ui: with --watch, react to file changes in real time

Experimental, tested on OSX so far.
Rapid successive file changes can cause it to get stuck.

hledger-ui/Hledger/UI/AccountsScreen.hs

@@ -289,7 +289,8 @@ asHandle ui0@UIState{
         -- EvKey (KChar 'l') [MCtrl] -> do
         VtyEvent (EvKey KEsc        []) -> continue $ resetScreens d ui
         VtyEvent (EvKey (KChar c)   []) | c `elem` ['?'] -> continue $ setMode Help ui
-        VtyEvent (EvKey (KChar 'g') []) -> liftIO (uiReloadJournalIfChanged copts d j ui) >>= continue
+        e | e `elem` [VtyEvent (EvKey (KChar 'g') []), AppEvent FileChange] ->
+          liftIO (uiReloadJournalIfChanged copts d j ui) >>= continue
         VtyEvent (EvKey (KChar 'I') []) -> continue $ uiCheckBalanceAssertions d (toggleIgnoreBalanceAssertions ui)
         VtyEvent (EvKey (KChar 'a') []) -> suspendAndResume $ clearScreen >> setCursorPosition 0 0 >> add copts j >> uiReloadJournalIfChanged copts d j ui
         VtyEvent (EvKey (KChar 'E') []) -> suspendAndResume $ void (runEditor endPos (journalFilePath j)) >> uiReloadJournalIfChanged copts d j ui

hledger-ui/Hledger/UI/ErrorScreen.hs

@@ -92,7 +92,8 @@ esHandle ui@UIState{
             (pos,f) = case parsewithString hledgerparseerrorpositionp esError of
                         Right (f,l,c) -> (Just (l, Just c),f)
                         Left  _       -> (endPos, journalFilePath j)
-        VtyEvent (EvKey (KChar 'g') []) -> liftIO (uiReloadJournalIfChanged copts d j (popScreen ui)) >>= continue . uiCheckBalanceAssertions d
+        e | e `elem` [VtyEvent (EvKey (KChar 'g') []), AppEvent FileChange] ->
+          liftIO (uiReloadJournalIfChanged copts d j (popScreen ui)) >>= continue . uiCheckBalanceAssertions d
 --           (ej, _) <- liftIO $ journalReloadIfChanged copts d j
 --           case ej of
 --             Left err -> continue ui{aScreen=s{esError=err}} -- show latest parse error

hledger-ui/Hledger/UI/Main.hs

@@ -11,18 +11,22 @@ module Hledger.UI.Main where
 
 -- import Control.Applicative
 -- import Lens.Micro.Platform ((^.))
+import Control.Concurrent
 import Control.Monad
 -- import Control.Monad.IO.Class (liftIO)
--- import Data.Default
+import Data.Default (def)
 -- import Data.Monoid              -- 
 import Data.List
 import Data.Maybe
 -- import Data.Text (Text)
 import qualified Data.Text as T
 -- import Data.Time.Calendar
+import Graphics.Vty (mkVty)
 import Safe
 import System.Exit
-
+import System.Directory
+import System.FilePath
+import System.FSNotify
 import Brick
 
 import Hledger
@@ -143,5 +147,36 @@ runBrickUi uopts@UIOpts{cliopts_=copts@CliOpts{reportopts_=ropts}} j = do
       , appDraw         = \ui    -> sDraw   (aScreen ui) ui
       }
 
-  void $ defaultMain brickapp ui
+  -- start one or more background jobs reporting changes in the directories of our files
+  -- XXX misses quick successive saves (then refuses to reload manually)
+  --   withManagerConf defaultConfig{confDebounce=Debounce 1000} $ \mgr -> do
+  eventChan <- newChan
+  withManager $ \mgr -> do
+    dbg1IO "fsnotify using polling ?" $ isPollingManager mgr
+    files <- mapM canonicalizePath $ map fst $ jfiles j
+    let directories = nub $ sort $ map takeDirectory files
+    dbg1IO "files" files
+    dbg1IO "directories to watch" directories
 
