refactor ExportActions

This will allow disabling exports for remotes that are not configured to
allow them. Also, exportSupported will be useful for the external
special remote to probe.

This commit was supported by the NSF-funded DataLad project

Types/Remote.hs

@@ -19,6 +19,7 @@ module Types.Remote
 	, Verification(..)
 	, unVerified
 	, ExportLocation(..)
+	, ExportActions(..)
 	)
 	where
 
@@ -63,91 +64,75 @@ instance Eq (RemoteTypeA a) where
 	x == y = typename x == typename y
 
 {- An individual remote. -}
-data RemoteA a = Remote {
+data RemoteA a = Remote
 	-- each Remote has a unique uuid
-	uuid :: UUID,
+	{ uuid :: UUID
 	-- each Remote has a human visible name
-	name :: RemoteName,
+	, name :: RemoteName
 	-- Remotes have a use cost; higher is more expensive
-	cost :: Cost,
+	, cost :: Cost
 
 	-- Transfers a key's contents from disk to the remote.
 	-- The key should not appear to be present on the remote until
 	-- all of its contents have been transferred.
-	storeKey :: Key -> AssociatedFile -> MeterUpdate -> a Bool,
+	, storeKey :: Key -> AssociatedFile -> MeterUpdate -> a Bool
 	-- Retrieves a key's contents to a file.
 	-- (The MeterUpdate does not need to be used if it writes
 	-- sequentially to the file.)
-	retrieveKeyFile :: Key -> AssociatedFile -> FilePath -> MeterUpdate -> a (Bool, Verification),
+	, retrieveKeyFile :: Key -> AssociatedFile -> FilePath -> MeterUpdate -> a (Bool, Verification)
 	-- Retrieves a key's contents to a tmp file, if it can be done cheaply.
 	-- It's ok to create a symlink or hardlink.
-	retrieveKeyFileCheap :: Key -> AssociatedFile -> FilePath -> a Bool,
+	, retrieveKeyFileCheap :: Key -> AssociatedFile -> FilePath -> a Bool
 	-- Removes a key's contents (succeeds if the contents are not present)
-	removeKey :: Key -> a Bool,
+	, removeKey :: Key -> a Bool
 	-- Uses locking to prevent removal of a key's contents,
 	-- thus producing a VerifiedCopy, which is passed to the callback.
 	-- If unable to lock, does not run the callback, and throws an
 	-- error.
 	-- This is optional; remotes do not have to support locking.
-	lockContent :: forall r. Maybe (Key -> (VerifiedCopy -> a r) -> a r),
+	, lockContent :: forall r. Maybe (Key -> (VerifiedCopy -> a r) -> a r)
 	-- Checks if a key is present in the remote.
 	-- Throws an exception if the remote cannot be accessed.
-	checkPresent :: Key -> a Bool,
+	, checkPresent :: Key -> a Bool
 	-- Some remotes can checkPresent without an expensive network
 	-- operation.
-	checkPresentCheap :: Bool,
-
-	-- Exports content to an ExportLocation.
-	-- The exported file should not appear to be present on the remote
-	-- until all of its contents have been transferred.
-	storeExport :: Maybe (FilePath -> Key -> ExportLocation -> MeterUpdate -> a Bool),
-	-- Retrieves exported content to a file.
-	-- (The MeterUpdate does not need to be used if it writes
-	-- sequentially to the file.)
-	retrieveExport :: Maybe (Key -> ExportLocation -> FilePath -> MeterUpdate -> a (Bool, Verification)),
-	-- Removes an exported file (succeeds if the contents are not present)
-	removeExport :: Maybe (Key -> ExportLocation -> a Bool),
-	-- Checks if anything is exported to the remote at the specified
-	-- ExportLocation.
-	-- Throws an exception if the remote cannot be accessed.
-	checkPresentExport :: Maybe (Key -> ExportLocation -> a Bool),
-	-- Renames an already exported file.
-	renameExport :: Maybe (Key -> ExportLocation -> ExportLocation -> a Bool),
-
+	, checkPresentCheap :: Bool
+	-- Some remotes support exports of trees.
+	, exportActions :: ExportActions a
 	-- Some remotes can provide additional details for whereis.
-	whereisKey :: Maybe (Key -> a [String]),
+	, whereisKey :: Maybe (Key -> a [String])
 	-- Some remotes can run a fsck operation on the remote,
 	-- without transferring all the data to the local repo
 	-- The parameters are passed to the fsck command on the remote.
-	remoteFsck :: Maybe ([CommandParam] -> a (IO Bool)),
+	, remoteFsck :: Maybe ([CommandParam] -> a (IO Bool))
 	-- Runs an action to repair the remote's git repository.
-	repairRepo :: Maybe (a Bool -> a (IO Bool)),
+	, repairRepo :: Maybe (a Bool -> a (IO Bool))
 	-- a Remote has a persistent configuration store
-	config :: RemoteConfig,
+	, config :: RemoteConfig
 	-- git repo for the Remote
-	repo :: Git.Repo,
+	, repo :: Git.Repo
 	-- a Remote's configuration from git
-	gitconfig :: RemoteGitConfig,
+	, gitconfig :: RemoteGitConfig
 	-- a Remote can be assocated with a specific local filesystem path
-	localpath :: Maybe FilePath,
+	, localpath :: Maybe FilePath
 	-- a Remote can be known to be readonly
-	readonly :: Bool,
+	, readonly :: Bool
 	-- a Remote can be globally available. (Ie, "in the cloud".)
-	availability :: Availability,
+	, availability :: Availability
 	-- the type of the remote
-	remotetype :: RemoteTypeA a,
+	, remotetype :: RemoteTypeA a
 	-- For testing, makes a version of this remote that is not
 	-- available for use. All its actions should fail.
-	mkUnavailable :: a (Maybe (RemoteA a)),
+	, mkUnavailable :: a (Maybe (RemoteA a))
 	-- Information about the remote, for git annex info to display.
-	getInfo :: a [(String, String)],
+	, getInfo :: a [(String, String)]
 	-- Some remotes can download from an url (or uri).
-	claimUrl :: Maybe (URLString -> a Bool),
+	, claimUrl :: Maybe (URLString -> a Bool)
 	-- Checks that the url is accessible, and gets information about
 	-- its contents, without downloading the full content.
 	-- Throws an exception if the url is inaccessible.
-	checkUrl :: Maybe (URLString -> a UrlContents)
-}
+	, checkUrl :: Maybe (URLString -> a UrlContents)
+	}
 
