require 'eymiha'
require 'eymiha/url/url_exception'
require 'eymiha/url/url_normalizer'

optional_require 'win32/registry'

module Eymiha
  
  # UrlOpener opens a URL in a user's URL viewer of choice. URLs are
  # normalized prior to being opened.
  #
  # Instances use the Kernel::system method to open the resource in its
  # own Thread to avoid blocking. Any problems are raised through a
  # caller-supplied exception handler's handle(Exception) method.
  #
  # For Apple and Windows, the viewer-of-choice is defaulted to the user's
  # designated viewer in the environment. For other platforms, the caller
  # must assign the viewer prior to opening the URL.
  class UrlOpener
    
    @@url_viewer = nil
    
    # Sets and returns the user's default URL viewer-or-choice.
    def self.url_viewer=(url_viewer)
      @@url_viewer = url_viewer
    end
    
    # Returns the user's default URL viewer-of-choice.
    def self.url_viewer
      @@url_viewer
    end
    
    @@relative_base = nil
    
    # Sets and returns the default directory for opening relative file
    # resources. The directory is validated prior to assignment - if invalid
    # a UrlException will be raised.
    def self.relative_base=(relative_base)
      if UrlNormalizer.valid_relative_base? relative_base
        @@relative_base = relative_base
      else
        raise UrlException, "Invalid relative file base '#{relative_base}'"
      end
    end
    
    # Returns the default directory for opening relative file resources.
    def self.relative_base
      @@relative_base
    end
    
    @@exception_handler = nil
    
    # Sets and returns the default exception handler. Problems are reported
    # through its handle method, so it should either have the method, or
    # construct it or delegate at runtime.
    def self.exception_handler=(exception_handler)
      @@exceptionHandler = exception_handler
    end
    
    # Returns the default exception handler.
    def self.exception_handler
      @@exception_handler
    end
    
    attr_accessor :url_viewer, :exception_handler
    attr_reader :relative_base
    
    # Constructs and returns a new instance, using the default exception
    # handler, directory for opening relative file resources, and viewer of
    # choice.
    def initialize(exception_handler=@@exception_handler,
                   relative_base=@@relative_base,
                   url_viewer=@@url_viewer)
      @exception_handler = exception_handler
      @relative_base = relative_base
      @url_viewer = url_viewer
      @url_normalizer = UrlNormalizer.new
    end
    
    # Sets and Returns the directory for opening relative file resources. The
    # directory is validated prior to assignment - if invalid a UrlException
    # will be raised.
    def relative_base=(relative_base)
      if UrlNormalizer.valid_relative_base? relative_base
        @relative_base = relative_base
      else
        raise UrlException, "Invalid relative file base '#{relative_base}'"
      end
    end
    
    # opens the given URL in the user's viewer of choice. The method uses a
    # separate Thread to avoid blocking. Local file resources are opened
    # relative to the value of the current relative base directory, and any
    # problems are reported through the exception handler.
    def open url
      Thread.new {
        begin
          send "open_#{Config::CONFIG['target_vendor']}".to_sym,
          @url_normalizer.normalize(url.to_s,@relative_base)
        rescue Exception => exception
          @exception_handler.handle exception
        end
        terminate
      }
    end
    
    def method_missing(method,*args)
      open_other(*args) if method.to_s =~ /^open_/
    end
    
    private
    
    def open_apple url
      system "#{url_viewer||"open"} #{url}"
    end
    
    def windows_browser
      @@windows_browser ||=
        Win32::Registry::HKEY_CLASSES_ROOT.
        open('htmlfile\shell\open\command') { |reg|
        reg_type, reg_value = reg.read('')
        return reg_value
      }
    end
    
    def open_pc url
      system "#{url_viewer||windows_browser} #{url}"
    end
    
    def open_other *args
      if @url_viewer
        system "#{@url_viewer} #{args.join(' ')}"
      else
        raise UrlException,
        "No program was designated to open the URL."
      end
    end
    
  end
  
end