-- | Showing various data types as text.
module Data.Text.Show
export
{       showBool;

        showNat;
        showBinaryNat;  digitBinary;
        showDecimalNat; digitDecimal;
        showHexNat;     digitHex;
        showBaseNat;
}
import Data.Numeric.Word
import Data.Text.Base
import Data.Text.Char
import Data.Text.Operator
where


-------------------------------------------------------------------------------
-- | Convert a Bool to a String.
showBool (x : Bool): Text
 = if x then "True" 
        else "False"


-- | Show a natural number.
showNat (x: Nat): Text
 = showBaseNat 10 digitDecimal 0 'X' x


-------------------------------------------------------------------------------
-- | Show a natural number, in binary.
showBinaryNat (x: Nat): Text
 = showBaseNat 2 digitBinary 0 'X' x

digitBinary (n: Nat): Char
 = case n of
        0       -> '0'
        1       -> '1'
        _       -> 'X'


-------------------------------------------------------------------------------
-- | Show a natural number in decimal.
showDecimalNat (x: Nat): Text
 = showBaseNat 10 digitDecimal 0 'X' x

digitDecimal (n: Nat): Word32
 = case n of
        0       -> '0'
        1       -> '1'
        2       -> '2'
        3       -> '3'
        4       -> '4'
        5       -> '5'
        6       -> '6'
        7       -> '7'
        8       -> '8'
        9       -> '9'
        _       -> 'X'


-------------------------------------------------------------------------------
-- | Show a natural number in hex.
showHexNat (x: Nat): Text
 = showBaseNat 16 digitHex 0 'X' x

digitHex (n: Nat): Char
 = case n of
        0       -> '0'
        1       -> '1'
        2       -> '2'
        3       -> '3'
        4       -> '4'
        5       -> '5'
        6       -> '6'
        7       -> '7'
        8       -> '8'
        9       -> '9'
        10      -> 'a'
        11      -> 'b'
        12      -> 'c'
        13      -> 'd'
        14      -> 'e'
        15      -> 'f'
        _       -> 'X'


-------------------------------------------------------------------------------
-- | Show a natural number using an arbitrary base encoding.
showBaseNat 
        (base:  Nat)            -- ^ Base of encoding.
        (digit: Nat -> Char)    -- ^ Show a digit in this base.
        (width: Nat)            -- ^ Width of output, or 0 to not pad.
        (pad:   Char)           -- ^ Character to pad output with.
        (x:     Nat)            -- ^ Number to print.
        : Text
 = do   s       = showBaseNat' base digit width pad True x
        if x < 0 
         then "-" % s 
         else s

showBaseNat' base digit width pad first x
 | and (x == 0) first
 = showBaseNat' base digit (width - 1) pad False x 
        % "0"

 | and (x == 0) (width > 0)
 = showBaseNat' base digit (width - 1) pad False x
        % textOfChar pad

 | x == 0  
 = ""

 | otherwise
 = showBaseNat' base digit (width - 1) pad False (div x base) 
        % textOfChar (digit (rem x base))