Add a channel abstraction to use for networking

1 files changed, 15 insertions, 10 deletions

diff --git a/src/channel.moon b/src/channel.moon
index 968ae09..6f87d46 100644
--- a/src/channel.moon
+++ b/src/channel.moon
@@ -34,26 +34,31 @@ class FaultyChannel extends Channel
 		@avg_latency = 0 -- in ms
 		@latency_std = 0
 		-- Latency can never be below 0, but can go up as much as it likes
-		@avg_loss = 0 -- between 0 (never) and 1 (always)
-		@loss_std = 0.1
-		-- Loss is always a percentage between 0 and 1
+		@loss = 0.1 -- between 0 (never) and 1 (always)
 		super(settings)
-	normal: (avg, std, n) =>
+	@normal_at: (avg, std, n) ->
 		assert(avg and std and n, string.format("normal(avg, std, n) called with %q %q %q", tostring(avg), tostring(std), tostring(n)))
 		-- Normal curve probability at N
 		(1/ (math.sqrt(2*math.pi) * avg)) * math.exp(-(n - avg)^2 / (2 * (std^2)))
+	@normal: (avg, std) =>
+		-- Box-Muller transform
+		bm = math.sqrt(-2 * math.log(math.random())) * math.cos(2 * math.pi * math.random())
+		-- Box-Muller gives us std = e^-0.5 , avg = 0
+		((bm / math.exp(-1/2)) * std) + avg
 	poll: =>
 		@pump!
 		#@buffer > 0
 	send: (message) =>
 		-- Do we deliver?
-		if @normal(@avg_loss, @loss_std, math.random()) < 0.5
+		rng = math.random()
+		if @loss > rng
 			return
 		-- How long does it take?
-		time = @normal(@avg_latency, @latency_std, math.random())
+		-- Only uses the positive half of the normal distribution, double the standard deviation?
+		time = @@normal(@avg_latency, @latency_std * 2, math.random())
 		if time < 0 then
 			time = 0 -- We can't deliver messages in the past
-		table.insert(@to_deliver, {message,time})
+		table.insert(@to_deliver, {message,@@time + time})
 	recv: =>
 		@pump!
 		table.remove(@buffer, 1)
@@ -62,11 +67,11 @@ class FaultyChannel extends Channel
 		deliver_len = #@to_deliver
 		for k,tbl in ipairs(@to_deliver)
 			{m, t} = tbl
+			@to_deliver[defrag] = tbl
 			if @@time > t
-				@to_deliver[k] = nil
 				table.insert(@buffer, m)
-			if @to_deliver[defrag] == nil
-				@to_deliver[defrag] = tbl
+			else
+				defrag = defrag + 1
 		for i = defrag, deliver_len do
 			@to_deliver[i] = nil