# encoding: utf-8
require 'money/bank/variable_exchange'
require 'money/money/arithmetic'
require 'money/money/parsing'
require 'money/money/formatting'

# Represents an amount of money in a given currency.
class Money
  include Comparable
  include Arithmetic
  include Formatting
  include Parsing

  # The BigDecimal amount with as many decimal-places as the currency
  #
  # @return [BigDecimal]
  attr_reader :amount

  # The currency the money is in.
  #
  # @return [Currency]
  attr_reader :currency

  # The +Money::Bank+ based object used to perform currency exchanges with.
  #
  # @return [Money::Bank::*]
  attr_reader :bank

  # Class Methods
  class << self
    # Each Money object is associated to a bank object, which is responsible
    # for currency exchange. This property allows you to specify the default
    # bank object. The default value for this property is an instance of
    # +Bank::VariableExchange.+ It allows one to specify custom exchange rates.
    #
    # @return [Money::Bank::*]
    attr_accessor :default_bank

    # The default currency, which is used when +Money.new+ is called without an
    # explicit currency argument. The default value is Currency.new("USD"). The
    # value must be a valid +Money::Currency+ instance.
    #
    # @return [Money::Currency]
    attr_accessor :default_currency

    # Use this to disable i18n even if it's used by other objects in your app.
    #
    # @return [true,false]
    attr_accessor :use_i18n

    # The default BigDecimal::ROUND_MODE (BigDecimal::ROUND_HALF_UP)
    #
    # @return [Integer]
    attr_accessor :default_rounding_mode

    # Use this to enable the ability to assume the currency from a passed symbol
    #
    # @return [true,false]
    attr_accessor :assume_from_symbol
  end

  # Set the default bank for creating new +Money+ objects.
  self.default_bank = Bank::VariableExchange.instance

  # Set the default currency for creating new +Money+ object.
  self.default_currency = Currency.new("USD")

  # Set the default rounding-mode
  self.default_rounding_mode = BigDecimal::ROUND_HALF_UP

  # Default to using i18n
  self.use_i18n = true

  # Default to not using currency symbol assumptions when parsing
  self.assume_from_symbol = false

  # Create a new money object with value 0.
  #
  # @param [Currency, String, Symbol] currency The currency to use.
  #
  # @return [Money]
  #
  # @example
  #   Money.zero #=> #<Money amount:0.0 currency:USD>
  def self.zero(currency = default_currency)
    Money.new(0, currency)
  end

  # Alias for Money.zero
  #
  # @param [Currency, String, Symbol] currency The currency to use.
  #
  # @return [Money]
  #
  # @example
  #   Money.empty #=> #<Money amount:0.0 currency:USD>
  def self.empty(currency = default_currency)
    zero(currency)
  end

  # Creates a new Money object of the given value, using the Canadian
  # dollar currency.
  #
  # @param [Numeric] amount The amount.
  #
  # @return [Money]
  #
  # @example
  #   n = Money.ca_dollar(1.00)
  #   n.amount   #=> 1.000
  #   n.currency #=> #<Money::Currency id: cad>
  def self.ca_dollar(amount)
    Money.new(amount, "CAD")
  end

  # Creates a new Money object of the given value, using Indian Rupee currency.
  #
  # @param [Numeric] amount The amount.
  #
  # @return [Money]
  #
  # @example
  #   n = Money.inr(100)
  #   n.amount    #=> 100
  #   n.currency #=> #<Money::Currency id: inr>
  def self.inr(amount)
    Money.new(amount, "INR")
  end

  # Creates a new Money object of the given value, using the American dollar
  # currency.
  #
  # @param [Numeric] amount The amount.
  #
  # @return [Money]
  #
  # @example
  #   n = Money.us_dollar(100)
  #   n.amount    #=> 100
  #   n.currency #=> #<Money::Currency id: usd>
  def self.us_dollar(amount)
    Money.new(amount, "USD")
  end

