/*
* Copyright (c) 2011, the Dart project authors.
*
* Licensed under the Eclipse Public License v1.0 (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.eclipse.org/legal/epl-v10.html
*
* 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 com.google.dart.tools.ui.text.dart;
import org.eclipse.core.runtime.Assert;
import org.eclipse.jface.text.BadLocationException;
import org.eclipse.jface.text.IDocument;
import org.eclipse.jface.text.ITextViewer;
/**
* Describes the context of an invocation of content assist in a text viewer. The context knows the
* document, the invocation offset and can lazily compute the identifier prefix preceding the
* invocation offset. It may know the viewer.
* <p>
* Subclasses may add information to their environment. For example, source code editors may provide
* specific context information such as an AST.
* </p>
* <p>
* Clients may instantiate and subclass.
* </p>
* Provisional API: This class/interface is part of an interim API that is still under development
* and expected to change significantly before reaching stability. It is being made available at
* this early stage to solicit feedback from pioneering adopters on the understanding that any code
* that uses this API will almost certainly be broken (repeatedly) as the API evolves.
*/
public class ContentAssistInvocationContext {
/* state */
private final ITextViewer fViewer;
private final IDocument fDocument;
private final int fOffset;
/* cached additional info */
private CharSequence fPrefix;
/**
* Creates a new context for the given document and offset.
*
* @param document the document that content assist is invoked in
* @param offset the offset into the document where content assist is invoked at
*/
public ContentAssistInvocationContext(IDocument document, int offset) {
Assert.isNotNull(document);
Assert.isTrue(offset >= 0);
fViewer = null;
fDocument = document;
fOffset = offset;
}
/**
* Equivalent to {@linkplain #ContentAssistInvocationContext(ITextViewer, int)
* ContentAssistInvocationContext(viewer, viewer.getSelectedRange().x)}.
*
* @param viewer the text viewer that content assist is invoked in
*/
public ContentAssistInvocationContext(ITextViewer viewer) {
this(viewer, viewer.getSelectedRange().x);
}
/**
* Creates a new context for the given viewer and offset.
*
* @param viewer the text viewer that content assist is invoked in
* @param offset the offset into the viewer's document where content assist is invoked at
*/
public ContentAssistInvocationContext(ITextViewer viewer, int offset) {
Assert.isNotNull(viewer);
fViewer = viewer;
fDocument = null;
fOffset = offset;
}
/**
* Creates a new context with no viewer or invocation offset set.
*/
protected ContentAssistInvocationContext() {
fDocument = null;
fViewer = null;
fOffset = -1;
}
/**
* Computes the identifier (as specified by {@link Character#isJavaIdentifierPart(char)}) that
* immediately precedes the invocation offset.
*
* @return the prefix preceding the content assist invocation offset, <code>null</code> if there
* is no document
* @throws BadLocationException if accessing the document fails
*/
public CharSequence computeIdentifierPrefix() throws BadLocationException {
if (fPrefix == null) {
IDocument document = getDocument();
if (document == null) {
return null;
}
int end = getInvocationOffset();
int start = end;
while (--start >= 0) {
if (!Character.isJavaIdentifierPart(document.getChar(start))) {
break;
}
}
start++;
fPrefix = document.get(start, end - start);
}
return fPrefix;
}
/**
* Invocation contexts are equal if they describe the same context and are of the same type. This
* implementation checks for <code>null</code> values and class equality. Subclasses should extend
* this method by adding checks for their context relevant fields (but not necessarily cached
* values).
* <p>
* Example:
*
* <pre>
* class MyContext extends ContentAssistInvocationContext {
* private final Object fState;
* private Object fCachedInfo;
*
* ...
*
* public boolean equals(Object obj) {
* if (!super.equals(obj))
* return false;
* MyContext other= (MyContext) obj;
* return fState.equals(other.fState);
* }
* }
* </pre>
* </p>
* <p>
* Subclasses should also extend {@link Object#hashCode()}.
* </p>
*
* @param obj {@inheritDoc}
* @return {@inheritDoc}
*/
@Override
public boolean equals(Object obj) {
if (obj == null) {
return false;
}
if (!getClass().equals(obj.getClass())) {
return false;
}
ContentAssistInvocationContext other = (ContentAssistInvocationContext) obj;
return (fViewer == null && other.fViewer == null || fViewer != null
&& fViewer.equals(other.fViewer))
&& fOffset == other.fOffset
&& (fDocument == null && other.fDocument == null || fDocument != null
&& fDocument.equals(other.fDocument));
}
/**
* Returns the document that content assist is invoked on, or <code>null</code> if not known.
*
* @return the document or <code>null</code>
*/
public IDocument getDocument() {
if (fDocument == null) {
if (fViewer == null) {
return null;
}
return fViewer.getDocument();
}
return fDocument;
}
/**
* Returns the invocation offset.
*
* @return the invocation offset
*/
public int getInvocationOffset() {
return fOffset;
}
/**
* Returns the viewer, <code>null</code> if not available.
*
* @return the viewer, possibly <code>null</code>
*/
public ITextViewer getViewer() {
return fViewer;
}
/*
* @see java.lang.Object#hashCode()
*/
@Override
public int hashCode() {
return 23459213 << 5 | (fViewer == null ? 0 : fViewer.hashCode() << 3) | fOffset;
}
}