hledger/hledger-lib/Hledger/Data/Amount.hs

{-|
A simple 'Amount' is some quantity of money, shares, or anything else.
It has a (possibly null) 'CommoditySymbol' and a numeric quantity:

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

It may also have an assigned 'Price', representing this amount's per-unit
or total cost in a different commodity. If present, this is rendered like
so:

@
  EUR 2 \@ $1.50  (unit price)
  EUR 2 \@\@ $3   (total price)
@

A 'MixedAmount' is zero or more simple amounts, so can represent multiple
commodities; this is the type most often used:

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

When a mixed amount has been \"normalised\", it has no more than one amount
in each commodity and no zero amounts; or it has just a single zero amount
and no others.

Limited arithmetic with simple and mixed amounts is supported, best used
with similar amounts since it mostly ignores assigned prices and commodity
exchange rates.

-}

{-# LANGUAGE BangPatterns       #-}
{-# LANGUAGE CPP                #-}
{-# LANGUAGE OverloadedStrings  #-}
{-# LANGUAGE RecordWildCards    #-}
{-# LANGUAGE StandaloneDeriving #-}

module Hledger.Data.Amount (
  -- * Amount
  amount,
  nullamt,
  missingamt,
  num,
  usd,
  eur,
  gbp,
  per,
  hrs,
  at,
  (@@),
  amountWithCommodity,
  -- ** arithmetic
  amountCost,
  amountIsZero,
  amountLooksZero,
  amountAndPriceIsZero,
  amountAndPriceLooksZero,
  divideAmount,
  multiplyAmount,
  divideAmountAndPrice,
  multiplyAmountAndPrice,
  amountTotalPriceToUnitPrice,
  -- ** rendering
  AmountDisplayOpts(..),
  noColour,
  noPrice,
  oneLine,
  amountstyle,
  styleAmount,
  styleAmountExceptPrecision,
  amountUnstyled,
  showAmountB,
  showAmount,
  cshowAmount,
  showAmountWithZeroCommodity,
  showAmountDebug,
  showAmountWithoutPrice,
  amountSetPrecision,
  withPrecision,
  amountSetFullPrecision,
  setAmountInternalPrecision,
  withInternalPrecision,
  setAmountDecimalPoint,
  withDecimalPoint,
  canonicaliseAmount,
  -- * MixedAmount
  nullmixedamt,
  missingmixedamt,
  mixed,
  amounts,
  filterMixedAmount,
  filterMixedAmountByCommodity,
  mapMixedAmount,
  normaliseMixedAmountSquashPricesForDisplay,
  normaliseMixedAmount,
  unifyMixedAmount,
  mixedAmountStripPrices,
  -- ** arithmetic
  mixedAmountCost,
  divideMixedAmount,
  multiplyMixedAmount,
  divideMixedAmountAndPrice,
  multiplyMixedAmountAndPrice,
  averageMixedAmounts,
  isNegativeAmount,
  isNegativeMixedAmount,
  mixedAmountIsZero,
  mixedAmountLooksZero,
  mixedAmountAndPriceIsZero,
  mixedAmountAndPriceLooksZero,
  mixedAmountTotalPriceToUnitPrice,
  -- ** rendering
  styleMixedAmount,
  mixedAmountUnstyled,
  showMixedAmount,
  showMixedAmountOneLine,
  showMixedAmountDebug,
  showMixedAmountWithoutPrice,
  showMixedAmountOneLineWithoutPrice,
  showMixedAmountElided,
  showMixedAmountWithZeroCommodity,
  showMixedAmountB,
  showMixedAmountLinesB,
  wbToText,
  wbUnpack,
  mixedAmountSetPrecision,
  mixedAmountSetFullPrecision,
  canonicaliseMixedAmount,
  -- * misc.
  ltraceamount,
  tests_Amount
) where

import Control.Monad (foldM)
import Data.Decimal (DecimalRaw(..), decimalPlaces, normalizeDecimal, roundTo)
import Data.Default (Default(..))
import Data.Foldable (toList)
import Data.List (intercalate, intersperse, mapAccumL, partition)
import Data.List.NonEmpty (NonEmpty(..), nonEmpty)
import qualified Data.Map.Strict as M
import Data.Maybe (fromMaybe)
#if !(MIN_VERSION_base(4,11,0))
import Data.Semigroup ((<>))
#endif
import qualified Data.Text as T
import qualified Data.Text.Lazy.Builder as TB
import Data.Word (Word8)
import Safe (headDef, lastDef, lastMay)
import Text.Printf (printf)

import Hledger.Data.Types
import Hledger.Data.Commodity
import Hledger.Utils

deriving instance Show MarketPrice


-- | Options for the display of Amount and MixedAmount.
data AmountDisplayOpts = AmountDisplayOpts
  { displayPrice         :: Bool       -- ^ Whether to display the Price of an Amount.
  , displayZeroCommodity :: Bool       -- ^ If the Amount rounds to 0, whether to display its commodity string.
  , displayColour        :: Bool       -- ^ Whether to colourise negative Amounts.
  , displayNormalised    :: Bool       -- ^ Whether to normalise MixedAmounts before displaying.
  , displayOneLine       :: Bool       -- ^ Whether to display on one line.
  , displayMinWidth      :: Maybe Int  -- ^ Minimum width to pad to
  , displayMaxWidth      :: Maybe Int  -- ^ Maximum width to clip to
  } deriving (Show)

-- | Display Amount and MixedAmount with no colour.
instance Default AmountDisplayOpts where def = noColour

-- | Display Amount and MixedAmount with no colour.
noColour :: AmountDisplayOpts
noColour = AmountDisplayOpts { displayPrice         = True
                             , displayColour        = False
                             , displayZeroCommodity = False
                             , displayNormalised    = True
                             , displayOneLine       = False
                             , displayMinWidth      = Nothing
                             , displayMaxWidth      = Nothing
                             }

