defmodule Money do
import Kernel, except: [abs: 1, round: 1]
@moduledoc """
Defines a `Money` struct along with convenience methods for working with currencies.
## Examples
iex> money = Money.new(500, :USD)
%Money{amount: 500, currency: :USD}
iex> money = Money.add(money, 550)
%Money{amount: 1050, currency: :USD}
iex> Money.to_string(money)
"$10.50"
## Configuration
You can set defaults in your Mix configuration to make working with `Money` a little easier.
config :money,
default_currency: :EUR, # this allows you to do Money.new(100)
separator: ".", # change the default thousands separator for Money.to_string
delimiter: ",", # change the default decimal delimiter for Money.to_string
symbol: false, # don’t display the currency symbol in Money.to_string
symbol_on_right: false, # position the symbol
symbol_space: false, # add a space between symbol and number
fractional_unit: true, # display units after the delimiter
strip_insignificant_zeros: false, # don’t display the insignificant zeros or the delimiter
code: false, # add the currency code after the number
minus_sign_first: true, # display the minus sign before the currency symbol for Money.to_string
strip_insignificant_fractional_unit: false # don't display the delimiter or fractional units if the fractional units are only insignificant zeros
"""
@type t :: %__MODULE__{
amount: integer,
currency: atom
}
defstruct amount: 0, currency: :USD
alias Money.Currency
alias Money.DisplayOptions
alias Money.ParseOptions
@spec new(integer) :: t
@doc ~S"""
Create a new `Money` struct using a default currency.
The default currency can be set in the system Mix config.
## Config
config :money,
default_currency: :USD
## Examples
Money.new(123)
%Money{amount: 123, currency: :USD}
"""
def new(amount) do
currency = Application.get_env(:money, :default_currency)
if currency do
new(amount, currency)
else
raise ArgumentError, "to use Money.new/1 you must set a default currency in your application config."
end
end
@spec new(integer, atom | String.t()) :: t
@doc """
Create a new `Money` struct from currency sub-units (cents)
## Examples
iex> Money.new(1_000_00, :USD)
%Money{amount: 1_000_00, currency: :USD}
"""
def new(int, currency) when is_integer(int),
do: %Money{amount: int, currency: Currency.to_atom(currency)}
@spec parse(String.t() | number | Decimal.t(), atom | String.t(), Keyword.t()) :: {:ok, t} | :error
@doc ~S"""
Parse a value into a `Money` type.
The following options are available:
* `:separator` - default `","`, sets the separator for groups of thousands.
"1,000"
* `:delimiter` - default `"."`, sets the decimal delimiter.
"1.23"
## Examples
iex> Money.parse("$1,234.56", :USD)
{:ok, %Money{amount: 123456, currency: :USD}}
iex> Money.parse("1.234,56", :EUR, separator: ".", delimiter: ",")
{:ok, %Money{amount: 123456, currency: :EUR}}
iex> Money.parse("1.234,56", :WRONG)
:error
iex> Money.parse(1_234.56, :USD)
{:ok, %Money{amount: 123456, currency: :USD}}
iex> Money.parse(1_234, :USD)
{:ok, %Money{amount: 123400, currency: :USD}}
iex> Money.parse(-1_234.56, :USD)
{:ok, %Money{amount: -123456, currency: :USD}}
iex> Money.parse(Decimal.from_float(1_234.56), :USD)
{:ok, %Money{amount: 123456, currency: :USD}}
"""
def parse(value, currency \\ nil, opts \\ [])
def parse(value, nil, opts) do
currency = Application.get_env(:money, :default_currency)
if currency do
parse(value, currency, opts)
else
raise ArgumentError, "to use Money.new/1 you must set a default currency in your application config."
