    {-
    Copyright (c) 2006-2011 John Goerzen <jgoerzen@complete.org>

    All rights reserved.

    For license and copyright information, see the file LICENSE
    -}

    {- |
       Module     : Data.Quantity
       Copyright  : Copyright (C) 2006-2011 John Goerzen
       License    : BSD3

       Maintainer : John Goerzen <jgoerzen@complete.org>
       Stability  : provisional
       Portability: portable

    Tools for rendering sizes

    Written by John Goerzen, jgoerzen\@complete.org -}

    module Data.Quantity (
                              renderNum,
                              renderNums,
                              parseNum,
                              parseNumInt,
                              quantifyNum,
                              quantifyNums,
                              SizeOpts(..),
                              binaryOpts,
                              siOpts
                         )

    where
    import Data.List
    import Text.Printf
    import Data.Char

    {- | The options for 'quantifyNum' and 'renderNum' -}
    data SizeOpts = SizeOpts { base :: Int, -- ^ The base from which calculations are made
                               powerIncr :: Int, -- ^ The increment to the power for each new suffix
                               firstPower :: Int, -- ^ The first power for which suffixes are given
                               suffixes :: String -- ^ The suffixes themselves
                             }

    {- | Predefined definitions for byte measurement in groups of 1024, from 0 to
    2**80 -}
    binaryOpts :: SizeOpts
    binaryOpts = SizeOpts {base = 2,
                           firstPower = 0,
                           suffixes = " KMGTPEZY",
                           powerIncr = 10}

    {- | Predefined definitions for SI measurement, from 10**-24 to 10**24. -}
    siOpts :: SizeOpts
    siOpts = SizeOpts {base = 10,
                       firstPower = -24,
                       suffixes = "yzafpnum kMGTPEZY",
                       powerIncr = 3}

    {- | Takes a number and returns a new (quantity, suffix) combination.
    The space character is used as the suffix for items around 0. -}
    quantifyNum :: (Ord a, Real a, Floating b, Ord b) => SizeOpts -> a -> (b, Char)
    quantifyNum opts n = (\(x, s) -> (head x, s)) $ quantifyNums opts [n]

    {- | Like 'quantifyNum', but takes a list of numbers.  The first number in
    the list will be evaluated for the suffix.  The same suffix and scale will
    be used for the remaining items in the list.  Please see 'renderNums' for
    an example of how this works.

    It is invalid to use this function on an empty list. -}
    quantifyNums :: (Ord a, Real a, Floating b, Ord b) => SizeOpts -> [a] -> ([b], Char)
    quantifyNums _ [] = error "Attempt to use quantifyNums on an empty list"
    quantifyNums opts (headnum:xs) =
        (map (\n -> procnum n) (headnum:xs), suffix)
        where number = case fromRational . toRational $ headnum of
                         0 -> 1
                         x -> x
              incrList = map idx2pwr [0..length (suffixes opts) - 1]
              incrIdxList = zip incrList [0..]
              idx2pwr i = i * powerIncr opts + firstPower opts
              finderfunc (x, _) = (fromIntegral $ base opts) ** (fromIntegral x)
                                  <= (abs number)
              -- Find the largest item that does not exceed the number given.
              -- If the number is larger than the larger item in the list,
              -- that's fine; we'll just write it in terms of what we have.

              (usedexp, expidx) =
                  case find finderfunc (reverse incrIdxList) of
                      Just x -> x
                      Nothing -> head incrIdxList -- If not found, it's smaller than the first
              suffix = (suffixes opts !! (fromIntegral expidx))
              procnum n = (fromRational . toRational $ n) /
                          ((fromIntegral (base opts) ** (fromIntegral usedexp)))
              --(posres, possuf) = quantifyNum opts (headnum * (-1))

    {- | Render a number into a string, based on the given quantities.  This is
    useful for displaying quantities in terms of bytes or in SI units.  Give this
    function the 'SizeOpts' for the desired output, and a precision (number of
    digits to the right of the decimal point), and you get a string output.

