001package org.apache.maven.plugin.plugin;
002
003import org.apache.maven.plugin.AbstractMojo;
004import org.apache.maven.plugin.MojoExecutionException;
005import org.apache.maven.plugins.annotations.Mojo;
006import org.apache.maven.plugins.annotations.Parameter;
007
008import org.w3c.dom.Document;
009import org.w3c.dom.Element;
010import org.w3c.dom.Node;
011import org.w3c.dom.NodeList;
012import org.xml.sax.SAXException;
013
014import javax.xml.parsers.DocumentBuilder;
015import javax.xml.parsers.DocumentBuilderFactory;
016import javax.xml.parsers.ParserConfigurationException;
017import java.io.IOException;
018import java.io.InputStream;
019import java.util.ArrayList;
020import java.util.Iterator;
021import java.util.List;
022
023/**
024 * Display help information on maven-plugin-plugin.<br/>
025 * Call <code>mvn plugin:help -Ddetail=true -Dgoal=&lt;goal-name&gt;</code> to display parameter details.
026 * @author
027 * @version
028 */
029@Mojo( name = "help", requiresProject = false, threadSafe = true )
030public class HelpMojo
031    extends AbstractMojo
032{
033    /**
034     * If <code>true</code>, display all settable properties for each goal.
035     *
036     */
037    @Parameter( property = "detail", defaultValue = "false" )
038    private boolean detail;
039
040    /**
041     * The name of the goal for which to show help. If unspecified, all goals will be displayed.
042     *
043     */
044    @Parameter( property = "goal" )
045    private java.lang.String goal;
046
047    /**
048     * The maximum length of a display line, should be positive.
049     *
050     */
051    @Parameter( property = "lineLength", defaultValue = "80" )
052    private int lineLength;
053
054    /**
055     * The number of spaces per indentation level, should be positive.
056     *
057     */
058    @Parameter( property = "indentSize", defaultValue = "2" )
059    private int indentSize;
060
061    // groupId/artifactId/plugin-help.xml
062    private static final String PLUGIN_HELP_PATH = "/META-INF/maven/org.apache.maven.plugins/maven-plugin-plugin/plugin-help.xml";
063
064    private Document build()
065        throws MojoExecutionException
066    {
067        getLog().debug( "load plugin-help.xml: " + PLUGIN_HELP_PATH );
068        InputStream is = getClass().getResourceAsStream( PLUGIN_HELP_PATH );
069        try
070        {
071            DocumentBuilderFactory dbFactory = DocumentBuilderFactory.newInstance();
072            DocumentBuilder dBuilder = dbFactory.newDocumentBuilder();
073            return dBuilder.parse( is );
074        }
075        catch ( IOException e )
076        {
077            throw new MojoExecutionException( e.getMessage(), e );
078        }
079        catch ( ParserConfigurationException e )
080        {
081            throw new MojoExecutionException( e.getMessage(), e );
082        }
083        catch ( SAXException e )
084        {
085            throw new MojoExecutionException( e.getMessage(), e );
086        }
087    }
088
089    /**
090     * {@inheritDoc}
091     */
092    public void execute()
093        throws MojoExecutionException
094    {
095        if ( lineLength <= 0 )
096        {
097            getLog().warn( "The parameter 'lineLength' should be positive, using '80' as default." );
098            lineLength = 80;
099        }
100        if ( indentSize <= 0 )
101        {
102            getLog().warn( "The parameter 'indentSize' should be positive, using '2' as default." );
103            indentSize = 2;
104        }
105
106        Document doc = build();
107
108        StringBuilder sb = new StringBuilder();
109        Node plugin = getSingleChild( doc, "plugin" );
110
111
112        String name = getValue( plugin, "name" );
113        String version = getValue( plugin, "version" );
114        String id = getValue( plugin, "groupId" ) + ":" + getValue( plugin, "artifactId" ) + ":" + version;
115        if ( isNotEmpty( name ) && !name.contains( id ) )
116        {
117            append( sb, name + " " + version, 0 );
118        }
119        else
120        {
121            if ( isNotEmpty( name ) )
122            {
123                append( sb, name, 0 );
124            }
125            else
126            {
127                append( sb, id, 0 );
128            }
129        }
130        append( sb, getValue( plugin, "description" ), 1 );
131        append( sb, "", 0 );
132
133        //<goalPrefix>plugin</goalPrefix>
134        String goalPrefix = getValue( plugin, "goalPrefix" );
135
136        Node mojos1 = getSingleChild( plugin, "mojos" );
137
138        List<Node> mojos = findNamedChild( mojos1, "mojo" );
139
140        if ( goal == null || goal.length() <= 0 )
141        {
142            append( sb, "This plugin has " + mojos.size() + ( mojos.size() > 1 ? " goals:" : " goal:" ), 0 );
143            append( sb, "", 0 );
144        }
145
146        for ( Node mojo : mojos )
147        {
148            writeGoal( sb, goalPrefix, (Element) mojo );
149        }
150
151        if ( getLog().isInfoEnabled() )
152        {
153            getLog().info( sb.toString() );
154        }
155    }
156
157
158    private static boolean isNotEmpty( String string )
159    {
160        return string != null && string.length() > 0;
161    }
162
163    private String getValue( Node node, String elementName )
164        throws MojoExecutionException
165    {
166        return getSingleChild( node, elementName ).getTextContent();
167    }
168
169    private Node getSingleChild( Node node, String elementName )
170        throws MojoExecutionException
171    {
172        List<Node> namedChild = findNamedChild( node, elementName );