  # Creates a new Money object of the given value, using the Euro currency.
  #
  # @param [Numeric] amount The amount.
  #
  # @return [Money]
  #
  # @example
  #   n = Money.euro(100)
  #   n.amount    #=> 100
  #   n.currency #=> #<Money::Currency id: eur>
  def self.euro(amount)
    Money.new(amount, "EUR")
  end

  # Adds a new exchange rate to the default bank and return the rate.
  #
  # @param [Currency, String, Symbol] from_currency Currency to exchange from.
  # @param [Currency, String, Symbol] to_currency Currency to exchange to.
  # @param [Numeric] rate Rate to exchange with.
  #
  # @return [Numeric]
  #
  # @example
  #   Money.add_rate("USD", "CAD", 1.25) #=> 1.25
  def self.add_rate(from_currency, to_currency, rate)
    Money.default_bank.add_rate(from_currency, to_currency, rate)
  end


  # Creates a new Money object of +amount+ value, with given +currency+.
  # The amount is rounded to number of decimal-places in the currency
  #
  # Alternatively you can use the convenience
  # methods like {Money.ca_dollar} and {Money.us_dollar}.
  #
  # @param [Numeric, String] amount The money amount.
  # @param [Currency, String, Symbol] currency The currency format.
  # @param [Money::Bank::*] bank The exchange bank to use.
  #
  # @return [Money]
  #
  # @example
  #   Money.new(100.1235)
  #   #=> #<Money @amount=100.124 @currency="USD">
  #
  #   Money.new("100.123")
  #   #=> #<Money @amount=100.123 @currency="USD">
  #
  def initialize(amount, currency = Money.default_currency, bank = Money.default_bank)
    ensure_numeric(amount)
    amount = BigDecimal.new(amount.to_s) unless amount.is_a?(BigDecimal)
    @currency = Currency.wrap(currency, Currency.default_subunit_to_unit)
    @amount = amount.round(@currency.decimal_places, Money.default_rounding_mode)
    @bank = bank
  end

  # Return string representation of currency object
  #
  # @return [String]
  #
  # @example
  #   Money.new(100, :USD).currency_as_string #=> "USD"
  def currency_as_string
    currency.to_s
  end

  # Set currency object using a string
  #
  # @param [String] val The currency string.
  #
  # @return [Money::Currency]
  #
  # @example
  #   Money.new(100).currency_as_string("CAD") #=> #<Money::Currency id: cad>
  def currency_as_string=(val)
    @currency = Currency.wrap(val)
  end

  # Returns a Fixnum hash value based on the +cents+ and +currency+ attributes
  # in order to use functions like & (intersection), group_by, etc.
  #
  # @return [Fixnum]
  #
  # @example
  #   Money.new(100).hash #=> 908351
  def hash
    [amount.hash, currency.hash].hash
  end

  # Uses +Currency#symbol+. If +nil+ is returned, defaults to "¤".
  #
  # @return [String]
  #
  # @example
  #   Money.new(100, "USD").symbol #=> "$"
  def symbol
    currency.symbol || "¤"
  end

  # Common inspect function
  #
  # @return [String]
  def inspect
    "#<Money amount:#{self.to_s} currency:#{currency}>"
  end

  # Returns the amount of money as a string.
  #
  # @return [String]
  #
  # @example
  #   Money.ca_dollar(100).to_s #=> "100.00"
  def to_s
    s = sprintf("%0.#{@currency.decimal_places}f", amount)
    s.gsub(".", decimal_mark)
  end

  # Return the amount.
  #
  # @return [BigDecimal]
  #
  # @example
  #   Money.us_dollar(100).to_d => BigDecimal.new("100")
  def to_d
    amount
  end

  # Return the amount of money as a float. Floating points cannot guarantee
  # precision. Therefore, this function should only be used when you no longer
  # need to represent currency or working with another system that requires
  # decimals.
  #
  # @return [Float]
  #
  # @example
  #   Money.us_dollar(100).to_f => 1.0
  def to_f
    @amount.to_f
  end

