From 68fc738a3c99a6bb109268b1cda3b9f93a1e1a2f Mon Sep 17 00:00:00 2001
From: Jason Volk <jason@zemos.net>
Date: Mon, 4 Jan 2021 03:52:37 -0800
Subject: [PATCH] modules/client/keys/changes: Implement c2s r0.6.1 13.11.5.2.4
 keys/changes (changed half).

---
 modules/client/keys/changes.cc | 72 +++++++++++++++++++++++++++++++++-
 1 file changed, 71 insertions(+), 1 deletion(-)

diff --git a/modules/client/keys/changes.cc b/modules/client/keys/changes.cc
index 53117be52..bcc1d399c 100644
--- a/modules/client/keys/changes.cc
+++ b/modules/client/keys/changes.cc
@@ -60,8 +60,78 @@ m::resource::response
 get__keys_changes(client &client,
                   const m::resource::request &request)
 {
-	return m::resource::response
+	char buf[2][128];
+	const string_view range[2]
+	{
+		url::decode(buf[0], request.query["from"]),
+		url::decode(buf[1], request.query["to"])
+	};
+
+	const auto from
+	{
+		m::sync::sequence(m::sync::make_since(range[0]))
+	};
+
+	const auto to
+	{
+		m::sync::sequence(m::sync::make_since(range[1]))
+	};
+
+	const m::user::mitsein mitsein
+	{
+		request.user_id
+	};
+
+	m::resource::response::chunked::json response
 	{
 		client, http::OK
 	};
+
+	if(likely(request.query.get("changed", true)))
+	{
+		json::stack::array out
+		{
+			response, "changed"
+		};
+
+		m::events::type::for_each_in("ircd.device.keys", [&from, &to, &out, &mitsein]
+		(const string_view &type, const m::event::idx &event_idx)
+		{
+			if(event_idx < from || event_idx >= to)
+				return true;
+
+			const bool room_id_prefetched
+			{
+				m::prefetch(event_idx, "room_id")
+			};
+
+			m::get(std::nothrow, event_idx, "sender", [&out, &mitsein, &event_idx]
+			(const m::user::id &user_id)
+			{
+				m::get(std::nothrow, event_idx, "room_id", [&out, &mitsein, &user_id]
+				(const m::room::id &room_id)
+				{
+					if(!m::user::room::is(room_id, user_id))
+						return;
+
+					if(!mitsein.has(user_id))
+						return;
+
+					out.append(user_id);
+				});
+			});
+
+			return true;
+		});
+	}
+
+	if(likely(request.query.get("left", true)))
+	{
+		json::stack::array out
+		{
+			response, "left"
+		};
+	}
+
+	return std::move(response);
 }