TemplateEngine.scala

/**
 * Copyright (C) 2009-2011 the original author or authors.
 * See the notice.md file distributed with this work for additional
 * information regarding copyright ownership.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.fusesource.scalate

import java.io.{ File, PrintWriter, StringWriter }
import java.net.URLClassLoader
import java.util.concurrent.ConcurrentHashMap
import java.util.concurrent.atomic.AtomicBoolean

import org.fusesource.scalate.filter._
import org.fusesource.scalate.jade.JadeCodeGenerator
import org.fusesource.scalate.layout.{ LayoutStrategy, NullLayoutStrategy }
import org.fusesource.scalate.mustache.MustacheCodeGenerator
import org.fusesource.scalate.scaml.ScamlCodeGenerator
import org.fusesource.scalate.ssp.SspCodeGenerator
import org.fusesource.scalate.support._
import org.fusesource.scalate.util._

import scala.collection.immutable.TreeMap
import scala.collection.mutable.HashMap
import scala.compat.Platform
import scala.language.existentials
import scala.util.control.Exception
import scala.util.parsing.input.{ OffsetPosition, Position }
import scala.xml.NodeSeq

object TemplateEngine {

  val log = Log(getClass)

  def apply(sourceDirectories: Iterable[File], mode: String): TemplateEngine = {
    new TemplateEngine(sourceDirectories, mode)
  }

  /**
   * The default template types available in Scalate
   */
  val templateTypes: List[String] = List("mustache", "ssp", "scaml", "jade")
}

/**
 * A TemplateEngine is used to compile and load Scalate templates.
 * The TemplateEngine takes care of setting up the Scala compiler
 * and caching compiled templates for quicker subsequent loads
 * of a requested template.
 *
 * The TemplateEngine uses a ''workingDirectory'' to store the generated scala source code and the bytecode. By default
 * this uses a dynamically generated directory. You can configure this yourself to use whatever directory you wish.
 * Or you can use the ''scalate.workdir'' system property to specify the workingDirectory
 *
 * @author <a href="http://hiramchirino.com">Hiram Chirino</a>
 */
class TemplateEngine(
  var sourceDirectories: Iterable[File] = None,
  var mode: String = System.getProperty("scalate.mode", "production")) {
  import TemplateEngine.log._

  private case class CacheEntry(
    template: Template,
    dependencies: Set[String],
    timestamp: Long) {

    def isStale() = timestamp != 0 && dependencies.exists {
      resourceLoader.lastModified(_) > timestamp
    }
  }

  /**
   * Whether or not markup sensitive characters for HTML/XML elements like &amp; &gt; &lt; are escaped or not
   */
  var escapeMarkup = true

  /**
   * Set to false if you don't want the template engine to ever cache any of the compiled templates.
   *
   * If not explicitly configured this property can be configured using the ''scalate.allowCaching'' system property
   */
  var allowCaching = "true" == System.getProperty("scalate.allowCaching", "true")

  /**
   * If true, then the template engine will check to see if the template has been updated since last compiled
   * so that it can be reloaded.  Defaults to true.  YOu should set to false in production environments since
   * the templates should not be changing.
   *
   * If not explicitly configured this property can be configured using the ''scalate.allowReload'' system property
   */
  var allowReload = "true" == System.getProperty("scalate.allowReload", "true")

  private[this] var compilerInstalled = true

  /**
   * Whether a custom classpath should be combined with the deduced classpath
   */
  var combinedClassPath = false

  /**
   * Sets the import statements used in each generated template class
   */
  var importStatements: List[String] = List(
    "import _root_.scala.collection.JavaConverters._",
    "import _root_.org.fusesource.scalate.support.TemplateConversions._",
    "import _root_.org.fusesource.scalate.util.Measurements._")

  /**
   * Loads resources such as the templates based on URIs
   */
  var resourceLoader: ResourceLoader = FileResourceLoader(sourceDirectoriesForwarder)

