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-- ldgallery - A static generator which turns a collection of tagged
-- pictures into a searchable web gallery.
--
-- Copyright (C) 2019-2020 Pacien TRAN-GIRARD
--
-- This program is free software: you can redistribute it and/or modify
-- it under the terms of the GNU Affero General Public License as
-- published by the Free Software Foundation, either version 3 of the
-- License, or (at your option) any later version.
--
-- This program is distributed in the hope that it will be useful,
-- but WITHOUT ANY WARRANTY; without even the implied warranty of
-- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
-- GNU Affero General Public License for more details.
--
-- You should have received a copy of the GNU Affero General Public License
-- along with this program. If not, see <https://www.gnu.org/licenses/>.
module Caching
( Cache
, noCache
, ItemCache
, buildItemCache
, useCached
) where
import Control.Monad (when)
import qualified Data.Map.Strict as Map
import System.Directory (removePathForcibly, doesDirectoryExist, doesFileExist)
import FileProcessors (FileProcessor)
import Resource (GalleryItem(..), flattenGalleryTree)
import Files
type Cache a = FileProcessor a -> FileProcessor a
noCache :: Cache a
noCache processor itemPath resPath inputFsPath outputFsPath =
removePathForcibly outputFsPath
>> processor itemPath resPath inputFsPath outputFsPath
type ItemCache = Path -> Maybe GalleryItem
buildItemCache :: Maybe GalleryItem -> ItemCache
buildItemCache cachedItems = lookupCache
where
withKey item = (webPath $ Resource.path item, item)
cachedItemList = maybe [] flattenGalleryTree cachedItems
cachedMap = Map.fromList (map withKey cachedItemList)
lookupCache path = Map.lookup (webPath path) cachedMap
useCached :: ItemCache -> (GalleryItem -> Maybe a) -> Cache a
useCached cache propGetter processor itemPath resPath inputFsPath outputFsPath =
do
isDir <- doesDirectoryExist outputFsPath
when isDir $ removePathForcibly outputFsPath
fileExists <- doesFileExist outputFsPath
if fileExists then
do
needUpdate <- isOutdated True inputFsPath outputFsPath
case (needUpdate, cache itemPath >>= propGetter) of
(False, Just props) -> fromCache props
_ -> update
else
update
where
update = processor itemPath resPath inputFsPath outputFsPath
fromCache props =
putStrLn ("From cache:\t" ++ outputFsPath)
>> return props
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