balance, lib: make StringFormat singular; cleanup

Pass around a StringFormat rather than [StringFormat].
Also more balance report item rendering refactoring.

hledger-lib/Hledger/Data/StringFormat.hs

@@ -7,7 +7,8 @@
 module Hledger.Data.StringFormat (
           parseStringFormat
         , formatString
-        , StringFormat(..)
+        , StringFormat
+        , StringFormatComponent(..)
         , ReportItemField(..)
         -- , stringformatp
         , tests
@@ -24,8 +25,10 @@ import Text.Printf (printf)
 
 
 -- | A format specification/template to use when rendering report line items as text.
--- These are currently supported by the balance command.
-data StringFormat =
+-- (Currently supported by the balance command in single-column mode).
+type StringFormat = [StringFormatComponent]
+
+data StringFormatComponent =
     FormatLiteral String
   | FormatField Bool        -- Left justified ?
                 (Maybe Int) -- Min width
@@ -33,6 +36,7 @@ data StringFormat =
                 ReportItemField       -- Field name
   deriving (Show, Eq)
 
+
 -- | An id identifying which report item field to interpolate.  These
 -- are drawn from several hledger report types, so are not all
 -- applicable for a given report.
@@ -55,7 +59,7 @@ formatString leftJustified min max s = printf fmt s
       fmt = "%" ++ l ++ min' ++ max' ++ "s"
 
 -- | Parse a string format specification, or return a parse error.
-parseStringFormat :: String -> Either String [StringFormat]
+parseStringFormat :: String -> Either String StringFormat
 parseStringFormat input = case (runParser (stringformatp <* eof) () "(unknown)") input of
     Left y -> Left $ show y
     Right x -> Right x
@@ -71,7 +75,7 @@ field = do
     <|> try (string "total" >> return TotalField)
     <|> try (many1 digit >>= (\s -> return $ FieldNo $ read s))
 
-formatField :: Stream [Char] m Char => ParsecT [Char] st m StringFormat
+formatField :: Stream [Char] m Char => ParsecT [Char] st m StringFormatComponent
 formatField = do
     char '%'
     leftJustified <- optionMaybe (char '-')
@@ -86,7 +90,7 @@ formatField = do
         Just text -> Just m where ((m,_):_) = readDec text
         _ -> Nothing
 
-formatLiteral :: Stream [Char] m Char => ParsecT [Char] st m StringFormat
+formatLiteral :: Stream [Char] m Char => ParsecT [Char] st m StringFormatComponent
 formatLiteral = do
     s <- many1 c
     return $ FormatLiteral s
@@ -95,24 +99,24 @@ formatLiteral = do
       c =     (satisfy isPrintableButNotPercentage <?> "printable character")
           <|> try (string "%%" >> return '%')
 
-formatp :: Stream [Char] m Char => ParsecT [Char] st m StringFormat
+formatp :: Stream [Char] m Char => ParsecT [Char] st m StringFormatComponent
 formatp =
         formatField
     <|> formatLiteral
 
-stringformatp :: Stream [Char] m Char => ParsecT [Char] st m [StringFormat]
+stringformatp :: Stream [Char] m Char => ParsecT [Char] st m StringFormat
 stringformatp = many formatp
 
 ----------------------------------------------------------------------
 
-testFormat :: StringFormat -> String -> String -> Assertion
+testFormat :: StringFormatComponent -> String -> String -> Assertion
 testFormat fs value expected = assertEqual name expected actual
     where
         (name, actual) = case fs of
             FormatLiteral l -> ("literal", formatString False Nothing Nothing l)
             FormatField leftJustify min max _ -> ("field", formatString leftJustify min max value)
 
-testParser :: String -> [StringFormat] -> Assertion
+testParser :: String -> StringFormat -> Assertion
 testParser s expected = case (parseStringFormat s) of
     Left  error -> assertFailure $ show error
     Right actual -> assertEqual ("Input: " ++ s) expected actual

