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Affirmer understands and acknowledges that Creative Commons is not a + party to this document and has no duty or obligation with respect to + this CC0 or use of the Work. diff --git a/ChangeLog b/ChangeLog new file mode 100644 --- /dev/null +++ b/ChangeLog @@ -0,0 +1,17 @@ +The changes are recorded by the version control system, Darcs. To see a log +quickly from the terminal, run: + + $ darcs changes --repo http://dev.rel4tion.org/fr33domlover/json-state + +There is also a web interface at which, among other +things, can display the history log. + +To see the log in a local clone, first get a copy of the repository if you +haven't yet: + + $ darcs get http://dev.rel4tion.org/fr33domlover/json-state + +Then move into the newly created directory and run darcs: + + $ cd json-state + $ darcs changes diff --git a/INSTALL b/INSTALL new file mode 100644 --- /dev/null +++ b/INSTALL @@ -0,0 +1,13 @@ +Install from Hackage: + + $ cabal install json-state + +Install from unpacked release tarball or source repo: + + $ cd json-state + $ cabal install + +Just play with it without installing: + + $ cabal build + $ cabal repl diff --git a/NEWS b/NEWS new file mode 100644 --- /dev/null +++ b/NEWS @@ -0,0 +1,23 @@ +This file lists the user-visible interesting changes between releases. For a +full list of changes to the source, see the ChangeLog. + + + +json-state 0.1.0.0 -- (2015-09-17) +================================== + +General, build and documentation changes: + +* (This is the first release, so everything is new) + +New APIs, features and enhancements: + +* (This is the first release, so everything is a new feature) + +Bug fixes: + +* (This is just the first release, many bugs haven't been discovered yet) + +Dependency changes: + +* (This is the first release) diff --git a/README.md b/README.md new file mode 100644 --- /dev/null +++ b/README.md @@ -0,0 +1,14 @@ +See the .cabal file for more info and link to project website the version +control. + +The official download location is Hackage: + + + +This library is free software, and is committed to software freedom. It is +released to the public domain using the CC0 Public Domain Dedication. For the +boring "legal" details see the file 'COPYING'. + +See the file 'INSTALL' for hints on installation. The file 'ChangeLog' explains +how to see the history log of the changes done in the code. 'NEWS' provides a +friendly overview of the changes for each release. diff --git a/Setup.hs b/Setup.hs new file mode 100644 --- /dev/null +++ b/Setup.hs @@ -0,0 +1,2 @@ +import Distribution.Simple +main = defaultMain diff --git a/json-state.cabal b/json-state.cabal new file mode 100644 --- /dev/null +++ b/json-state.cabal @@ -0,0 +1,37 @@ +name: json-state +version: 0.1.0.0 +synopsis: Keep program state in JSON files. +description: + If your program manages simple state data not shared with other programs, + this package provide a lightweight alternative to full ACID databases. It + allows you to load state from JSON files and update those files + asynchronously and periodically. Version control (using Git) is supported. +homepage: http://rel4tion.org/projects/json-state/ +bug-reports: http://rel4tion.org/projects/json-state/tickets/ +license: PublicDomain +license-file: COPYING +author: fr33domlover +maintainer: fr33domlover@riseup.net +copyright: ♡ Copying is an act of love. Please copy, reuse and share. +category: Data, Database +build-type: Simple +extra-source-files: AUTHORS ChangeLog COPYING INSTALL NEWS README.md +cabal-version: >=1.10 + +source-repository head + type: darcs + location: http://dev.rel4tion.org/fr33domlover/json-state + +library + exposed-modules: Data.JsonState + other-modules: Control.Debounce + -- other-extensions: + build-depends: aeson + , aeson-pretty >=0.7 + , base >=4.7 && <5 + , bytestring + , libgit >=0.3.1 + , time-units >=1 + hs-source-dirs: src + default-language: Haskell2010 + ghc-options: -Wall diff --git a/src/Control/Debounce.hs b/src/Control/Debounce.hs new file mode 100644 --- /dev/null +++ b/src/Control/Debounce.hs @@ -0,0 +1,61 @@ +{- This file is part of json-state. + - + - Written in 2015 by fr33domlover . + - + - ♡ Copying is an act of love. Please copy, reuse and share. + - + - The author(s) have dedicated all copyright and related and neighboring + - rights to this software to the public domain worldwide. This software is + - distributed without any warranty. + - + - You should have received a copy of the CC0 Public Domain Dedication