From 0da4dec13cae6bc03978e8ca7bb48bda92ab450c Mon Sep 17 00:00:00 2001
From: Jason Volk <jason@zemos.net>
Date: Sat, 9 Jun 2018 14:32:46 -0700
Subject: [PATCH] ircd::m::event: Add topological before; improve prev
 iteration closure; reorg some util.

---
 include/ircd/m/event.h |  10 +++-
 ircd/m/event.cc        | 122 ++++++++++++++++++++++++++---------------
 2 files changed, 86 insertions(+), 46 deletions(-)

diff --git a/include/ircd/m/event.h b/include/ircd/m/event.h
index 1798b2dd4..581055c31 100644
--- a/include/ircd/m/event.h
+++ b/include/ircd/m/event.h
@@ -28,14 +28,17 @@ namespace ircd::m
 	bool bad(const id::event &, uint64_t &);
 	bool bad(const id::event &);
 
+	// Equality tests the event_id only! know this.
+	bool operator==(const event &a, const event &b);
+
 	// Depth comparison; expect unstable sorting.
 	bool operator<(const event &, const event &);
 	bool operator>(const event &, const event &);
 	bool operator<=(const event &, const event &);
 	bool operator>=(const event &, const event &);
 
-	// Equality tests the event_id only! know this.
-	bool operator==(const event &a, const event &b);
+	// Topological
+	bool before(const event &a, const event &b); // A directly referenced by B
 
 	id::event make_id(const event &, id::event::buf &buf, const const_buffer &hash);
 	id::event make_id(const event &, id::event::buf &buf);
@@ -142,7 +145,8 @@ struct ircd::m::event
 
 namespace ircd::m
 {
-	void for_each(const event::prev &, const std::function<void (const event::id &)> &);
+	bool for_each(const event::prev &, const event::id::closure_bool &);
+	void for_each(const event::prev &, const event::id::closure &);
 	size_t degree(const event::prev &);
 	size_t count(const event::prev &);
 
diff --git a/ircd/m/event.cc b/ircd/m/event.cc
index e5b61f954..c755d0ffd 100644
--- a/ircd/m/event.cc
+++ b/ircd/m/event.cc
@@ -255,10 +255,27 @@ ircd::m::make_id(const event &event,
 }
 
 bool
-ircd::m::operator==(const event &a, const event &b)
+ircd::m::before(const event &a,
+                const event &b)
 {
-	assert(json::get<"room_id"_>(a) == json::get<"room_id"_>(b));
-	return at<"event_id"_>(a) == at<"event_id"_>(b);
+	const event::prev prev_b{b};
+	const json::array &prev_b_events
+	{
+		json::get<"prev_events"_>(prev_b)
+	};
+
+	for(const json::array &prev_event : prev_b_events)
+	{
+		const event::id prev_event_id
+		{
+			unquote(prev_event.at(0))
+		};
+
+		if(prev_event_id == at<"event_id"_>(a))
+			return true;
+	}
+
+	return false;
 }
 
 bool
@@ -289,6 +306,13 @@ ircd::m::operator<(const event &a, const event &b)
 	return at<"depth"_>(a) < at<"depth"_>(b);
 }
 
+bool
+ircd::m::operator==(const event &a, const event &b)
+{
+	assert(json::get<"room_id"_>(a) == json::get<"room_id"_>(b));
+	return at<"event_id"_>(a) == at<"event_id"_>(b);
+}
+
 bool
 ircd::m::bad(const id::event &event_id)
 {
@@ -378,46 +402,6 @@ ircd::m::degree(const event &event)
 	return degree(event::prev{event});
 }
 
-size_t
-ircd::m::degree(const event::prev &prev)
-{
-	size_t ret{0};
-	json::for_each(prev, [&ret]
-	(const auto &, const json::array &prevs)
-	{
-		ret += prevs.count();
-	});
-
-	return ret;
-}
-
-size_t
-ircd::m::count(const event::prev &prev)
-{
-	size_t ret{0};
-	m::for_each(prev, [&ret](const event::id &event_id)
-	{
-		++ret;
-	});
-
-	return ret;
-}
-
-void
-ircd::m::for_each(const event::prev &prev,
-                  const std::function<void (const event::id &)> &closure)
-{
-	json::for_each(prev, [&closure]
-	(const auto &key, const json::array &prevs)
-	{
-		for(const json::array &prev : prevs)
-		{
-			const event::id &id{unquote(prev[0])};
-			closure(id);
-		}
-	});
-}
-
 std::string
 ircd::m::pretty(const event::prev &prev)
 {
@@ -518,6 +502,58 @@ ircd::m::pretty_oneline(std::ostream &s,
 	return s;
 }
 
+size_t
+ircd::m::degree(const event::prev &prev)
+{
+	size_t ret{0};
+	json::for_each(prev, [&ret]
+	(const auto &, const json::array &prevs)
+	{
+		ret += prevs.count();
+	});
+
+	return ret;
+}
+
+size_t
+ircd::m::count(const event::prev &prev)
+{
+	size_t ret{0};
+	m::for_each(prev, [&ret](const event::id &event_id)
+	{
+		++ret;
+	});
+
+	return ret;
+}
+
+void
+ircd::m::for_each(const event::prev &prev,
+                  const event::id::closure &closure)
+{
+	m::for_each(prev, event::id::closure_bool{[&closure]
+	(const event::id &event_id)
+	{
+		closure(event_id);
+		return true;
+	}});
+}
+
+bool
+ircd::m::for_each(const event::prev &prev,
+                  const event::id::closure_bool &closure)
+{
+	return json::until(prev, [&closure]
+	(const auto &key, const json::array &prevs)
+	{
+		for(const json::array &prev : prevs)
+			if(!closure(event::id(unquote(prev.at(0)))))
+				return false;
+
+		return true;
+	});
+}
+
 bool
 ircd::m::my(const event &event)
 {