# Copyright, 2012, by Samuel G. D. Williams. <http://www.codeotaku.com>
# 
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
# 
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
# 
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
# THE SOFTWARE.

require_relative 'middleware'

module Rack
	class Request
		def current_locale
			env[Utopia::Localization::CURRENT_LOCALE_KEY]
		end
		
		def default_locale
			localization.default_locale
		end
		
		def all_locales
			localization.all_locales
		end
		
		def localization
			env[Utopia::Localization::LOCALIZATION_KEY]
		end
	end
end

module Utopia
	# If you request a URL which has localized content, a localized redirect would be returned based on the content requested.
	class Localization
		RESOURCE_NOT_FOUND = [400, {}, []].freeze
		
		HTTP_ACCEPT_LANGUAGE = 'HTTP_ACCEPT_LANGUAGE'.freeze
		LOCALIZATION_KEY = 'utopia.localization'.freeze
		CURRENT_LOCALE_KEY = 'utopia.localization.current_locale'.freeze
		
		def initialize(app, options = {})
			@app = app

			@default_locale = options[:default_locale] || "en"
			@all_locales = options[:locales] || ["en"]
			
			@nonlocalized = options.fetch(:nonlocalized, [])
		end

		attr :all_locales
		attr :default_locale
		
		def preferred_locales(env)
			request_preferred_locales(env) | browser_preferred_locales(env) | [@default_locale, nil]
		end
		
		def request_preferred_locales(env)
			path = Path[env['PATH_INFO']]
			
			if all_locales.include? path.first
				request_locale = path.first
				
				# Remove the localization prefix.
				path.delete_at(0)
				env['PATH_INFO'] = path.to_s
				
				return [request_locale]
			else
				return []
			end
		end
		
		def browser_preferred_locales(env)
			accept_languages = env[HTTP_ACCEPT_LANGUAGE]
			
			# No user prefered languages:
			return [] unless accept_languages

			languages = accept_languages.split(',').map { |language|
				language.split(';q=').tap{|x| x[1] = (x[1] || 1.0).to_f}
			}.sort{|a, b| b[1] <=> a[1]}.collect(&:first)
			
			# Returns languages based on the order of the first argument
			return languages & @all_locales
		end
		
		def nonlocalized?(env)
			path_info = env['PATH_INFO']
			
			@nonlocalized.any? { |pattern| path_info[pattern] != nil }
		end
		
		# Set the Vary: header on the response to indicate that this response should include the header in the cache key.
		def vary(env, response)
			headers = response[1]
			
			# This response was based on the Accept-Language header:
			if headers['Vary']
				headers['Vary'] += ',Accept-Language'
			else
				headers['Vary'] = 'Accept-Language'
			end
			
			# Althought this header is generally not supported, we supply it anyway as it is useful for debugging:
			if locale = env[CURRENT_LOCALE_KEY]
				# Set the Content-Location to point to the localized URI as requested:
				headers['Content-Location'] = "/#{locale}" + env['PATH_INFO']
			end
			
			return response
		end
		
		def call(env)
			return @app.call(env) if nonlocalized?(env)
			
			env[LOCALIZATION_KEY] = self
			
			response = nil
			
			# We have a non-localized request, but there might be a localized resource. We return the best localization possible:
			preferred_locales(env).each do |locale|
				env[CURRENT_LOCALE_KEY] = locale
				
				response = @app.call(env)
				
				break unless response[0] >= 400
			end
			
			return vary(env, response)
		end
	end
end