From 44ab0a143566a1ea331945b3cd828fed1559fbf1 Mon Sep 17 00:00:00 2001
From: Joshua Clayton <joshua.clayton@gmail.com>
Date: Sun, 15 May 2016 07:51:54 -0400
Subject: [PATCH] Read unchanged results from the cache

At some point, this also needs to md5 the tags list itself and factor
that in (since if the tagging algorithm changes, and new tokens get
uncovered, it'd invalidate the cache)
---
 app/Main.hs                              |  4 +--
 src/Unused/Cache.hs                      | 34 ++++++++++++++++++++++++
 src/Unused/Cache/DirectoryFingerprint.hs | 22 +++++++++++++++
 unused.cabal                             |  3 +++
 4 files changed, 61 insertions(+), 2 deletions(-)
 create mode 100644 src/Unused/Cache.hs
 create mode 100644 src/Unused/Cache/DirectoryFingerprint.hs

diff --git a/app/Main.hs b/app/Main.hs
index 209ce40..96ae6c5 100644
--- a/app/Main.hs
+++ b/app/Main.hs
@@ -8,6 +8,7 @@ import Unused.Types (ParseResponse, RemovalLikelihood(..))
 import Unused.ResponseFilter (withOneOccurrence, withLikelihoods, ignoringPaths)
 import Unused.Grouping (CurrentGrouping(..), groupedResponses)
 import Unused.CLI (SearchRunner(..), withoutCursor, renderHeader, executeSearch, printParseError, printSearchResults, resetScreen, withInterruptHandler)
+import Unused.Cache
 
 data Options = Options
     { oSearchRunner :: SearchRunner
@@ -37,8 +38,7 @@ run options = withoutCursor $ do
     terms <- pure . lines =<< getContents
     renderHeader terms
 
-    results <- unlines <$> executeSearch (oSearchRunner options) terms
-
+    results <- cached $ unlines <$> executeSearch (oSearchRunner options) terms
     let response = parseLines results
 
     resetScreen
diff --git a/src/Unused/Cache.hs b/src/Unused/Cache.hs
new file mode 100644
index 0000000..861451c
--- /dev/null
+++ b/src/Unused/Cache.hs
@@ -0,0 +1,34 @@
+module Unused.Cache
+    ( cached
+    ) where
+
+import System.Directory
+import Unused.Cache.DirectoryFingerprint (sha)
+
+cached :: IO String -> IO String
+cached f = maybe (writeCache =<< f) return =<< readCache
+
+writeCache :: String -> IO String
+writeCache contents = do
+    createDirectoryIfMissing True cacheDirectory
+    fileName <- cacheFileName
+    writeFile fileName contents
+    return contents
+
+readCache :: IO (Maybe String)
+readCache = do
+    putStrLn "\n\nCalculating cache fingerprint... "
+    fileName <- cacheFileName
+    exists <- doesFileExist fileName
+
+    if exists
+        then Just <$> readFile fileName
+        else return Nothing
+
+cacheFileName :: IO String
+cacheFileName = do
+    currentSha <- sha
+    return $ cacheDirectory ++ "/" ++ currentSha ++ ".cache"
+
+cacheDirectory :: String
+cacheDirectory = "tmp/unused"
diff --git a/src/Unused/Cache/DirectoryFingerprint.hs b/src/Unused/Cache/DirectoryFingerprint.hs
new file mode 100644
index 0000000..067860e
--- /dev/null
+++ b/src/Unused/Cache/DirectoryFingerprint.hs
@@ -0,0 +1,22 @@
+module Unused.Cache.DirectoryFingerprint
+    ( sha
+    ) where
+
+import System.Process
+
+sha :: IO String
+sha =
+    getSha <$> (fileList >>= sortInput >>= md5Result)
+  where
+    getSha = head' . lines
+    head' (x:_) = x
+    head' _ = ""
+
+fileList :: IO String
+fileList = readProcess "find" [".", "-type", "f", "-not", "-path", "*/tmp/unused/*", "-exec", "md5", "{}", "+"] ""
+
+sortInput :: String -> IO String
+sortInput = readProcess "sort" ["-k", "2"]
+
+md5Result :: String -> IO String
+md5Result = readProcess "md5" []
diff --git a/unused.cabal b/unused.cabal
index 6f6574f..9253be0 100644
--- a/unused.cabal
+++ b/unused.cabal
@@ -27,6 +27,8 @@ library
                      , Unused.Grouping.Internal
                      , Unused.Grouping.Types
                      , Unused.LikelihoodCalculator
+                     , Unused.Cache
+                     , Unused.Cache.DirectoryFingerprint
                      , Unused.CLI
                      , Unused.CLI.Search
                      , Unused.CLI.SearchError
@@ -41,6 +43,7 @@ library
                      , parsec
                      , containers
                      , filepath
+                     , directory
                      , regex-tdfa
                      , terminal-progress-bar
                      , ansi-terminal