hledger/Hledger/Cli/Balance.hs

@@ -408,40 +408,47 @@ This implementation turned out to be a bit convoluted but implements the followi
               EUR -1
     b         USD -1  ; Account 'b' has two amounts. The account name is printed on the last line.
 -}
--- | Render one balance report line item as plain text suitable for console output.
-balanceReportItemAsText :: ReportOpts -> [StringFormat] -> BalanceReportItem -> [String]
-balanceReportItemAsText opts fmt ((_, accountName, depth), Mixed amounts) =
-    -- 'amounts' could contain several quantities of the same commodity with different price.
-    -- In order to combine them into single value (which is expected) we take the first price and
-    -- use it for the whole mixed amount. This could be suboptimal. XXX
-    let Mixed normAmounts = normaliseMixedAmountSquashPricesForDisplay (Mixed amounts) in
-    case normAmounts of
-      [] -> []
-      [a] -> [formatBalanceReportItem fmt ((Just accountName'), depth, a)]
-      (as) -> multiline as
-    where
+-- | Render one balance report line item as plain text suitable for console output (or
+-- whatever string format is specified).
+balanceReportItemAsText :: ReportOpts -> StringFormat -> BalanceReportItem -> [String]
+balanceReportItemAsText opts fmt ((_, accountName, depth), amt) =
+    let
       accountName' = maybeAccountNameDrop opts accountName
-      multiline :: [Amount] -> [String]
-      multiline []     = []
-      multiline [a]    = [formatBalanceReportItem fmt ((Just accountName'), depth, a)]
-      multiline (a:as) = (formatBalanceReportItem fmt (Nothing, depth, a)) : multiline as
+      -- 'amounts' could contain several quantities of the same commodity with different price.
+      -- In order to combine them into single value (which is expected) we take the first price and
+      -- use it for the whole mixed amount. This could be suboptimal. XXX
+      amt' = normaliseMixedAmountSquashPricesForDisplay amt
+    in
+     formatBalanceReportItem fmt (accountName', depth, amt')
 
-formatBalanceReportItem :: [StringFormat] -> (Maybe AccountName, Int, Amount) -> String
-formatBalanceReportItem [] (_, _, _) = ""
-formatBalanceReportItem (fmt:fmts) (macctname, depth, amount) =
-  format fmt (macctname, depth, amount) ++
-  formatBalanceReportItem fmts (macctname, depth, amount)
-  where
-    format :: StringFormat -> (Maybe AccountName, Int, Amount) -> String
-    format (FormatLiteral s) _ = s
-    format (FormatField ljust min max field) (macctname, depth, total) = case field of
-      DepthSpacerField -> formatString ljust Nothing max $ replicate d ' '
-                          where d = case min of
-                                     Just m  -> depth * m
-                                     Nothing -> depth
-      AccountField     -> formatString ljust min max $ fromMaybe "" macctname
-      TotalField       -> formatString ljust min max $ showAmountWithoutPrice total
-      _                -> ""
+-- | Render a balance report item using the given StringFormat, generating one or more lines of text.
+formatBalanceReportItem :: StringFormat -> (AccountName, Int, MixedAmount) -> [String]
+formatBalanceReportItem [] _ = [""]
+formatBalanceReportItem fmt (acctname, depth, Mixed amts) =
+  case amts of
+    []     -> []
+    [a]    -> [formatLine fmt (Just acctname, depth, a)]
+    (a:as) -> [formatLine fmt (Just acctname, depth, a)] ++
+              [formatLine fmt (Nothing, depth, a) | a <- as]
+
+-- | Render one line of a balance report item using the given StringFormat, maybe omitting the account name.
+formatLine :: StringFormat -> (Maybe AccountName, Int, Amount) -> String
+formatLine [] _ = ""
+formatLine (fmt:fmts) (macctname, depth, amount) =
+  formatComponent fmt (macctname, depth, amount) ++
+  formatLine fmts (macctname, depth, amount)
+
+-- | Render one StringFormat component of one line of a balance report item.
+formatComponent :: StringFormatComponent -> (Maybe AccountName, Int, Amount) -> String
+formatComponent (FormatLiteral s) _ = s
+formatComponent (FormatField ljust min max field) (macctname, depth, total) = case field of
+  DepthSpacerField -> formatString ljust Nothing max $ replicate d ' '
+                      where d = case min of
+                                 Just m  -> depth * m
+                                 Nothing -> depth
+  AccountField     -> formatString ljust min max $ fromMaybe "" macctname
+  TotalField       -> formatString ljust min max $ showAmountWithoutPrice total
+  _                -> ""
 
 -- multi-column balance reports
 

hledger/Hledger/Cli/Options.hs

@@ -467,11 +467,11 @@ maybeAccountNameDrop opts a | tree_ opts = a
 
 -- | Parse the format option if provided, possibly returning an error,
 -- otherwise get the default value.
-lineFormatFromOpts :: ReportOpts -> Either String [StringFormat]
+lineFormatFromOpts :: ReportOpts -> Either String StringFormat
 lineFormatFromOpts = maybe (Right defaultBalanceLineFormat) parseStringFormat . format_
 
 -- | Default line format for balance report: "%20(total)  %2(depth_spacer)%-(account)"
-defaultBalanceLineFormat :: [StringFormat]
+defaultBalanceLineFormat :: StringFormat
 defaultBalanceLineFormat = [
       FormatField False (Just 20) Nothing TotalField
     , FormatLiteral "  "