148 lines
5.1 KiB
Haskell
148 lines
5.1 KiB
Haskell
{-|
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An 'Amount' is some quantity of money, shares, or anything else.
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A simple amount is a commodity, quantity pair (where commodity can be anything):
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@
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$1
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£-50
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EUR 3.44
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GOOG 500
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1.5h
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90apples
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0
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@
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A mixed amount (not yet implemented) is one or more simple amounts:
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@
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$50, EUR 3, AAPL 500
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16h, $13.55, oranges 6
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@
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Commodities may be convertible or not. A mixed amount containing only
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convertible commodities can be converted to a simple amount. Arithmetic
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examples:
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@
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$1 - $5 = $-4
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$1 + EUR 0.76 = $2
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EUR0.76 + $1 = EUR 1.52
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EUR0.76 - $1 = 0
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($5, 2h) + $1 = ($6, 2h)
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($50, EUR 3, AAPL 500) + ($13.55, oranges 6) = $67.51, AAPL 500, oranges 6
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($50, EUR 3) * $-1 = $-53.96
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($50, AAPL 500) * $-1 = error
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@
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-}
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module Ledger.Amount
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where
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import qualified Data.Map as Map
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import Ledger.Utils
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import Ledger.Types
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import Ledger.Commodity
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instance Show Amount where show = showAmount
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instance Show MixedAmount where show = showMixedAmount
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instance Num Amount where
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abs (Amount c q p) = Amount c (abs q) p
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signum (Amount c q p) = Amount c (signum q) p
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fromInteger i = Amount (comm "") (fromInteger i) Nothing
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(+) = amountop (+)
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(-) = amountop (-)
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(*) = amountop (*)
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instance Num MixedAmount where
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fromInteger i = Mixed [Amount (comm "") (fromInteger i) Nothing]
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negate (Mixed as) = Mixed $ map negate as
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(+) (Mixed as) (Mixed bs) = normaliseMixedAmount $ Mixed $ filter (not . isZeroAmount) $ as ++ bs
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(*) = error "programming error, mixed amounts do not support multiplication"
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abs = error "programming error, mixed amounts do not support abs"
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signum = error "programming error, mixed amounts do not support signum"
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-- | Apply a binary arithmetic operator to two amounts - converting to the
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-- second one's commodity, adopting the lowest precision, and discarding
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-- any price information. (Using the second commodity is best since sum
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-- and other folds start with a no-commodity amount.)
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amountop :: (Double -> Double -> Double) -> Amount -> Amount -> Amount
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amountop op a@(Amount ac aq ap) b@(Amount bc bq bp) =
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Amount bc ((quantity $ convertAmountTo bc a) `op` bq) Nothing
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-- | Convert an amount to the specified commodity using the appropriate
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-- exchange rate (which is currently always 1).
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convertAmountTo :: Commodity -> Amount -> Amount
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convertAmountTo c2 (Amount c1 q p) = Amount c2 (q * conversionRate c1 c2) Nothing
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-- | Get the string representation of an amount, based on its commodity's
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-- display settings.
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showAmount :: Amount -> String
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showAmount (Amount (Commodity {symbol=sym,side=side,spaced=spaced,comma=comma,precision=p}) q pri)
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| sym=="AUTO" = "" -- can display one of these in an error message
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| side==L = printf "%s%s%s%s" sym space quantity price
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| side==R = printf "%s%s%s%s" quantity space sym price
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where
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space = if spaced then " " else ""
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quantity = commad $ printf ("%."++show p++"f") q
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commad = if comma then punctuatethousands else id
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price = case pri of (Just pamt) -> " @ " ++ showMixedAmount pamt
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Nothing -> ""
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-- | Add thousands-separating commas to a decimal number string
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punctuatethousands :: String -> String
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punctuatethousands s =
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sign ++ (addcommas int) ++ frac
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where
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(sign,num) = break isDigit s
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(int,frac) = break (=='.') num
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addcommas = reverse . concat . intersperse "," . triples . reverse
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triples [] = []
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triples l = [take 3 l] ++ (triples $ drop 3 l)
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-- | Does this amount appear to be zero when displayed with its given precision ?
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isZeroAmount :: Amount -> Bool
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isZeroAmount a = nonzerodigits == ""
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where nonzerodigits = filter (`elem` "123456789") $ showAmount a
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-- | Access a mixed amount's components.
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amounts :: MixedAmount -> [Amount]
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amounts (Mixed as) = as
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-- | Does this mixed amount appear to be zero - empty, or
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-- containing only simple amounts which appear to be zero ?
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isZeroMixedAmount :: MixedAmount -> Bool
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isZeroMixedAmount = all isZeroAmount . amounts . normaliseMixedAmount
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-- | Get the string representation of a mixed amount, showing each of
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-- its component amounts.
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showMixedAmount :: MixedAmount -> String
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showMixedAmount m = concat $ intersperse ", " $ map show as
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where (Mixed as) = normaliseMixedAmount m
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-- | Get the string representation of a mixed amount, and if it
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-- appears to be all zero just show a bare 0, ledger-style.
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showMixedAmountOrZero :: MixedAmount -> String
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showMixedAmountOrZero a
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| isZeroMixedAmount a = "0"
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| otherwise = showMixedAmount a
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-- | Simplify a mixed amount by combining any of its component amounts
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-- which have the same commodity.
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normaliseMixedAmount :: MixedAmount -> MixedAmount
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normaliseMixedAmount (Mixed as) = Mixed $ map sum $ grouped
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where
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grouped = [filter (hassymbol s) as | s <- symbols]
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symbols = sort $ nub $ map (symbol . commodity) as
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hassymbol s a = s == (symbol $ commodity a)
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-- | The empty mixed amount.
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nullamt :: MixedAmount
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nullamt = Mixed []
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-- | A temporary value for parsed transactions which had no amount specified.
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missingamt :: MixedAmount
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missingamt = Mixed [Amount (Commodity {symbol="AUTO",side=L,spaced=False,comma=False,precision=0}) 0 Nothing]
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