module Schmobile
  class Middleware

    def initialize(app, options = {})
      @app     = app
      @options = options
    end

    def call(env)
      request = Rack::Request.new(env)

      if request.is_mobile? && redirect?(request)
        [ 301, { "Location" => redirect_location(request) }, [] ]
      else
        @app.call(env)
      end
    end

    # Returns true if this middleware has been configured with a redirect_to and the requested path
    # is not already below the configured redirect_to
    def redirect?(request)
      redirecting = true

      if @options.key?(:redirect_if)
        redirecting = @options[:redirect_if].call(request)
      end

      if @options.key?(:redirect_to)
        redirecting &&= request.path !~ /^#{@options[:redirect_to]}/
      else
        redirecting = false
      end

      redirecting ? redirect_location(request) : nil
    end

    def redirect_location(request)
      "#{@options[:redirect_to]}#{redirect_with(request)}"
    end

    def redirect_with(request)
      build_path(@options[:redirect_with].to_s, request)
    end

    private

    def build_path(destination, request)
      final_destination = destination.dup
      destination.scan(/\{\{\w+\}\}/) do |call|
        func = call.scan(/\w+/).first.to_s
        if request.respond_to?(func)
          final_destination.sub!(/\{\{#{func}\}\}/, request.send(func))
        end
      end
      final_destination
    end

  end
end