-- | Display Amount and MixedAmount with no prices.
noPrice :: AmountDisplayOpts
noPrice = def{displayPrice=False}

-- | Display Amount and MixedAmount on one line with no prices.
oneLine :: AmountDisplayOpts
oneLine = def{displayOneLine=True, displayPrice=False}

-------------------------------------------------------------------------------
-- Amount styles

-- | Default amount style
amountstyle = AmountStyle L False (Precision 0) (Just '.') Nothing

-------------------------------------------------------------------------------
-- Amount

instance Num Amount where
    abs a@Amount{aquantity=q}    = a{aquantity=abs q}
    signum a@Amount{aquantity=q} = a{aquantity=signum q}
    fromInteger i                = nullamt{aquantity=fromInteger i}
    negate a                     = transformAmountAndPrice negate a
    (+)                          = similarAmountsOp (+)
    (-)                          = similarAmountsOp (-)
    (*)                          = similarAmountsOp (*)

-- | The empty simple amount.
amount, nullamt :: Amount
amount = Amount{acommodity="", aquantity=0, aprice=Nothing, astyle=amountstyle, aismultiplier=False}
nullamt = amount

-- | A temporary value for parsed transactions which had no amount specified.
missingamt :: Amount
missingamt = amount{acommodity="AUTO"}

-- Handy amount constructors for tests.
-- usd/eur/gbp round their argument to a whole number of pennies/cents.
num n = amount{acommodity="",  aquantity=n}
hrs n = amount{acommodity="h", aquantity=n,           astyle=amountstyle{asprecision=Precision 2, ascommodityside=R}}
usd n = amount{acommodity="$", aquantity=roundTo 2 n, astyle=amountstyle{asprecision=Precision 2}}
eur n = amount{acommodity="€", aquantity=roundTo 2 n, astyle=amountstyle{asprecision=Precision 2}}
gbp n = amount{acommodity="£", aquantity=roundTo 2 n, astyle=amountstyle{asprecision=Precision 2}}
per n = amount{acommodity="%", aquantity=n,           astyle=amountstyle{asprecision=Precision 1, ascommodityside=R, ascommodityspaced=True}}
amt `at` priceamt = amt{aprice=Just $ UnitPrice priceamt}
amt @@ priceamt = amt{aprice=Just $ TotalPrice priceamt}

-- | Apply a binary arithmetic operator to two amounts, which should
-- be in the same commodity if non-zero (warning, this is not checked).
-- A zero result keeps the commodity of the second amount.
-- The result's display style is that of the second amount, with
-- precision set to the highest of either amount.
-- Prices are ignored and discarded.
-- Remember: the caller is responsible for ensuring both amounts have the same commodity.
similarAmountsOp :: (Quantity -> Quantity -> Quantity) -> Amount -> Amount -> Amount
similarAmountsOp op !Amount{acommodity=_,  aquantity=q1, astyle=AmountStyle{asprecision=p1}}
                    !Amount{acommodity=c2, aquantity=q2, astyle=s2@AmountStyle{asprecision=p2}} =
   -- trace ("a1:"++showAmountDebug a1) $ trace ("a2:"++showAmountDebug a2) $ traceWith (("= :"++).showAmountDebug)
   amount{acommodity=c2, aquantity=q1 `op` q2, astyle=s2{asprecision=max p1 p2}}
  --  c1==c2 || q1==0 || q2==0 =
  --  otherwise = error "tried to do simple arithmetic with amounts in different commodities"

-- | Convert an amount to the specified commodity, ignoring and discarding
-- any assigned prices and assuming an exchange rate of 1.
amountWithCommodity :: CommoditySymbol -> Amount -> Amount
amountWithCommodity c a = a{acommodity=c, aprice=Nothing}

-- | Convert a amount to its "cost" or "selling price" in another commodity,
-- using its attached transaction price if it has one.  Notes:
--
-- - price amounts must be MixedAmounts with exactly one component Amount
--   (or there will be a runtime error XXX)
--
-- - price amounts should be positive in the Journal
--   (though this is currently not enforced)
amountCost :: Amount -> Amount
amountCost a@Amount{aquantity=q, aprice=mp} =
    case mp of
      Nothing                                  -> a
      Just (UnitPrice  p@Amount{aquantity=pq}) -> p{aquantity=pq * q}
      Just (TotalPrice p@Amount{aquantity=pq}) -> p{aquantity=pq}

-- | Replace an amount's TotalPrice, if it has one, with an equivalent UnitPrice.
-- Has no effect on amounts without one.
-- Also increases the unit price's display precision to show one extra decimal place,
-- to help keep transaction amounts balancing.
-- Does Decimal division, might be some rounding/irrational number issues.
amountTotalPriceToUnitPrice :: Amount -> Amount
amountTotalPriceToUnitPrice
    a@Amount{aquantity=q, aprice=Just (TotalPrice pa@Amount{aquantity=pq, astyle=ps})}
    = a{aprice = Just $ UnitPrice pa{aquantity=abs (pq/q), astyle=ps{asprecision=pp}}}
  where
    -- Increase the precision by 1, capping at the max bound.
    pp = case asprecision ps of
                NaturalPrecision -> NaturalPrecision
                Precision p      -> Precision $ if p == maxBound then maxBound else p + 1
amountTotalPriceToUnitPrice a = a

-- | Divide an amount's quantity by a constant.
divideAmount :: Quantity -> Amount -> Amount
divideAmount n a@Amount{aquantity=q} = a{aquantity=q/n}

-- | Multiply an amount's quantity by a constant.
multiplyAmount :: Quantity -> Amount -> Amount
multiplyAmount n a@Amount{aquantity=q} = a{aquantity=q*n}

-- | Apply a function to an amount's quantity (and its total price, if it has one).
transformAmountAndPrice :: (Quantity -> Quantity) -> Amount -> Amount
transformAmountAndPrice f a@Amount{aquantity=q,aprice=p} = a{aquantity=f q, aprice=f' <$> p}
  where
    f' (TotalPrice a@Amount{aquantity=pq}) = TotalPrice a{aquantity = f pq}
    f' p = p

