift

@@ -82,12 +82,7 @@ struct ContentView: View {
     @StateObject var navigationCoordinator: NavigationCoordinator = NavigationCoordinator()
     @AppStorage("has_seen_suggested_users") private var hasSeenSuggestedUsers = false
     let sub_id = UUID().description
-    var damus_filter: DamusFilter {
-        get {
-            return DamusFilter(hide_nsfw_tagged_content: self.damus_state?.settings.hide_nsfw_tagged_content ?? true)
-        }
-    }
-    
+
     @Environment(\.colorScheme) var colorScheme
     
     // connect retry timer
@@ -97,7 +92,13 @@ struct ContentView: View {
         Text("Are you lost?", comment: "Text asking the user if they are lost in the app.")
         .id("what")
     }
-    
+
+    func content_filter(_ fstate: FilterState) -> ((NostrEvent) -> Bool) {
+        var filters = ContentFilters.defaults(damus_state!.settings)
+        filters.append(fstate.filter)
+        return ContentFilters(filters: filters).filter
+    }
+
     var PostingTimelineView: some View {
         VStack {
             ZStack {
@@ -105,10 +106,10 @@ struct ContentView: View {
                     // This is needed or else there is a bug when switching from the 3rd or 2nd tab to first. no idea why.
                     mystery
                     
-                    contentTimelineView(filter: damus_filter.get_filter(.posts))
+                    contentTimelineView(filter: content_filter(.posts))
                         .tag(FilterState.posts)
                         .id(FilterState.posts)
-                    contentTimelineView(filter: damus_filter.get_filter(.posts_and_replies))
+                    contentTimelineView(filter: content_filter(.posts_and_replies))
                         .tag(FilterState.posts_and_replies)
                         .id(FilterState.posts_and_replies)
                 }

damus/Models/ContentFilters.swift

@@ -7,15 +7,9 @@
 
 import Foundation
 
-protocol ContentFilter {
-    /// Function that implements the content filtering logic
-    /// - Parameter ev: The nostr event to be processed
-    /// - Returns: Must return `true` to show events, and return `false` to hide/filter events
-    func filter(ev: NostrEvent) -> Bool
-}
 
 /// Simple filter to determine whether to show posts or all posts and replies.
-enum FilterState : Int, ContentFilter {
+enum FilterState : Int {
     case posts_and_replies = 1
     case posts = 0
 
@@ -30,29 +24,31 @@ enum FilterState : Int, ContentFilter {
 }
 
 /// Simple filter to determine whether to show posts with #nsfw tags
-struct NSFWTagFilter: ContentFilter {
-    func filter(ev: NostrEvent) -> Bool {
+func nsfw_tag_filter(ev: NostrEvent) -> Bool {
         return ev.referenced_hashtags.first(where: { t in t.hashtag == "nsfw" }) == nil
-    }
 }
 
 /// Generic filter with various tweakable settings
-struct DamusFilter: ContentFilter {
-    let hide_nsfw_tagged_content: Bool
-    
+struct ContentFilters {
+    var filters: [(NostrEvent) -> Bool]
+
     func filter(ev: NostrEvent) -> Bool {
-        if self.hide_nsfw_tagged_content {
-            return NSFWTagFilter().filter(ev: ev)
-        }
-        else {
-            return true
+        for filter in filters {
+            if !filter(ev) {
+                return false
+            }
         }
+
+        return true
+    }
+}
+
+extension ContentFilters {
+    static func defaults(_ settings: UserSettingsStore) -> [(NostrEvent) -> Bool] {
+        var filters = Array<(NostrEvent) -> Bool>()
+        if settings.hide_nsfw_tagged_content {
+            filters.append(nsfw_tag_filter)
+        }
+        return filters
     }
-    
-    func get_filter(_ filter_state: FilterState) -> ((NostrEvent) -> Bool) {
-        return { ev in
-            return filter_state.filter(ev: ev) && self.filter(ev: ev)
-        }
-    }
-    
 }

damus/Views/SearchHomeView.swift

@@ -14,10 +14,10 @@ struct SearchHomeView: View {
     @StateObject var model: SearchHomeModel
     @State var search: String = ""
     @FocusState private var isFocused: Bool
-    var damus_filter: DamusFilter {
-        get {
-            return DamusFilter(hide_nsfw_tagged_content: self.damus_state.settings.hide_nsfw_tagged_content)
-        }
+
+    var content_filter: (NostrEvent) -> Bool {
+        let filters = ContentFilters.defaults(self.damus_state.settings)
+        return ContentFilters(filters: filters).filter
     }
 
     let preferredLanguages = Set(Locale.preferredLanguages.map { localeToLanguage($0) })
@@ -55,7 +55,7 @@ struct SearchHomeView: View {
             damus: damus_state,
             show_friend_icon: true,
             filter: { ev in
-                if !damus_filter.filter(ev: ev) {
+                if !content_filter(ev) {
                     return false
                 }