package com.bazaarvoice.dropwizard.webjars;
import com.google.common.base.Charsets;
import com.google.common.cache.CacheBuilder;
import com.google.common.cache.CacheLoader;
import com.google.common.cache.LoadingCache;
import com.google.common.io.ByteStreams;
import com.google.common.io.Resources;
import com.google.common.net.MediaType;
import org.eclipse.jetty.http.MimeTypes;
import org.eclipse.jetty.io.Buffer;
import java.net.URL;
import java.nio.charset.Charset;
/** Locates an loads a particular WebJar asset from the classpath. */
class AssetLoader extends CacheLoader<AssetId, Asset> {
public static final Asset NOT_FOUND = new Asset(null, null);
// For determining content type and content encoding
private static final MimeTypes MIME_TYPES = new MimeTypes();
private static final MediaType DEFAULT_MEDIA_TYPE = MediaType.HTML_UTF_8;
private static final Charset DEFAULT_CHARSET = Charsets.UTF_8;
private final LoadingCache<String, String> versionCache;
AssetLoader(CacheLoader<String, String> versionLoader) {
versionCache = CacheBuilder.newBuilder()
.maximumSize(10)
.build(versionLoader);
}
@Override
public Asset load(AssetId id) throws Exception {
String version = versionCache.getUnchecked(id.library);
if (VersionLoader.NOT_FOUND.equals(version)) {
return NOT_FOUND;
}
// Sometimes the WebJar has multiple releases which gets represented by a -# suffix to the version number
// inside of pom.properties. When this happens, the files inside of the jar don't include the WebJar
// release number as part of the file path. For example, the angularjs 1.1.1 WebJar has a version inside of
// pom.properties of 1.1.1-1. But the path to angular.js inside of the jar is
// META-INF/resources/webjars/angularjs/1.1.1/angular.js.
//
// Alternatively sometimes the developer of the library includes a -suffix in the true library version. In
// these cases the WebJar pom.properties will include that suffix in the version number, and the file paths
// inside of the jar will also include the suffix. For example, the backbone-marionette 1.0.0-beta6 WebJar
// has a version inside of pom.properties of 1.0.0-beta6. The path to backbone.marionette.js is also
// META-INF/resources/webjars/backbone-marionette/1.0.0-beta6/backbone.marionette.js.
//
// So based on the data inside of pom.properties it's going to be impossible to determine whether a -suffix
// should be stripped off or not. A reasonable heuristic however is going to be to just keep trying over
// and over starting with the most specific version number, then stripping a suffix off at a time until
// there are no more suffixes and the right version number is determined.
do {
String path = String.format("META-INF/resources/webjars/%s/%s/%s", id.library, version, id.resource);
try {
URL resource = Resources.getResource(path);
// Determine the media type of this resource
MediaType mediaType = getMediaType(path);
// We know that this version was valid. Update the version cache to make sure that we remember it
// for next time around.
versionCache.put(id.library, version);
return new Asset(ByteStreams.toByteArray(resource.openStream()), mediaType);
} catch (IllegalArgumentException e) {
// ignored
}
// Trim a suffix off of the version number
int hyphen = version.lastIndexOf('-');
if (hyphen == -1) {
return NOT_FOUND;
}
version = version.substring(0, hyphen);
}
while (true);
}
private MediaType getMediaType(String path) {
Buffer mimeType = MIME_TYPES.getMimeByExtension(path);
if (mimeType == null) {
return DEFAULT_MEDIA_TYPE;
}
MediaType mediaType;
try {
mediaType = MediaType.parse(mimeType.toString());
if (mediaType.is(MediaType.ANY_TEXT_TYPE)) {
mediaType = mediaType.withCharset(DEFAULT_CHARSET);
}
} catch (IllegalArgumentException e) {
return DEFAULT_MEDIA_TYPE;
}
return mediaType;
}
}