-- | Divide an amount's quantity (and its total price, if it has one) by a constant.
divideAmountAndPrice :: Quantity -> Amount -> Amount
divideAmountAndPrice n = transformAmountAndPrice (/n)

-- | Multiply an amount's quantity (and its total price, if it has one) by a constant.
multiplyAmountAndPrice :: Quantity -> Amount -> Amount
multiplyAmountAndPrice n = transformAmountAndPrice (*n)

-- | Is this amount negative ? The price is ignored.
isNegativeAmount :: Amount -> Bool
isNegativeAmount Amount{aquantity=q} = q < 0

-- | Round an Amount's Quantity to its specified display precision. If that is
-- NaturalPrecision, this does nothing.
amountRoundedQuantity :: Amount -> Quantity
amountRoundedQuantity Amount{aquantity=q, astyle=AmountStyle{asprecision=p}} = case p of
    NaturalPrecision -> q
    Precision p'     -> roundTo p' q

-- | Does mixed amount appear to be zero when rendered with its
-- display precision ?
amountLooksZero :: Amount -> Bool
amountLooksZero = (0==) . amountRoundedQuantity

-- | Does mixed amount and its price appear to be zero when rendered with its
-- display precision ?
amountAndPriceLooksZero :: Amount -> Bool
amountAndPriceLooksZero amt = amountLooksZero amt && priceLooksZero
  where
    priceLooksZero = case aprice amt of
      Just (TotalPrice p) -> amountLooksZero p
      _                   -> True

-- | Is this amount exactly zero, ignoring its display precision ?
amountIsZero :: Amount -> Bool
amountIsZero Amount{aquantity=q} = q == 0

-- | Are this amount and its price exactly zero, ignoring its display precision ?
amountAndPriceIsZero :: Amount -> Bool
amountAndPriceIsZero amt@Amount{aquantity=q} = q == 0 && priceIsZero
  where
    priceIsZero = case aprice amt of
      Just (TotalPrice p) -> amountIsZero p
      _                   -> True

-- | Set an amount's display precision, flipped.
withPrecision :: Amount -> AmountPrecision -> Amount
withPrecision = flip amountSetPrecision

-- | Set an amount's display precision.
amountSetPrecision :: AmountPrecision -> Amount -> Amount
amountSetPrecision p a@Amount{astyle=s} = a{astyle=s{asprecision=p}}

-- | Increase an amount's display precision, if needed, to enough decimal places
-- to show it exactly (showing all significant decimal digits, excluding trailing
-- zeros).
amountSetFullPrecision :: Amount -> Amount
amountSetFullPrecision a = amountSetPrecision p a
  where
    p                = max displayprecision naturalprecision
    displayprecision = asprecision $ astyle a
    naturalprecision = Precision . decimalPlaces . normalizeDecimal $ aquantity a

-- | Set an amount's internal precision, ie rounds the Decimal representing
-- the amount's quantity to some number of decimal places.
-- Rounding is done with Data.Decimal's default roundTo function:
-- "If the value ends in 5 then it is rounded to the nearest even value (Banker's Rounding)".
-- Does not change the amount's display precision.
-- Intended only for internal use, eg when comparing amounts in tests.
setAmountInternalPrecision :: Word8 -> Amount -> Amount
setAmountInternalPrecision p a@Amount{ aquantity=q, astyle=s } = a{
   astyle=s{asprecision=Precision p}
  ,aquantity=roundTo p q
  }

-- | Set an amount's internal precision, flipped.
-- Intended only for internal use, eg when comparing amounts in tests.
withInternalPrecision :: Amount -> Word8 -> Amount
withInternalPrecision = flip setAmountInternalPrecision

-- | Set (or clear) an amount's display decimal point.
setAmountDecimalPoint :: Maybe Char -> Amount -> Amount
setAmountDecimalPoint mc a@Amount{ astyle=s } = a{ astyle=s{asdecimalpoint=mc} }

-- | Set (or clear) an amount's display decimal point, flipped.
withDecimalPoint :: Amount -> Maybe Char -> Amount
withDecimalPoint = flip setAmountDecimalPoint

showAmountPrice :: Amount -> WideBuilder
showAmountPrice amt = case aprice amt of
    Nothing              -> mempty
    Just (UnitPrice  pa) -> WideBuilder (TB.fromString " @ ")  3 <> showAmountB noColour pa
    Just (TotalPrice pa) -> WideBuilder (TB.fromString " @@ ") 4 <> showAmountB noColour (sign pa)
  where sign = if aquantity amt < 0 then negate else id

showAmountPriceDebug :: Maybe AmountPrice -> String
showAmountPriceDebug Nothing                = ""
showAmountPriceDebug (Just (UnitPrice pa))  = " @ "  ++ showAmountDebug pa
showAmountPriceDebug (Just (TotalPrice pa)) = " @@ " ++ showAmountDebug pa

-- | Given a map of standard commodity display styles, apply the
-- appropriate one to this amount. If there's no standard style for
-- this amount's commodity, return the amount unchanged.
styleAmount :: M.Map CommoditySymbol AmountStyle -> Amount -> Amount
styleAmount styles a =
  case M.lookup (acommodity a) styles of
    Just s  -> a{astyle=s}
    Nothing -> a

-- | Like styleAmount, but keep the number of decimal places unchanged.
styleAmountExceptPrecision :: M.Map CommoditySymbol AmountStyle -> Amount -> Amount
styleAmountExceptPrecision styles a@Amount{astyle=AmountStyle{asprecision=origp}} =
  case M.lookup (acommodity a) styles of
    Just s  -> a{astyle=s{asprecision=origp}}
    Nothing -> a

-- | Reset this amount's display style to the default.
amountUnstyled :: Amount -> Amount
amountUnstyled a = a{astyle=amountstyle}