  /**
   * A list of directories which are searched to load requested templates.
   */
  var templateDirectories = List("")

  var packagePrefix = ""

  var bootClassName = "scalate.Boot"
  var bootInjections: List[AnyRef] = List(this)

  private[this] val booted = new AtomicBoolean()

  def boot(): Unit = {
    if (booted.compareAndSet(false, true)) {

      if (allowReload) {
        // Is the Scala compiler on the class path?
        try {
          getClass.getClassLoader.loadClass("scala.tools.nsc.settings.ScalaSettings")
        } catch {
          case e: Throwable =>
            // if it's not, then disable class reloading..
            debug("Scala compiler not found on the class path. Template reloading disabled.")
            allowReload = false
            compilerInstalled = false
        }
      }

      ClassLoaders.findClass(bootClassName, List(classLoader, Thread.currentThread.getContextClassLoader)) match {
        case Some(clazz) =>
          Boots.invokeBoot(clazz, bootInjections)

        case _ =>
          info("No bootstrap class " + bootClassName + " found on classloader: " + classLoader)
      }
    }
  }

  /**
   * A forwarder so we can refer to whatever the current latest value of sourceDirectories is even if the value
   * is mutated after the TemplateEngine is constructed
   */
  protected def sourceDirectoriesForwarder = {
    this.sourceDirectories
  }

  /**
   * The supported template engines and their default extensions
   */
  var codeGenerators: Map[String, CodeGenerator] = Map("ssp" -> new SspCodeGenerator, "scaml" -> new ScamlCodeGenerator,
    "mustache" -> new MustacheCodeGenerator, "jade" -> new JadeCodeGenerator)

  var filters: Map[String, Filter] = Map()

  def filter(name: String) = codeGenerators.get(name).map(gen =>
    new Filter() {
      def filter(context: RenderContext, content: String) = {
        context.capture(compileText(name, content))
      }
    }).orElse(filters.get(name))

  var pipelines: Map[String, List[Filter]] = Map()

  /**
   * Maps file extensions to possible template extensions for custom mappins such as for
   * Map("js" -> Set("coffee"), "css" => Set("sass", "scss"))
   */
  var extensionToTemplateExtension: collection.mutable.Map[String, collection.mutable.Set[String]] = collection.mutable.Map()

  /**
   * Returns the mutable set of template extensions which are mapped to the given URI extension.
   */
  def templateExtensionsFor(extension: String): collection.mutable.Set[String] = {
    extensionToTemplateExtension.getOrElseUpdate(extension, collection.mutable.Set())
  }

  private[this] val attempt = Exception.ignoring(classOf[Throwable])

  /**
   * Returns the file extensions understood by Scalate; all the template engines and pipelines including
   * the wiki markup languages.
   */
  def extensions: Set[String] = (codeGenerators.keySet ++ pipelines.keySet).toSet

  // Attempt to load all the built in filters.. Some may not load do to missing classpath
  // dependencies.
  attempt(filters += "plain" -> PlainFilter)
  attempt(filters += "javascript" -> JavascriptFilter)
  attempt(filters += "coffeescript" -> CoffeeScriptFilter)
  attempt(filters += "css" -> CssFilter)
  attempt(filters += "cdata" -> CdataFilter)
  attempt(filters += "escaped" -> EscapedFilter)

  attempt {
    CoffeeScriptPipeline(this)
  }

  var layoutStrategy: LayoutStrategy = NullLayoutStrategy

  lazy val compiler = createCompiler
  var compilerInitialized = false

  /**
   * Factory method to create a compiler for this TemplateEngine.
   * Override if you wish to contorl the compilation in a different way
   * such as in side SBT or something.
   */
  protected def createCompiler: Compiler = {
    compilerInitialized = true
    ScalaCompiler.create(this)
  }

  def shutdown() = if (compilerInitialized) compiler.shutdown

  def sourceDirectory = new File(workingDirectory, "src")
  def bytecodeDirectory = new File(workingDirectory, "classes")
  def libraryDirectory = new File(workingDirectory, "lib")
  def tmpDirectory = new File(workingDirectory, "tmp")

  var classpath: String = null

  private[this] var _workingDirectory: File = null

  var classLoader = getClass().getClassLoader()

