/* -*- Mode: java; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
 *
 * The contents of this file are subject to the Netscape Public
 * License Version 1.1 (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.mozilla.org/NPL/
 *
 * Software distributed under the License is distributed on an "AS
 * IS" basis, WITHOUT WARRANTY OF ANY KIND, either express oqr
 * implied. See the License for the specific language governing
 * rights and limitations under the License.
 *
 * The Original Code is Rhino code, released
 * May 6, 1998.
 *
 * The Initial Developer of the Original Code is Netscape
 * Communications Corporation.  Portions created by Netscape are
 * Copyright (C) 1997-1999 Netscape Communications Corporation. All
 * Rights Reserved.
 *
 * Contributor(s): 
 *
 * Alternatively, the contents of this file may be used under the
 * terms of the GNU Public License (the "GPL"), in which case the
 * provisions of the GPL are applicable instead of those above.
 * If you wish to allow use of your version of this file only
 * under the terms of the GPL and not to allow others to use your
 * version of this file under the NPL, indicate your decision by
 * deleting the provisions above and replace them with the notice
 * and other provisions required by the GPL.  If you do not delete
 * the provisions above, a recipient may use your version of this
 * file under either the NPL or the GPL.
 */

import org.mozilla.javascript.*;
import java.io.*;

/**
 * The shell program.
 *
 * Can execute scripts interactively or in batch mode at the command line.
 * An example of controlling the JavaScript engine.
 *
 * @author Norris Boyd
 */
public class Shell extends ScriptableObject {

    /**
     * Main entry point.
     *
     * Process arguments as would a normal Java program. Also
     * create a new Context and associate it with the current thread.
     * Then set up the execution environment and begin to
     * execute scripts.
     */
    public static void main(String args[]) {
        // Associate a new Context with this thread
        Context cx = Context.enter();

        // A bit of shorthand: since Shell extends ScriptableObject,
        // we can make it the global object.
        global = new Shell();

        // Initialize the standard objects (Object, Function, etc.)
        // This must be done before scripts can be executed.
        cx.initStandardObjects(global);

        // Define some global functions particular to the shell. Note
        // that these functions are not part of ECMA.
        String[] names = { "print", "quit", "version", "load", "help" };
        try {
            global.defineFunctionProperties(names, Shell.class,
                                            ScriptableObject.DONTENUM);
        } catch (PropertyException e) {
            throw new Error(e.getMessage());
        }

        args = processOptions(cx, args);

        // Set up "arguments" in the global scope to contain the command
        // line arguments after the name of the script to execute
        Object[] array = args;
        if (args.length > 0) {
            int length = args.length - 1;
            array = new Object[length];
            System.arraycopy(args, 1, array, 0, length);
        }
        Scriptable argsObj = cx.newArray(global, array);
        global.defineProperty("arguments", argsObj,
                              ScriptableObject.DONTENUM);

        processSource(cx, args.length == 0 ? null : args[0]);

        cx.exit();
    }

    /**
     * Parse arguments.
     */
    public static String[] processOptions(Context cx, String args[]) {
        for (int i=0; i < args.length; i++) {
            String arg = args[i];
            if (!arg.startsWith("-")) {
                String[] result = new String[args.length - i];
                for (int j=i; j < args.length; j++)
                    result[j-i] = args[j];
                return result;
            }
            if (arg.equals("-version")) {
                if (++i == args.length)
                    usage(arg);
                double d = cx.toNumber(args[i]);
                if (d != d)
                    usage(arg);
                cx.setLanguageVersion((int) d);
                continue;
            }
            usage(arg);
        }
        return new String[0];
    }

    /**
     * Return name of this class, the global object.
     *
     * This method must be implemented in all concrete classes
     * extending ScriptableObject.
     *
     * @see org.mozilla.javascript.Scriptable#getClassName
     */
    public String getClassName() {
        return "global";
    }

    /**
     * Print a usage message.
     */
    public static void usage(String s) {
        p("Didn't understand \"" + s + "\".");
        p("Valid arguments are:");
        p("-version 100|110|120|130");
        System.exit(1);
    }