-- | Get the string representation of an amount, based on its
-- commodity's display settings. String representations equivalent to
-- zero are converted to just \"0\". The special "missing" amount is
-- displayed as the empty string.
--
-- > showAmount = wbUnpack . showAmountB noColour
showAmount :: Amount -> String
showAmount = wbUnpack . showAmountB noColour

-- | General function to generate a WideBuilder for an Amount, according the
-- supplied AmountDisplayOpts. The special "missing" amount is displayed as
-- the empty string. This is the main function to use for showing
-- Amounts, constructing a builder; it can then be converted to a Text with
-- wbToText, or to a String with wbUnpack.
showAmountB :: AmountDisplayOpts -> Amount -> WideBuilder
showAmountB _ Amount{acommodity="AUTO"} = mempty
showAmountB opts a@Amount{astyle=style} =
    color $ case ascommodityside style of
      L -> c' <> space <> quantity' <> price
      R -> quantity' <> space <> c' <> price
  where
    quantity = showamountquantity a
    (quantity',c) | amountLooksZero a && not (displayZeroCommodity opts) = (WideBuilder (TB.singleton '0') 1,"")
                  | otherwise = (quantity, quoteCommoditySymbolIfNeeded $ acommodity a)
    space = if not (T.null c) && ascommodityspaced style then WideBuilder (TB.singleton ' ') 1 else mempty
    c' = WideBuilder (TB.fromText c) (textWidth c)
    price = if displayPrice opts then showAmountPrice a else mempty
    color = if displayColour opts && isNegativeAmount a then colorB Dull Red else id

-- | Colour version. For a negative amount, adds ANSI codes to change the colour,
-- currently to hard-coded red.
--
-- > cshowAmount = wbUnpack . showAmountB def{displayColour=True}
cshowAmount :: Amount -> String
cshowAmount = wbUnpack . showAmountB def{displayColour=True}

-- | Get the string representation of an amount, without any \@ price.
--
-- > showAmountWithoutPrice = wbUnpack . showAmountB noPrice
showAmountWithoutPrice :: Amount -> String
showAmountWithoutPrice = wbUnpack . showAmountB noPrice

-- | Like showAmount, but show a zero amount's commodity if it has one.
--
-- > showAmountWithZeroCommodity = wbUnpack . showAmountB noColour{displayZeryCommodity=True}
showAmountWithZeroCommodity :: Amount -> String
showAmountWithZeroCommodity = wbUnpack . showAmountB noColour{displayZeroCommodity=True}

-- | Get a string representation of an amount for debugging,
-- appropriate to the current debug level. 9 shows maximum detail.
showAmountDebug :: Amount -> String
showAmountDebug Amount{acommodity="AUTO"} = "(missing)"
showAmountDebug Amount{..} = printf "Amount {acommodity=%s, aquantity=%s, aprice=%s, astyle=%s}" (show acommodity) (show aquantity) (showAmountPriceDebug aprice) (show astyle)

-- | Get a Text Builder for the string representation of the number part of of an amount,
-- using the display settings from its commodity. Also returns the width of the
-- number.
showamountquantity :: Amount -> WideBuilder
showamountquantity amt@Amount{astyle=AmountStyle{asdecimalpoint=mdec, asdigitgroups=mgrps}} =
    signB <> intB <> fracB
  where
    Decimal e n = amountRoundedQuantity amt

    strN = T.pack . show $ abs n
    len = T.length strN
    intLen = max 1 $ len - fromIntegral e
    dec = fromMaybe '.' mdec
    padded = T.replicate (fromIntegral e + 1 - len) "0" <> strN
    (intPart, fracPart) = T.splitAt intLen padded

    intB = applyDigitGroupStyle mgrps intLen $ if e == 0 then strN else intPart
    signB = if n < 0 then WideBuilder (TB.singleton '-') 1 else mempty
    fracB = if e > 0 then WideBuilder (TB.singleton dec <> TB.fromText fracPart) (fromIntegral e + 1) else mempty

-- | Split a string representation into chunks according to DigitGroupStyle,
-- returning a Text builder and the number of separators used.
applyDigitGroupStyle :: Maybe DigitGroupStyle -> Int -> T.Text -> WideBuilder
applyDigitGroupStyle Nothing                       l s = WideBuilder (TB.fromText s) l
applyDigitGroupStyle (Just (DigitGroups _ []))     l s = WideBuilder (TB.fromText s) l
applyDigitGroupStyle (Just (DigitGroups c (g:gs))) l s = addseps (g:|gs) (toInteger l) s
  where
    addseps (g:|gs) l s
        | l' > 0    = addseps gs' l' rest <> WideBuilder (TB.singleton c <> TB.fromText part) (fromIntegral g + 1)
        | otherwise = WideBuilder (TB.fromText s) (fromInteger l)
      where
        (rest, part) = T.splitAt (fromInteger l') s
        gs' = fromMaybe (g:|[]) $ nonEmpty gs
        l' = l - toInteger g

-- like journalCanonicaliseAmounts
-- | Canonicalise an amount's display style using the provided commodity style map.
canonicaliseAmount :: M.Map CommoditySymbol AmountStyle -> Amount -> Amount
canonicaliseAmount styles a@Amount{acommodity=c, astyle=s} = a{astyle=s'}
  where s' = M.findWithDefault s c styles

-------------------------------------------------------------------------------
-- MixedAmount

instance Num MixedAmount where
    fromInteger i = Mixed [fromInteger i]
    negate (Mixed as) = Mixed $ map negate as
    (+) (Mixed as) (Mixed bs) = normaliseMixedAmount $ Mixed $ as ++ bs
    (*)    = error' "error, mixed amounts do not support multiplication" -- PARTIAL:
    abs    = error' "error, mixed amounts do not support abs"
    signum = error' "error, mixed amounts do not support signum"

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

-- | A temporary value for parsed transactions which had no amount specified.
missingmixedamt :: MixedAmount
missingmixedamt = Mixed [missingamt]

