Command less: added help

builtins/src/main/java/org/jline/builtins/Less.java

@@ -23,6 +23,7 @@
 import java.util.regex.Pattern;
 import java.util.regex.PatternSyntaxException;
 
+import org.jline.builtins.Source.ResourceSource;
 import org.jline.keymap.BindingReader;
 import org.jline.keymap.KeyMap;
 import org.jline.terminal.Attributes;
@@ -113,15 +114,16 @@ public void run(List<Source> sources) throws IOException, InterruptedException {
         if (sources == null || sources.isEmpty()) {
             throw new IllegalArgumentException("No sources");
         }
+        sources.add(0, new ResourceSource("less-help.txt", "HELP -- Press SPACE for more, or q when done"));
         this.sources = sources;
 
-        sourceIdx = 0;
+        sourceIdx = 1;
         openSource();
 
         try {
             size.copy(terminal.getSize());
 
-            if (quitIfOneScreen && sources.size() == 1) {
+            if (quitIfOneScreen && sources.size() == 2) {
                 if (display(true)) {
                     return;
                 }
@@ -363,13 +365,16 @@ else if (buffer.length() > 0 && (buffer.charAt(0) == '/' || buffer.charAt(0) ==
                                 }
                                 break;
                             case PREV_FILE:
-                                if (sourceIdx > 0) {
+                                if (sourceIdx > 1) {
                                     sourceIdx--;
                                     openSource();
                                 } else {
                                     message = "No previous file";
                                 }
                                 break;
+                            case HELP:
+                                help();
+                                break;
                         }
                         buffer.setLength(0);
                     }
@@ -404,16 +409,56 @@ else if (buffer.length() > 0 && (buffer.charAt(0) == '/' || buffer.charAt(0) ==
         }
     }
 
+    private void help() throws IOException {
+        int saveSourceIdx = sourceIdx;
+        int saveFirstLineToDisplay = firstLineToDisplay;
+        int saveFirstColumnToDisplay = firstColumnToDisplay;
+        int saveOffsetInLine = offsetInLine;
+        boolean savePrintLineNumbers = printLineNumbers;
+
+        printLineNumbers = false;
+        sourceIdx = 0;
+        try {
+            openSource();
+            Operation op = null;
+            do {
+                checkInterrupted();
+
+                op = bindingReader.readBinding(keys, null, false);
+                if (op != null) {
+                    switch (op) {
+                    case FORWARD_ONE_WINDOW_OR_LINES:
+                        moveForward(getStrictPositiveNumberInBuffer(window));
+                        break;
+                    case BACKWARD_ONE_WINDOW_OR_LINES:
+                        moveBackward(getStrictPositiveNumberInBuffer(window));
+                        break;               
+                    }
+                }
+                display(false);
+            } while (op != Operation.EXIT);
+        } catch (IOException|InterruptedException exp) {
+            // Do nothing
+        } finally {
+            sourceIdx = saveSourceIdx;
+            openSource();
+            firstLineToDisplay = saveFirstLineToDisplay;
+            firstColumnToDisplay = saveFirstColumnToDisplay;
+            offsetInLine = saveOffsetInLine;
+            printLineNumbers = savePrintLineNumbers;
+        }
+    }
+
     protected void openSource() throws IOException {
         if (reader != null) {
             reader.close();
         }
         Source source = sources.get(sourceIdx);
         InputStream in = source.read();
-        if (sources.size() == 1) {
+        if (sources.size() == 2 || sourceIdx == 0) {
             message = source.getName();
         } else {
-            message = source.getName() + " (file " + (sourceIdx + 1) + " of " + sources.size() + ")";
+            message = source.getName() + " (file " + sourceIdx + " of " + (sources.size() - 1)+ ")";
         }
         reader = new BufferedReader(new InputStreamReader(new InterruptibleInputStream(in)));
         firstLineInMemory = 0;
@@ -531,7 +576,7 @@ void moveBackward(int lines) throws IOException {
 
     private void eof() {
         nbEof++;
-        if (sourceIdx < sources.size() - 1) {
+        if (sourceIdx > 0 && sourceIdx < sources.size() - 1) {
             message = "(END) - Next: " + sources.get(sourceIdx + 1).getName();
         } else {
             message = "(END)";

