defmodule Number do
	@moduledoc """
	Number library.
	"""

	@doc """
	Round

	## Examples
		iex> Number.round( 123 )
		123
		iex> Number.round( 123.456 )
		123.456
		iex> Number.round( 123.456, 2 )
		123.46
		iex> Number.round( 123.456, 1 )
		123.5
	"""
	def round( value, precision \\ -1 ) # <- default parameter function is separately declared
	def round( value, precision ) when is_float( value ) == true, do: if precision >= 0, do: value |> Float.round( precision ), else: value
	def round( value, _ ) when is_integer( value ) == true, do: value

	@doc """
	To number return float or integer)

	## Examples
		iex> Number.to_number( 123 )
		123
		iex> Number.to_number( 123.456 )
		123.456
		iex> Number.to_number( Decimal.new( 123456.78 ) )
		123456.78
		iex> Number.to_number( "123456.78" )
		123456.78
	"""
	def to_number( value ) when is_binary( value ) == true, do: value |> String.to_float
	def to_number( value ), do: if Decimal.decimal?( value ) == true, do: value |> Decimal.to_float, else: value

	@doc """
	To string

	## Examples
		iex> Number.to_string( 123 )
		"123"
		iex> Number.to_string( 123.456 )
		"123.456"
		iex> Number.to_string( 123.456, 2 )
		"123.46"
		iex> Number.to_string( 123.456, 1 )
		"123.5"
		iex> Number.to_string( Decimal.new( 123.456 ) )
		"123.456"
		iex> Number.to_string( "123.456" )
		"123.456"
	"""
	def to_string( value, precision \\ -1 ) # <- default parameter function is separately declared
	def to_string( value, precision ) when is_float( value ) == true, do: value |> Number.round( precision ) |> Float.to_string
	def to_string( value, _ ) when is_integer( value ) == true, do: value |> Integer.to_string
	def to_string( value, precision ) when is_binary( value ) == true, do: value |> String.to_float |> Number.round( precision ) |> Float.to_string
	def to_string( value, precision ), do: if Decimal.decimal?( value ) == true, do: Decimal.to_float( value ) |> Number.round( precision ) |> Float.to_string

	@doc """
	Pad number at zero (return string)

	## Examples
		iex> Number.pad_zero( 123 )
		"00000000000123"
	"""
	def pad_zero( number, length \\ 14 ), do: pad( number, length, "0" )

	@doc """
	Pad number at any (return string)

	## Examples
		iex> Number.pad( 123, 6, "_" )
		"___123"
	"""
	def pad( number, length, padding ) when is_integer( number ) do
		number |> Integer.to_string |> String.pad_leading( length, padding )
	end

	@doc """
	Calculate percent (return string)

	## Examples
		iex> Number.percent( 100, 8 )
		"12.5%"
		iex> Number.percent( 0, 8 )
		"0.0%"
		iex> Number.percent( 100, 0 )
		"(n/a)"
	"""
	def percent( numerator, denominator, precision \\ 2 ) do
		cond do
			denominator == 0 || denominator == nil -> "(n/a)"
			denominator != 0 -> Number.to_string( numerator / denominator, precision ) <> "%"
		end
	end

	@doc """
	Add comma (return string)

	## Examples
		iex> Number.add_comma( 123 )
		"123"
		iex> Number.add_comma( 1234 )
		"1,234"
		iex> Number.add_comma( 1234.56 )
		"1,234.56"
		iex> Number.add_comma( 123456.78 )
		"123,456.78"
		iex> Number.add_comma( 1234567.890123, -1 )
		"1,234,567.890,123"
		iex> Number.add_comma( 1234567.890123 )
		"1,234,567.89"
		iex> Number.add_comma( Decimal.new( 123456.78 ) )
		"123,456.78"
		iex> Number.add_comma( "123456.78" )
		"123,456.78"
	"""
	def add_comma( value, precision \\ 2 ), do: value |> Number.to_string( precision ) |> _insert_comma
	defp _insert_comma( value ), do: Regex.replace( ~r/(\d)(?=(\d\d\d)+(?!\d))/, value, "\\1," )

	@doc """
	To integer (return integer)

	## Examples
		iex> Number.to_integer( 1234 )
		1234
		iex> Number.to_integer( 1234.56 )
		1234
		iex> Number.to_integer( Decimal.new( 1234.56 ) )
		1234
		iex> Number.to_integer( "1234.56" )
		1234
	"""
	def to_integer( value ), do: value |> Number.to_string |> _head_split_dot
	defp _head_split_dot( value ), do: value |> String.split( "." ) |> List.first |> String.to_integer

	@doc """
	To percent (return string)

	## Examples
		iex> Number.to_percent( 123 )
		"12300%"
		iex> Number.to_percent( 0.123 )
		"12.3%"
		iex> Number.to_percent( 0.123456 )
		"12.35%"
		iex> Number.to_percent( Decimal.new( 0.123 ) )
		"12.3%"
		iex> Number.to_percent( Decimal.new( 0.123456 ) )
		"12.35%"
		iex> Number.to_percent( "0.123" )
		"12.3%"
		iex> Number.to_percent( "0.123456" )
		"12.35%"
	"""
	def to_percent( value, precision \\ 2 ), do: Number.to_number( value ) * 100 |> Number.to_string( precision ) |> _add_percent
	defp _add_percent( value ), do: value <> "%"

	@doc """
	Add sign (return string)

	## Examples
		iex> Number.add_sign( 0 )
		"±0"
		iex> Number.add_sign( 123 )
		"+123"
		iex> Number.add_sign( -123 )
		"-123"
		iex> Number.add_sign( 0.0 )
		"±0.0"
		iex> Number.add_sign( 0.00 )
		"±0.0"
		iex> Number.add_sign( 0.001 )
		"+0.0"
		iex> Number.add_sign( 0.001, 3 )
		"+0.001"
		iex> Number.add_sign( 0.001, -1 )
		"+0.001"
		iex> Number.add_sign( 0.09, 2 )
		"+0.09"
		iex> Number.add_sign( 0.09, 1 )
		"+0.1"
		iex> Number.add_sign( -0.001 )
		"0.0"
		iex> Number.add_sign( -0.001, 3 )
		"-0.001"
		iex> Number.add_sign( -0.001, -1 )
		"-0.001"
	"""
	def add_sign( value, precision \\ 2 ) do
		cond do
			Number.to_number( value ) == 0 -> "±" <> Number.to_string( value, precision )
			Number.to_number( value ) >  0 -> "+"  <> Number.to_string( value, precision )
			Number.to_number( value ) <  0 -> Number.to_string( value, precision )
		end
	end
end