require 'wait'
module PageMagic
  # class Session - coordinates access to the browser though page objects.
  class Session
    URL_MISSING_MSG = 'a path must be mapped or a url supplied'
    REGEXP_MAPPING_MSG = 'URL could not be derived because mapping is a Regexp'

    attr_reader :raw_session, :transitions

    # Create a new session instance
    # @param [Object] capybara_session an instance of a capybara session
    # @param [String] url url to start the session at.
    def initialize(capybara_session, url = nil)
      @raw_session = capybara_session
      visit(url: url) if url
      @transitions = {}
    end

    # Map paths to Page classes. The session will auto load page objects from these mapping when
    # the {Session#current_path}
    # is matched.
    # @example
    #   self.define_page_mappings '/' => HomePage, %r{/messages/d+}
    # @param [Hash] transitions - paths mapped to page classes
    # @option transitions [String] path as literal
    # @option transitions [Regexp] path as a regexp for dynamic matching.
    def define_page_mappings(transitions)
      @transitions = transitions
    end

    # @return [Object] returns page object representing the currently loaded page on the browser. If no mapping
    # is found then nil returned
    def current_page
      mapping = find_mapped_page(current_path)
      @current_page = mapping.new(self) if mapping
      @current_page
    end

    # Direct the browser to the given page or url. {Session#current_page} will be set be an instance of the given/mapped
    # page class
    # @overload visit(page: page_object)
    #  @param [Object] page page class. The required url will be generated using the session's base url and the mapped
    #   path
    # @overload visit(url: url)
    #  @param [String] url url to be visited.
    # @overload visit(page: page_class, url: url)
    #  @param [String] url url to be visited.
    #  @param [Object] page the supplied page class will be instantiated to be used against the given url.
    # @raise [InvalidURLException] if a page is supplied and there isn't a mapped path for it
    # @raise [InvalidURLException] if neither a page or url are supplied
    # @raise [InvalidURLException] if the mapped path for a page is a Regexp
    def visit(page = nil, url: nil)
      if url
        raw_session.visit(url)
      elsif (path = transitions.key(page))
        fail InvalidURLException, REGEXP_MAPPING_MSG if path.is_a?(Regexp)
        raw_session.visit(url(current_url, path))
      else
        fail InvalidURLException, URL_MISSING_MSG
      end
      @current_page = page.new(self) if page
      self
    end

    # @return [String] path in the browser
    def current_path
      raw_session.current_path
    end

    # @return [String] full url in the browser
    def current_url
      raw_session.current_url
    end

    # Wait until a the supplied block returns true
    # @example
    #   wait_until do
    #     (rand % 2) == 0
    #   end
    def wait_until(&block)
      @wait ||= Wait.new
      @wait.until(&block)
    end

    # proxies unknown method calls to the currently loaded page object
    # @return [Object] returned object from the page object method call
    def method_missing(name, *args, &block)
      current_page.send(name, *args, &block)
    end

    # @param args see {::Object#respond_to?}
    # @return [Boolean] true if self or the current page object responds to the give method name
    def respond_to?(*args)
      super || current_page.respond_to?(*args)
    end

    private

    def url(base_url, path)
      path = path.sub(%r{^/}, '')
      base_url = base_url.sub(%r{/$}, '')
      "#{base_url}/#{path}"
    end

    def find_mapped_page(path)
      mapping = transitions.keys.find do |key|
        string_matches?(path, key)
      end
      transitions[mapping]
    end

    def string_matches?(string, matcher)
      if matcher.is_a?(Regexp)
        string =~ matcher
      elsif matcher.is_a?(String)
        string == matcher
      else
        false
      end
    end
  end
end