From 257276d0820c5d4c47d01dece59f4212f4cd4ed9 Mon Sep 17 00:00:00 2001
From: Jason Volk <jason@zemos.net>
Date: Wed, 4 Apr 2018 22:41:39 -0700
Subject: [PATCH] modules/federation: Add backfill_ids endpoint handler.

---
 modules/Makefile.am                |   2 +
 modules/federation/backfill_ids.cc | 128 +++++++++++++++++++++++++++++
 2 files changed, 130 insertions(+)
 create mode 100644 modules/federation/backfill_ids.cc

diff --git a/modules/Makefile.am b/modules/Makefile.am
index b17d42793..2a3245987 100644
--- a/modules/Makefile.am
+++ b/modules/Makefile.am
@@ -250,6 +250,7 @@ federation_federation_state_la_SOURCES = federation/state.cc
 federation_federation_make_leave_la_SOURCES = federation/make_leave.cc
 federation_federation_send_leave_la_SOURCES = federation/send_leave.cc
 federation_federation_backfill_la_SOURCES = federation/backfill.cc
+federation_federation_backfill_ids_la_SOURCES = federation/backfill_ids.cc
 
 federation_module_LTLIBRARIES = \
 	federation/federation_send.la \
@@ -267,6 +268,7 @@ federation_module_LTLIBRARIES = \
 	federation/federation_make_leave.la \
 	federation/federation_send_leave.la \
 	federation/federation_backfill.la \
+	federation/federation_backfill_ids.la \
 	###
 
 ###############################################################################
diff --git a/modules/federation/backfill_ids.cc b/modules/federation/backfill_ids.cc
new file mode 100644
index 000000000..cc436dadd
--- /dev/null
+++ b/modules/federation/backfill_ids.cc
@@ -0,0 +1,128 @@
+// Matrix Construct
+//
+// Copyright (C) Matrix Construct Developers, Authors & Contributors
+// Copyright (C) 2016-2018 Jason Volk <jason@zemos.net>
+//
+// Permission to use, copy, modify, and/or distribute this software for any
+// purpose with or without fee is hereby granted, provided that the above
+// copyright notice and this permission notice is present in all copies. The
+// full license for this software is available in the LICENSE file.
+
+using namespace ircd;
+
+mapi::header
+IRCD_MODULE
+{
+	"federation backfill event IDs"
+};
+
+resource
+backfill_ids_resource
+{
+	"/_matrix/federation/v1/backfill_ids/",
+	{
+		"federation backfill ID's",
+		resource::DIRECTORY,
+	}
+};
+
+conf::item<size_t>
+backfill_ids_limit_max
+{
+	{ "name",     "ircd.federation.backfill_ids.limit.max" },
+	{ "default",  2048L /* TODO: hiiigherrrr */            },
+};
+
+conf::item<size_t>
+backfill_ids_limit_default
+{
+	{ "name",     "ircd.federation.backfill_ids.limit.default" },
+	{ "default",  64L                                          },
+};
+
+static size_t
+calc_limit(const resource::request &request)
+{
+	const auto &limit
+	{
+		request.query["limit"]
+	};
+
+	if(!limit)
+		return size_t(backfill_ids_limit_default);
+
+	size_t ret
+	{
+		lex_cast<size_t>(limit)
+	};
+
+	return std::min(ret, size_t(backfill_ids_limit_max));
+}
+
+resource::response
+get__backfill_ids(client &client,
+                  const resource::request &request)
+{
+	m::room::id::buf room_id
+	{
+		url::decode(request.parv[0], room_id)
+	};
+
+	m::event::id::buf event_id
+	{
+		request.query["v"]?
+			url::decode(request.query.at("v"), event_id):
+			m::head(room_id)
+	};
+
+	const size_t limit
+	{
+		calc_limit(request)
+	};
+
+	m::room::messages it
+	{
+		room_id, event_id
+	};
+
+	 //TODO: chunk direct to socket
+	const unique_buffer<mutable_buffer> buf
+	{
+		512 * limit //TODO: XXX
+	};
+
+	json::stack out{buf};
+	{
+		json::stack::object top{out};
+		json::stack::member pdus_m
+		{
+			top, "pdu_ids"
+		};
+
+		json::stack::array pdus
+		{
+			pdus_m
+		};
+
+		size_t count{0};
+		for(; it && count < limit; ++count, --it)
+			pdus.append(it.event_id());
+	}
+
+	return resource::response
+	{
+		client, json::object
+		{
+			out.completed()
+		}
+	};
+}
+
+resource::method
+method_get
+{
+	backfill_ids_resource, "GET", get__backfill_ids,
+	{
+		method_get.VERIFY_ORIGIN
+	}
+};