```{-# LANGUAGE StandaloneDeriving #-}
{-|
An 'Amount' is some quantity of money, shares, or anything else.

A simple amount is a 'Commodity', quantity pair:

@
\$1
£-50
EUR 3.44
GOOG 500
1.5h
90 apples
0
@

An amount may also have a per-unit price, or conversion rate, in terms
of some other commodity. If present, this is displayed after \@:

@
EUR 3 \@ \$1.35
@

A 'MixedAmount' is zero or more simple amounts.  Mixed amounts are
usually normalised so that there is no more than one amount in each
commodity, and no zero amounts (or, there is just a single zero amount
and no others.):

@
\$50 + EUR 3
16h + \$13.55 + AAPL 500 + 6 oranges
0
@

We can do limited arithmetic with simple or mixed amounts: either
price-preserving arithmetic with similarly-priced amounts, or
price-discarding arithmetic which ignores and discards prices.

-}

module Ledger.Amount
where
import Ledger.Utils
import Ledger.Types
import Ledger.Commodity

instance Show Amount where show = showAmount
instance Show MixedAmount where show = showMixedAmount
deriving instance Show HistoricalPrice

instance Num Amount where
abs (Amount c q p) = Amount c (abs q) p
signum (Amount c q p) = Amount c (signum q) p
fromInteger i = Amount (comm "") (fromInteger i) Nothing
(+) = amountop (+)
(-) = amountop (-)
(*) = amountop (*)

instance Ord Amount where
compare (Amount ac aq ap) (Amount bc bq bp) = compare (ac,aq,ap) (bc,bq,bp)

instance Num MixedAmount where
fromInteger i = Mixed [Amount (comm "") (fromInteger i) Nothing]
negate (Mixed as) = Mixed \$ map negateAmountPreservingPrice as
(+) (Mixed as) (Mixed bs) = normaliseMixedAmount \$ Mixed \$ as ++ bs
(*)    = error "programming error, mixed amounts do not support multiplication"
abs    = error "programming error, mixed amounts do not support abs"
signum = error "programming error, mixed amounts do not support signum"

instance Ord MixedAmount where
compare (Mixed as) (Mixed bs) = compare as bs

negateAmountPreservingPrice a = (-a){price=price a}

-- | Apply a binary arithmetic operator to two amounts, converting to the
-- second one's commodity (and display precision), discarding any price
-- information. (Using the second commodity is best since sum and other
-- folds start with a no-commodity amount.)
amountop :: (Double -> Double -> Double) -> Amount -> Amount -> Amount
amountop op a@(Amount _ _ _) (Amount bc bq _) =
Amount bc (quantity (convertAmountTo bc a) `op` bq) Nothing

-- | Convert an amount to the specified commodity using the appropriate
-- exchange rate (which is currently always 1).
convertAmountTo :: Commodity -> Amount -> Amount
convertAmountTo c2 (Amount c1 q _) = Amount c2 (q * conversionRate c1 c2) Nothing

-- | Convert mixed amount to the specified commodity
convertMixedAmountTo :: Commodity -> MixedAmount -> Amount
convertMixedAmountTo c2 (Mixed ams) = Amount c2 total Nothing
where
total = sum . map (quantity . convertAmountTo c2) \$ ams

-- | Convert an amount to the commodity of its saved price, if any.
costOfAmount :: Amount -> Amount
costOfAmount a@(Amount _ _ Nothing) = a
costOfAmount (Amount _ q (Just price))
| isZeroMixedAmount price = nullamt
| otherwise = Amount pc (pq*q) Nothing
where (Amount pc pq _) = head \$ amounts price

-- | Get the string representation of an amount, based on its commodity's
-- display settings.
showAmount :: Amount -> String
showAmount (Amount (Commodity {symbol="AUTO"}) _ _) = "" -- can appear in an error message
showAmount a@(Amount (Commodity {symbol=sym,side=side,spaced=spaced}) _ pri) =
case side of
L -> printf "%s%s%s%s" sym space quantity price
R -> printf "%s%s%s%s" quantity space sym price
where
space = if spaced then " " else ""
quantity = showAmount' a
price = case pri of (Just pamt) -> " @ " ++ showMixedAmount pamt
Nothing -> ""

-- | Get the string representation of an amount, without any \@ price.
showAmountWithoutPrice :: Amount -> String
showAmountWithoutPrice a = showAmount a{price=Nothing}

-- | Get the string representation (of the number part of) of an amount
showAmount' :: Amount -> String
showAmount' (Amount (Commodity {comma=comma,precision=p}) q _) = quantity
where
quantity = commad \$ printf ("%."++show p++"f") q
commad = if comma then punctuatethousands else id

-- | Add thousands-separating commas to a decimal number string
punctuatethousands :: String -> String
punctuatethousands s =
sign ++ addcommas int ++ frac
where
(sign,num) = break isDigit s
(int,frac) = break (=='.') num
addcommas = reverse . concat . intersperse "," . triples . reverse
triples [] = []
triples l  = take 3 l : triples (drop 3 l)

-- | Does this amount appear to be zero when displayed with its given precision ?
isZeroAmount :: Amount -> Bool
isZeroAmount = null . filter (`elem` "123456789") . showAmountWithoutPrice

-- | Is this amount "really" zero, regardless of the display precision ?
