User tagging and autocompletion

Co-authored-by: William Casarin <jb55@jb55.com>
Changelog-Added: User tagging and autocompletion in posts
Closes: #347
Fixes: #411, #63

damus/ContentView.swift

@@ -302,7 +302,7 @@ struct ContentView: View {
             case .report(let target):
                 MaybeReportView(target: target)
             case .post:
-                PostView(replying_to: nil, references: [])
+                PostView(replying_to: nil, references: [], damus_state: damus_state!)
             case .reply(let event):
                 ReplyView(replying_to: event, damus: damus_state!)
             }

damus/Views/PostView.swift

@@ -16,10 +16,11 @@ let POST_PLACEHOLDER = NSLocalizedString("Type your post here...", comment: "Tex
 
 struct PostView: View {
     @State var post: String = ""
-
-    let replying_to: NostrEvent?
     @FocusState var focus: Bool
+    
+    let replying_to: NostrEvent?
     let references: [ReferencedId]
+    let damus_state: DamusState
 
     @Environment(\.presentationMode) var presentationMode
 
@@ -74,6 +75,7 @@ struct PostView: View {
                 TextEditor(text: $post)
                     .focused($focus)
                     .textInputAutocapitalization(.sentences)
+
                 if post.isEmpty {
                     Text(POST_PLACEHOLDER)
                         .padding(.top, 8)
@@ -82,6 +84,14 @@ struct PostView: View {
                         .allowsHitTesting(false)
                 }
             }
+
+            // This if-block observes @ for tagging
+            if let searching = get_searching_string(post) {
+                VStack {
+                    Spacer()
+                    UserSearch(damus_state: damus_state, search: searching, post: $post)
+                }.zIndex(1)
+            }
         }
         .onAppear() {
             DispatchQueue.main.asyncAfter(deadline: .now() + 0.5) {
@@ -92,3 +102,23 @@ struct PostView: View {
     }
 }
 
+func get_searching_string(_ post: String) -> String? {
+    guard let last_word = post.components(separatedBy: .whitespacesAndNewlines).last else {
+        return nil
+    }
+    
+    guard last_word.count >= 2 else {
+        return nil
+    }
+    
+    guard last_word.first! == "@" else {
+        return nil
+    }
+    
+    // don't include @npub... strings
+    guard last_word.count != 64 else {
+        return nil
+    }
+    
+    return String(last_word.dropFirst())
+}

damus/Views/Posting/UserSearch.swift

@@ -0,0 +1,87 @@
+//
+//  UserAutocompletion.swift
+//  damus
+//
+//  Created by William Casarin on 2023-01-28.
+//
+
+import SwiftUI
+
+struct SearchedUser: Identifiable {
+    let petname: String?
+    let profile: Profile?
+    let pubkey: String
+    
+    var id: String {
+        return pubkey
+    }
+}
+
+struct UserSearch: View {
+    let damus_state: DamusState
+    let search: String
+    @Binding var post: String
+    
+    var users: [SearchedUser] {
+        guard let contacts = damus_state.contacts.event else {
+            return []
+        }
+        
+        return search_users(profiles: damus_state.profiles, tags: contacts.tags, search: search)
+    }
+    
+    var body: some View {
+        ScrollView {
+            LazyVStack {
+                ForEach(users) { user in
+                    UserView(damus_state: damus_state, pubkey: user.pubkey)
+                        .onTapGesture {
+                            guard let pk = bech32_pubkey(user.pubkey) else {
+                                return
+                            }
+                            post = post.replacingOccurrences(of: "@"+search, with: "@"+pk)
+                        }
+                }
+            }
+        }
+    }
+}
+
+struct UserSearch_Previews: PreviewProvider {
+    static let search: String = "jb55"
+    @State static var post: String = "some @jb55"
+    
+    static var previews: some View {
+        UserSearch(damus_state: test_damus_state(), search: search, post: $post)
+    }
+}
+
+
+func search_users(profiles: Profiles, tags: [[String]], search: String) -> [SearchedUser] {
+    var seen_user = Set<String>()
+    return tags.reduce(into: Array<SearchedUser>()) { arr, tag in
+        guard tag.count >= 2 && tag[0] == "p" else {
+            return
+        }
+        
+        let pubkey = tag[1]
+        guard !seen_user.contains(pubkey) else {
+            return
+        }
+        seen_user.insert(pubkey)
+        
+        var petname: String? = nil
+        if tag.count >= 4 {
+            petname = tag[3]
+        }
+        
+        let profile = profiles.lookup(id: pubkey)
+        
+        guard ((petname?.hasPrefix(search) ?? false) || (profile?.name?.hasPrefix(search) ?? false)) else {
+            return
+        }
+        
+        let searched_user = SearchedUser(petname: petname, profile: profile, pubkey: pubkey)
+        arr.append(searched_user)
+    }
+}

damus/Views/ReplyView.swift

@@ -47,7 +47,7 @@ struct ReplyView: View {
             ScrollView {
                 EventView(damus: damus, event: replying_to, has_action_bar: false)
             }
-            PostView(replying_to: replying_to, references: references)
+            PostView(replying_to: replying_to, references: gather_reply_ids(our_pubkey: damus.pubkey, from: replying_to), damus_state: damus)
         }
         .onAppear {
             references =  gather_reply_ids(our_pubkey: damus.pubkey, from: replying_to)