along + - with this software. If not, see + - . + -} + +-- | This is similar to the same module from "auto-update" package, except here +-- the caller can pass a parameter to the debounced action. Also, the returned +-- action comes in 2 versions. +-- +-- The first is non-blocking at the cost of a small chance a parameter isn't +-- passed and is instead discarded. This can happen if the action is called +-- from different threads simultanously. One empties the 'MVar', and the other +-- happens to fill it first, and then the parameter the former thread passed is +-- discarded. If you run the action from a single thread, there is no problem, +-- or if missing at a hopefully small chance isn't a problem. +-- +-- The second is blocking, but only in the small chance described above. +-- Otherwise it doesn't block in practice. +-- +-- Also, exceptions aren't handled. This includes async exceptions and any +-- exceptions thrown by the given action. +module Control.Debounce + ( mkDebounce + ) +where + +import Control.Monad (forever, void) +import Control.Concurrent (forkIO, threadDelay) +import Control.Concurrent.MVar +import Data.Time.Units + +mkDebounce :: TimeUnit t + => t -- ^ Time delay between calls to the action + -> (a -> IO ()) -- ^ Action to perform + -> IO ( a -> IO () -- Never-blocking version + , a -> IO () -- Possibly-blocking version + ) +mkDebounce interval action = do + paramVar <- newEmptyMVar + let run = void $ forkIO $ forever $ do + param <- takeMVar paramVar + action param + threadDelay $ fromInteger $ toMicroseconds interval + actNB param = do + void $ tryTakeMVar paramVar + void $ tryPutMVar paramVar param + actPB param = do + void $ tryTakeMVar paramVar + putMVar paramVar param + run + return (actNB, actPB) diff --git a/src/Data/JsonState.hs b/src/Data/JsonState.hs new file mode 100644 --- /dev/null +++ b/src/Data/JsonState.hs @@ -0,0 +1,166 @@ +{- This file is part of json-state. + - + - Written in 2015 by fr33domlover . + - + - ♡ Copying is an act of love. Please copy, reuse and share. + - + - The author(s) have dedicated all copyright and related and neighboring + - rights to this software to the public domain worldwide. This software is + - distributed without any warranty. + - + - You should have received a copy of the CC0 Public Domain Dedication along + - with this software. If not, see + - . + -} + +-- | This module provides a function for loading a state value from a JSON +-- file, and a function which generates a safe scalable saver function. The +-- JSON files are written using the @aeson-pretty@ package, so that they are +-- easy to read and modify manually if needed. +-- +-- The save function generator, @mkSaveState@, returns a function which +-- saves settings when called, but only at most once in @t@, the time interval +-- passed to the generator. For example, if you pass an interval of 3 seconds, +-- you can safely call the generated save function even 100 times a second, and +-- the JSON file will still get updated just once in 3 seconds, avoiding an +-- overload of file I/O. +-- +-- The actual saving happens in a dedicated worker thread, so even when a save +-- does occur, it won't block the caller thread. The generator can be called +-- once at program start, and the returned save function saved in application +-- state. +-- +-- 'mkSaveStateVC' works similarly, but additionally provides a saver function +-- which commits the change into a git repo. +-- +-- Note that while this simple periodic save-to-file method can serve a simple +-- standalone application well, it won't work if you wish your data to be +-- shared by multiple applications and allow them to read and write it at the +-- same time. If that's the case, check out the @acid-state@ package, and other +-- persistence related packages. +module Data.JsonState + ( loadState + , mkSaveState + , mkSaveStateVC + , mkSaveStateChoose + , stateFilePath + ) +where + +import Control.Debounce (mkDebounce) +import Control.Monad (liftM, when) +import Data.Aeson (FromJSON, ToJSON, eitherDecode) +import Data.Aeson.Encode.Pretty (encodePretty) +import Data.Time.Units (TimeUnit) +import Lib.Git +import System.IO.Error (tryIOError) + +import qualified Data.ByteString.Lazy as B + +-- | Try to load state from a file. +-- +-- If an error occurs, 'Left' a pair is returned. The boolean indicates whether +-- reading the file failed ('False') or parsing the content failed ('True'). +-- The string is an error description. +-- +-- If the operation succeeds, 'Right' the loaded state data is