#!/usr/bin/env ruby
#
# = Stock: A Dividend Yield Calculator
#
# Given a key/value pair of a stock symbol and how many shares you own, this
# program will spit out the yearly dividend amounts you will yield from holding
# it. Based on data from Yahoo! Finance.
#
# == Installation
# Install to ~/bin and run
# => <tt>chmod 777 stock</tt>
#
# Then edit your Shell config so that executables can be loaded from `~/bin`...
# => <tt>export PATH = $HOME/bin:$PATH</tt>
#
# Reload your shell with `source ~/.profile` and type
# => <tt>stock T=100</tt>
# to see how much you'll be making yearly through dividends.
#
# Author:: Tom Scott
# Homepage:: http://tinyurl.com/div-yield

require 'net/http'
require 'bigdecimal'

symbols_arr = Array.new
shares_of = {}

# A small function that shows the user how to use `stock`, then exits with error code=1
def usage(msg)
  if msg
    puts msg
    puts "-----------------------------------------------------------------"
  end
  puts "Usage: stock {symbol}={shares} - prints out the current price and"
  puts "yearly dividend yield in USD, based on how many shares you own."
  exit 1
end

unless ARGV.empty?
  ARGV.each do |arg|
    unless arg == ''
      arg_arr = arg.split '='
      symbol = arg_arr[0]
      shares_of[symbol] = arg_arr[1].to_i
      symbols_arr.push(symbol)
    end
  end

  symbols = symbols_arr.join '+'
  opts = 'syl9'
  url = "http://download.finance.yahoo.com/d/quotes.csv?s=#{symbols}&f=#{opts}"
  values  = Net::HTTP.get URI(url)
  stocks  = values.split "\n"

  unless stocks.empty?
    stocks.each do |stock_str|
      # raw data
      stock     = stock_str.split ','
      symbol    = stock[0].split('"').join('')
      shares_of_stock = BigDecimal.new(shares_of[symbol].to_s)
      dividend  = stock[1].to_f
      price     = stock[2].to_f

      if shares_of_stock > 0
        # calculations
        div_per_share = (price*dividend/100).round(2)
        div_yield     = (div_per_share*shares_of_stock).round(2)

        # presentation
        puts "#{symbol}:\t$#{div_yield}/year\t\t(@ #{div_per_share}/share)"
      else
        usage("You must specify more than 0 shares of #{symbol}.")
      end
    end
    exit 0
  else
    symbols_str = symbols_arr.join ' '
    usage("Search query failed for stocks #{symbols_str}.")
  end
else
  usage("No arguments specified.")
end