end
end
if Code.ensure_loaded?(Decimal) do
@parser Decimal
else
@parser Float
end
def parse(str, currency, opts) when is_binary(str) do
%ParseOptions{separator: _separator, delimiter: delimiter} = ParseOptions.get(opts)
value =
str
|> prepare_parse_string(delimiter)
|> add_missing_leading_digit
case @parser.parse(value) do
{float, _} -> parse(float, currency, [])
:error -> :error
end
rescue
_ -> :error
end
def parse(number, currency, _opts) when is_number(number) do
{:ok, new(Kernel.round(number * Currency.sub_units_count!(currency)), currency)}
end
if Code.ensure_loaded?(Decimal) do
def parse(%Decimal{} = decimal, currency, _opts) do
{:ok,
decimal
|> Decimal.mult(Currency.sub_units_count!(currency))
|> Decimal.round(0, Decimal.Context.get().rounding)
|> Decimal.to_integer()
|> new(currency)}
end
end
defp prepare_parse_string(characters, delimiter, acc \\ [])
defp prepare_parse_string([], _delimiter, acc),
do: acc |> Enum.reverse() |> Enum.join()
defp prepare_parse_string(["-" | tail], delimiter, acc),
do: prepare_parse_string(tail, delimiter, ["-" | acc])
defp prepare_parse_string(["0" | tail], delimiter, acc),
do: prepare_parse_string(tail, delimiter, ["0" | acc])
defp prepare_parse_string(["1" | tail], delimiter, acc),
do: prepare_parse_string(tail, delimiter, ["1" | acc])
defp prepare_parse_string(["2" | tail], delimiter, acc),
do: prepare_parse_string(tail, delimiter, ["2" | acc])
defp prepare_parse_string(["3" | tail], delimiter, acc),
do: prepare_parse_string(tail, delimiter, ["3" | acc])
defp prepare_parse_string(["4" | tail], delimiter, acc),
do: prepare_parse_string(tail, delimiter, ["4" | acc])
defp prepare_parse_string(["5" | tail], delimiter, acc),
do: prepare_parse_string(tail, delimiter, ["5" | acc])
defp prepare_parse_string(["6" | tail], delimiter, acc),
do: prepare_parse_string(tail, delimiter, ["6" | acc])
defp prepare_parse_string(["7" | tail], delimiter, acc),
do: prepare_parse_string(tail, delimiter, ["7" | acc])
defp prepare_parse_string(["8" | tail], delimiter, acc),
do: prepare_parse_string(tail, delimiter, ["8" | acc])
defp prepare_parse_string(["9" | tail], delimiter, acc),
do: prepare_parse_string(tail, delimiter, ["9" | acc])
defp prepare_parse_string([delimiter | tail], delimiter, acc),
do: prepare_parse_string(tail, delimiter, ["." | acc])
defp prepare_parse_string([_head | tail], delimiter, acc),
do: prepare_parse_string(tail, delimiter, acc)
defp prepare_parse_string(string, delimiter, _acc),
do: prepare_parse_string(String.codepoints(string), delimiter)
defp add_missing_leading_digit(<<"-.">> <> tail),
do: "-0." <> tail
defp add_missing_leading_digit(<<".">> <> tail),
do: "0." <> tail
defp add_missing_leading_digit(str), do: str
@spec parse!(String.t() | number | Decimal.t(), atom | String.t(), Keyword.t()) :: t
@doc ~S"""
Parse a value into a `Money` type.
Similar to `parse/3` but returns a `%Money{}` or raises an error if parsing fails.
## Examples
iex> Money.parse!("1,234.56", :USD)
%Money{amount: 123456, currency: :USD}
iex> Money.parse!("wrong", :USD)
** (ArgumentError) unable to parse "wrong" with currency :USD
"""
def parse!(value, currency \\ nil, opts \\ []) do
case parse(value, currency, opts) do
{:ok, money} -> money
:error -> raise ArgumentError, "unable to parse #{inspect(value)} with currency #{inspect(currency)}"
end
end
@spec compare(t, t) :: -1 | 0 | 1
@doc ~S"""
Compares two `Money` structs with each other.
They must each be of the same currency and then their amounts are compared.
If the first amount is larger than the second `1` is returned, if less than
`-1` is returned, if both amounts are equal `0` is returned.
