Almost got everythign working.

Issues left to resolve:

 * Removing a reaction doesn't properly remove it from UI, but the event
   is recorded correctly.
 * Since contacts are not being saved there will be issues with
   "following" users and you could overwrite your follower's list with
an empty list.
 * Caching is no longer working.
 * I skipped chat room implementation.
 * Rendering shared event's doesn't work and needs to be revised.

web/js/event.js

@@ -0,0 +1,123 @@
+/* EVENT */
+
+/* event_refs_pubkey checks if the event (ev) is directed at the public key 
+ * (pubkey) by checking its type, tags, and key.
+ */
+function event_refs_pubkey(ev, pubkey) {
+	if (!(ev.kind === 1 || ev.kind === 42))
+		return false
+	if (ev.pubkey === pubkey)
+		return false
+	for (const tag of ev.tags) {
+		if (tag.length >= 2 && tag[0] === "p" && tag[1] === pubkey)
+			return true
+	}
+	return false
+}
+
+function event_calculate_pow(ev) {
+	const id_bits = leading_zero_bits(ev.id)
+	for (const tag of ev.tags) {
+		if (tag.length >= 3 && tag[0] === "nonce") {
+			const target = +tag[2]
+			if (isNaN(target))
+				return 0
+
+			// if our nonce target is smaller than the difficulty,
+			// then we use the nonce target as the actual difficulty
+			return min(target, id_bits)
+		}
+	}
+
+	// not a valid pow if we don't have a difficulty target
+	return 0
+}
+
+/* event_can_reply returns a boolean value based on if you can "reply" to the
+ * event in the manner of a chat.
+ */
+function event_can_reply(ev) {
+	return ev.kind === KIND_NOTE || ev.kind === 42
+}
+
+/* event_is_timeline returns a boolean based on if the event should be rendered
+ * in a GUI
+ */
+function event_is_timeline(ev) {
+	return ev.kind === KIND_NOTE || ev.kind === 42 || ev.kind === 6
+}	
+
+function event_get_tag_refs(tags) {
+	let ids = []
+	let pubkeys = []
+	let root, reply
+	for (const tag of tags) {
+		if (tag.length >= 4 && tag[0] == "e") {
+			ids.push(tag[1])
+			if (tag[3] === "root") {
+				root = tag[1]
+			} else if (tag[3] === "reply") {
+				reply = tag[1]
+			}
+		} else if (tag.length >= 2 && tag[0] == "e") {
+			ids.push(tag[1])
+		} else if (tag.length >= 2 && tag[0] == "p") {
+			pubkeys.push(tag[1])
+		}
+	}
+	if (!(root && reply) && ids.length > 0) {
+		if (ids.length === 1)
+			return {root: ids[0], reply: ids[0], pubkeys}
+		else if (ids.length >= 2)
+			return {root: ids[0], reply: ids[1], pubkeys}
+		return {pubkeys}
+	}
+	return {root, reply, pubkeys}
+}
+
+function event_is_spam(ev, contacts, pow) {
+	if (contacts.friend_of_friends.has(ev.pubkey))
+		return true
+	return ev.pow >= pow
+}
+
+function event_cmp_created(a, b) {
+	if (a.created_at > b.created_at)
+		return 1;
+	if (a.created_at < b.created_at)
+		return -1;
+	return 0;
+}
+
+/* event_refs_event checks if event A references event B in its tags.
+ */
+function event_refs_event(a, b) {
+	for (const tag of a.tags) {
+		if (tag.length >= 2 && tag[0] === "e" && tag[1] == b.id)
+			return true;
+	}
+	return false;
+}
+
+function event_get_last_tags(ev) {
+	let o = {};
+	for (const tag of ev.tags) {
+		if (tag.length >= 2 && (tag[0] === "e" || tag[0] === "p"))
+			o[tag[0]] = tag[1];
+	}
+	return o;
+}
+
+/* event_get_reacted_to returns the reacted to event & pubkey (e, p). Returns 
+ * undefined if invalid or incomplete.
+ */
+function event_parse_reaction(ev) {
+	if (!is_valid_reaction_content(ev.content) || ev.kind != KIND_REACTION) {
+		return;
+	}
+	const o = event_get_last_tags(ev);	
+	if (o["e"]) {
+		return o;
+	}
+}
+