CSSFixer.scala

/*
Requires

  libraryDependencies += "com.helger" % "ph-css" % "4.0.0"

Use in boot.scala:

    (new CSSFixer).fixCSS("css" :: "styles" :: Nil, Full("/newRoot"))
*/

package code.lib

import java.io.StringWriter

import com.helger.css.ECSSVersion
import com.helger.css.decl.visit.{AbstractModifyingCSSUrlVisitor, CSSVisitor}
import com.helger.css.reader.CSSReader
import com.helger.css.writer.CSSWriter
import net.liftweb.common.{Full, Box}
import net.liftweb.http._

class CSSFixer {
  def convertRoot(root: String, css: String): String = {
    val cssDef = CSSReader.readFromString(css, ECSSVersion.CSS30)
    CSSVisitor.visitCSSUrl(cssDef, new CSSURLFixer(root))
    val s = new StringWriter
    val cssWriter = new CSSWriter(ECSSVersion.CSS30)
    cssWriter.writeCSS(cssDef, s)
    s.toString
  }

  def fixCSS(path: List[String], prefix: Box[String]) {

    val liftReq: LiftRules.LiftRequestPF = new LiftRules.LiftRequestPF {
      def functionName = "PH-CSS URL Fixer"

      def isDefinedAt(r: Req): Boolean = {
        r.path.partPath == path
      }

      def apply(r: Req): Boolean = {
        r.path.partPath == path
      }
    }

    val cssFixer: LiftRules.DispatchPF = new LiftRules.DispatchPF {
      def functionName = "default css fixer"

      def isDefinedAt(r: Req): Boolean = {
        r.path.partPath == path
      }

      def apply(r: Req): () => Box[LiftResponse] = {
        val cssPath = path.mkString("/", "/", ".css")
        () => {
          LiftRules.loadResourceAsString(cssPath) map { (css: String) =>
            CSSResponse(convertRoot(prefix openOr (S.contextPath), css))
          }
        }
      }
    }
    LiftRules.dispatch.prepend(cssFixer)
    LiftRules.liftRequest.append(liftReq)
  }
}

class CSSURLFixer(root: String) extends AbstractModifyingCSSUrlVisitor {
  def getModifiedURI(s: String) = if (s.startsWith("/")) root + s else s
}