//
// another example of the Java AWT, showing use of Scrollpane class.
// see class definition and main method for details.
//
import java.awt.* ;
import java.awt.event.* ;
import java.io.* ;
import java.util.* ;

//
// a ScrollExample object is a CloseableFrame containing a Scrollpane;
//      the Scrollpane in turn contains an n-by-1 array of Label objects
//      containing lines of text.  the Scrollpane automatically provides
//      horizontal and vertical scrollbars if needed (depending on the
//      size of the window).
//
class ScrollExample extends CloseableFrame {

        ScrollExample(String[] textLines) {

                super("ScrollExample") ;
                setLayout(new BorderLayout()) ;

                // make a Label for each element of textLines.
                Panel p1 = new Panel(new GridLayout(0,1)) ;
                for (int i = 0 ; i < textLines.length ; i++) {
                        Label l = new Label(textLines[i]) ;
                        p1.add(l) ;
                }
                
                ScrollPane pane = new ScrollPane() ;
                pane.add(p1) ;

                add(pane, "Center") ;

                setSize(600, 400) ;
                show() ;
        }


        //
        // ---- main ---------------------------------------------------
        //
        // command-line arguments are file to read and display, and
        //      (optionally) a number for expanding tabs (if not
        //      specified, tabs are not expanded, with somewhat
        //      odd-looking results).
        // (no claims are made about the efficiency of the code
        //      used to convert the file into a String array --
        //      this is simply a quick way to provide a non-trivial
        //      amount of text for the Scrollpane.)
        //
        public static void main(String[] args) {

                if (args.length < 1) {
                        System.out.println("Arguments are filename " +
                                "tab-expansion") ;
                        System.exit(-1) ;
                }

                int tabSize = 0 ;
                if (args.length > 1) 
                        tabSize = Integer.parseInt(args[1]) ;

                String[] lines = new String[0] ;        
                                // array to pass to constructor

                try {
                        // read file into a Vector (which can
                        //      grow as needed).
                        BufferedReader br = new BufferedReader
                                (new FileReader(args[0])) ;
                        Vector sv = new Vector() ;
                        String l = br.readLine() ;
                        while (l != null) {
                                sv.addElement(l) ;
                                l = br.readLine() ;
                        }
                        br.close() ;
                        // now that we know how many lines, copy
                        //      to array for constructor.
                        lines = new String[sv.size()] ;
                        for (int i = 0 ; i < lines.length ; i++) 
                                lines[i] = expandTabs(tabSize,
                                        (String) sv.elementAt(i)) ;

                } catch (IOException e) {
                        System.out.println("Unable to read file " +
                                args[0]) ;
                        System.exit(-1) ;
                }

                if (lines.length == 0) {
                        System.out.println("Empty file " + args[0]) ;
                        System.exit(-1) ;
                }

                ScrollExample e = new ScrollExample(lines) ;
        }

        // returns result of expanding tab characters in "line".
        static String expandTabs(int tabSize, String line) {
                if (tabSize <= 0)
                        return line ;

                StringBuffer sb = new StringBuffer() ;
                int scanPos = 0 ;       
                while (scanPos < line.length()) {
                        // scanPos = next position to scan for tab.
                        // tabPos = position containing tab currently 
                        //      being expanded.
                        int tabPos = line.indexOf('\t', scanPos) ;
                        if (tabPos < 0) {
                                sb.append(line.substring(scanPos)) ;
                                scanPos = line.length() ;
                        }
                        else {
                                sb.append(line.substring(scanPos,
                                        tabPos)) ;
                                int numSp = tabSize - 
                                        (sb.length() % tabSize) ;
                                for (int i = 0 ; i < numSp ; i++)
                                        sb.append(' ') ;
                                scanPos = tabPos + 1 ;
                        }
                }
                return sb.toString() ;
        }
}