-- | Convert amounts in various commodities into a normalised MixedAmount.
mixed :: [Amount] -> MixedAmount
mixed = normaliseMixedAmount . Mixed

-- | Simplify a mixed amount's component amounts:
--
-- * amounts in the same commodity are combined unless they have different prices or total prices
--
-- * multiple zero amounts, all with the same non-null commodity, are replaced by just the last of them, preserving the commodity and amount style (all but the last zero amount are discarded)
--
-- * multiple zero amounts with multiple commodities, or no commodities, are replaced by one commodity-less zero amount
--
-- * an empty amount list is replaced by one commodity-less zero amount
--
-- * the special "missing" mixed amount remains unchanged
--
normaliseMixedAmount :: MixedAmount -> MixedAmount
normaliseMixedAmount = normaliseHelper False

normaliseHelper :: Bool -> MixedAmount -> MixedAmount
normaliseHelper squashprices (Mixed as)
  | missingkey `M.member` amtMap = missingmixedamt -- missingamt should always be alone, but detect it even if not
  | M.null nonzeros= Mixed [newzero]
  | otherwise      = Mixed $ toList nonzeros
  where
    newzero = maybe nullamt snd . M.lookupMin $ M.filter (not . T.null . acommodity) zeros
    (zeros, nonzeros) = M.partition amountAndPriceIsZero amtMap
    amtMap = foldr (\a -> M.insertWith sumSimilarAmountsUsingFirstPrice (key a) a) mempty as
    key Amount{acommodity=c,aprice=p} = (c, if squashprices then Nothing else priceKey <$> p)
      where
        priceKey (UnitPrice  x) = (acommodity x, Just $ aquantity x)
        priceKey (TotalPrice x) = (acommodity x, Nothing)
    missingkey = key missingamt

-- | Like normaliseMixedAmount, but combine each commodity's amounts
-- into just one by throwing away all prices except the first. This is
-- only used as a rendering helper, and could show a misleading price.
normaliseMixedAmountSquashPricesForDisplay :: MixedAmount -> MixedAmount
normaliseMixedAmountSquashPricesForDisplay = normaliseHelper True

-- | Unify a MixedAmount to a single commodity value if possible.
-- Like normaliseMixedAmount, this consolidates amounts of the same commodity
-- and discards zero amounts; but this one insists on simplifying to
-- a single commodity, and will return Nothing if this is not possible.
unifyMixedAmount :: MixedAmount -> Maybe Amount
unifyMixedAmount = foldM combine 0 . amounts
  where
    combine amount result
      | amountIsZero amount                    = Just result
      | amountIsZero result                    = Just amount
      | acommodity amount == acommodity result = Just $ amount + result
      | otherwise                              = Nothing

-- | Sum same-commodity amounts in a lossy way, applying the first
-- price to the result and discarding any other prices. Only used as a
-- rendering helper.
sumSimilarAmountsUsingFirstPrice :: Amount -> Amount -> Amount
sumSimilarAmountsUsingFirstPrice a b = (a + b){aprice=p}
  where
    p = case (aprice a, aprice b) of
        (Just (TotalPrice ap), Just (TotalPrice bp))
          -> Just . TotalPrice $ ap{aquantity = aquantity ap + aquantity bp }
        _ -> aprice a

-- -- | Sum same-commodity amounts. If there were different prices, set
-- -- the price to a special marker indicating "various". Only used as a
-- -- rendering helper.
-- sumSimilarAmountsNotingPriceDifference :: [Amount] -> Amount
-- sumSimilarAmountsNotingPriceDifference [] = nullamt
-- sumSimilarAmountsNotingPriceDifference as = undefined

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

-- | Filter a mixed amount's component amounts by a predicate.
filterMixedAmount :: (Amount -> Bool) -> MixedAmount -> MixedAmount
filterMixedAmount p (Mixed as) = Mixed $ filter p as

-- | Return an unnormalised MixedAmount containing exactly one Amount
-- with the specified commodity and the quantity of that commodity
-- found in the original. NB if Amount's quantity is zero it will be
-- discarded next time the MixedAmount gets normalised.
filterMixedAmountByCommodity :: CommoditySymbol -> MixedAmount -> MixedAmount
filterMixedAmountByCommodity c (Mixed as) = Mixed as'
  where
    as' = case filter ((==c) . acommodity) as of
            []   -> [nullamt{acommodity=c}]
            as'' -> [sum as'']

-- | Apply a transform to a mixed amount's component 'Amount's.
mapMixedAmount :: (Amount -> Amount) -> MixedAmount -> MixedAmount
mapMixedAmount f (Mixed as) = Mixed $ map f as

-- | Convert all component amounts to cost/selling price where
-- possible (see amountCost).
mixedAmountCost :: MixedAmount -> MixedAmount
mixedAmountCost = mapMixedAmount amountCost

-- | Divide a mixed amount's quantities by a constant.
divideMixedAmount :: Quantity -> MixedAmount -> MixedAmount
divideMixedAmount n = mapMixedAmount (divideAmount n)

-- | Multiply a mixed amount's quantities by a constant.
multiplyMixedAmount :: Quantity -> MixedAmount -> MixedAmount
multiplyMixedAmount n = mapMixedAmount (multiplyAmount n)

-- | Divide a mixed amount's quantities (and total prices, if any) by a constant.
-- The total prices will be kept positive regardless of the multiplier's sign.
divideMixedAmountAndPrice :: Quantity -> MixedAmount -> MixedAmount
divideMixedAmountAndPrice n = mapMixedAmount (divideAmountAndPrice n)

-- | Multiply a mixed amount's quantities (and total prices, if any) by a constant.
-- The total prices will be kept positive regardless of the multiplier's sign.
multiplyMixedAmountAndPrice :: Quantity -> MixedAmount -> MixedAmount
multiplyMixedAmountAndPrice n = mapMixedAmount (multiplyAmountAndPrice n)

