balance: add -V/--value to show as market value

Initial support of market value reporting and currency conversion,
similar in spirit to Ledger's.  The balance command now has a -V/--value
flag that converts all the reported amounts using their "default market
price". That is the latest market price (P directive, formerly called
"historical prices") found in the journal for their commodity that is on
or before the report end date.

Unlike Ledger, hledger's -V only uses the market prices recorded with P
directives, ignoring transaction prices recorded as part of posting
amounts (which -B/--cost uses). Using -B and -V together is allowed.

hledger-lib/Hledger/Data/Types.hs

@@ -180,7 +180,7 @@ data HistoricalPrice = HistoricalPrice {
       hdate :: Day,
       hcommodity :: Commodity,
       hamount :: Amount
-    } deriving (Eq,Typeable,Data) -- & Show (in Amount.hs)
+    } deriving (Eq,Ord,Typeable,Data) -- & Show (in Amount.hs)
 
 type Year = Integer
 

hledger-lib/Hledger/Reports/ReportOptions.hs

@@ -88,6 +88,7 @@ data ReportOpts = ReportOpts {
     ,drop_           :: Int
     ,row_total_      :: Bool
     ,no_total_       :: Bool
+    ,value_          :: Bool
  } deriving (Show, Data, Typeable)
 
 instance Default ReportOpts where def = defreportopts
@@ -121,6 +122,7 @@ defreportopts = ReportOpts
     def
     def
     def
+    def
 
 rawOptsToReportOpts :: RawOpts -> IO ReportOpts
 rawOptsToReportOpts rawopts = do
@@ -153,6 +155,7 @@ rawOptsToReportOpts rawopts = do
     ,drop_        = intopt "drop" rawopts
     ,row_total_   = boolopt "row-total" rawopts
     ,no_total_    = boolopt "no-total" rawopts
+    ,value_       = boolopt "value" rawopts
     }
 
 accountlistmodeopt :: RawOpts -> AccountListMode

hledger/Hledger/Cli/Balance.hs

@@ -242,6 +242,9 @@ module Hledger.Cli.Balance (
  ,tests_Hledger_Cli_Balance
 ) where
 
+import Data.List (sort)
+import Data.Time.Calendar (Day)
+import Data.Maybe (fromMaybe)
 import System.Console.CmdArgs.Explicit as C
 import Text.CSV
 import Test.HUnit
@@ -270,6 +273,7 @@ balancemode = (defCommandMode $ ["balance"] ++ aliases) { -- also accept but don
      ,flagNone ["average","A"] (\opts -> setboolopt "average" opts) "multicolumn mode: show a row average column"
      ,flagNone ["row-total","T"] (\opts -> setboolopt "row-total" opts) "multicolumn mode: show a row total column"
      ,flagNone ["no-total","N"] (\opts -> setboolopt "no-total" opts) "don't show the final total row"
+     ,flagNone ["value","V"] (setboolopt "value") "show amounts as their market value in their default valuation commodity"
      ]
      ++ outputflags
     ,groupHidden = []
@@ -288,25 +292,73 @@ balance opts@CliOpts{reportopts_=ropts} j = do
       let format   = outputFormatFromOpts opts
           interval = intervalFromOpts ropts
           baltype  = balancetype_ ropts
+          valuedate = fromMaybe d $ queryEndDate False $ queryFromOpts d ropts
       case interval of
         NoInterval -> do
           let report = balanceReport ropts (queryFromOpts d ropts) j
+              convert | value_ ropts = balanceReportValue j valuedate
+                      | otherwise    = id
               render = case format of
                 "csv" -> \ropts r -> (++ "\n") $ printCSV $ balanceReportAsCsv ropts r
                 _     -> balanceReportAsText
-          writeOutput opts $ render ropts report
+          writeOutput opts $ render ropts $ convert report
         _ -> do
           let report = multiBalanceReport ropts (queryFromOpts d ropts) j
+              convert | value_ ropts = multiBalanceReportValue j valuedate
+                      | otherwise    = id
               render = case format of
                 "csv" -> \ropts r -> (++ "\n") $ printCSV $ multiBalanceReportAsCsv ropts r
                 _     -> case baltype of
                   PeriodBalance     -> periodBalanceReportAsText
                   CumulativeBalance -> cumulativeBalanceReportAsText
                   HistoricalBalance -> historicalBalanceReportAsText
-          writeOutput opts $ render ropts report
+          writeOutput opts $ render ropts $ convert report
 