  /**
   * By default lets bind the context so we get to reuse its methods in a template
   */
  var bindings = Binding("context", "_root_." + classOf[RenderContext].getName, true, None, "val", false) :: Nil

  val finderCache = new ConcurrentHashMap[String, String]
  private[this] val templateCache = new HashMap[String, CacheEntry]
  private[this] var _cacheHits = 0
  private[this] var _cacheMisses = 0

  // Discover bits that can enhance the default template engine configuration. (like filters)
  ClassFinder.discoverCommands[TemplateEngineAddOn]("META-INF/services/org.fusesource.scalate/addon.index").foreach { addOn =>
    debug("Installing Scalate add on " + addOn.getClass)
    addOn(this)
  }

  override def toString = getClass.getSimpleName + "(sourceDirectories: " + sourceDirectories + ")"

  /**
   * Returns true if this template engine is being used in development mode.
   */
  def isDevelopmentMode = mode != null && mode.toLowerCase.startsWith("d")

  /**
   * If not explicitly configured this will default to using the ''scalate.workdir'' system property to specify the
   * directory used for generating the scala source code and compiled bytecode - otherwise a temporary directory is used
   */
  def workingDirectory: File = {
    // Use a temp working directory if none is configured.
    if (_workingDirectory == null) {
      val value = System.getProperty("scalate.workdir", "")
      if (value != null && value.length > 0) {
        _workingDirectory = new File(value)
      } else {
        val f = File.createTempFile("scalate-", "-workdir")
        // now lets delete the file so we can make a new directory there instead
        f.delete
        if (f.mkdirs) {
          _workingDirectory = f
          f.deleteOnExit
        } else {
          warn("Could not delete file %s so we could create a temp directory", f)
          _workingDirectory = new File(new File(System.getProperty("java.io.tmpdir")), "_scalate")
        }
      }
    }
    _workingDirectory
  }

  def workingDirectory_=(value: File) = {
    this._workingDirectory = value
  }

  /**
   * Compiles the given Moustache template text and returns the template
   */
  def compileMoustache(text: String, extraBindings: Iterable[Binding] = Nil): Template = {
    compileText("mustache", text, extraBindings)
  }

  /**
   * Compiles the given SSP template text and returns the template
   */
  def compileSsp(text: String, extraBindings: Iterable[Binding] = Nil): Template = {
    compileText("ssp", text, extraBindings)
  }

  /**
   * Compiles the given SSP template text and returns the template
   */
  def compileScaml(text: String, extraBindings: Iterable[Binding] = Nil): Template = {
    compileText("scaml", text, extraBindings)
  }

  /**
   * Compiles the given text using the given extension (such as ssp or scaml for example to denote what parser to use)
   * and return the template
   */
  def compileText(extension: String, text: String, extraBindings: Iterable[Binding] = Nil): Template = {
    tmpDirectory.mkdirs()
    val file = File.createTempFile("_scalate_tmp_", "." + extension, tmpDirectory)
    IOUtil.writeText(file, text)
    val loader = FileResourceLoader(List(tmpDirectory))
    compile(TemplateSource.fromUri(file.getName, loader), extraBindings)
  }

  /**
   * Compiles a template source without placing it in the template cache. Useful for temporary
   * templates or dynamically created template
   */
  def compile(source: TemplateSource, extraBindings: Iterable[Binding] = Nil): Template = {
    compileAndLoad(source, extraBindings, 0)._1
  }

  /**
   * Generates the Scala code for a template.  Useful for generating scala code that
   * will then be compiled into the application as part of a build process.
   */
  def generateScala(source: TemplateSource, extraBindings: Iterable[Binding] = Nil) = {
    source.engine = this
    generator(source).generate(this, source, bindings ++ extraBindings)
  }