-- | Calculate the average of some mixed amounts.
averageMixedAmounts :: [MixedAmount] -> MixedAmount
averageMixedAmounts [] = 0
averageMixedAmounts as = fromIntegral (length as) `divideMixedAmount` sum as

-- | Is this mixed amount negative, if we can tell that unambiguously?
-- Ie when normalised, are all individual commodity amounts negative ?
isNegativeMixedAmount :: MixedAmount -> Maybe Bool
isNegativeMixedAmount m =
  case amounts $ normaliseMixedAmountSquashPricesForDisplay m of
    []  -> Just False
    [a] -> Just $ isNegativeAmount a
    as | all isNegativeAmount as -> Just True
    as | not (any isNegativeAmount as) -> Just False
    _ -> Nothing  -- multiple amounts with different signs

-- | Does this mixed amount appear to be zero when rendered with its
-- display precision ?
mixedAmountLooksZero :: MixedAmount -> Bool
mixedAmountLooksZero = all amountLooksZero . amounts . normaliseMixedAmountSquashPricesForDisplay

-- | Does this mixed amount and its price appear to be zero when rendered with its
-- display precision ?
mixedAmountAndPriceLooksZero :: MixedAmount -> Bool
mixedAmountAndPriceLooksZero = all amountAndPriceLooksZero . amounts . normaliseMixedAmountSquashPricesForDisplay

-- | Is this mixed amount exactly zero, ignoring display precisions ?
mixedAmountIsZero :: MixedAmount -> Bool
mixedAmountIsZero = all amountIsZero . amounts . normaliseMixedAmountSquashPricesForDisplay

-- | Is this mixed amount exactly zero, ignoring display precisions ?
mixedAmountAndPriceIsZero :: MixedAmount -> Bool
mixedAmountAndPriceIsZero = all amountAndPriceIsZero . amounts . normaliseMixedAmountSquashPricesForDisplay

-- -- | MixedAmount derived Eq instance in Types.hs doesn't know that we
-- -- want $0 = EUR0 = 0. Yet we don't want to drag all this code over there.
-- -- For now, use this when cross-commodity zero equality is important.
-- mixedAmountEquals :: MixedAmount -> MixedAmount -> Bool
-- mixedAmountEquals a b = amounts a' == amounts b' || (mixedAmountLooksZero a' && mixedAmountLooksZero b')
--     where a' = normaliseMixedAmountSquashPricesForDisplay a
--           b' = normaliseMixedAmountSquashPricesForDisplay b

-- | Given a map of standard commodity display styles, apply the
-- appropriate one to each individual amount.
styleMixedAmount :: M.Map CommoditySymbol AmountStyle -> MixedAmount -> MixedAmount
styleMixedAmount styles = mapMixedAmount (styleAmount styles)

-- | Reset each individual amount's display style to the default.
mixedAmountUnstyled :: MixedAmount -> MixedAmount
mixedAmountUnstyled = mapMixedAmount amountUnstyled

-- | Get the string representation of a mixed amount, after
-- normalising it to one amount per commodity. Assumes amounts have
-- no or similar prices, otherwise this can show misleading prices.
--
-- > showMixedAmount = wbUnpack . showMixedAmountB noColour
showMixedAmount :: MixedAmount -> String
showMixedAmount = wbUnpack . showMixedAmountB noColour

-- | Get the one-line string representation of a mixed amount.
--
-- > showMixedAmountOneLine = wbUnpack . showMixedAmountB oneLine
showMixedAmountOneLine :: MixedAmount -> String
showMixedAmountOneLine = wbUnpack . showMixedAmountB oneLine

-- | Like showMixedAmount, but zero amounts are shown with their
-- commodity if they have one.
--
-- > showMixedAmountWithZeroCommodity = wbUnpack . showMixedAmountB noColour{displayZeroCommodity=True}
showMixedAmountWithZeroCommodity :: MixedAmount -> String
showMixedAmountWithZeroCommodity = wbUnpack . showMixedAmountB noColour{displayZeroCommodity=True}

-- | Get the string representation of a mixed amount, without showing any transaction prices.
-- With a True argument, adds ANSI codes to show negative amounts in red.
--
-- > showMixedAmountWithoutPrice c = wbUnpack . showMixedAmountB noPrice{displayColour=c}
showMixedAmountWithoutPrice :: Bool -> MixedAmount -> String
showMixedAmountWithoutPrice c = wbUnpack . showMixedAmountB noPrice{displayColour=c}

-- | Get the one-line string representation of a mixed amount, but without
-- any \@ prices.
-- With a True argument, adds ANSI codes to show negative amounts in red.
--
-- > showMixedAmountOneLineWithoutPrice c = wbUnpack . showMixedAmountB oneLine{displayColour=c}
showMixedAmountOneLineWithoutPrice :: Bool -> MixedAmount -> String
showMixedAmountOneLineWithoutPrice c = wbUnpack . showMixedAmountB oneLine{displayColour=c}

-- | Like showMixedAmountOneLineWithoutPrice, but show at most the given width,
-- with an elision indicator if there are more.
-- With a True argument, adds ANSI codes to show negative amounts in red.
--
-- > showMixedAmountElided w c = wbUnpack . showMixedAmountB oneLine{displayColour=c, displayMaxWidth=Just w}
showMixedAmountElided :: Int -> Bool -> MixedAmount -> String
showMixedAmountElided w c = wbUnpack . showMixedAmountB oneLine{displayColour=c, displayMaxWidth=Just w}

-- | Get an unambiguous string representation of a mixed amount for debugging.
showMixedAmountDebug :: MixedAmount -> String
showMixedAmountDebug m | m == missingmixedamt = "(missing)"
                       | otherwise       = printf "Mixed [%s]" as
    where as = intercalate "\n       " $ map showAmountDebug $ amounts m