See `cmp/2` for a similar function that returns `:lt`, `:eq` or `:gt` instead.
## Examples
iex> Money.compare(Money.new(100, :USD), Money.new(100, :USD))
0
iex> Money.compare(Money.new(100, :USD), Money.new(101, :USD))
-1
iex> Money.compare(Money.new(101, :USD), Money.new(100, :USD))
1
"""
def compare(%Money{currency: cur} = a, %Money{currency: cur} = b) do
case a.amount - b.amount do
x when x > 0 -> 1
x when x < 0 -> -1
x when x == 0 -> 0
end
end
def compare(a, b), do: fail_currencies_must_be_equal(a, b)
@doc """
Compares two `Money` structs with each other.
They must each be of the same currency and then their amounts are compared.
If the first amount is larger than the second `:gt` is returned, if less than
`:lt` is returned, if both amounts are equal `:eq` is returned.
See `compare/2` for a similar function that returns `-1`, `0` or `1` instead.
## Examples
iex> Money.cmp(Money.new(100, :USD), Money.new(100, :USD))
:eq
iex> Money.cmp(Money.new(100, :USD), Money.new(101, :USD))
:lt
iex> Money.cmp(Money.new(101, :USD), Money.new(100, :USD))
:gt
"""
@spec cmp(t, t) :: :lt | :eq | :gt
def cmp(a, b) do
case compare(a, b) do
x when x == -1 -> :lt
x when x == 0 -> :eq
x when x == 1 -> :gt
end
end
@spec zero?(t) :: boolean
@doc ~S"""
Returns true if the amount of a `Money` struct is zero
## Examples
iex> Money.zero?(Money.new(0, :USD))
true
iex> Money.zero?(Money.new(1, :USD))
false
"""
def zero?(%Money{amount: amount}) do
amount == 0
end
@spec positive?(t) :: boolean
@doc ~S"""
Returns true if the amount of a `Money` is greater than zero
## Examples
iex> Money.positive?(Money.new(0, :USD))
false
iex> Money.positive?(Money.new(1, :USD))
true
iex> Money.positive?(Money.new(-1, :USD))
false
"""
def positive?(%Money{amount: amount}) do
amount > 0
end
@spec negative?(t) :: boolean
@doc ~S"""
Returns true if the amount of a `Money` is less than zero
## Examples
iex> Money.negative?(Money.new(0, :USD))
false
iex> Money.negative?(Money.new(1, :USD))
false
iex> Money.negative?(Money.new(-1, :USD))
true
"""
def negative?(%Money{amount: amount}) do
amount < 0
end
@spec equals?(t, t) :: boolean
@doc ~S"""
Returns true if two `Money` of the same currency have the same amount
## Examples
iex> Money.equals?(Money.new(100, :USD), Money.new(100, :USD))
true
iex> Money.equals?(Money.new(101, :USD), Money.new(100, :USD))
false
iex> Money.equals?(Money.new(100, :USD), Money.new(100, :CAD))
false
"""
def equals?(%Money{amount: amount, currency: cur}, %Money{amount: amount, currency: cur}), do: true
def equals?(%Money{}, %Money{}), do: false
@spec neg(t) :: t
@doc ~S"""
Returns a `Money` with the amount negated.
## Examples
iex> Money.new(100, :USD) |> Money.neg
%Money{amount: -100, currency: :USD}
iex> Money.new(-100, :USD) |> Money.neg
%Money{amount: 100, currency: :USD}
"""
def neg(%Money{amount: amount, currency: cur}),
do: %Money{amount: -amount, currency: cur}
@spec abs(t) :: t
@doc ~S"""
Returns a `Money` with the arithmetical absolute of the amount.
