require 'sinatra/base'
require 'sinatra/paypal/version'
require 'sinatra/paypal/paypal-helper'
require 'sinatra/paypal/paypal-request'

module PayPal

	module Helpers

		def paypal_form_url
			PaypalHelper.form_url(settings.paypal.sandbox?)
		end

		def html_payment_form(item, data = {})
			# it is valid to send a nil item through - we might be going to set the fields in
			# javascript - but if it isn't null then there are certain fields that need to be
			# set
			if !item.nil?
				raise 'item.code required' if !item.respond_to?(:code) || item.code.nil?
				raise 'item.price required' if !item.respond_to?(:price) || item.price.nil?
				raise 'item.price must be a number above zero' if item.price.to_f <= 0
			end

			raise 'cannot generate a payment form without settings.paypal.email' if settings.paypal.email.nil?

			erb :_payment, :views => File.join(File.dirname(__FILE__), '/paypal'), :locals => {
				:custom_data => data,
				:item => item
			}
		end
	end

	def self.registered(app)
		app.helpers PayPal::Helpers
		app._paypal_register_default_callbacks

		app.set :paypal, OpenStruct.new({
			:return_url => '/payment/complete',
			:notify_url => '/payment/validate',
			:sandbox? => app.settings.development?,
			:email => nil
		})

		app.post '/payment/validate' do
			paypal_helper = PaypalHelper.new(app.settings.paypal.sandbox?)
			paypal_request = PaypalRequest.new(params)
			
			# first we check the request against paypal to make sure it is ok
			if settings.production?
				halt 500, 'request could not be validated' if !paypal_helper.ipn_valid? params
			end
			
			# check transaction log to make sure this not a replay attack
			if app._call_paypal_method(:repeated?, paypal_request)
				# we also want to return 200, because if it is paypal sending this, it will send 
				# it again and again until it gets a 200 back
				halt 200, 'already processed'
			end

			app._call_paypal_method(:validate!, paypal_request)
			
			# check that the payment is complete. we still return 200 if not, but
			# we don't need to do anymore processing (except for marking it as accountable, if it is)
			if paypal_request.complete?
				app._call_paypal_method(:complete, paypal_request)
			end

			app._call_paypal_method(:finish, paypal_request)

			return 200
		end
	end

	# Register a payment callback. All callbacks are called
	# with a single argument of the type +PaypalRequest+ containing all the
	# data for the notification.
	#
	# 	payment :complete do |p|
	# 		# process the payment here
	# 		# don't forget to check that the price is correct!
	# 	end
	#
	def payment(name, &block)
		raise "#{name.to_s} is not a valid payment callback" if !_paypal_valid_blocks.include? name
		_paypal_register_callback name, &block
	end

	def _paypal_register_default_callbacks
		_paypal_valid_blocks.each do |key|
			_paypal_register_callback(key) { |p| }
		end
	end

	def _paypal_register_callback(key, &block)
		self.class.send :define_method, _paypal_method_name(key), &block
	end

	def _paypal_valid_blocks
		[:complete, :finish, :validate!, :repeated?]
	end

	def _call_paypal_method(key, paypal_request)
		self.send _paypal_method_name(key), paypal_request
	end

	def _paypal_method_name(key)
		"payment_event_#{key}".to_sym
	end

end


module Sinatra
	register PayPal
end