filter branches (incomplete)

Promosing work toward metadata driven filter branches. A few methods
to construct them are stubbed out; all the data types and pure code
seems good.

This commit was sponsored by Walter Somerville.

1 files changed, 220 insertions, 0 deletions

diff --git a/Annex/View.hs b/Annex/View.hs
new file mode 100644
index 000000000..620e71f0e
--- /dev/null
+++ b/Annex/View.hs
@@ -0,0 +1,220 @@
+{- metadata based branch views
+ -
+ - Copyright 2014 Joey Hess <joey@kitenet.net>
+ -
+ - Licensed under the GNU GPL version 3 or higher.
+ -}
+
+{-# LANGUAGE CPP #-}
+
+module Annex.View where
+
+import Common.Annex
+import Logs.MetaData
+import Types.MetaData
+import qualified Git.Types as Git
+import qualified Git.Ref
+import qualified Git.DiffTree
+import qualified Git.Branch
+import qualified Git.Index
+import Git.Sha (nullSha)
+import Utility.QuickCheck
+
+import qualified Data.Set as S
+import Data.Char
+
+#ifdef WITH_TDFA
+import Text.Regex.TDFA
+import Text.Regex.TDFA.String
+#endif
+
+type View = [(MetaField, ViewFilter)]
+
+data ViewFilter
+	= FilterValues (S.Set MetaValue)
+#ifdef WITH_TDFA
+	| FilterGlob String Regex
+#endif
+
+instance Show ViewFilter where
+	show (FilterValues s) = show s
+	show (FilterGlob s _) = s
+
+instance Eq ViewFilter where
+	FilterValues x == FilterValues y = x == y
+	FilterGlob x _ == FilterGlob y _ = x == y
+	_ == _ = False
+
+instance Arbitrary ViewFilter where
+	arbitrary = do
+		size <- arbitrarySizedBoundedIntegral `suchThat` (< 100)
+		FilterValues . S.fromList <$> vector size
+
+{- Can a ViewFilter match multiple different MetaValues? -}
+multiValue :: ViewFilter -> Bool
+multiValue (FilterValues s) = S.size s > 1
+#ifdef WITH_TDFA
+multiValue (FilterGlob _ _) = True
+#endif
+
+type FileView = FilePath
+type MkFileView = FilePath -> FileView
+
+{- Checks if metadata matches a filter, and if so returns the value,
+ - or values that match. -}
+matchFilter :: MetaData -> MetaField -> ViewFilter -> Maybe [MetaValue]
+matchFilter metadata metafield (FilterValues s) = nonEmptyList $
+	S.intersection s (currentMetaDataValues metafield metadata)
+#ifdef WITH_TDFA
+matchFilter metadata metafield (FilterGlob _ r) = nonEmptyList $
+	S.filter matching (currentMetaDataValues metafield metadata)
+  where
+	matching = either (const False) (const True) . execute r . fromMetaValue
+#endif
+
+nonEmptyList :: S.Set a -> Maybe [a]
+nonEmptyList s
+	| S.null s = Nothing
+	| otherwise = Just $ S.toList s
+
+{- Converts a filepath used in a reference branch to the
+ - filename that will be used in the view.
+ -
+ - No two filenames from the same branch should yeild the same result,
+ - so all directory structure needs to be included in the output file
+ - in some way. However, the branch's directory structure is not relevant
+ - in the view.
+ -
+ - So, from dir/subdir/file.foo, generate file(dir)(subdir).foo
+ -}
+fileViewFromReference :: MkFileView
+fileViewFromReference f = base ++ concatMap (\d -> "(" ++ d ++ ")") dirs ++ concat extensions
+  where
+	(path, basefile) = splitFileName f
+	dirs = filter (/= ".") $ map dropTrailingPathSeparator (splitPath path)
+	(base, extensions) = splitShortExtensions basefile
+
+{- Generates views for a file from a branch, based on its metadata
+ - and the filename used in the branch.
+ -
+ - Note that a file may appear multiple times in a view, when it
+ - has multiple matching values for a MetaField used in the View.
+ -}
+fileViews :: View -> MkFileView -> FilePath -> MetaData -> Maybe [FileView]
+fileViews view mkfileview file metadata
+	| any isNothing matches = Nothing
+	| otherwise = Just $ map (</> mkfileview file) $
+		pathProduct $ map (map fromMetaValue) $ visible matches
+  where
+  	matches :: [Maybe [MetaValue]]
+	matches = map (uncurry $ matchFilter metadata) view
+	visible :: [Maybe [MetaValue]] -> [[MetaValue]]
