;feat:ui: implement live updating for the transaction page

Author: alerque

hledger-ui/Hledger/UI/UIScreens.hs

@@ -63,7 +63,7 @@ screenUpdate opts d j = \case
   BS sst -> BS $ bsUpdate opts d j sst
   IS sst -> IS $ isUpdate opts d j sst
   RS sst -> RS $ rsUpdate opts d j sst
-  TS sst -> TS $ tsUpdate sst
+  TS sst -> TS $ tsUpdate opts d j sst
   ES sst -> ES $ esUpdate sst
 
 -- | Construct an error screen.
@@ -360,12 +360,17 @@ tsNew acct nts nt =
     ,_tssTransaction  = nt
     }
 
--- | Update a transaction screen. 
--- This currently does nothing because the initialisation in rsHandle is not so easy to extract.
--- To see the updated transaction, one must exit and re-enter the transaction screen.
--- See also tsHandle.
-tsUpdate :: TransactionScreenState -> TransactionScreenState
-tsUpdate tss = 
+-- | Update a transaction screen by refreshing the current transaction from the journal.
+-- This preserves the current transaction selection while updating its data.
+-- XXX Caveat, this works by showing the transaction at the same index in the processed ledger,
+-- if transactions have been inserted or removed before the one shown this will just show
+-- whatever transaction landed at the same index in the new data set.
+tsUpdate :: UIOpts -> Day -> Journal -> TransactionScreenState -> TransactionScreenState
+tsUpdate _ _ j tss@TSS{_tssTransaction=(currentIdx,currentTxn)} = 
   dbgui "tsUpdate" $
-  tss `seq` tss  -- Force evaluation to prevent accumulation
-
+  let 
+    -- Find the updated version of the current transaction in the journal
+    updatedTxn = case find (\t -> tindex t == tindex currentTxn) (jtxns j) of
+      Just t  -> t
+      Nothing -> currentTxn  -- fallback to current if not found
+  in tss { _tssTransaction = (currentIdx, updatedTxn) }

hledger-ui/Hledger/UI/UIState.hs

@@ -366,8 +366,8 @@ resetScreens d ui@UIState{astartupopts=origopts, ajournal=j, aScreen=s,aPrevScre
 -- (using the ui state's current options), preserving the screen navigation history.
 -- Note, does not save the reporting date.
 --
--- XXX Currently this does not properly regenerate the transaction screen or error screen,
--- which depend on state from their parent(s); those screens' handlers must do additional work, which is fragile.
+-- XXX Currently this does not properly regenerate or error screen,
+-- which depends on state from their parent(s); that screens' handler must do additional work, which is fragile.
 regenerateScreens :: Journal -> Day -> UIState -> UIState
 regenerateScreens j d ui@UIState{aScreen=s} = 
   let !ui' = ui{ajournal=j, aScreen=s'}
@@ -378,6 +378,6 @@ regenerateScreens j d ui@UIState{aScreen=s} =
         BS ass -> BS $! bsUpdate (aopts ui') d j ass
         IS ass -> IS $! isUpdate (aopts ui') d j ass
         RS rss -> RS $! rsUpdate (aopts ui') d j rss
-        TS tss -> TS $! tsUpdate tss
+        TS tss -> TS $! tsUpdate (aopts ui') d j tss
         ES _   -> s
   in ui'