173        if ( namedChild.isEmpty() )
174        {
175            throw new MojoExecutionException( "Could not find " + elementName + " in plugin-help.xml" );
176        }
177        if ( namedChild.size() > 1 )
178        {
179            throw new MojoExecutionException( "Multiple " + elementName + " in plugin-help.xml" );
180        }
181        return namedChild.get( 0 );
182    }
183
184    private List<Node> findNamedChild( Node node, String elementName )
185    {
186        List<Node> result = new ArrayList<Node>();
187        NodeList childNodes = node.getChildNodes();
188        for ( int i = 0; i < childNodes.getLength(); i++ )
189        {
190            Node item = childNodes.item( i );
191            if ( elementName.equals( item.getNodeName() ) )
192            {
193                result.add( item );
194            }
195        }
196        return result;
197    }
198
199    private Node findSingleChild( Node node, String elementName )
200        throws MojoExecutionException
201    {
202        List<Node> elementsByTagName = findNamedChild( node, elementName );
203        if ( elementsByTagName.isEmpty() )
204        {
205            return null;
206        }
207        if ( elementsByTagName.size() > 1 )
208        {
209            throw new MojoExecutionException( "Multiple " + elementName + "in plugin-help.xml" );
210        }
211        return elementsByTagName.get( 0 );
212    }
213
214    private void writeGoal( StringBuilder sb, String goalPrefix, Element mojo )
215        throws MojoExecutionException
216    {
217        String mojoGoal = getValue( mojo, "goal" );
218        Node configurationElement = findSingleChild( mojo, "configuration" );
219                Node description = findSingleChild( mojo, "description" );
220        if ( goal == null || goal.length() <= 0 || mojoGoal.equals( goal ) )
221        {
222            append( sb, goalPrefix + ":" + mojoGoal, 0 );
223            Node deprecated = findSingleChild( mojo, "deprecated" );
224            if ( ( deprecated != null ) && isNotEmpty( deprecated.getNodeValue() ) )
225            {
226                append( sb, "Deprecated. " + deprecated, 1 );
227                if ( detail && description != null )
228                {
229                    append( sb, "", 0 );
230                    append( sb, description.getTextContent(), 1 );
231                }
232            }
233            else if (description != null )
234            {
235                append( sb, description.getTextContent(), 1 );
236            }
237            append( sb, "", 0 );
238
239            if ( detail )
240            {
241                Node parametersNode = getSingleChild( mojo, "parameters" );
242                List<Node> parameters = findNamedChild( parametersNode, "parameter" );
243                append( sb, "Available parameters:", 1 );
244                append( sb, "", 0 );
245
246                for ( Node parameter : parameters )
247                {
248                    writeParameter( sb, parameter, configurationElement );
249                }
250            }
251        }
252    }
253
254    private void writeParameter( StringBuilder sb, Node parameter, Node configurationElement )
255        throws MojoExecutionException
256    {
257        String parameterName = getValue( parameter, "name" );
258        String parameterDescription = getValue( parameter, "description" );
259
260        Node fieldConfigurationElement = findSingleChild( configurationElement, parameterName );
261
262        String parameterDefaultValue = "";
263        if ( fieldConfigurationElement != null && fieldConfigurationElement.getNodeValue() != null )
264        {
265            parameterDefaultValue = " (Default: " + ((Element)fieldConfigurationElement).getAttribute( "default-value" ) + ")";
266        }
267        append( sb, parameterName + parameterDefaultValue, 2 );
268        Node deprecated = findSingleChild( parameter, "deprecated" );
269        if ( ( deprecated != null ) && isNotEmpty( deprecated.getNodeValue() ) )
270        {
271            append( sb, "Deprecated. " + deprecated.getNodeValue(), 3 );
272            append( sb, "", 0 );
273        }
274        append( sb, parameterDescription, 3 );
275        if ( "true".equals( getValue( parameter, "required" ) ) )
276        {
277            append( sb, "Required: Yes", 3 );
278        }
279        Node expression = findSingleChild( parameter, "expression" );
280        if ( ( expression != null ) && isNotEmpty( expression.getNodeValue() ) )
281        {
282                String property = getPropertyFromExpression( expression.getNodeValue() );
283            append( sb, "User property: " + property, 3 );
284        }
285
286        append( sb, "", 0 );
287    }
288
289    /**
290     * <p>Repeat a String <code>n</code> times to form a new string.</p>
291     *
292     * @param str    String to repeat
293     * @param repeat number of times to repeat str
294     * @return String with repeated String
295     * @throws NegativeArraySizeException if <code>repeat < 0</code>
296     * @throws NullPointerException       if str is <code>null</code>
297     */
298    private static String repeat( String str, int repeat )
299    {
300        StringBuilder buffer = new StringBuilder( repeat * str.length() );
301
302        for ( int i = 0; i < repeat; i++ )
303        {
304            buffer.append( str );
305        }
306
307        return buffer.toString();
308    }
309
310    /**
311     * Append a description to the buffer by respecting the indentSize and lineLength parameters.
