functions.rb

# small monkey patch, real patch is submitted to extlib/merb/dm, hoping for inclusion soon
class NilClass
  def to_currency
    "-"
  end

  def to_account_balance
    "-"
  end
end

class Date
  def inspect
    "<Date: #{self.to_s}>"
  end

  def weekday
    #week starts on monday
    WEEKDAYS[cwday - 1]
  end

  def is_holiday?
    Holiday.all.include?(self)
  end

  def count_weekday_uptil(weekday, d2)
    return 0 if d2 < self
    num_weeks = ((d2 - self) / 7).floor
    d_ = self + num_weeks
    add_one = ((d_.cwday)..((d2.cwday < d_.cwday ? 7 : d2.cwday))).include?(WEEKDAYS.index(weekday) + 1) ? 1 : 0
    num_weeks + add_one
  end

  def holiday_bump(direction = nil)
    hols = $holidays
    new_date = self
    return new_date unless hols
    while hols.keys.include?(new_date)
      direction ||= hols[new_date].shift_meeting
      case direction
        when :before
          new_date -= 1 
        when :after
          new_date += 1
      end
    end
    return new_date
  end  
  
  def holidays_shifted_today
    return self-1 if was_yesterday_holiday_shifted_today?
    return self+1 if is_tommorow_holiday_shifted_today?
    return self
  end
  
  def weekdays
    days       = []
    days      << self.weekday
    days      << self.holidays_shifted_today.weekday
    days.uniq
  end
  
  def to_yaml( opts={} )
    YAML::quick_emit( self, opts ) do |out|
      out.scalar( "tag:yaml.org,2002:timestamp", self.strftime("%Y-%m-%d"), :plain )
    end
  end

  def days360(other)
    y1 = self.year;   y2 = other.year
    m1 = self.month;  m2 = other.month
    d1 = self.day;    d2 = other.day

    d1 = (d1 == 31) ? 30 : d1
    d2 = (d2 == 31) ? 30 : d2
    
    360 * (y2-y1) + 30 * (m2-m1) + (d2-d1)
  end

  # def self.min_date
  #   Mfi.first.in_operation_since||Date.new(2000, 01, 01)
  # end

  # def self.max_date
  #   today+1000
  # end

  private
  def was_yesterday_holiday_shifted_today?
    yesterday = self-1
    return true if $holidays[yesterday] and $holidays[yesterday].shift_meeting==:after
    return false
  end

  def is_tommorow_holiday_shifted_today?
    yesterday = self+1
    return true if $holidays[yesterday] and $holidays[yesterday].shift_meeting==:before
    return false
  end
end

module Misfit
  module Config
    attr_accessor :hols
    
    def self.compile_nomentculature
      if Mfi.first.center_manager
        name = Mfi.first.center_manager
      else
        name = "manager"
      end

      define_method :center_manager do
        name
      end
    end

    def self.holidays
      @hols ||= Holiday.all.map{|h| [h.date, h]}.to_hash
    end

    def self.refresh_holidays
      @hols = nil
    end
  end
end

class Hash
  #Hash diffs are easy
  def diff(other)
    keys = self.keys
    keys.each.select{|k| self[k] != other[k]}
  end

  def / (other)
    rhash = {}
    keys.each do |k|
      if self.has_key?(k) and other.has_key?(k)
        rhash[k] = self[k]/other[k]
      else
        rhash[k] = nil
      end
    end
    rhash
  end

  def - (other)
    rhash = {}
    keys.each do |k|
      if has_key?(k) and other.has_key?(k)
        rhash[k] = self[k] - other[k]
      else
        rhash[k] = self[k]
      end
    end
    rhash
  end

  def +(other)
    rhash = {}
    (keys + other.keys).uniq.each do |k|
      if has_key?(k) and other.has_key?(k)
        rhash[k] = self[k] + other[k]
      elsif other.has_key?(k)
        rhash[k] = other[k]
      elsif has_key?(k)
        rhash[k] = self[k]
      end
    end
    rhash
  end

end

class String
  def join_snake(str='')
    self.split('_').map{|x| x}.join(str)
  end

  def camelcase(str='')
    self.split('_').map{|x| x.capitalize}.join(str)
  end
end

class Numeric
  alias_method :round_orig, :round
  def round(n=0)
    (self * (10.0 ** n)).round_orig * (10.0 ** (-n))
  end

  def to_account_balance
    as_currency = self.abs.to_currency
    (self < 0) ? "#{as_currency} Dr" : (self > 0) ? "#{as_currency} Cr" : "#{as_currency}"
  end
end

class Integer
  alias_method :round_orig, :round
  def round(n=0)
    (self * (10.0 ** n)).round_orig * (10.0 ** (-n))
  end
end

class Float
  alias_method :round_orig, :round
  def round(n=0)
    (self * (10.0 ** n)).round_orig * (10.0 ** (-n))
  end
end

class Array
  # Takes a function and groups by a nested array return by dm-aggrgates using the given function
  def group_by_function(func)
    group_by{|x| 
      func.call(x[0])
    }.map{|k,v| 
      [k, v.map{|x| x[1]}.reduce{|s,x| 
         s+=x
       }]
    }.sort_by{|x| x[0]}
  end
end

module ExcelFormula
  def pmt(interest, installments, present_value, future_value, paid_before=1)  
    vPow = (1 + interest) ** installments
    actual_interest_rate = (paid_before == 0 ? interest : interest/(1 + interest))
    (vPow * present_value - future_value)/(vPow - 1) * actual_interest_rate
  end
end

module FinancialFunctions
  def npv(cashflows, discount_rate)
    (cashflows.enum_for(:each_with_index).collect{|x,i| x/((1+discount_rate)**i)}).inject(0){|a,b| a+b}
  end

  def irr(cash_flows, iterations = 100)
    (1..iterations).inject do |rate,|
      npv = cash_flows.enum_for(:each_with_index).inject {|(m,),(c,t)| m+c/(1.0+rate)**t}
      rate * (1 - npv / cash_flows.first)
    end
  end
end

module DmPagination
  class PaginationBuilder
    def url(params)
      @context.params.delete(:action) if @context.params[:action] == 'index'
      @context.url(@context.params.merge(params).reject{|k,v| k=="_message"})
    end
  end
end