  /**
   * Generates the Scala code for a template.  Useful for generating scala code that
   * will then be compiled into the application as part of a build process.
   */
  def generateScala(uri: String, extraBindings: Iterable[Binding]): Code = {
    generateScala(uriToSource(uri), extraBindings)
  }

  /**
   * Generates the Scala code for a template.  Useful for generating scala code that
   * will then be compiled into the application as part of a build process.
   */
  def generateScala(uri: String): Code = {
    generateScala(uriToSource(uri))
  }

  /**
   * The number of times a template load request was serviced from the cache.
   */
  def cacheHits = templateCache.synchronized { _cacheHits }

  /**
   * The number of times a template load request could not be serviced from the cache
   * and was loaded from disk.
   */
  def cacheMisses = templateCache.synchronized { _cacheMisses }

  /**
   * Expire specific template source and then compile and cache again
   */
  def expireAndCompile(source: TemplateSource, extraBindings: Iterable[Binding] = Nil): Unit = {

    templateCache.synchronized {

      templateCache.get(source.uri) match {
        case None => {
          sourceMapLog.info(s"${source.uri} not exist in cache just compiling")
          cache(source, compileAndLoadEntry(source, extraBindings))
        }
        case Some(entry) => {

          sourceMapLog.info(s"${source.uri} found in cache to expire")
          templateCache.remove(source.uri)

          cache(source, compileAndLoadEntry(source, extraBindings))

          sourceMapLog.info(s"${source.uri} removed from cache and compiled")
        }
      }
    }
  }

  /**
   * Compiles and then caches the specified template.  If the template
   * was previously cached, the previously compiled template instance
   * is returned.  The cache entry in invalidated and then template
   * is re-compiled if the template file has been updated since
   * it was last compiled.
   */
  def load(
    source: TemplateSource,
    extraBindings: Iterable[Binding] = Nil): Template = {

    source.engine = this
    templateCache.synchronized {

      // on the first load request, check to see if the INVALIDATE_CACHE JVM option is enabled
      if (_cacheHits == 0 && _cacheMisses == 0 && java.lang.Boolean.getBoolean("org.fusesource.scalate.INVALIDATE_CACHE")) {
        // this deletes generated scala and class files.
        invalidateCachedTemplates
      }

      // Determine whether to build/rebuild the template, load existing .class files from the file system,
      // or reuse an existing template that we've already loaded
      templateCache.get(source.uri) match {

        // Not in the cache..
        case None =>
          _cacheMisses += 1
          try {
            // Try to load a pre-compiled template from the classpath
            cache(source, loadPrecompiledEntry(source, extraBindings))
          } catch {
            case _: Throwable =>
              // It was not pre-compiled... compile and load it.
              cache(source, compileAndLoadEntry(source, extraBindings))
          }

        // It was in the cache..
        case Some(entry) =>
          // check for staleness
          if (allowReload && entry.isStale) {
            // Cache entry is stale, re-compile it
            _cacheMisses += 1
            cache(source, compileAndLoadEntry(source, extraBindings))
          } else {
            // Cache entry is valid
            _cacheHits += 1
            entry.template
          }
      }
    }
  }

  /**
   * Compiles and then caches the specified template.  If the template
   * was previously cached, the previously compiled template instance
   * is returned.  The cache entry in invalidated and then template
   * is re-compiled if the template file has been updated since
   * it was last compiled.
   */
  def load(file: File, extraBindings: Iterable[Binding]): Template = {
    load(TemplateSource.fromFile(file), extraBindings)
  }

  /**
   * Compiles and then caches the specified template.  If the template
   * was previously cached, the previously compiled template instance
   * is returned.  The cache entry in invalidated and then template
   * is re-compiled if the template file has been updated since
   * it was last compiled.
   */
  def load(file: File): Template = {
    load(TemplateSource.fromFile(file))
  }

  /**
   * Compiles and then caches the specified template.  If the template
   * was previously cached, the previously compiled template instance
   * is returned.  The cache entry in invalidated and then template
   * is re-compiled if the template file has been updated since
   * it was last compiled.
   */
  def load(uri: String, extraBindings: Iterable[Binding]): Template = {
    load(uriToSource(uri), extraBindings)
  }

