From 884163fcf94f1ca7799da56de86b90321396301b Mon Sep 17 00:00:00 2001
From: SherwoodCH <lorenz.wolf@bluewin.ch>
Date: Thu, 16 Apr 2015 23:58:37 +0200
Subject: [PATCH] introduce offset handling

---
 src/HMB/Internal/Handler.hs    | 14 +---------
 src/HMB/Internal/Log/Writer.hs | 49 +++++++++++++++++++++++++---------
 2 files changed, 38 insertions(+), 25 deletions(-)

diff --git a/src/HMB/Internal/Handler.hs b/src/HMB/Internal/Handler.hs
index 3c72158..bac7a92 100644
--- a/src/HMB/Internal/Handler.hs
+++ b/src/HMB/Internal/Handler.hs
@@ -86,15 +86,9 @@ sendProduceResponse socket responsemessage = do
 -- FetchRequest
 -----------------
 
-requestLog :: Request -> IO [Log]
-requestLog req = mapM readLog [
-      (BS.unpack(topicName x), fromIntegral(rqFtPartitionNumber y))
-      | x <- rqFtTopics req, y <- partitions x
-    ]
-
 packPartitionsToFtRsPayload :: TopicName -> Partition -> IO RsFtPayload
 packPartitionsToFtRsPayload t p = do
-    log <- readLog (BS.unpack $ t, fromIntegral $ rqFtPartitionNumber p)
+    log <- readLog (BS.unpack $ t, fromIntegral $ rqFtPartitionNumber p, fromIntegral $ rqFtFetchOffset p)
     return $ RsFtPayload
         0
         0
@@ -102,9 +96,6 @@ packPartitionsToFtRsPayload t p = do
         (fromIntegral $ BL.length $ foldl (\acc ms -> BL.append acc (buildMessageSet ms)) BL.empty log)
         log
 
---packLogToFtRsPayload :: Log -> [RsFtPayload]
---packLogToFtRsPayload log = packMsToFtRsPayload log
-
 packLogToFtRs :: Topic -> IO Response
 packLogToFtRs t = do
     rss <- (mapM (packPartitionsToFtRsPayload $ topicName t) $ partitions t)
@@ -116,11 +107,8 @@ packLogToFtRs t = do
 
 handleFetchRequest :: Request -> Socket -> IO()
 handleFetchRequest req sock = do
-  logs <- requestLog req
   rs <- mapM packLogToFtRs (rqFtTopics req)
   let rsms = ResponseMessage 0 1 rs
-  print rsms
   let msg = buildFtRsMessage rsms
   SBL.sendAll sock msg
-  print $ "send resp:" ++  show msg
 
diff --git a/src/HMB/Internal/Log/Writer.hs b/src/HMB/Internal/Log/Writer.hs
index 9bdb7c5..3cc34bf 100644
--- a/src/HMB/Internal/Log/Writer.hs
+++ b/src/HMB/Internal/Log/Writer.hs
@@ -6,7 +6,7 @@ import qualified Data.ByteString.Lazy as BL
 import Data.Binary.Put
 import System.Directory
 import Control.Conditional
-
+import Control.Monad
 import Kafka.Protocol
 
 import Data.Binary.Get
@@ -25,22 +25,45 @@ logFile o = (show $ fromIntegral o) ++ ".log"
 getPath :: String -> String -> String
 getPath folder file = folder ++ "/" ++ file
 
-buildLog :: Log -> BL.ByteString
-buildLog [] = BL.empty
-buildLog (x:xs) = 
-  BL.append (buildMessageSet x) (buildLog xs) 
+buildLog :: Offset -> Log -> BL.ByteString
+buildLog o [] = BL.empty
+buildLog o (x:xs) =
+  (BL.append (buildLogEntry x o) (buildLog (o + 1) xs))
 
 writeLog :: MessageInput -> IO() 
 writeLog (topicName, partitionNumber, log) = do
   createDirectoryIfMissing False $ logFolder topicName partitionNumber
   let filePath = getPath (logFolder topicName partitionNumber) (logFile 0)
   ifM (doesFileExist filePath) 
-    (BL.appendFile filePath $ buildLog log)
-    (BL.writeFile filePath $ buildLog log)
+      (appendToLog filePath (topicName,partitionNumber, log)) 
+      (newLog filePath (topicName,partitionNumber, log))
 
+appendToLog :: String -> MessageInput -> IO() 
+appendToLog filepath (t, p, log)  = do 
+  o <- getMaxOffsetOfLog (t, p, log)
+  print o  --TODO: is needed for preventing file lock ...
+  let l =  buildLog (o + 1) log
+  BL.appendFile filepath l
+  return ()
+
+newLog :: String -> MessageInput -> IO()
+newLog filepath (t, p, log) = do 
+  let l = buildLog 0 log
+  BL.writeFile filepath l
+  return ()
+
+maxOffset :: [Offset] -> Offset 
+maxOffset [x] = x
+maxOffset (x:xs) = max x (maxOffset xs)
+
+getMaxOffsetOfLog :: MessageInput -> IO Offset
+getMaxOffsetOfLog (t, p, _) = do 
+  log <- readLogFromBeginning (t,p) --TODO: optimieren, dass nich gesamter log gelesen werden muss 
+  return (maxOffset $ [ offset x | x <- log ])
 
--- todo: move to reader
 
+
+-- todo: move to reader
 getLog :: Get Log
 getLog = do
   empty <- isEmpty
@@ -55,9 +78,11 @@ parseLog a = do
   input <- BL.readFile a
   return (runGet getLog input)
 
-
-readLog :: (String, Int) -> IO Log
-readLog (t, p) = parseLog $ 
+readLogFromBeginning :: (String, Int) -> IO Log
+readLogFromBeginning (t, p) = parseLog $ 
     getPath (logFolder t p) (logFile 0)
 
-
+readLog :: (String, Int, Int) -> IO Log
+readLog (t, p, o) = do 
+  log <- readLogFromBeginning (t,p)
+  return ([ x | x <- log, fromIntegral(offset x) >= o])