;csv: refactor amount parsing

hledger-lib/Hledger/Read/CsvReader.hs

@@ -1024,19 +1024,35 @@ getAmount rules record currency p1IsVirtual n =
              "\t=> value: " ++ showMixedAmount a -- XXX not sure this is showing all the right info
            | (f,a) <- fs]
 
+-- | Figure out the expected balance (assertion or assignment) specified for posting N,
+-- if any (and its parse position).
+getBalance :: CsvRules -> CsvRecord -> String -> Int -> Maybe (Amount, GenericSourcePos)
+getBalance rules record currency n = do
+  v <- (fieldval ("balance"++show n)
+        -- for posting 1, also recognise the old field name
+        <|> if n==1 then fieldval "balance" else Nothing)
+  case v of
+    "" -> Nothing
+    s  -> Just (
+            parseBalanceAmount rules record currency n s
+           ,nullsourcepos  -- parse position to show when assertion fails,
+           )               -- XXX the csv record's line number would be good
+  
   where
-    -- | Given a non-empty amount string to parse, along with a possibly
+    fieldval = fmap strip . hledgerFieldValue rules record :: HledgerFieldName -> Maybe String
-    -- non-empty currency symbol to prepend, parse as a hledger amount (as
+
-    -- in journal format), or raise an error.
+-- | Given a non-empty amount string (from CSV) to parse, along with a
-    -- The CSV rules and record are provided for the error message.
+-- possibly non-empty currency symbol to prepend,
-    parseAmount :: CsvRules -> CsvRecord -> String -> String -> MixedAmount
+-- parse as a hledger MixedAmount (as in journal format), or raise an error.
-    parseAmount rules record currency amountstr =
+-- The whole CSV record is provided for the error message.
+parseAmount :: CsvRules -> CsvRecord -> String -> String -> MixedAmount
+parseAmount rules record currency s =
   either mkerror (Mixed . (:[])) $  -- PARTIAL:
   runParser (evalStateT (amountp <* eof) nulljournal) "" $
-      T.pack $ (currency++) $ simplifySign amountstr
+  T.pack $ (currency++) $ simplifySign s
   where
     mkerror e = error' $ unlines
-          ["error: could not parse \""++amountstr++"\" as an amount"
+      ["error: could not parse \""++s++"\" as an amount"
       ,showRecord record
       ,showRules rules record
       -- ,"the default-currency is: "++fromMaybe "unspecified" (getDirective "default-currency" rules)
@@ -1046,22 +1062,17 @@ getAmount rules record currency p1IsVirtual n =
         ++"or add or change your skip rule"
       ]
 
--- | Figure out the expected balance (assertion or assignment) specified for posting N,
+-- XXX unify these
--- if any (and its parse position).
+-- | Almost but not quite the same as parseAmount.
-getBalance :: CsvRules -> CsvRecord -> String -> Int -> Maybe (Amount, GenericSourcePos)
+-- Given a non-empty amount string (from CSV) to parse, along with a
-getBalance rules record currency n =
+-- possibly non-empty currency symbol to prepend,
-  (fieldval ("balance"++show n)
+-- parse as a hledger Amount (as in journal format), or raise an error.
-    -- for posting 1, also recognise the old field name
+-- The CSV record and the field's numeric suffix are provided for the error message.
-    <|> if n==1 then fieldval "balance" else Nothing)
+parseBalanceAmount :: CsvRules -> CsvRecord -> String -> Int -> String -> Amount
-  >>= parsebalance currency n . strip
+parseBalanceAmount rules record currency n s =
-  where
+  either (mkerror n s) id $
-    parsebalance currency n s
-      | null s    = Nothing
-      | otherwise = Just
-          (either (mkerror n s) id $
     runParser (evalStateT (amountp <* eof) nulljournal) "" $
     T.pack $ (currency++) $ simplifySign s
-          ,nullsourcepos)  -- XXX parse position to show when assertion fails,
                   -- the csv record's line number would be good
   where
     mkerror n s e = error' $ unlines
@@ -1071,8 +1082,6 @@ getBalance rules record currency n =
       -- ,"the default-currency is: "++fromMaybe "unspecified" mdefaultcurrency
       ,"the parse error is:      "++customErrorBundlePretty e
       ]
-    -- mdefaultcurrency = rule "default-currency"
-    fieldval = hledgerFieldValue rules record :: HledgerFieldName -> Maybe String
 
 -- | Make a balance assertion for the given amount, with the given parse
 -- position (to be shown in assertion failures), with the assertion type