  /**
   * Compiles and then caches the specified template.  If the template
   * was previously cached, the previously compiled template instance
   * is returned.  The cache entry in invalidated and then template
   * is re-compiled if the template file has been updated since
   * it was last compiled.
   */
  def load(uri: String): Template = {
    load(uriToSource(uri))
  }

  /**
   * Returns a template source for the given URI and current resourceLoader
   */
  def source(uri: String): TemplateSource = TemplateSource.fromUri(uri, resourceLoader)

  /**
   * Returns a template source of the given type of template for the given URI and current resourceLoader
   */
  def source(uri: String, templateType: String): TemplateSource = source(uri).templateType(templateType)

  /**
   * Returns true if the URI can be loaded as a template
   */
  def canLoad(source: TemplateSource, extraBindings: Iterable[Binding] = Nil): Boolean = {
    try {
      load(source, extraBindings) != null
    } catch {
      case e: ResourceNotFoundException => false
    }
  }

  /**
   * Returns true if the URI can be loaded as a template
   */
  def canLoad(uri: String): Boolean = {
    canLoad(uriToSource(uri))
  }

  /**
   * Returns true if the URI can be loaded as a template
   */
  def canLoad(uri: String, extraBindings: Iterable[Binding]): Boolean = {
    canLoad(uriToSource(uri), extraBindings)
  }

  /**
   *  Invalidates all cached Templates.
   */
  def invalidateCachedTemplates() = {
    templateCache.synchronized {
      templateCache.clear
      finderCache.clear
      IOUtil.recursiveDelete(sourceDirectory)
      IOUtil.recursiveDelete(bytecodeDirectory)
      sourceDirectory.mkdirs
      bytecodeDirectory.mkdirs
    }
  }

  // Layout as text methods
  //-------------------------------------------------------------------------

  /**
   *  Renders the given template URI using the current layoutStrategy
   */
  def layout(uri: String, context: RenderContext, extraBindings: Iterable[Binding]): Unit = {
    val template = load(uri, extraBindings)
    layout(template, context)
  }

  /**
   * Renders the given template using the current layoutStrategy
   */
  def layout(template: Template, context: RenderContext): Unit = {
    RenderContext.using(context) {
      val source = template.source
      if (source != null && source.uri != null) {
        context.withUri(source.uri) {
          layoutStrategy.layout(template, context)
        }
      } else {
        layoutStrategy.layout(template, context)
      }
    }
  }

  /**
   * Renders the given template URI returning the output
   */
  def layout(
    uri: String,
    attributes: Map[String, Any] = Map(),
    extraBindings: Iterable[Binding] = Nil): String = {
    val template = load(uri, extraBindings)
    layout(uri, template, attributes)
  }

  def layout(
    uri: String,
    out: PrintWriter,
    attributes: Map[String, Any]): Unit = {
    val template = load(uri)
    layout(uri, template, out, attributes)
  }

  protected def layout(
    uri: String,
    template: Template,
    out: PrintWriter,
    attributes: Map[String, Any]): Unit = {
    val context = createRenderContext(uri, out)
    for ((key, value) <- attributes) {
      context.attributes(key) = value
    }
    layout(template, context)
  }

  /**
   * Renders the given template returning the output
   */
  def layout(
    uri: String,
    template: Template,
    attributes: Map[String, Any]): String = {
    val buffer = new StringWriter()
    val out = new PrintWriter(buffer)
    layout(uri, template, out, attributes)
    buffer.toString
  }

  // can't use multiple methods with default arguments so lets manually expand them here...
  def layout(uri: String, context: RenderContext): Unit = layout(uri, context, Nil)
  def layout(uri: String, template: Template): String = layout(uri, template, Map[String, Any]())