-- | General function to generate a WideBuilder for a MixedAmount, according the
-- supplied AmountDisplayOpts. This is the main function to use for showing
-- MixedAmounts, constructing a builder; it can then be converted to a Text with
-- wbToText, or to a String with wbUnpack.
--
-- If a maximum width is given then:
-- - If displayed on one line, it will display as many Amounts as can
--   fit in the given width, and further Amounts will be elided.
-- - If displayed on multiple lines, any Amounts longer than the
--   maximum width will be elided.
showMixedAmountB :: AmountDisplayOpts -> MixedAmount -> WideBuilder
showMixedAmountB opts ma
    | displayOneLine opts = showMixedAmountOneLineB opts ma
    | otherwise           = WideBuilder (wbBuilder . mconcat $ intersperse sep lines) width
  where
    lines = showMixedAmountLinesB opts ma
    width = headDef 0 $ map wbWidth lines
    sep = WideBuilder (TB.singleton '\n') 0

-- | Helper for showMixedAmountB to show a MixedAmount on multiple lines. This returns
-- the list of WideBuilders: one for each Amount in the MixedAmount (possibly
-- normalised), and padded/elided to the appropriate width. This does not
-- honour displayOneLine: all amounts will be displayed as if displayOneLine
-- were False.
showMixedAmountLinesB :: AmountDisplayOpts -> MixedAmount -> [WideBuilder]
showMixedAmountLinesB opts@AmountDisplayOpts{displayMaxWidth=mmax,displayMinWidth=mmin} ma =
    map (adBuilder . pad) elided
  where
    Mixed amts = if displayNormalised opts then normaliseMixedAmountSquashPricesForDisplay ma else ma

    astrs = amtDisplayList (wbWidth sep) (showAmountB opts) amts
    sep   = WideBuilder (TB.singleton '\n') 0
    width = maximum $ fromMaybe 0 mmin : map (wbWidth . adBuilder) elided

    pad amt = amt{ adBuilder = WideBuilder (TB.fromText $ T.replicate w " ") w <> adBuilder amt }
      where w = width - wbWidth (adBuilder amt)

    elided = maybe id elideTo mmax astrs
    elideTo m xs = maybeAppend elisionStr short
      where
        elisionStr = elisionDisplay (Just m) (wbWidth sep) (length long) $ lastDef nullAmountDisplay short
        (short, long) = partition ((m>=) . wbWidth . adBuilder) xs

-- | Helper for showMixedAmountB to deal with single line displays. This does not
-- honour displayOneLine: all amounts will be displayed as if displayOneLine
-- were True.
showMixedAmountOneLineB :: AmountDisplayOpts -> MixedAmount -> WideBuilder
showMixedAmountOneLineB opts@AmountDisplayOpts{displayMaxWidth=mmax,displayMinWidth=mmin} ma =
    WideBuilder (wbBuilder . pad . mconcat . intersperse sep $ map adBuilder elided) . max width $ fromMaybe 0 mmin
  where
    Mixed amts = if displayNormalised opts then normaliseMixedAmountSquashPricesForDisplay ma else ma

    width  = maybe 0 adTotal $ lastMay elided
    astrs  = amtDisplayList (wbWidth sep) (showAmountB opts) amts
    sep    = WideBuilder (TB.fromString ", ") 2
    n      = length amts

    pad = (WideBuilder (TB.fromText $ T.replicate w " ") w <>)
      where w = fromMaybe 0 mmin - width

    elided = maybe id elideTo mmax astrs
    elideTo m = addElide . takeFitting m . withElided
    -- Add the last elision string to the end of the display list
    addElide [] = []
    addElide xs = maybeAppend (snd $ last xs) $ map fst xs
    -- Return the elements of the display list which fit within the maximum width
    -- (including their elision strings)
    takeFitting m = dropWhileRev (\(a,e) -> m < adTotal (fromMaybe a e))
    dropWhileRev p = foldr (\x xs -> if null xs && p x then [] else x:xs) []

    -- Add the elision strings (if any) to each amount
    withElided = zipWith (\num amt -> (amt, elisionDisplay Nothing (wbWidth sep) num amt)) [n-1,n-2..0]

data AmountDisplay = AmountDisplay
  { adBuilder :: !WideBuilder  -- ^ String representation of the Amount
  , adTotal   :: !Int            -- ^ Cumulative length of MixedAmount this Amount is part of,
                                --   including separators
  }

nullAmountDisplay :: AmountDisplay
nullAmountDisplay = AmountDisplay mempty 0

amtDisplayList :: Int -> (Amount -> WideBuilder) -> [Amount] -> [AmountDisplay]
amtDisplayList sep showamt = snd . mapAccumL display (-sep)
  where
    display tot amt = (tot', AmountDisplay str tot')
      where
        str  = showamt amt
        tot' = tot + (wbWidth str) + sep

-- The string "m more", added to the previous running total
elisionDisplay :: Maybe Int -> Int -> Int -> AmountDisplay -> Maybe AmountDisplay
elisionDisplay mmax sep n lastAmt
  | n > 0     = Just $ AmountDisplay (WideBuilder (TB.fromText str) len) (adTotal lastAmt + len)
  | otherwise = Nothing
  where
    fullString = T.pack $ show n ++ " more.."
    -- sep from the separator, 7 from " more..", 1 + floor (logBase 10 n) from number
    fullLength = sep + 8 + floor (logBase 10 $ fromIntegral n)

    str | Just m <- mmax, fullLength > m = T.take (m - 2) fullString <> ".."
        | otherwise                      = fullString
    len = case mmax of Nothing -> fullLength
                       Just m  -> max 2 $ min m fullLength

maybeAppend :: Maybe a -> [a] -> [a]
maybeAppend Nothing  = id
maybeAppend (Just a) = (++[a])

-- | Compact labelled trace of a mixed amount, for debugging.
ltraceamount :: String -> MixedAmount -> MixedAmount
ltraceamount s = traceWith (((s ++ ": ") ++).showMixedAmount)