## Examples
iex> Money.new(-100, :USD) |> Money.abs
%Money{amount: 100, currency: :USD}
iex> Money.new(100, :USD) |> Money.abs
%Money{amount: 100, currency: :USD}
"""
def abs(%Money{amount: amount, currency: cur}),
do: %Money{amount: Kernel.abs(amount), currency: cur}
@spec add(t, t | integer | float) :: t
@doc ~S"""
Adds two `Money` together or an integer (cents) amount to a `Money`
## Examples
iex> Money.add(Money.new(100, :USD), Money.new(50, :USD))
%Money{amount: 150, currency: :USD}
iex> Money.add(Money.new(100, :USD), 50)
%Money{amount: 150, currency: :USD}
iex> Money.add(Money.new(100, :USD), 5.55)
%Money{amount: 655, currency: :USD}
"""
def add(%Money{amount: a, currency: cur}, %Money{amount: b, currency: cur}),
do: Money.new(a + b, cur)
def add(%Money{amount: amount, currency: cur}, addend) when is_integer(addend),
do: Money.new(amount + addend, cur)
def add(%Money{} = m, addend) when is_float(addend),
do: add(m, Kernel.round(addend * 100))
def add(a, b), do: fail_currencies_must_be_equal(a, b)
@spec subtract(t, t | integer | float) :: t
@doc ~S"""
Subtracts one `Money` from another or an integer (cents) from a `Money`
## Examples
iex> Money.subtract(Money.new(150, :USD), Money.new(50, :USD))
%Money{amount: 100, currency: :USD}
iex> Money.subtract(Money.new(150, :USD), 50)
%Money{amount: 100, currency: :USD}
iex> Money.subtract(Money.new(150, :USD), 1.25)
%Money{amount: 25, currency: :USD}
"""
def subtract(%Money{amount: a, currency: cur}, %Money{amount: b, currency: cur}),
do: Money.new(a - b, cur)
def subtract(%Money{amount: a, currency: cur}, subtractend) when is_integer(subtractend),
do: Money.new(a - subtractend, cur)
def subtract(%Money{} = m, subtractend) when is_float(subtractend),
do: subtract(m, Kernel.round(subtractend * 100))
def subtract(a, b), do: fail_currencies_must_be_equal(a, b)
@spec multiply(t, integer | float | Decimal.t()) :: t
@doc ~S"""
Multiplies a `Money` by an amount
## Examples
iex> Money.multiply(Money.new(100, :USD), 10)
%Money{amount: 1000, currency: :USD}
iex> Money.multiply(Money.new(100, :USD), 1.5)
%Money{amount: 150, currency: :USD}
"""
def multiply(%Money{amount: amount, currency: cur}, multiplier) when is_integer(multiplier),
do: Money.new(amount * multiplier, cur)
def multiply(%Money{amount: amount, currency: cur}, multiplier) when is_float(multiplier),
do: Money.new(Kernel.round(amount * multiplier), cur)
if Code.ensure_loaded?(Decimal) do
def multiply(%Money{amount: amount, currency: cur}, %Decimal{} = multiplier),
do:
amount
|> Decimal.mult(multiplier)
|> Decimal.round(0, Decimal.Context.get().rounding)
|> Decimal.to_integer()
|> Money.new(cur)
end
@spec divide(t, integer) :: [t]
@doc ~S"""
Divides up `Money` by an amount
## Examples
iex> Money.divide(Money.new(100, :USD), 2)
[%Money{amount: 50, currency: :USD}, %Money{amount: 50, currency: :USD}]
iex> Money.divide(Money.new(101, :USD), 2)
[%Money{amount: 51, currency: :USD}, %Money{amount: 50, currency: :USD}]
"""
def divide(%Money{amount: amount, currency: cur}, denominator) when is_integer(denominator) do
value = div(amount, denominator)
rem = rem(amount, denominator)
do_divide(cur, value, rem, denominator, [])
end
defp do_divide(_currency, _value, _rem, 0, acc), do: acc |> Enum.reverse()
defp do_divide(currency, value, 0, count, acc) do
acc = [new(next_amount(value, 0, count), currency) | acc]
count = decrement_abs(count)
do_divide(currency, value, 0, count, acc)
end
defp do_divide(currency, value, rem, count, acc) do
acc = [new(next_amount(value, rem, count), currency) | acc]
rem = decrement_abs(rem)
count = decrement_abs(count)
do_divide(currency, value, rem, count, acc)
end
defp next_amount(0, -1, count) when count > 0, do: -1
defp next_amount(value, 0, _count), do: value
defp next_amount(value, _rem, _count), do: increment_abs(value)
defp increment_abs(n) when n >= 0, do: n + 1
defp increment_abs(n) when n < 0, do: n - 1
defp decrement_abs(n) when n >= 0, do: n - 1
defp decrement_abs(n) when n < 0, do: n + 1
@spec to_string(t, Keyword.t()) :: String.t()
@doc ~S"""
Converts a `Money` struct to a string representation
The following options are available:
* `:separator` - default `","`, sets the separator for groups of thousands.
