require "net/http"
require "cgi"
require "uri"
require "rubygems"
require "json"
require "longurl/constants"
require "longurl/exceptions"
require "longurl/url"

module LongURL

  class Service
    
    def initialize(params = {})
      if params[:cache].nil?
        @@cache = Hash.new
      elsif params[:cache] == false
        @@cache = nil
      else
        @@cache = params[:cache]
      end
      @@supported_services = cached_or_fetch_supported_services
    end
    
    def query_supported_service_only(url)
      check url
      raise LongURL::UnsupportedService unless service_supported?(url)
      (@@cache && cached_query(url)) || query(url)
    end
    
    def cached_query(url)
      @@cache[url] ||= query(url)
    end

    def query(url)
      escaped_url = check_and_escape(url)
      Net::HTTP.start(EndPoint.host, EndPoint.port) do |http|
        handle_response http.get("#{EndPoint.path}?format=json&url=#{escaped_url}")
      end
    rescue Timeout::Error, Errno::ENETUNREACH, Errno::ETIMEDOUT, SocketError
      raise LongURL::NetworkError
    end
        
    # Check among supported services by longurl.org if given <tt>url</tt> is supported.
    # Returns true if supported, false otherwise.
    def service_supported?(url)
      @@supported_services.include? URI.parse(url).host.downcase
    end
    
    protected
    
    # Returns a list of supported services.
    # Use cache to get the list or fetch it if cache is empty.
    def cached_or_fetch_supported_services
      if @@cache
        @@cache['supported_services'] ||= fetch_supported_services
      else
        fetch_supported_services
      end
    end
    
    # Check given <tt>url</tt> using LongURL::URL.check
    def check(url)
      LongURL::URL.check url
    end
    
    # Check given url and escape it for http query argument passing.
    def check_and_escape(url)
      check url
      CGI.escape url
    end
    
    # Fetch supported services from longurl.org api.
    # Returns supported services in an Array.
    # Raises LongURL::NetworkError in case of a network error (timeout, ...)
    def fetch_supported_services
      Net::HTTP.start(ServiceEndPoint.host, ServiceEndPoint.port) do |http|
        response = http.get("#{ServiceEndPoint.path}?format=json")
        parsed = JSON.parse(response.body)
        parsed.values.flatten
      end
    rescue Timeout::Error, Errno::ENETUNREACH, Errno::ETIMEDOUT, SocketError
      raise LongURL::NetworkError
    rescue
      raise LongURL::UnknownError
    end
    
    def handle_response(response)
      parsed = JSON.parse(response.body)
      parsed = parsed.first if parsed.is_a?(Array)
      if parsed['long_url']
        parsed['long_url']
      elsif parsed['message'] # Error
        raise exception_regarding_message(parsed['message'])
      else
        raise LongURL::UnknownError
      end
    end
    
    def exception_class_regarding_message(message)
      case message
      when 'Unsupported service.'
        LongURL::UnsupportedService
      when 'Connection timeout'
        LongURL::NetworkError
      when 'Could not expand URL. Please check that you have submitted a valid URL.'
        LongURL::InvalidURL
      else
        LongURL::UnknownError
      end
    end

  end  

end