-- | Set the display precision in the amount's commodities.
mixedAmountSetPrecision :: AmountPrecision -> MixedAmount -> MixedAmount
mixedAmountSetPrecision p = mapMixedAmount (amountSetPrecision p)

-- | In each component amount, increase the display precision sufficiently
-- to render it exactly (showing all significant decimal digits).
mixedAmountSetFullPrecision :: MixedAmount -> MixedAmount
mixedAmountSetFullPrecision = mapMixedAmount amountSetFullPrecision

mixedAmountStripPrices :: MixedAmount -> MixedAmount
mixedAmountStripPrices = mapMixedAmount (\a -> a{aprice=Nothing})

-- | Canonicalise a mixed amount's display styles using the provided commodity style map.
canonicaliseMixedAmount :: M.Map CommoditySymbol AmountStyle -> MixedAmount -> MixedAmount
canonicaliseMixedAmount styles = mapMixedAmount (canonicaliseAmount styles)

-- | Replace each component amount's TotalPrice, if it has one, with an equivalent UnitPrice.
-- Has no effect on amounts without one.
-- Does Decimal division, might be some rounding/irrational number issues.
mixedAmountTotalPriceToUnitPrice :: MixedAmount -> MixedAmount
mixedAmountTotalPriceToUnitPrice = mapMixedAmount amountTotalPriceToUnitPrice


-------------------------------------------------------------------------------
-- tests

tests_Amount = tests "Amount" [
   tests "Amount" [

     test "amountCost" $ do
       amountCost (eur 1) @?= eur 1
       amountCost (eur 2){aprice=Just $ UnitPrice $ usd 2} @?= usd 4
       amountCost (eur 1){aprice=Just $ TotalPrice $ usd 2} @?= usd 2
       amountCost (eur (-1)){aprice=Just $ TotalPrice $ usd (-2)} @?= usd (-2)

    ,test "amountLooksZero" $ do
       assertBool "" $ amountLooksZero amount
       assertBool "" $ amountLooksZero $ usd 0

    ,test "negating amounts" $ do
       negate (usd 1) @?= (usd 1){aquantity= -1}
       let b = (usd 1){aprice=Just $ UnitPrice $ eur 2} in negate b @?= b{aquantity= -1}

    ,test "adding amounts without prices" $ do
       (usd 1.23 + usd (-1.23)) @?= usd 0
       (usd 1.23 + usd (-1.23)) @?= usd 0
       (usd (-1.23) + usd (-1.23)) @?= usd (-2.46)
       sum [usd 1.23,usd (-1.23),usd (-1.23),-(usd (-1.23))] @?= usd 0
       -- highest precision is preserved
       asprecision (astyle $ sum [usd 1 `withPrecision` Precision 1, usd 1 `withPrecision` Precision 3]) @?= Precision 3
       asprecision (astyle $ sum [usd 1 `withPrecision` Precision 3, usd 1 `withPrecision` Precision 1]) @?= Precision 3
       -- adding different commodities assumes conversion rate 1
       assertBool "" $ amountLooksZero (usd 1.23 - eur 1.23)

    ,test "showAmount" $ do
      showAmount (usd 0 + gbp 0) @?= "0"

  ]

  ,tests "MixedAmount" [

     test "adding mixed amounts to zero, the commodity and amount style are preserved" $
      sum (map (Mixed . (:[]))
               [usd 1.25
               ,usd (-1) `withPrecision` Precision 3
               ,usd (-0.25)
               ])
        @?= Mixed [usd 0 `withPrecision` Precision 3]

    ,test "adding mixed amounts with total prices" $ do
      sum (map (Mixed . (:[]))
       [usd 1 @@ eur 1
       ,usd (-2) @@ eur 1
       ])
        @?= Mixed [usd (-1) @@ eur 2 ]

    ,test "showMixedAmount" $ do
       showMixedAmount (Mixed [usd 1]) @?= "$1.00"
       showMixedAmount (Mixed [usd 1 `at` eur 2]) @?= "$1.00 @ €2.00"
       showMixedAmount (Mixed [usd 0]) @?= "0"
       showMixedAmount (Mixed []) @?= "0"
       showMixedAmount missingmixedamt @?= ""

    ,test "showMixedAmountWithoutPrice" $ do
      let a = usd 1 `at` eur 2
      showMixedAmountWithoutPrice False (Mixed [a]) @?= "$1.00"
      showMixedAmountWithoutPrice False (Mixed [a, -a]) @?= "0"

    ,tests "normaliseMixedAmount" [
       test "a missing amount overrides any other amounts" $
        normaliseMixedAmount (Mixed [usd 1, missingamt]) @?= missingmixedamt
      ,test "unpriced same-commodity amounts are combined" $
        normaliseMixedAmount (Mixed [usd 0, usd 2]) @?= Mixed [usd 2]
      ,test "amounts with same unit price are combined" $
        normaliseMixedAmount (Mixed [usd 1 `at` eur 1, usd 1 `at` eur 1]) @?= Mixed [usd 2 `at` eur 1]
      ,test "amounts with different unit prices are not combined" $
        normaliseMixedAmount (Mixed [usd 1 `at` eur 1, usd 1 `at` eur 2]) @?= Mixed [usd 1 `at` eur 1, usd 1 `at` eur 2]
      ,test "amounts with total prices are combined" $
        normaliseMixedAmount (Mixed  [usd 1 @@ eur 1, usd 1 @@ eur 1]) @?= Mixed [usd 2 @@ eur 2]
    ]

    ,test "normaliseMixedAmountSquashPricesForDisplay" $ do
       normaliseMixedAmountSquashPricesForDisplay (Mixed []) @?= Mixed [nullamt]
       assertBool "" $ mixedAmountLooksZero $ normaliseMixedAmountSquashPricesForDisplay
        (Mixed [usd 10
               ,usd 10 @@ eur 7
               ,usd (-10)
               ,usd (-10) @@ eur 7
               ])

  ]

 ]