"1,000"
* `:delimiter` - default `"."`, sets the decimal delimiter.
"1.23"
* `:symbol` - default `true`, sets whether to display the currency symbol or not.
* `:symbol_on_right` - default `false`, display the currency symbol on the right of the number, eg: 123.45€
* `:symbol_space` - default `false`, add a space between currency symbol and number, eg: € 123,45 or 123.45 €
* `:fractional_unit` - default `true`, show the remaining units after the delimiter
* `:strip_insignificant_zeros` - default `false`, strip zeros after the delimiter
* `:code` - default `false`, append the currency code after the number
* `:minus_sign_first` - default `true`, display the minus sign before the currency symbol for negative values
* `:strip_insignificant_fractional_unit` - default `false`, don't display the delimiter or fractional units if the fractional units are only insignificant zeros
## Examples
iex> Money.to_string(Money.new(123456, :GBP))
"£1,234.56"
iex> Money.to_string(Money.new(123456, :EUR), separator: ".", delimiter: ",")
"€1.234,56"
iex> Money.to_string(Money.new(123456, :EUR), symbol: false)
"1,234.56"
iex> Money.to_string(Money.new(123456, :EUR), symbol: false, separator: "")
"1234.56"
iex> Money.to_string(Money.new(123456, :EUR), fractional_unit: false)
"€1,234"
iex> Money.to_string(Money.new(123450, :EUR), strip_insignificant_zeros: true)
"€1,234.5"
iex> Money.to_string(Money.new(123450, :EUR), code: true)
"€1,234.50 EUR"
iex> Money.to_string(Money.new(-123450, :EUR))
"-€1,234.50"
iex> Money.to_string(Money.new(-123450, :EUR), minus_sign_first: false)
"€-1,234.50"
iex> Money.to_string(Money.new(123400, :EUR), strip_insignificant_fractional_unit: true)
"€1,234"
iex> Money.to_string(Money.new(123450, :EUR), strip_insignificant_fractional_unit: true)
"€1,234.50"
It can also be interpolated (It implements the String.Chars protocol)
To control the formatting, you can use the above options in your config,
more information is in the introduction to `Money`
## Examples
iex> "Total: #{Money.new(100_00, :USD)}"
"Total: $100.00"
"""
def to_string(%Money{} = money, opts \\ []) do
%DisplayOptions{
symbol: symbol,
symbol_on_right: symbol_on_right,
symbol_space: symbol_space,
code: code,
minus_sign_first: minus_sign_first
} = opts = DisplayOptions.get(money, opts)
number = format_number(money, opts)
sign = if negative?(money), do: "-"
space = if symbol_space, do: " "
code = if code, do: " #{money.currency}"
parts =
cond do
symbol_on_right ->
[sign, number, space, symbol, code]
negative?(money) and symbol == " " ->
[sign, number, code]
negative?(money) and minus_sign_first ->
[sign, symbol, space, number, code]
true ->
[symbol, space, sign, number, code]
end
parts
|> Enum.join()
|> String.trim()
end
if Code.ensure_loaded?(Decimal) do
@spec to_decimal(t) :: Decimal.t()
@doc ~S"""
Converts a `Money` struct to a `Decimal` representation
## Examples
iex> Money.to_decimal(Money.new(123456, :GBP))
#Decimal<1234.56>
iex> Money.to_decimal(Money.new(-123420, :EUR))
#Decimal<-1234.20>
"""
def to_decimal(%Money{} = money) do
sign = if money.amount >= 0, do: 1, else: -1
coef = Money.abs(money).amount
exp = -Money.Currency.exponent!(money)
Decimal.new(sign, coef, exp)
end
@spec round(t, integer()) :: t
@doc ~S"""
Rounds a `Money` struct using a given number of places. `round` respects the
rounding mode within the current Decimal context.