  # Conversation to +self+.
  #
  # @return [self]
  def to_money(given_currency = nil)
    given_currency = Currency.wrap(given_currency) if given_currency
    if given_currency.nil? || self.currency == given_currency
      self
    else
      exchange_to(given_currency)
    end
  end

  # Receive the amount of this money object in another Currency.
  #
  # @param [Currency, String, Symbol] other_currency Currency to exchange to.
  #
  # @return [Money]
  #
  # @example
  #   Money.new(2000, "USD").exchange_to("EUR")
  #   Money.new(2000, "USD").exchange_to(Currency.new("EUR"))
  def exchange_to(other_currency)
    other_currency = Currency.wrap(other_currency)
    @bank.exchange_with(self, other_currency)
  end

  # Receive a money object with the same amount as the current Money object
  # in american dollars.
  #
  # @return [Money]
  #
  # @example
  #   n = Money.new(100, "CAD").as_us_dollar
  #   n.currency #=> #<Money::Currency id: usd>
  def as_us_dollar
    exchange_to("USD")
  end

  # Receive a money object with the same amount as the current Money object
  # in canadian dollar.
  #
  # @return [Money]
  #
  # @example
  #   n = Money.new(100, "USD").as_ca_dollar
  #   n.currency #=> #<Money::Currency id: cad>
  def as_ca_dollar
    exchange_to("CAD")
  end

  # Receive a money object with the same amount as the current Money object
  # in euro.
  #
  # @return [Money]
  #
  # @example
  #   n = Money.new(100, "USD").as_euro
  #   n.currency #=> #<Money::Currency id: eur>
  def as_euro
    exchange_to("EUR")
  end

  # Allocates money between different parties without loosing pennies.
  # After the mathematically split has been performed, left over pennies will
  # be distributed round-robin amongst the parties. This means that parties
  # listed first will likely receive more pennies then ones that are listed later
  #
  # @param [0.50, 0.25, 0.25] to give 50% of the cash to party1, 25% ot party2, and 25% to party3.
  #
  # @return [Array<Money, Money, Money>]
  #
  # @example
  #   Money.new(0.005, "USD").allocate([0.3,0.7)) #=> [Money.new(2), Money.new(3)]
  #   Money.new(1.00, "USD").allocate([0.33,0.33,0.33]) #=> [Money.new(0.334), Money.new(0.333), Money.new(0.333)]
  def allocate(splits)
    allocations = splits.inject(0.0) {|sum, i| sum += i }
    raise ArgumentError, "splits add to more then 100%" if (allocations - 1.0) > Float::EPSILON

    amount_in_subunits = self.to_subunits
    left_over = amount_in_subunits

    amounts = splits.collect do |ratio|
      fraction = (amount_in_subunits * ratio / allocations).floor
      left_over -= fraction
      fraction
    end

    left_over.times { |i| amounts[i % amounts.length] += 1 }

    amounts.collect { |amount| Money.from_subunits(amount, currency) }
  end

  # Split money amongst parties evenly without loosing pennies.
  #
  # @param [2] number of parties.
  #
  # @return [Array<Money, Money, Money>]
  #
  # @example
  #   Money.new(100, "USD").split(3) #=> [Money.new(34), Money.new(33), Money.new(33)]
  def split(num)
    raise ArgumentError, "need at least one party" if num < 1
    amount_in_subunits = to_subunits
    low_subunits = amount_in_subunits / num
    low = Money.from_subunits(low_subunits, currency)
    high = Money.from_subunits(low_subunits + 1, currency)
    remainder = amount_in_subunits % num
    (0...num).collect do |index|
      index < remainder ? high : low
    end
  end

  def ensure_numeric(amount)
    raise ArgumentError, "Invalid amount: #{amount}" unless numeric?(amount)
  end

  def numeric?(amount)
    Kernel.Float(amount) rescue false
  end

  def to_subunits
    (amount * currency.subunit_to_unit).to_i
  end

  def self.from_subunits(amount, currency = Money.default_currency)
    adjusted_amount = BigDecimal.new(amount.to_s) / currency.subunit_to_unit
    Money.new(adjusted_amount, currency)
  end

end