LiftExtractJs.scala

import scala.xml._
import net.liftweb.http.js._
import JsCmds._ 
import JE._
import net.liftweb.util.Helpers._

/**
 * Extract JS from a NodeSeq
 * Useful when using Lift SetHtml/Replace and it doesn't run the embedeed JS
 * 
 * CAUTION : the <lift:snippet>, if not eager eval, are expanded only later : 
 * if JS are expected in them it won't be found
 */
object ExtractJs {
  val regexp = """(?s).*// \<\!\[CDATA\[(.*)\]\]\>.*""".r
 
    
  def extractJsFromNodes(html : NodeSeq) : JsCmd = {
    var js = Noop
    
    def recurse(in: NodeSeq) : Unit = {
      in foreach {
        case node : Elem if node.label == "script" =>  
          node.attribute("type") match {
            case Some(s) if s.toString == "text/javascript" =>
              node.toString match{
                case regexp(content) =>
                  js = js & JsRaw(content)
                case _ => println("should have been match")
                println(node.toString)
              }
            case _ => //do not process that script tag, not javascript
          }
        case node : Elem =>  recurse(node.child);
        case g:Group => recurse(g.child)
        case _  => // ?
      }
    }

    recurse(html)
    js
  }

  /*
   * Extract script tag from content, build a sequence of JsCmd from them, pass the
   * filtered content to a NodeSeq => JsCmd command and add extracted commands
   */ 
  private[this] def extractAndFilterAndExec(content:NodeSeq)(command: NodeSeq => JsCmd) : JsCmd = {
    val js = ExtractJs.extractJsFromNodes(content)
    //filter script tag from xml
    val xml = ("script [type=text/javascript]" #> NodeSeq.Empty)(content)
    command(xml) & js
  }

  //override JsCmd Replace and SetHtml

  /**
   * Replacement for Lift JsCmd.Replace that:
   * - parse HTML content to find <script> tags ;
   * - filter them out of content ;
   * - add the list of JS commands from <script> tags after the Replace command.
   */
  def execReplace(id: String, content: NodeSeq) : JsCmd = {
    extractAndFilterAndExec(content){ filteredXML => Replace(id, filteredXML) }
  }

  /**
   * Replacement for Lift JsCmd.Replace that:
   * - parse HTML content to find <script> tags ;
   * - filter them out of content ;
   * - add the list of JS commands from <script> tags after the Replace command.
   */
  def execSetHtml(id: String, content: NodeSeq) : JsCmd = {
    extractAndFilterAndExec(content){ filteredXML => SetHtml(id, filteredXML) }
  }
}