/**
* Returns the best supported encoding for a given client.
*
* @param client The client preferences to use.
* @return The best supported encoding for the given call.
*/
public Encoding getBestEncoding(ClientInfo client) {
Encoding bestEncoding = null;
Encoding currentEncoding = null;
Preference<Encoding> currentPref = null;
float bestScore = 0F;
for (Iterator<Encoding> iter = getSupportedEncodings().iterator(); iter.hasNext(); ) {
currentEncoding = iter.next();
for (Iterator<Preference<Encoding>> iter2 = client.getAcceptedEncodings().iterator();
iter2.hasNext(); ) {
currentPref = iter2.next();
if (currentPref.getMetadata().equals(Encoding.ALL)
|| currentPref.getMetadata().equals(currentEncoding)) {
// A match was found, compute its score
if (currentPref.getQuality() > bestScore) {
bestScore = currentPref.getQuality();
bestEncoding = currentEncoding;
}
}
}
}
return bestEncoding;
}
@Override
public PreferenceWriter append(Preference<?> pref) {
append(pref.getMetadata().getName());
if (pref.getQuality() < 1F) {
append(";q=");
appendQuality(pref.getQuality());
}
if (pref.getParameters() != null) {
Parameter param;
for (Iterator<Parameter> iter = pref.getParameters().iterator(); iter.hasNext(); ) {
param = iter.next();
if (param.getName() != null) {
append(';').append(param.getName());
if ((param.getValue() != null) && (param.getValue().length() > 0)) {
append('=').append(param.getValue());
}
}
}
}
return this;
}
/**
* Returns an enriched list of preferences. Contains the user preferences, implied user parent
* preferences (quality between 0.005 and 0.006), default preference (quality of 0.003), default
* parent preference (quality of 0.002), all preference (quality of 0.001).<br>
* <br>
* This necessary to compensate the misconfiguration of many browsers which don't expose all the
* metadata actually understood by end users.
*
* @param <T>
* @param userPreferences The user preferences to enrich.
* @param defaultValue The default value.
* @param allValue The ALL value.
* @return The enriched user preferences.
*/
@SuppressWarnings("unchecked")
protected <T extends Metadata> List<Preference<T>> getEnrichedPreferences(
List<Preference<T>> userPreferences, T defaultValue, T allValue) {
List<Preference<T>> result = new ArrayList<Preference<T>>();
// 0) List all undesired metadata
List<T> undesired = null;
for (Preference<T> pref : userPreferences) {
if (pref.getQuality() == 0) {
if (undesired == null) {
undesired = new ArrayList<T>();
}
undesired.add(pref.getMetadata());
}
}
// 1) Add the user preferences
result.addAll(userPreferences);
// 2) Add the user parent preferences
T parent;
for (int i = 0; i < result.size(); i++) {
Preference<T> userPref = result.get(i);
parent = (T) userPref.getMetadata().getParent();
// Add the parent, if it is not proscribed.
if ((parent != null)) {
if (canAdd(parent, undesired)) {
result.add(new Preference<T>(parent, 0.005f + (0.001f * userPref.getQuality())));
}
}
}
// 3) Add the default preference
if (defaultValue != null && canAdd(defaultValue, undesired)) {
Preference<T> defaultPref = new Preference<T>(defaultValue, 0.003f);
result.add(defaultPref);
T defaultParent = (T) defaultValue.getParent();
if (defaultParent != null && canAdd(defaultParent, undesired)) {
result.add(new Preference<T>(defaultParent, 0.002f));
}
}
// 5) Add "all" preference
for (int i = result.size() - 1; i >= 0; i--) {
// Remove any existing preference
if (result.get(i).getMetadata().equals(allValue)) {
result.remove(i);
}
}
result.add(new Preference<T>(allValue, 0.001f));
// 6) Return the enriched preferences
return result;
}
/**
* Scores a list of metadata relatively to enriched client preferences.
*
* @param metadataList The list of metadata to score.
* @return The score.
*/
private <T extends Metadata> float scoreMetadata(
List<T> metadataList, List<Preference<T>> prefs) {
float result = -1.0F;
float current;
if ((metadataList != null) && !metadataList.isEmpty()) {
for (Preference<T> pref : prefs) {
for (T metadata : metadataList) {
if (pref.getMetadata().includes(metadata)) {
current = pref.getQuality();
} else {
current = -1.0F;
}
if (current > result) {
result = current;
}
}
}
} else {
result = 0.0F;
}
return result;
}
/**
* Creates a new SortedMetadata from the given Metadata.
*
* @param preferences
*/
@SuppressWarnings({"unchecked", "rawtypes"})
private SortedMetadata(Collection<Preference<T>> preferences) {
SortedMap<Float, Collection<T>> map =
new TreeMap<Float, Collection<T>>(Collections.reverseOrder());
for (Preference<T> preference : preferences) {
Float quality = preference.getQuality();
Collection<T> metadatas = map.get(quality);
if (metadatas == null) {
metadatas = new ArrayList<T>(2);
map.put(quality, metadatas);
}
metadatas.add(preference.getMetadata());
}
Collection<Collection<T>> values = map.values();
this.metadatas = Collections.unmodifiableList(new ArrayList(values));
}