+    forM_ directories $ \d -> watchDir
+      mgr
+      d
+      -- predicate: ignore changes not involving our files
+      (\fev -> case fev of
+        Added    f _ -> f `elem` files
+        Modified f _ -> f `elem` files
+        Removed  f _ -> f `elem` files
+        )
+      -- action: send event to app
+      (\fev -> do
+        -- return $ dbglog "fsnotify" $ showFSNEvent fev -- not working
+        dbg1IO "fsnotify" $ showFSNEvent fev
+        writeChan eventChan FileChange
+        )
+
+    -- start the brick app. Must be inside the withManager block.
+    void $ customMain (mkVty def) (Just eventChan) brickapp ui
+
+showFSNEvent (Added    f _) = "Added "    ++ show f
+showFSNEvent (Modified f _) = "Modified " ++ show f
+showFSNEvent (Removed  f _) = "Removed "  ++ show f

hledger-ui/Hledger/UI/RegisterScreen.hs

@@ -267,7 +267,8 @@ rsHandle ui@UIState{
         VtyEvent (EvKey (KChar 'q') []) -> halt ui
         VtyEvent (EvKey KEsc        []) -> continue $ resetScreens d ui
         VtyEvent (EvKey (KChar c)   []) | c `elem` ['?'] -> continue $ setMode Help ui
-        VtyEvent (EvKey (KChar 'g') []) -> liftIO (uiReloadJournalIfChanged copts d j ui) >>= continue
+        e | e `elem` [VtyEvent (EvKey (KChar 'g') []), AppEvent FileChange] ->
+          liftIO (uiReloadJournalIfChanged copts d j ui) >>= continue
         VtyEvent (EvKey (KChar 'I') []) -> continue $ uiCheckBalanceAssertions d (toggleIgnoreBalanceAssertions ui)
         VtyEvent (EvKey (KChar 'a') []) -> suspendAndResume $ clearScreen >> setCursorPosition 0 0 >> add copts j >> uiReloadJournalIfChanged copts d j ui
         VtyEvent (EvKey (KChar 't') [])    -> continue $ regenerateScreens j d $ setReportPeriod (DayPeriod d) ui

hledger-ui/Hledger/UI/TransactionScreen.hs

@@ -129,7 +129,7 @@ tsHandle ui@UIState{aScreen=s@TransactionScreen{tsTransaction=(i,t)
         VtyEvent (EvKey (KChar 'E') []) -> suspendAndResume $ void (runEditor pos f) >> uiReloadJournalIfChanged copts d j ui
           where
             (pos,f) = let GenericSourcePos f l c = tsourcepos t in (Just (l, Just c),f)
-        VtyEvent (EvKey (KChar 'g') []) -> do
+        e | e `elem` [VtyEvent (EvKey (KChar 'g') []), AppEvent FileChange] -> do
           d <- liftIO getCurrentDay
           (ej, _) <- liftIO $ journalReloadIfChanged copts d j
           case ej of

hledger-ui/Hledger/UI/UIOptions.hs

@@ -26,7 +26,8 @@ prognameandversion = progname ++ " " ++ version :: String
 
 uiflags = [
   -- flagNone ["debug-ui"]  (\opts -> setboolopt "rules-file" opts) "run with no terminal output, showing console"
-   flagReq  ["theme"] (\s opts -> Right $ setopt "theme" s opts) "THEME" ("use this custom display theme ("++intercalate ", " themeNames++")")
+   flagNone ["watch"] (\opts -> setboolopt "watch" opts) "watch for data changes and reload automatically"
+  ,flagReq  ["theme"] (\s opts -> Right $ setopt "theme" s opts) "THEME" ("use this custom display theme ("++intercalate ", " themeNames++")")
   ,flagReq  ["register"] (\s opts -> Right $ setopt "register" s opts) "ACCTREGEX" "start in the (first) matched account's register"
   ,flagNone ["flat"] (\opts -> setboolopt "flat" opts) "show full account names, unindented"
   -- ,flagReq ["drop"] (\s opts -> Right $ setopt "drop" s opts) "N" "with --flat, omit this many leading account name components"
@@ -51,7 +52,7 @@ uimode =  (mode "hledger-ui" [("command","ui")]
 
 -- hledger-ui options, used in hledger-ui and above
 data UIOpts = UIOpts {
-     debug_ui_ :: Bool
+     watch_ :: Bool
     ,cliopts_   :: CliOpts
  } deriving (Show)
 
@@ -65,8 +66,8 @@ rawOptsToUIOpts :: RawOpts -> IO UIOpts
 rawOptsToUIOpts rawopts = checkUIOpts <$> do
   cliopts <- rawOptsToCliOpts rawopts
   return defuiopts {
-              debug_ui_ = boolopt "debug-ui" rawopts
-             ,cliopts_   = cliopts
+              watch_   = boolopt "watch" rawopts
+             ,cliopts_ = cliopts
              }
 
 checkUIOpts :: UIOpts -> UIOpts

hledger-ui/Hledger/UI/UITypes.hs

@@ -82,7 +82,9 @@ data Name =
   | RegisterList
   deriving (Ord, Show, Eq)
 
-data AppEvent = DummyEvent
+data AppEvent =
+  FileChange
+  deriving (Eq, Show)
 