  /**
   *  Renders the given template source using the current layoutStrategy
   */
  def layout(source: TemplateSource): String = layout(source, Map[String, Any]())
  /**
   *  Renders the given template source using the current layoutStrategy
   */
  def layout(source: TemplateSource, attributes: Map[String, Any]): String = {
    val template = load(source)
    layout(source.uri, template, attributes)
  }
  /**
   *  Renders the given template source using the current layoutStrategy
   */
  def layout(
    source: TemplateSource,
    context: RenderContext,
    extraBindings: Iterable[Binding]): Unit = {
    val template = load(source, extraBindings)
    layout(template, context)
  }

  /**
   *  Renders the given template source using the current layoutStrategy
   */
  def layout(source: TemplateSource, context: RenderContext): Unit = {
    val template = load(source)
    layout(template, context)
  }

  // Layout as markup methods
  //-------------------------------------------------------------------------

  /**
   * Renders the given template URI returning the output
   */
  def layoutAsNodes(
    uri: String,
    attributes: Map[String, Any] = Map(),
    extraBindings: Iterable[Binding] = Nil): NodeSeq = {
    val template = load(uri, extraBindings)
    layoutAsNodes(uri, template, attributes)
  }

  /**
   * Renders the given template returning the output
   */
  def layoutAsNodes(
    uri: String,
    template: Template,
    attributes: Map[String, Any]): NodeSeq = {
    // TODO there is a much better way of doing this by adding native NodeSeq
    // support into the generated templates - especially for Scaml!
    // for now lets do it a crappy way...

    val buffer = new StringWriter()
    val out = new PrintWriter(buffer)
    val context = createRenderContext(uri, out)
    for ((key, value) <- attributes) {
      context.attributes(key) = value
    }
    //layout(template, context)
    context.captureNodeSeq(template)
  }

  // can't use multiple methods with default arguments so lets manually expand them here...
  def layoutAsNodes(uri: String, template: Template): NodeSeq = layoutAsNodes(uri, template, Map[String, Any]())

  /**
   * Factory method used by the layout helper methods that should be overloaded by template engine implementations
   * if they wish to customize the render context implementation
   */
  protected def createRenderContext(uri: String, out: PrintWriter): RenderContext = new DefaultRenderContext(uri, this, out)

  private def loadPrecompiledEntry(
    source: TemplateSource,
    extraBindings: Iterable[Binding]) = {
    source.engine = this
    val className = source.className
    val template = loadCompiledTemplate(className, allowCaching)
    template.source = source
    if (allowCaching && allowReload && resourceLoader.exists(source.uri)) {
      // Even though the template was pre-compiled, it may go or is stale
      // We still need to parse the template to figure out it's dependencies..
      val code = generateScala(source, extraBindings)
      val entry = CacheEntry(template, code.dependencies, lastModified(template.getClass))
      if (entry.isStale) {
        // Throw an exception since we should not load stale pre-compiled classes.
        throw new StaleCacheEntryException(source)
      }
      // Yay the template is not stale.  Lets use it.
      entry
    } else {
      // If we are not going to be cache reloading.. then we
      // don't need to do the extra work.
      CacheEntry(template, Set(), 0)
    }
  }

  private def compileAndLoadEntry(
    source: TemplateSource,
    extraBindings: Iterable[Binding]) = {
    val (template, dependencies) = compileAndLoad(source, extraBindings, 0)
    CacheEntry(template, dependencies, Platform.currentTime)
  }

  private def cache(source: TemplateSource, ce: CacheEntry): Template = {
    if (allowCaching) {
      templateCache += (source.uri -> ce)
    }
    val answer = ce.template
    debug("Loaded uri: " + source.uri + " template: " + answer)
    answer
  }

