Add Reposts view

Changelog-Added: Reposts view
Closes: #376

damus/Models/RepostsModel.swift

@@ -0,0 +1,77 @@
+//
+//  RepostsModel.swift
+//  damus
+//
+//  Created by Terry Yiu on 1/22/23.
+//
+
+import Foundation
+
+class RepostsModel: ObservableObject {
+    let state: DamusState
+    let target: String
+    let sub_id: String
+    let profiles_id: String
+
+    @Published var reposts: [NostrEvent]
+
+    init (state: DamusState, target: String) {
+        self.state = state
+        self.target = target
+        self.sub_id = UUID().description
+        self.profiles_id = UUID().description
+        self.reposts = []
+    }
+
+    func get_filter() -> NostrFilter {
+        var filter = NostrFilter.filter_kinds([NostrKind.boost.rawValue])
+        filter.referenced_ids = [target]
+        filter.limit = 500
+        return filter
+    }
+
+    func subscribe() {
+        let filter = get_filter()
+        let filters = [filter]
+        self.state.pool.subscribe(sub_id: sub_id, filters: filters, handler: handle_nostr_event)
+    }
+
+    func unsubscribe() {
+        self.state.pool.unsubscribe(sub_id: sub_id)
+    }
+
+    func handle_event(relay_id: String, ev: NostrEvent) {
+        guard ev.kind == NostrKind.boost.rawValue else {
+            return
+        }
+
+        guard let reposted_event = last_etag(tags: ev.tags) else {
+            return
+        }
+
+        guard reposted_event == self.target else {
+            return
+        }
+
+        if insert_uniq_sorted_event(events: &self.reposts, new_ev: ev, cmp: { a, b in a.created_at < b.created_at } ) {
+            objectWillChange.send()
+        }
+    }
+
+    func handle_nostr_event(relay_id: String, ev: NostrConnectionEvent) {
+        guard case .nostr_event(let nev) = ev else {
+            return
+        }
+
+        switch nev {
+        case .event(_, let ev):
+            handle_event(relay_id: relay_id, ev: ev)
+
+        case .notice(_):
+            break
+        case .eose(_):
+            load_profiles(profiles_subid: profiles_id, relay_id: relay_id, events: reposts, damus_state: state)
+            break
+        }
+    }
+}