 -- | hledger-ui screen types & instances.
 -- Each screen type has generically named initialisation, draw, and event handling functions,

hledger-ui/doc/hledger-ui.1

@@ -39,8 +39,13 @@ Note: if invoking hledger\-ui as a hledger subcommand, write
 Any QUERYARGS are interpreted as a hledger search query which filters
 the data.
 .TP
-.B \f[C]\-\-flat\f[]
-show full account names, unindented
+.B \f[C]\-\-watch\f[]
+watch for data changes and reload automatically
+.RS
+.RE
+.TP
+.B \f[C]\-\-theme=default|terminal|greenterm\f[]
+use this custom display theme
 .RS
 .RE
 .TP
@@ -49,8 +54,8 @@ start in the (first) matched account\[aq]s register screen
 .RS
 .RE
 .TP
-.B \f[C]\-\-theme=default|terminal|greenterm\f[]
-use this custom display theme
+.B \f[C]\-\-flat\f[]
+show full account names, unindented
 .RS
 .RE
 .TP

hledger-ui/doc/hledger-ui.1.info

@@ -37,14 +37,17 @@ options as shown above.
    Any QUERYARGS are interpreted as a hledger search query which filters
 the data.
 
-`--flat'
-     show full account names, unindented
+`--watch'
+     watch for data changes and reload automatically
+
+`--theme=default|terminal|greenterm'
+     use this custom display theme
 
 `--register=ACCTREGEX'
      start in the (first) matched account's register screen
 
-`--theme=default|terminal|greenterm'
-     use this custom display theme
+`--flat'
+     show full account names, unindented
 
 `-V --value'
      show amounts as their current market value in their default
@@ -351,17 +354,17 @@ Tag Table:
 Node: Top88
 Node: OPTIONS823
 Ref: #options922
-Node: KEYS3786
-Ref: #keys3883
-Node: SCREENS6284
-Ref: #screens6371
-Node: Accounts screen6461
-Ref: #accounts-screen6591
-Node: Register screen8629
-Ref: #register-screen8786
-Node: Transaction screen10674
-Ref: #transaction-screen10834
-Node: Error screen11701
-Ref: #error-screen11825
+Node: KEYS3850
+Ref: #keys3947
+Node: SCREENS6348
+Ref: #screens6435
+Node: Accounts screen6525
+Ref: #accounts-screen6655
+Node: Register screen8693
+Ref: #register-screen8850
+Node: Transaction screen10738
+Ref: #transaction-screen10898
+Node: Error screen11765
+Ref: #error-screen11889
 
 End Tag Table

hledger-ui/doc/hledger-ui.1.m4.md

@@ -49,14 +49,17 @@ Note: if invoking hledger-ui as a hledger subcommand, write `--` before options
 
 Any QUERYARGS are interpreted as a hledger search query which filters the data.
 
-`--flat`
-: show full account names, unindented
+`--watch`
+: watch for data changes and reload automatically
+
+`--theme=default|terminal|greenterm`
+: use this custom display theme
 
 `--register=ACCTREGEX`
 : start in the (first) matched account's register screen
 
-`--theme=default|terminal|greenterm`
-: use this custom display theme
+`--flat`
+: show full account names, unindented
 
 `-V --value`
 : show amounts as their current market value in their default valuation commodity

hledger-ui/doc/hledger-ui.1.txt

@@ -35,13 +35,16 @@ OPTIONS
        Any  QUERYARGS  are interpreted as a hledger search query which filters
        the data.
 
-       --flat show full account names, unindented
+       --watch
+              watch for data changes and reload automatically
+
+       --theme=default|terminal|greenterm
+              use this custom display theme
 
        --register=ACCTREGEX
               start in the (first) matched account's register screen
 
-       --theme=default|terminal|greenterm
-              use this custom display theme
+       --flat show full account names, unindented
 
        -V --value
               show amounts as their current market value in their default val-

hledger-ui/hledger-ui.cabal

@@ -65,7 +65,9 @@ executable hledger-ui
     , cmdargs >= 0.8
     , containers
     , data-default
+    , directory
     , filepath
+    , fsnotify >= 0.2 && < 0.3
     , HUnit
     , microlens >= 0.4 && < 0.5
     , microlens-platform >= 0.2.3.1 && < 0.4

hledger-ui/package.yaml

@@ -56,7 +56,9 @@ executables:
       - cmdargs >= 0.8
       - containers
       - data-default
+      - directory
       - filepath
+      - fsnotify >= 0.2 && < 0.3
       - HUnit
       - microlens >= 0.4 && < 0.5
       - microlens-platform >= 0.2.3.1 && < 0.4