+	visible = map (fromJust . snd) .
+		filter (multiValue . fst) .
+		zip (map snd view)
+
+pathProduct :: [[FilePath]] -> [FilePath]
+pathProduct [] = []
+pathProduct (l:ls) = foldl combinel l ls
+  where
+	combinel xs ys = [combine x y | x <- xs, y <- ys]
+
+{- Extracts the metadata from a fileview, based on the view that was used
+ - to construct it. -}
+fromView :: View -> FileView -> MetaData
+fromView view f = foldr (uncurry updateMetaData) newMetaData (zip fields values)
+  where
+	visible = filter (multiValue . snd) view
+	fields = map fst visible
+	paths = splitDirectories $ dropFileName f
+	values = map toMetaValue paths
+
+{- Generates a git branch name for a View.
+ - 
+ - There is no guarantee that each view gets a unique branch name,
+ - but the branch name is used to express the view as well as possible.
+ -}
+branchView :: View -> Git.Branch
+branchView view
+	| null name = Git.Ref "refs/views"
+	| otherwise = Git.Ref $ "refs/views/" ++ name
+  where
+	name = intercalate "/" $ map branchbit view
+	branchbit b@(_metafield, viewfilter)
+		| multiValue viewfilter = branchbit' b
+		| otherwise = "(" ++ branchbit' b ++ ")"
+	branchbit' (metafield, viewfilter)
+		| metafield == tagMetaField = branchvals viewfilter
+		| otherwise = concat
+			[ forcelegal (fromMetaField metafield)
+			, "="
+			, branchvals viewfilter
+			]
+	branchvals (FilterValues set) = forcelegal $
+		intercalate "," $ map fromMetaValue $ S.toList set
+#ifdef WITH_TDFA
+	branchvals (FilterGlob glob _) = forcelegal $
+		replace "*" "ANY" $ replace "?" "_" glob
+#endif
+	forcelegal s
+		| Git.Ref.legal True s = s
+		| otherwise = map (\c -> if isAlphaNum c then c else '_') s
+
+prop_branchView_legal :: View -> Bool
+prop_branchView_legal = Git.Ref.legal False . show . branchView
+
+{- Applies a view to the currently checked out branch, generating a new
+ - branch for the view.
+ -}
+applyView :: View -> Annex Git.Branch
+applyView = applyView' fileViewFromReference
+
+{- Generates a new branch for a View, which must be a more specific
+ - version of the View originally used to generate the currently
+ - checked out branch.
+ -}
+refineView :: View -> Annex Git.Branch
+refineView = applyView' id
+
+{- Go through each file in the currently checked out branch.
+ - If the file is not annexed, skip it, unless it's a dotfile in the top.
+ - Look up the metadata of annexed files, and generate any FileViews,
+ - and stage them into the (temporary) index.
+ -}
+applyView' :: MkFileView -> View -> Annex Git.Branch
+applyView' mkfileview view = genViewBranch view $ do
+	error "TODO"
+
+{- Applies a view to the reference branch, generating a new branch
+ - for the View.
+ -
+ - This needs to work incrementally, to quickly update the view branch
+ - when the reference branch is changed. So, it works based on an
+ - old version of the reference branch, uses diffTree to find the
+ - changes, and applies those changes to the view branch.
+ -}
+updateView :: View -> Git.Ref -> Git.Ref -> Annex Git.Branch
+updateView view ref oldref = genViewBranch view $ do
+	(diffs, cleanup) <- inRepo $ Git.DiffTree.diffTree oldref ref
+	forM_ diffs go
+	void $ liftIO cleanup
+  where
+	go diff
+		| Git.DiffTree.dstsha diff == nullSha = error "TODO delete file"
+		| otherwise = error "TODO add file"
+
+{- Generates a branch for a view. This is done by creating a temporary
+ - index file, which starts off empty. An action is run to stage the files
+ - that will be in the branch. Then a commit is made, to the view branch.
+ - The view branch is not checked out, but entering it will display the
+ - view. -}
+genViewBranch :: View -> Annex () -> Annex Git.Branch
+genViewBranch view a = withTempIndex $ do
+	a
+	let branch = branchView view
+	void $ inRepo $ Git.Branch.commit True (show branch) branch []
+	return branch
+
+{- -}
+withTempIndex :: Annex a -> Annex a
+withTempIndex a = error "TODO"