devblog

2 files changed, 57 insertions, 6 deletions

diff --git a/doc/devblog/day_426__grab_bag.mdwn b/doc/devblog/day_426__grab_bag.mdwn
index 4a3bf908b..36e32077e 100644
--- a/doc/devblog/day_426__grab_bag.mdwn
+++ b/doc/devblog/day_426__grab_bag.mdwn
@@ -45,19 +45,19 @@ authentication. Which is a whole nother ball of complexity. So, I'm leaning
 instead to using a simple custom protocol something like:
 
 		> AUTH $localuuid $token
-		< AUTH-OK $remoteuuid
+		< AUTH-SUCCESS $remoteuuid
 		> SENDPACK $length
 		> $gitdata
 		< RECVPACK $length
 		< $gitdata
 		> GET $pos $key
-		< SENDING $length
+		< DATA $length
 		< $bytes
-		> GET-OK
+		> SUCCESS
 		> PUT $key
-		< SEND $pos
-		> SENDING $length
+		< PUT-FROM $pos
+		> DATA $length
 		> $bytes
-		< PUT-OK
+		< SUCCESS
 
 Today's work was sponsored by Riku Voipio.
diff --git a/doc/devblog/day_427__free_p2p.mdwn b/doc/devblog/day_427__free_p2p.mdwn
new file mode 100644
index 000000000..7c727587b
--- /dev/null
+++ b/doc/devblog/day_427__free_p2p.mdwn
@@ -0,0 +1,51 @@
+For a Haskell programmer, and day where a big thing is implemented
+without the least scrap of code that touches the IO monad is a good day.
+And this was a good day for me!
+
+Implemented the p2p protocol for tor hidden services. Its needs are somewhat
+similar to the external special remote protocol, but the two protocols are
+not fully overlapping with one-another. Rather than try to unify them, and
+so complicate both cases, I prefer to reuse as much code as possible between
+separate protocol implementations. The generating and parsing of messages
+is largely shared between them. I let the new p2p protocol otherwise
+develop in its own direction.
+
+But, I *do* want to make this p2p protocol reusable for other types of p2p
+networks than tor hidden services. This was an opportunity to use the Free
+monad, which I'd never used before. It worked out great, letting me write
+monadic code to handle requests and responses in the protocol, that reads
+the content of files and resumes transfers and so on, all independent
+of any concrete implementation.
+
+The whole implementation of the protocol only needed 74 lines of monadic code.
+It helped that I was able to factor out functions like this one, that is used
+both for handling a download, and by the remote when an upload is sent to it:
+
+	receiveContent :: Key -> Offset -> Len -> Proto Bool
+	receiveContent key offset len = do
+	        content <- receiveBytes len
+	        ok <- writeKeyFile key offset content
+	        sendMessage $ if ok then SUCCESS else FAILURE
+	        return ok
+
+To get transcripts of the protocol in action, the Free monad can be evaluated
+purely, providing the other side of the conversation:
+
+	ghci> putStrLn $ protoDump $ runPure (put (fromJust $ file2key "WORM--foo")) [PUT_FROM (Offset 10), SUCCESS]
+	> PUT WORM--foo
+	< PUT-FROM 10
+	> DATA 90
+	> bytes
+	< SUCCESS
+	result: True
+
+	ghci> putStrLn $ protoDump $ runPure (serve (toUUID "myuuid")) [GET (Offset 0) (fromJust $ file2key "WORM--foo")]
+	< GET 0 WORM--foo
+	> PROTO-ERROR must AUTH first
+	result: ()
+
+Am very happy with all this pure code and that I'm finally using Free monads.
+Next I need to get down the the dirty business of wiring this up to
+actual IO actions, and an actual network connection.
+
+Today's work was sponsored by Jake Vosloo on Patreon.