312     * <b>Note</b>: The last character is always a new line.
313     *
314     * @param sb          The buffer to append the description, not <code>null</code>.
315     * @param description The description, not <code>null</code>.
316     * @param indent      The base indentation level of each line, must not be negative.
317     */
318    private void append( StringBuilder sb, String description, int indent )
319    {
320        for ( String line : toLines( description, indent, indentSize, lineLength ) )
321        {
322            sb.append( line ).append( '\n' );
323        }
324    }
325
326    /**
327     * Splits the specified text into lines of convenient display length.
328     *
329     * @param text       The text to split into lines, must not be <code>null</code>.
330     * @param indent     The base indentation level of each line, must not be negative.
331     * @param indentSize The size of each indentation, must not be negative.
332     * @param lineLength The length of the line, must not be negative.
333     * @return The sequence of display lines, never <code>null</code>.
334     * @throws NegativeArraySizeException if <code>indent < 0</code>
335     */
336    private static List<String> toLines( String text, int indent, int indentSize, int lineLength )
337    {
338        List<String> lines = new ArrayList<String>();
339
340        String ind = repeat( "\t", indent );
341
342        String[] plainLines = text.split( "(\r\n)|(\r)|(\n)" );
343
344        for ( String plainLine : plainLines )
345        {
346            toLines( lines, ind + plainLine, indentSize, lineLength );
347        }
348
349        return lines;
350    }
351
352    /**
353     * Adds the specified line to the output sequence, performing line wrapping if necessary.
354     *
355     * @param lines      The sequence of display lines, must not be <code>null</code>.
356     * @param line       The line to add, must not be <code>null</code>.
357     * @param indentSize The size of each indentation, must not be negative.
358     * @param lineLength The length of the line, must not be negative.
359     */
360    private static void toLines( List<String> lines, String line, int indentSize, int lineLength )
361    {
362        int lineIndent = getIndentLevel( line );
363        StringBuilder buf = new StringBuilder( 256 );
364
365        String[] tokens = line.split( " +" );
366
367        for ( String token : tokens )
368        {
369            if ( buf.length() > 0 )
370            {
371                if ( buf.length() + token.length() >= lineLength )
372                {
373                    lines.add( buf.toString() );
374                    buf.setLength( 0 );
375                    buf.append( repeat( " ", lineIndent * indentSize ) );
376                }
377                else
378                {
379                    buf.append( ' ' );
380                }
381            }
382
383            for ( int j = 0; j < token.length(); j++ )
384            {
385                char c = token.charAt( j );
386                if ( c == '\t' )
387                {
388                    buf.append( repeat( " ", indentSize - buf.length() % indentSize ) );
389                }
390                else if ( c == '\u00A0' )
391                {
392                    buf.append( ' ' );
393                }
394                else
395                {
396                    buf.append( c );
397                }
398            }
399        }
400        lines.add( buf.toString() );
401    }
402
403    /**
404     * Gets the indentation level of the specified line.
405     *
406     * @param line The line whose indentation level should be retrieved, must not be <code>null</code>.
407     * @return The indentation level of the line.
408     */
409    private static int getIndentLevel( String line )
410    {
411        int level = 0;
412        for ( int i = 0; i < line.length() && line.charAt( i ) == '\t'; i++ )
413        {
414            level++;
415        }
416        for ( int i = level + 1; i <= level + 4 && i < line.length(); i++ )
417        {
418            if ( line.charAt( i ) == '\t' )
419            {
420                level++;
421                break;
422            }
423        }
424        return level;
425    }
426    
427    private String getPropertyFromExpression( String expression )
428    {
429        if ( expression != null && expression.startsWith( "${" ) && expression.endsWith( "}" )
430            && !expression.substring( 2 ).contains( "${" ) )
431        {
432            // expression="${xxx}" -> property="xxx"
433            return expression.substring( 2, expression.length() - 1 );
434        }
435        // no property can be extracted
436        return null;
437    }
438}