builtins/src/main/java/org/jline/builtins/Source.java

@@ -109,4 +109,28 @@ public StdInSource(InputStream in) {
         }
 
     }
+
+    class ResourceSource implements Source {
+        final String resource;
+        final String name;
+
+        public ResourceSource(String resource) {
+            this(resource, resource);
+        }
+
+        public ResourceSource(String resource, String name) {
+            this.resource = Objects.requireNonNull(resource);
+            this.name = name;
+        }
+
+        @Override
+        public String getName() {
+            return name;
+        }
+
+        @Override
+        public InputStream read() throws IOException {
+            return getClass().getResourceAsStream(resource);
+        }
+    }
 }

builtins/src/main/resources/org/jline/builtins/less-help.txt

@@ -0,0 +1,77 @@
+
+                   SUMMARY OF LESS COMMANDS
+
+      Commands marked with * may be preceded by a number, N.
+      Notes in parentheses indicate the behavior if N is given.
+      A key preceded by a caret indicates the Ctrl key; thus ^K is ctrl-K.
+
+  h  H                 Display this help.
+  q  :q  Q  :Q  ZZ     Exit.
+ ---------------------------------------------------------------------------
+
+                           MOVING
+
+  e  ^E  j  ^N  CR  *  Forward  one line   (or N lines).
+  y  ^Y  k  ^K  ^P  *  Backward one line   (or N lines).
+  f  ^F  ^V  SPACE  *  Forward  one window (or N lines).
+  b  ^B  ESC-v      *  Backward one window (or N lines).
+  z                 *  Forward  one window (and set window to N).
+  w                 *  Backward one window (and set window to N).
+  ESC-SPACE         *  Forward  one window, but don't stop at end-of-file.
+  d  ^D             *  Forward  one half-window (and set half-window to N).
+  u  ^U             *  Backward one half-window (and set half-window to N).
+  ESC-)  RightArrow *  Left  one half screen width (or N positions).
+  ESC-(  LeftArrow  *  Right one half screen width (or N positions).
+  g  <  ESC-<       *  Go to first line in file (or line N).
+  G  >  ESC->       *  Go to last line in file (or line N).
+        ---------------------------------------------------
+        Default "window" is the screen height.
+        Default "half-window" is half of the screen height.
+ ---------------------------------------------------------------------------
+
+                          SEARCHING
+
+  /pattern          *  Search forward for (N-th) matching line.
+  ?pattern          *  Search backward for (N-th) matching line.
+  n  N              *  Repeat previous search (for N-th occurrence).
+  ESC-n  ESC-N      *  Repeat previous search, spanning files.
+  ESC-u                Undo (toggle) search highlighting.
+ ---------------------------------------------------------------------------
+
+                        CHANGING FILES
+
+  :n                *  Examine the (N-th) next file from the command line.
+  :p                *  Examine the (N-th) previous file from the command line.
+ ---------------------------------------------------------------------------
+
+                    MISCELLANEOUS COMMANDS
+
+  -<flag>              Toggle a command line option [see OPTIONS below].
+  --<name>             Toggle a command line option, by name.
+ ---------------------------------------------------------------------------
+
+                           OPTIONS
+
+        Most options may be changed either on the command line,
+        or from within less by using the - or -- command.
+        Options may be given in one of two forms: either a single
+        character preceded by a -, or a name preceded by --.
+
+  -?  ........  --help
+                  Display help (from command line).
+  -e  ........  --quit-at-eof  
+                  Quit at second end of file.
+  -E  ........  --QUIT-AT-EOF
+                  Quit at end of file.
+  -i  ........  --ignore-case
+                  Ignore case in searches that do not contain uppercase.
+  -I  ........  --IGNORE-CASE
+                  Ignore case in all searches.
+  -N  ........  --LINE-NUMBERS
+                  Display line numbers.
+  -q  -Q  ....  --quiet  --QUIET  --silent --SILENT
+                  Quiet the terminal bell.
+  -S  ........  --chop-long-lines
+                  Chop (truncate) long lines rather than wrapping.
+  -x [N[,...]]  --tabs=[N[,...]]
+                  Set tab stops (from command line).