 instance Show (RemoteA a) where
 	show remote = "Remote { name =\"" ++ name remote ++ "\" }"
@@ -175,3 +160,23 @@ unVerified a = do
 -- The FilePath will be relative, and may contain unix-style path
 -- separators.
 newtype ExportLocation = ExportLocation FilePath
+
+data ExportActions a = ExportActions
+	{ exportSupported :: a Bool
+	-- Exports content to an ExportLocation.
+	-- The exported file should not appear to be present on the remote
+	-- until all of its contents have been transferred.
+	, storeExport :: FilePath -> Key -> ExportLocation -> MeterUpdate -> a Bool
+	-- Retrieves exported content to a file.
+	-- (The MeterUpdate does not need to be used if it writes
+	-- sequentially to the file.)
+	, retrieveExport :: Key -> ExportLocation -> FilePath -> MeterUpdate -> a (Bool, Verification)
+	-- Removes an exported file (succeeds if the contents are not present)
+	, removeExport :: Key -> ExportLocation -> a Bool
+	-- Checks if anything is exported to the remote at the specified
+	-- ExportLocation.
+	-- Throws an exception if the remote cannot be accessed.
+	, checkPresentExport :: Key -> ExportLocation -> a Bool
+	-- Renames an already exported file.
+	, renameExport :: Key -> ExportLocation -> ExportLocation -> a Bool
+	}