ui: add follow hashtag ui on search view

damus/Components/Search/SearchHeaderView.swift

@@ -0,0 +1,134 @@
+//
+//  SearchIconView.swift
+//  damus
+//
+//  Created by William Casarin on 2023-07-12.
+//
+
+import SwiftUI
+
+struct SearchHeaderView: View {
+    let state: DamusState
+    let described: DescribedSearch
+    @State var is_following: Bool
+
+    init(state: DamusState, described: DescribedSearch) {
+        self.state = state
+        self.described = described
+
+        let is_following = (described.is_hashtag.map {
+            ht in is_following_hashtag(contacts: state.contacts.event, hashtag: ht)
+        }) ?? false
+
+        self._is_following = State(wrappedValue: is_following)
+    }
+
+    var Icon: some View {
+        ZStack {
+            Circle()
+                .fill(Color(red: 0xF8/255.0, green: 0xE7/255.0, blue: 0xF8/255.0))
+                .frame(width: 54, height: 54)
+
+            switch described {
+            case .hashtag:
+                Text("#")
+                    .font(.largeTitle.bold())
+                    .foregroundStyle(PinkGradient)
+                    .mask(Text("#")
+                        .font(.largeTitle.bold()))
+
+            case .unknown:
+                Image(systemName: "magnifyingglass")
+                    .font(.title.bold())
+                    .foregroundStyle(PinkGradient)
+            }
+        }
+    }
+
+    var SearchText: Text {
+        switch described {
+        case .hashtag(let ht):
+            Text(verbatim: "#" + ht)
+        case .unknown:
+            Text("Search")
+        }
+    }
+
+    func unfollow(_ hashtag: String) {
+        is_following = false
+        handle_unfollow(state: state, unfollow: .t(hashtag))
+    }
+
+    func follow(_ hashtag: String) {
+        is_following = true
+        handle_follow(state: state, follow: .t(hashtag))
+    }
+
+    func FollowButton(_ ht: String) -> some View {
+        return Button(action: { follow(ht) }) {
+            Text("Follow hashtag")
+                .font(.footnote.bold())
+        }
+        .buttonStyle(GradientButtonStyle(padding: 10))
+    }
+
+    func UnfollowButton(_ ht: String) -> some View {
+        return Button(action: { unfollow(ht) }) {
+            Text("Unfollow hashtag")
+                .font(.footnote.bold())
+        }
+        .buttonStyle(GradientButtonStyle(padding: 10))
+    }
+
+    var body: some View {
+        HStack(alignment: .center, spacing: 30) {
+            Icon
+
+            VStack(alignment: .leading, spacing: 10.0) {
+                SearchText
+                    .foregroundStyle(DamusLogoGradient.gradient)
+                    .font(.title.bold())
+
+                if state.is_privkey_user, case .hashtag(let ht) = described {
+                    if is_following {
+                        UnfollowButton(ht)
+                    } else {
+                        FollowButton(ht)
+                    }
+                }
+            }
+        }
+        .onReceive(handle_notify(.followed)) { notif in
+            let ref = notif.object as! ReferencedId
+            guard hashtag_matches_search(desc: self.described, ref: ref) else { return }
+            self.is_following = true
+        }
+        .onReceive(handle_notify(.unfollowed)) { notif in
+            let ref = notif.object as! ReferencedId
+            guard hashtag_matches_search(desc: self.described, ref: ref) else { return }
+            self.is_following = false
+        }
+    }
+}
+
+func hashtag_matches_search(desc: DescribedSearch, ref: ReferencedId) -> Bool {
+    guard let ht = desc.is_hashtag, ref.key == "t" && ref.ref_id == ht
+    else { return false }
+    return true
+}
+
+func is_following_hashtag(contacts: NostrEvent?, hashtag: String) -> Bool {
+    guard let contacts else { return false }
+    return is_already_following(contacts: contacts, follow: .t(hashtag))
+}
+
+
+struct SearchHeaderView_Previews: PreviewProvider {
+    static var previews: some View {
+        VStack(alignment: .leading) {
+            SearchHeaderView(state: test_damus_state(), described: .hashtag("damus"))
+
+            SearchHeaderView(state: test_damus_state(), described: .unknown)
+        }
+    }
+}