-- Since we are using floating point, for now just test to some high precision.
isReallyZeroAmount :: Amount -> Bool
isReallyZeroAmount = null . filter (`elem` "123456789") . printf "%.10f" . quantity

-- | Access a mixed amount's components.
amounts :: MixedAmount -> [Amount]
amounts (Mixed as) = as

-- | Does this mixed amount appear to be zero - empty, or
-- containing only simple amounts which appear to be zero ?
isZeroMixedAmount :: MixedAmount -> Bool
isZeroMixedAmount = all isZeroAmount . amounts . normaliseMixedAmount

-- | Is this mixed amount "really" zero ? See isReallyZeroAmount.
isReallyZeroMixedAmount :: MixedAmount -> Bool
isReallyZeroMixedAmount = all isReallyZeroAmount . amounts . normaliseMixedAmount

-- | MixedAmount derives Eq in Types.hs, but that doesn't know that we
-- want \$0 = EUR0 = 0. Yet we don't want to drag all this code in there.
-- When zero equality is important, use this, for now; should be used
-- everywhere.
mixedAmountEquals :: MixedAmount -> MixedAmount -> Bool
mixedAmountEquals a b = amounts a' == amounts b' || (isZeroMixedAmount a' && isZeroMixedAmount b')
where a' = normaliseMixedAmount a
b' = normaliseMixedAmount b

-- | Get the string representation of a mixed amount, showing each of
-- its component amounts. NB a mixed amount can have an empty amounts
-- list in which case it shows as \"\".
showMixedAmount :: MixedAmount -> String
showMixedAmount m = concat \$ intersperse "\n" \$ map showfixedwidth as
where
(Mixed as) = normaliseMixedAmount m
width = maximum \$ map (length . show) as
showfixedwidth = printf (printf "%%%ds" width) . show

-- | Get the string representation of a mixed amount, but without
-- any \@ prices.
showMixedAmountWithoutPrice :: MixedAmount -> String
showMixedAmountWithoutPrice m = concat \$ intersperse "\n" \$ map showfixedwidth as
where
(Mixed as) = normaliseMixedAmountIgnoringPrice m
width = maximum \$ map (length . show) as
showfixedwidth = printf (printf "%%%ds" width) . showAmountWithoutPrice

-- | Get the string representation of a mixed amount, and if it
-- appears to be all zero just show a bare 0, ledger-style.
showMixedAmountOrZero :: MixedAmount -> String
showMixedAmountOrZero a
| isZeroMixedAmount a = "0"
| otherwise = showMixedAmount a

-- | Get the string representation of a mixed amount, or a bare 0,
-- without any \@ prices.
showMixedAmountOrZeroWithoutPrice :: MixedAmount -> String
showMixedAmountOrZeroWithoutPrice a
| isZeroMixedAmount a = "0"
| otherwise = showMixedAmountWithoutPrice a

-- | Simplify a mixed amount by combining any component amounts which have
-- the same commodity and the same price. Also removes zero amounts,
-- or adds a single zero amount if there are no amounts at all.
normaliseMixedAmount :: MixedAmount -> MixedAmount
normaliseMixedAmount (Mixed as) = Mixed as''
where
as'' = map sumSamePricedAmountsPreservingPrice \$ group \$ sort as'
sort = sortBy cmpsymbolandprice
cmpsymbolandprice a1 a2 = compare (sym a1,price a1) (sym a2,price a2)
group = groupBy samesymbolandprice
samesymbolandprice a1 a2 = (sym a1 == sym a2) && (price a1 == price a2)
sym = symbol . commodity
as' | null nonzeros = [head \$ zeros ++ [nullamt]]
| otherwise = nonzeros
(zeros,nonzeros) = partition isReallyZeroAmount as

sumSamePricedAmountsPreservingPrice [] = nullamt
sumSamePricedAmountsPreservingPrice as = (sum as){price=price \$ head as}

-- | Simplify a mixed amount by combining any component amounts which have
-- the same commodity, ignoring and discarding their unit prices if any.
-- Also removes zero amounts, or adds a single zero amount if there are no
-- amounts at all.
normaliseMixedAmountIgnoringPrice :: MixedAmount -> MixedAmount
normaliseMixedAmountIgnoringPrice (Mixed as) = Mixed as''
where
as'' = map sumAmountsDiscardingPrice \$ group \$ sort as'
group = groupBy samesymbol where samesymbol a1 a2 = sym a1 == sym a2
sort = sortBy (comparing sym)
sym = symbol . commodity
as' | null nonzeros = [head \$ zeros ++ [nullamt]]
| otherwise = nonzeros
where (zeros,nonzeros) = partition isZeroAmount as

sumAmountsDiscardingPrice [] = nullamt
sumAmountsDiscardingPrice as = (sum as){price=Nothing}

-- | Convert a mixed amount's component amounts to the commodity of their
-- saved price, if any.
costOfMixedAmount :: MixedAmount -> MixedAmount
costOfMixedAmount (Mixed as) = Mixed \$ map costOfAmount as

-- | The empty simple amount.
nullamt :: Amount
nullamt = Amount unknown 0 Nothing

-- | The empty mixed amount.
nullmixedamt :: MixedAmount
nullmixedamt = Mixed []

-- | A temporary value for parsed transactions which had no amount specified.
missingamt :: MixedAmount
missingamt = Mixed [Amount Commodity {symbol="AUTO",side=L,spaced=False,comma=False,precision=0} 0 Nothing]

```