## helper function for wager_to_shares (see betreal paper)
#def g(d,w,q,y,r,n,b)
#  return d*b*Math.log((1.0+Math.exp(d*q/b))*Math.exp((n*(w*r+y))/b)-1)-q
#end
#
## worst-case net worth after moving the outstanding shares from q to q+x
#def w(q,y,r,x,n
#
## qty demanded by an agent wanting to move the price in direction d (+1 or -1)
## who has y yootles and r shares, and the outstanding qty is q, the liquidity
## b, and n is always 1 for now (see betreal paper)
#def dem0(d,q,y,r,n,b)
#  if 
#end

# takes wager amount y, market price p, liquidity (b); returns shares acquirable
def wager_to_shares(y,p,b)
  #d = (w<0 ? -1 : 1) 
  return b*Math.log((p+Math.exp(y/b)-1)/p)
end

class MarketController < ApplicationController

  def info
     @team = Team.find(params[:team])
     @markets = @team.markets.find(:all, :order => "round")
     @round_names = ["Sweet Sixteen", "Elite Eight", "Final Four", "Championship Game"]
     @round_up = params[:round_up]
     @transaction = params[:transaction]
  end

  def buy
    market = Market.find(params[:market_id])
    num_shares = wager_to_shares(params[:trade][:cost].to_f, market.price, market.b)
    #num_shares = params[:trade][:shares].to_i
        
    trade = Trade.new
    trade.shares = num_shares
    trade.market = market
    trade.user = @user
    trade.cost = market.cost(trade.shares)
    trade.save

    market.outstanding_shares += num_shares
    market.volume += (num_shares).abs
    market.save

    unless holding = @user.holdings.find(:first, :conditions => ["market_id = ?", market.id])
      holding = Holding.new
      holding.market = market
      holding.user = @user
      holding.shares = 0
      holding.cost = 0
    end
    holding.shares += trade.shares
    holding.cost += trade.cost
    holding.save

    @user.portfolio_value -= trade.cost
    @user.save

    trade_info
  end

  def sell
    params[:trade][:shares] = -params[:trade][:shares].to_i
    buy
  end

end