 -- single-column balance reports
 
+-- | Convert all the amounts in a single-column balance report to
+-- their value on the given date in their default valuation
+-- commodities.
+balanceReportValue :: Journal -> Day -> BalanceReport -> BalanceReport
+balanceReportValue j d r = r'
+  where
+    (items,total) = r
+    r' = ([(n, mixedAmountValue j d a) |(n,a) <- items], mixedAmountValue j d total)
+
+mixedAmountValue :: Journal -> Day -> MixedAmount -> MixedAmount
+mixedAmountValue j d (Mixed as) = Mixed $ map (amountValue j d) as
+
+-- | Find the market value of this amount on the given date, in it's
+-- default valuation commodity, based on historical prices. If no
+-- default valuation commodity can be found, the amount is left
+-- unchanged.
+amountValue :: Journal -> Day -> Amount -> Amount
+amountValue j d a =
+  case commodityValue j d (acommodity a) of
+    Just v  -> v{aquantity=aquantity v * aquantity a
+                ,aprice=aprice a
+                }
+    Nothing -> a
+
+-- | Find the market value, if known, of one unit of this commodity on
+-- the given date, in the commodity in which it has most recently been
+-- market-priced (ie the commodity mentioned in the most recent
+-- applicable historical price directive before this date).
+commodityValue :: Journal -> Day -> Commodity -> Maybe Amount
+commodityValue j d c
+    | null applicableprices = Nothing
+    | otherwise             = Just $ hamount $ last applicableprices
+  where
+    applicableprices = [p | p <- sort $ historical_prices j, hcommodity p == c, hdate p <= d]
+
+-- | Find the best commodity to convert to when asked to show the
+-- market value of this commodity on the given date. That is, the one
+-- in which it has most recently been market-priced, ie the commodity
+-- mentioned in the most recent applicable historical price directive
+-- before this date.
+-- defaultValuationCommodity :: Journal -> Day -> Commodity -> Maybe Commodity
+-- defaultValuationCommodity j d c = hamount <$> commodityValue j d c
+
 -- | Render a single-column balance report as CSV.
 balanceReportAsCsv :: ReportOpts -> BalanceReport -> CSV
 balanceReportAsCsv opts (items, total) =
@@ -393,6 +445,19 @@ formatField opts accountName depth total ljust min max field = case field of
 
 -- multi-column balance reports
 
+-- | Convert all the amounts in a multi-column balance report to their
+-- value on the given date in their default valuation commodities
+-- (which are determined as of that date, not the report interval dates).
+multiBalanceReportValue :: Journal -> Day -> MultiBalanceReport -> MultiBalanceReport
+multiBalanceReportValue j d r = r'
+  where
+    MultiBalanceReport (spans, rows, (coltotals, rowtotaltotal, rowavgtotal)) = r
+    r' = MultiBalanceReport
+         (spans,
+          [(n, map convert rowamts, convert rowtotal, convert rowavg) | (n, rowamts, rowtotal, rowavg) <- rows],
+          (map convert coltotals, convert rowtotaltotal, convert rowavgtotal))
+    convert = mixedAmountValue j d
+
 -- | Render a multi-column balance report as CSV.
 multiBalanceReportAsCsv :: ReportOpts -> MultiBalanceReport -> CSV
 multiBalanceReportAsCsv opts (MultiBalanceReport (colspans, items, (coltotals,tot,avg))) =