returned. +loadState :: FromJSON s + => FilePath -- ^ File to load + -> IO (Either (Bool, String) s) +loadState file = do + errOrStr <- tryIOError (B.readFile file) + let pairOrStr = either (Left . (,) False . show) Right errOrStr + return $ pairOrStr >>= either (Left . (,) True) Right . eitherDecode + +saveAction :: ToJSON s => FilePath -> s -> IO () +saveAction file s = B.writeFile file $ encodePretty s + +-- | Prepare a save action which writes state into a JSON file. This action +-- defers the work to a separate dedicated thread, and ensures the file isn't +-- saved more than once within the given time interval. +-- +-- The action is non-blocking but there is a chance a save is missed if saves +-- are triggered simultaneously from different threads. +-- +-- You can call the returned action from your UI thread as a reaction to a +-- state change, without worrying about delay or IO load. +mkSaveState :: (TimeUnit t, ToJSON s) + => t -- ^ Minimal time interval between saves + -> FilePath -- ^ File to save + -> IO (s -> IO ()) +mkSaveState interval file = + liftM fst $ mkDebounce interval (saveAction file) + +saveActionVC :: ToJSON s => FilePath -> Config -> String -> (s, Bool) -> IO () +saveActionVC file cfg msg (s, git) = do + saveAction (configCwd cfg ++ '/' : file) s + when git $ runGit cfg $ do + add [file] + commit [] "json-state" "json@state" msg [] + +-- | Like 'mkSaveState', but also takes a repository path. Creates a Git +-- repository there if there isn't yet. Two save actions are returned. The +-- first one simply saves state to a file, just like in 'mkSaveState'. The +-- second one saves to file and then commits it into the Git repository. +-- +-- Note that the file path is relative to the repo path. For example, if you +-- have the repo in \"/home/joe/repo\" and the file is \"/home/joe/repo/file\", +-- pass just \"file\" as the file path. +mkSaveStateVC :: (TimeUnit t, ToJSON s) + => t -- ^ Minimal time interval between saves + -> FilePath -- ^ File to save, path relative to repo path + -> FilePath -- ^ Path of the Git repository + -> String -- ^ Commit message to use in automatic commits + -> IO ( s -> IO () + , s -> IO () + ) +mkSaveStateVC interval file repo msg = do + let cfg = makeConfig repo Nothing + runGit cfg $ initDB False + action <- liftM fst $ mkDebounce interval (saveActionVC file cfg msg) + let withgit s = action (s, True) + nogit s = action (s, False) + return (nogit, withgit) + +-- | This is a variant which returns a single save action, which either uses or +-- doesn't use a Git repo. If the repo path (3rd argument) is 'Nothing', then +-- Git isn't used at all and the file path is treated like 'mkSaveState' would. +-- Otherwise, i.e. if a repo path is specified, the returned action will commit +-- changes to the Git repo, and the repo and file path arguments are treated +-- like 'mkSaveStateVC' would, i.e. the file path is relative to the repo. +-- +-- If you use this function, also use 'stateFilePath' to determine the correct +-- path to pass to 'loadState'. +mkSaveStateChoose :: (TimeUnit t, ToJSON s) + => t + -- ^ Minimal time interval between saves + -> FilePath + -- ^ File to save. If the repo path (next argument) is + -- 'Nothing', no Git repo is used, and this path is relative + -- to the process working dir, or absolute. If a repo path is + -- specified, this path is relative to repo path, and the + -- returned action also commits the file to the Git repo. + -> Maybe FilePath + -- ^ Optional path of the Git repository. If you pass + -- 'Nothing', a Git repo won't be used. If you pass 'Just' a + -- repo path, the save action will commit the change. + -> String + -- ^ Commit message to use in automatic commits + -> IO (s -> IO ()) +mkSaveStateChoose interval file (Just repo) msg = + liftM snd $ mkSaveStateVC interval file repo msg +mkSaveStateChoose interval file Nothing _msg = + mkSaveState interval file + +-- | If you use 'mkSaveStateChoose' to save the state, that function combines +-- the repo path and the file path when needed, to determine the full path of +-- the state file. But then, how do you determine which path to pass to +-- 'loadState'? This is exactly what this function does. Pass it the optional +-- repo path and the file path you passed to 'mkSaveStateChoose', and you'll +-- get a full path you can pass to 'loadState'. +stateFilePath :: FilePath -> Maybe FilePath -> FilePath +stateFilePath file (Just dir@(_:_)) = + if last dir == '/' + then dir ++ file + else dir ++ '/' : file +stateFilePath file _ = file