#!/usr/bin/env ruby
#
# Calculator
#
# See file for options
#
# Created: Mon Jan 29 09:04:14 2007
#

require 'net/http'
require 'cgi'

def scan(page, re, host = "www.google.com")
  h = Net::HTTP.new(host, 80)
  resp, data = h.get(page, nil)
  if resp.message == "OK"
    data.scan(re) { |y| yield y}
  else
    puts "ERROR: #{resp}"
  end
end

########## Main ##########

puts "Type math expressions or 'q' to quit or 'u' to remove units"
puts

buffer = 0
while true do
  print buffer.to_s + " > "
  cmd = STDIN.gets.chomp

  # remove space from the front and back
  cmd = cmd.gsub(/^\s+/,"")
  cmd = cmd.gsub(/\s+$/,"")

  # quit?
  break if /^q/i.match cmd

  # remove the units?
  if /^u$/.match cmd then
    buffer = buffer.gsub(/\s.*/,"")
    next
  end

  # numbers are just numbers
  if /^\+?\-?[\d\.e]+$/.match cmd then
    buffer = cmd
    next
  end
  
  # use the buffer if the command starts with a function and put the
  # buffer in parens
  funs = ["sin","cos","tan","isin","icos","itan","sqrt","isqrt"]
  funs.each do |x|
    if cmd == x then
      cmd = x + "(" + buffer + ")"
      break
    end
  end

  # use the buffer if the command starts with an operator and put the
  # buffer in front
  ops = ["\\+","-","\\/","\\*","%","\\^"]
  ops.each do |x|
    if /^#{x}/.match cmd then
      cmd = buffer + " " + x
      break
    end
  end

  # if we just say 'in ...' add the buffer to the front
  # and make this the command
  if /^in /.match cmd then
    cmd = buffer + " " + cmd
  end

  page = "/search?q=" + CGI.escape(cmd)
  scan(page, /images\/calc_img\.gif.*<b>[^\=]+\=\s*([^<]+)\s*<\/b>/im) { |result|
    buffer = result[0]
  }
end