hledger/hledger-lib/Hledger/Data/Commodity.hs
2019-02-14 05:15:49 -08:00

82 lines
2.4 KiB
Haskell

{-|
A 'Commodity' is a symbol representing a currency or some other kind of
thing we are tracking, and some display preferences that tell how to
display 'Amount's of the commodity - is the symbol on the left or right,
are thousands separated by comma, significant decimal places and so on.
-}
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE CPP #-}
module Hledger.Data.Commodity
where
import Data.Char (isDigit)
import Data.List
import Data.Maybe (fromMaybe)
#if !(MIN_VERSION_base(4,11,0))
import Data.Monoid
#endif
import qualified Data.Text as T
-- import qualified Data.Map as M
import Hledger.Data.Types
import Hledger.Utils
-- characters that may not be used in a non-quoted commodity symbol
nonsimplecommoditychars = "0123456789-+.@*;\n \"{}=" :: String
isNonsimpleCommodityChar :: Char -> Bool
isNonsimpleCommodityChar c = isDigit c || c `textElem` otherChars
where
otherChars = "-+.@*;\n \"{}=" :: T.Text
textElem = T.any . (==)
quoteCommoditySymbolIfNeeded s | T.any (isNonsimpleCommodityChar) s = "\"" <> s <> "\""
| otherwise = s
commodity = ""
-- handy constructors for tests
-- unknown = commodity
-- usd = "$"
-- eur = "€"
-- gbp = "£"
-- hour = "h"
-- Some sample commodity' names and symbols, for use in tests..
commoditysymbols =
[("unknown","")
,("usd","$")
,("eur","")
,("gbp","£")
,("hour","h")
]
-- | Look up one of the sample commodities' symbol by name.
comm :: String -> CommoditySymbol
comm name = snd $ fromMaybe
(error' "commodity lookup failed")
(find (\n -> fst n == name) commoditysymbols)
-- | Find the conversion rate between two commodities. Currently returns 1.
conversionRate :: CommoditySymbol -> CommoditySymbol -> Double
conversionRate _ _ = 1
-- -- | Convert a list of commodities to a map from commodity symbols to
-- -- unique, display-preference-canonicalised commodities.
-- canonicaliseCommodities :: [CommoditySymbol] -> Map.Map String CommoditySymbol
-- canonicaliseCommodities cs =
-- Map.fromList [(s,firstc{precision=maxp}) | s <- symbols,
-- let cs = commoditymap ! s,
-- let firstc = head cs,
-- let maxp = maximum $ map precision cs
-- ]
-- where
-- commoditymap = Map.fromList [(s, commoditieswithsymbol s) | s <- symbols]
-- commoditieswithsymbol s = filter ((s==) . symbol) cs
-- symbols = nub $ map symbol cs