By default `round` rounds to zero decimal places, using the currency's
exponent. This results in rounding to whole values of the currency.
Currencies without an exponent are not rounded unless a different value is
passed for `places` other than the default.
## Examples
iex> Money.round(Money.new(123456, :GBP))
%Money{amount: 123500, currency: :GBP}
iex> Money.round(Money.new(-123420, :EUR))
%Money{amount: -123400, currency: :EUR}
iex> Money.round(Money.new(-123420, :EUR), -3)
%Money{amount: -100000, currency: :EUR}
# Round to tenth of exponent
iex> Money.round(Money.new(123425, :EUR), 1)
%Money{amount: 123430, currency: :EUR}
# Currencies round based on their exponent
iex> Money.round(Money.new(820412, :JPY))
%Money{amount: 820412, currency: :JPY}
iex> Money.round(Money.new(820412, :JPY), -3)
%Money{amount: 820000, currency: :JPY}
"""
def round(%Money{} = money, places \\ 0) when is_integer(places) do
{:ok, result} =
money
|> Money.to_decimal()
|> Decimal.round(places, Decimal.Context.get().rounding)
|> Money.parse(money.currency)
result
end
end
defp format_number(%Money{amount: amount} = money, %DisplayOptions{
separator: separator,
delimiter: delimiter,
fractional_unit: fractional_unit,
strip_insignificant_zeros: strip_insignificant_zeros,
strip_insignificant_fractional_unit: strip_insignificant_fractional_unit
}) do
exponent = Currency.exponent(money)
amount_abs = if amount < 0, do: -amount, else: amount
amount_str = Integer.to_string(amount_abs)
[sub_unit, super_unit] =
amount_str
|> String.pad_leading(exponent + 1, "0")
|> String.reverse()
|> String.split_at(exponent)
|> Tuple.to_list()
|> Enum.map(&String.reverse/1)
super_unit = super_unit |> reverse_group(3) |> Enum.join(separator)
sub_unit =
sub_unit
|> prepare_sub_unit(%{strip_insignificant_zeros: strip_insignificant_zeros})
|> prepare_sub_unit(%{strip_insignificant_fractional_unit: strip_insignificant_fractional_unit})
if fractional_unit and sub_unit != "" do
[super_unit, sub_unit] |> Enum.join(delimiter)
else
super_unit
end
end
defp prepare_sub_unit([value], options), do: prepare_sub_unit(value, options)
defp prepare_sub_unit([], _), do: ""
defp prepare_sub_unit(value, %{strip_insignificant_zeros: false}), do: value
defp prepare_sub_unit(value, %{strip_insignificant_zeros: true}), do: Regex.replace(~r/0+$/, value, "")
defp prepare_sub_unit(value, %{strip_insignificant_fractional_unit: false}), do: value
defp prepare_sub_unit(value, %{strip_insignificant_fractional_unit: true}) do
if Regex.match?(~r/[1-9]+/, value), do: value, else: ""
end
defp fail_currencies_must_be_equal(a, b) do
raise ArgumentError, message: "Currency of #{a.currency} must be the same as #{b.currency}"
end
defp reverse_group(str, count) when is_binary(str) do
reverse_group(str, Kernel.abs(count), [])
end
defp reverse_group("", _count, list) do
list
end
defp reverse_group(str, count, list) do
{first, last} = String.split_at(str, -count)
reverse_group(first, count, [last | list])
end
defimpl String.Chars do
def to_string(%Money{} = m) do
Money.to_string(m)
end
end
end