    Here are some examples:

    > Data.Quantity> renderNum binaryOpts 0 1048576
    > "1M"
    > Data.Quantity> renderNum binaryOpts 2 10485760
    > "10.00M"
    > Data.Quantity> renderNum binaryOpts 3 1048576
    > "1.000M"
    > Data.Quantity> renderNum binaryOpts 3 1500000
    > "1.431M"
    > Data.Quantity> renderNum binaryOpts 2 (1500 ** 3)
    > "3.14G"

    > Data.Quantity> renderNum siOpts 2 1024
    > "1.02k"
    > Data.Quantity> renderNum siOpts 2 1048576
    > "1.05M"
    > Data.Quantity> renderNum siOpts 2 0.001
    > "1.00m"
    > Data.Quantity> renderNum siOpts 2 0.0001
    > "100.00u"

    If you want more control over the output, see 'quantifyNum'. -}
    renderNum :: (Ord a, Real a) =>
                 SizeOpts
              -> Int                -- ^ Precision of the result
              -> a                  -- ^ The number to examine
              -> String
    renderNum opts prec number =
        (printf ("%." ++ show prec ++ "g") num) ++ [suffix]
        where (num, suffix) = (quantifyNum opts number)::(Double, Char)

    {- | Like 'renderNum', but operates on a list of numbers.  The first number
    in the list will be evaluated for the suffix.  The same suffix and scale will
    be used for the remaining items in the list.  See 'renderNum' for more
    examples.

    Also, unlike 'renderNum', the %f instead of %g printf format is used so that
    \"scientific\" notation is avoided in the output.

    Examples:

    > *Data.Quantity> renderNums binaryOpts 3 [1500000, 10240, 104857600]
    > ["1.431M","0.010M","100.000M"]
    > *Data.Quantity> renderNums binaryOpts 3 [1500, 10240, 104857600]
    > ["1.465K","10.000K","102400.000K"]

    -}
    renderNums :: (Ord a, Real a) =>
                  SizeOpts
               -> Int               -- ^ Prevision of the result
               -> [a]               -- ^ The numbers to examine
               -> [String]          -- ^ Result
    renderNums opts prec numbers =
        map printit convnums
        where printit num =
                  (printf ("%." ++ show prec ++ "f") num) ++ [suffix]
              (convnums, suffix) =
                  (quantifyNums opts numbers)::([Double], Char)

    {- | Parses a String, possibly generated by 'renderNum'.  Parses the suffix
    and applies it to the number, which is read via the Read class.

    Returns Left "error message" on error, or Right number on successful parse.

    If you want an Integral result, the convenience function 'parseNumInt' is for
    you.
    -}
    parseNum :: (Read a, Fractional a) =>
                SizeOpts            -- ^ Information on how to parse this data
             -> Bool                -- ^ Whether to perform a case-insensitive match
             -> String              -- ^ The string to parse
             -> Either String a
    parseNum opts insensitive inp =
        case reads inp of
          [] -> Left "Couldn't parse numeric component of input"
          [(num, "")] -> Right num  -- No suffix; pass number unhindered
          [(num, [suffix])] ->
              case lookup (caseTransformer suffix) suffixMap of
                Nothing -> Left $ "Unrecognized suffix " ++ show suffix
                Just power -> Right $ num * multiplier power
          [(_, suffix)] -> Left $ "Multi-character suffix " ++ show suffix
          _ -> Left "Multiple parses for input"
        where suffixMap = zip (map caseTransformer . suffixes $ opts)
                              (iterate (+ (powerIncr opts)) (firstPower opts))
              caseTransformer x
                  | insensitive = toLower x
                  | otherwise = x
              multiplier :: (Read a, Fractional a) => Int -> a
              multiplier power =
                  fromRational . toRational $
                               fromIntegral (base opts) ** fromIntegral power
    {- | Parse a number as with 'parseNum', but return the result as
    an 'Integral'.  Any type such as Integer, Int, etc. can be used for the
    result type.

    This function simply calls 'round' on the result of 'parseNum'.  A
    'Double' is used internally for the parsing of the numeric component.

    By using this function, a user can still say something like 1.5M and get an
    integral result. -}
    parseNumInt :: (Read a, Integral a) =>
                   SizeOpts         -- ^ Information on how to parse this data
                -> Bool             -- ^ Whether to perform a case-insensitive match
                -> String           -- ^ The string to parse
                -> Either String a
    parseNumInt opts insensitive inp =
        case (parseNum opts insensitive inp)::Either String Double of
          Left x -> Left x
          Right n -> Right (round n)