  /**
   * Returns the source file of the template URI
   */
  protected def sourceFileName(uri: String) = {
    // Write the source code to file..
    // to avoid paths like foo/bar/C:/whatnot on windows lets mangle the ':' character
    new File(sourceDirectory, uri.replace(':', '_') + ".scala")
  }

  protected def classFileName(uri: String) = {
    // Write the source code to file..
    // to avoid paths like foo/bar/C:/whatnot on windows lets mangle the ':' character
    new File(sourceDirectory, uri.replace(':', '_') + ".scala")
  }

  protected val sourceMapLog = Log(getClass, "SourceMap")

  private def compileAndLoad(
    source: TemplateSource,
    extraBindings: Iterable[Binding],
    attempt: Int): (Template, Set[String]) = {
    source.engine = this
    var code: Code = null
    try {
      val uri = source.uri

      // Can we use a pipeline to process the request?
      pipeline(source) match {
        case Some(p) =>
          val template = new PipelineTemplate(p, source.text)
          template.source = source
          return (template, Set(uri))
        case None =>
      }

      if (!compilerInstalled) {
        throw new ResourceNotFoundException(
          "Scala compiler not on the classpath.  You must either add it to the classpath or precompile all the templates")
      }

      val g = generator(source)
      // Generate the scala source code from the template
      code = g.generate(this, source, bindings ++ extraBindings)

      val sourceFile = sourceFileName(uri)
      sourceFile.getParentFile.mkdirs
      IOUtil.writeBinaryFile(sourceFile, code.source.getBytes("UTF-8"))

      // Compile the generated scala code
      compiler.compile(sourceFile)

      // Write the source map information to the class file
      val sourceMap = buildSourceMap(g.stratumName, uri, sourceFile, code.positions)

      sourceMapLog.debug("installing:" + sourceMap)

      storeSourceMap(new File(bytecodeDirectory, code.className.replace('.', '/') + ".class"), sourceMap)
      storeSourceMap(new File(bytecodeDirectory, code.className.replace('.', '/') + "$.class"), sourceMap)

      // Load the compiled class and instantiate the template object
      val template = loadCompiledTemplate(code.className)
      template.source = source

      (template, code.dependencies)

    } catch {
      // TODO: figure out why we sometimes get these InstantiationException errors that
      // go away if you redo
      case e: InstantiationException =>
        if (attempt == 0) {
          compileAndLoad(source, extraBindings, 1)
        } else {
          throw new TemplateException(e.getMessage, e)
        }

      case e: CompilerException =>
        // Translate the scala error location info
        // to the template locations..
        def template_pos(pos: Position) = {
          pos match {
            case p: OffsetPosition => {
              val filtered = code.positions.filterKeys(code.positions.ordering.compare(_, p) <= 0)
              if (filtered.isEmpty) {
                null
              } else {
                val (key, value) = filtered.last
                // TODO: handle the case where the line is different too.
                val colChange = pos.column - key.column
                if (colChange >= 0) {
                  OffsetPosition(value.source, value.offset + colChange)
                } else {
                  pos
                }
              }
            }
            case _ => null
          }
        }

        var newmessage = "Compilation failed:\n"
        val errors = e.errors.map {
          (olderror) =>
            val uri = source.uri
            val pos = template_pos(olderror.pos)
            if (pos == null) {
              newmessage += ":" + olderror.pos + " " + olderror.message + "\n"
              newmessage += olderror.pos.longString + "\n"
              olderror
            } else {
              newmessage += uri + ":" + pos + " " + olderror.message + "\n"
              newmessage += pos.longString + "\n"
              // TODO should we pass the source?
              CompilerError(uri, olderror.message, pos, olderror)
            }
        }
        error(e)
        if (e.errors.isEmpty) {
          throw e
        } else {
          throw new CompilerException(newmessage, errors)
        }
      case e: InvalidSyntaxException =>
        e.source = source
        throw e
      case e: TemplateException => throw e
      case e: ResourceNotFoundException => throw e
      case e: Throwable => throw new TemplateException(e.getMessage, e)
    }
  }

  /**
   * Gets a pipeline to use for the give uri string by looking up the uri's extension
   * in the the pipelines map.
   */
  protected def pipeline(source: TemplateSource): Option[List[Filter]] = {
    //sort the extensions so we match the longest first.
    for (ext <- pipelines.keys.toList.sortWith { case (x, y) => if (x.length == y.length) x.compareTo(y) < 0 else x.length > y.length } if source.uri.endsWith("." + ext)) {
      return pipelines.get(ext)
    }
    None
  }

