class Market < ActiveRecord::Base
 
  belongs_to :team
  has_many :holdings
  
  def b
    # the market depth
    return 1000.to_f
  end

  def value(num_shares)
    if num_shares < 0
       real_price = 1 - price
    else
       real_price = price
    end
    num_shares = -num_shares
    return ( b * Math.log( Math.exp( num_shares.to_f / b ) * real_price + ( 1 - real_price) ) ).abs    
  end

  def cost(num_shares)
    if num_shares < 0
      num_shares = -num_shares
      real_price = 1 - price
    else
      real_price = price
    end

    return b * Math.log( Math.exp( num_shares.to_f / b ) * real_price + ( 1-real_price) )

  end

  def num_shares(wager)
    if wager < 0
       real_price = 1 - price
    else
       real_price = price
    end

    shares = b*Math.log((real_price+Math.exp(wager.abs/b)-1)/real_price)
    if wager < 0
       return -shares 
    else
       return shares
    end

  end

end