  /**
   * Gets the code generator to use for the give uri string by looking up the uri's extension
   * in the the codeGenerators map.
   */
  protected def generator(source: TemplateSource): CodeGenerator = {
    extension(source) match {
      case Some(ext) =>
        generatorForExtension(ext)
      case None =>
        throw new TemplateException("Template file extension missing. Cannot determine which template processor to use.")
    }
  }

  /**
   * Extracts the extension from the source's uri though derived engines could override this behaviour to
   * auto default missing extensions or performing custom mappings etc.
   */
  protected def extension(source: TemplateSource): Option[String] = source.templateType

  /**
   * Returns the code generator for the given file extension
   */
  protected def generatorForExtension(extension: String) = codeGenerators.get(extension) match {
    case None =>
      val extensions = pipelines.keySet.toList ::: codeGenerators.keySet.toList
      throw new TemplateException("Not a template file extension (" + extensions.mkString(" | ") + "), you requested: " + extension);
    case Some(generator) => generator
  }

  private def loadCompiledTemplate(
    className: String,
    from_cache: Boolean = true): Template = {
    val cl = if (from_cache) {
      new URLClassLoader(Array(bytecodeDirectory.toURI.toURL), classLoader)
    } else {
      classLoader
    }
    val clazz = try {
      cl.loadClass(className)
    } catch {
      case e: ClassNotFoundException =>
        if (packagePrefix == "") {
          throw e
        } else {
          // Try without the package prefix.
          cl.loadClass(className.stripPrefix(packagePrefix).stripPrefix("."))
        }
    }
    clazz.asInstanceOf[Class[Template]].newInstance
  }

  /**
   * Figures out the modification time of the class.
   */
  private def lastModified(clazz: Class[_]): Long = {
    val codeSource = clazz.getProtectionDomain.getCodeSource
    if (codeSource != null && codeSource.getLocation.getProtocol == "file") {
      val location = new File(codeSource.getLocation.getPath)
      if (location.isDirectory) {
        val classFile = new File(location, clazz.getName.replace('.', '/') + ".class")
        if (classFile.exists) {
          return classFile.lastModified
        }
      } else {
        // class is inside an archive.. just use the modification time of the jar
        return location.lastModified
      }
    }
    // Bail out
    0
  }

  protected def buildSourceMap(
    stratumName: String,
    uri: String,
    scalaFile: File,
    positions: TreeMap[OffsetPosition, OffsetPosition]) = {
    val shortName = uri.split("/").last
    val longName = uri.stripPrefix("/")

    val stratum: SourceMapStratum = new SourceMapStratum(stratumName)
    val fileId = stratum.addFile(shortName, longName)

    // build a map of input-line -> List( output-line )
    var smap = new TreeMap[Int, List[Int]]()
    positions.foreach {
      case (out, in) =>
        val outs = out.line :: smap.getOrElse(in.line, Nil)
        smap += in.line -> outs
    }
    // sort the output lines..
    smap = smap.transform { (x, y) => y.sortWith(_ < _) }

    smap.foreach {
      case (in, outs) =>
        outs.foreach {
          out =>
            stratum.addLine(in, fileId, 1, out, 1)
        }
    }
    stratum.optimize

    val sourceMap: SourceMap = new SourceMap
    sourceMap.setOutputFileName(scalaFile.getName)
    sourceMap.addStratum(stratum, true)
    sourceMap.toString
  }

  protected def storeSourceMap(classFile: File, sourceMap: String) = {
    SourceMapInstaller.store(classFile, sourceMap)
  }

  /**
   * Creates a [[org.fusesource.scalate.TemplateSource]] from a URI
   */
  protected def uriToSource(uri: String) = TemplateSource.fromUri(uri, resourceLoader)

}