    /**
     * Print a help message.
     *
     * This method is defined as a JavaScript function.
     */
    public static void help(String s) {
        p("");
        p("Command                Description");
        p("=======                ===========");
        p("help()                 Display usage and help messages. ");
        p("defineClass(className) Define an extension using the Java class");
        p("                       named with the string argument. ");
        p("                       Uses ScriptableObject.defineClass(). ");
        p("load(['foo.js', ...])  Load JavaScript source files named by ");
        p("                       string arguments. ");
        p("loadClass(className)   Load a class named by a string argument.");
        p("                       The class must be a script compiled to a");
        p("                       class file. ");
        p("print([expr ...])      Evaluate and print expressions. ");
        p("quit()                 Quit the shell. ");
        p("version([number])      Get or set the JavaScript version number.");
        p("");
    }

    /**
     * Print the string values of its arguments.
     *
     * This method is defined as a JavaScript function.
     * Note that its arguments are of the "varargs" form, which
     * allows it to handle an arbitrary number of arguments
     * supplied to the JavaScript function.
     *
     */
    public static void print(Context cx, Scriptable thisObj,
                             Object[] args, Function funObj)
    {
        for (int i=0; i < args.length; i++) {
            if (i > 0)
                System.out.print(" ");

            // Convert the arbitrary JavaScript value into a string form.
            String s = Context.toString(args[i]);

            System.out.print(s);
        }
        System.out.println();
    }

    /**
     * Quit the shell.
     *
     * This only affects the interactive mode.
     *
     * This method is defined as a JavaScript function.
     */
    public static void quit() {
        quitting = true;
    }

    /**
     * Get and set the language version.
     *
     * This method is defined as a JavaScript function.
     */
    public static double version(Context cx, Scriptable thisObj,
                                 Object[] args, Function funObj)
    {
        double result = (double) cx.getLanguageVersion();
        if (args.length > 0) {
            double d = cx.toNumber(args[0]);
            cx.setLanguageVersion((int) d);
        }
        return result;
    }

    /**
     * Load and execute a set of JavaScript source files.
     *
     * This method is defined as a JavaScript function.
     *
     */
    public static void load(Context cx, Scriptable thisObj,
                            Object[] args, Function funObj)
    {
        for (int i=0; i < args.length; i++) {
            processSource(cx, cx.toString(args[i]));
        }
    }


    /**
     * Evaluate JavaScript source.
     *
     * @param cx the current context
     * @param filename the name of the file to compile, or null
     *                 for interactive mode.
     */
    public static void processSource(Context cx, String filename) {
        if (filename == null) {
            BufferedReader in = new BufferedReader
                (new InputStreamReader(System.in));
            String sourceName = "<stdin>";
            int lineno = 1;
            boolean hitEOF = false;
            do {
                int startline = lineno;
                System.err.print("js> ");
                System.err.flush();
                try {
                    String source = "";
                    // Collect lines of source to compile.
                    while(true) {
                        String newline;
                        newline = in.readLine();
                        if (newline == null) {
                            hitEOF = true;
                            break;
                        }
                        source = source + newline + "\n";
                        lineno++;
                        // Continue collecting as long as more lines
                        // are needed to complete the current
                        // statement.  stringIsCompilableUnit is also
                        // true if the source statement will result in
                        // any error other than one that might be
                        // resolved by appending more source.
                        if (cx.stringIsCompilableUnit(source))
                            break;
                    }
                    Object result = cx.evaluateString(global, source,
                                                      sourceName, startline,
                                                      null);
                    if (result != cx.getUndefinedValue()) {
                        System.err.println(cx.toString(result));
                    }
                }
                catch (WrappedException we) {
                    // Some form of exception was caught by JavaScript and
                    // propagated up.
                    System.err.println(we.getWrappedException().toString());
                    we.printStackTrace();
                }
                catch (EvaluatorException ee) {
                    // Some form of JavaScript error.
                    System.err.println("js: " + ee.getMessage());
                }
                catch (JavaScriptException jse) {
                    // Some form of JavaScript error.
                    System.err.println("js: " + jse.getMessage());
                }
                catch (IOException ioe) {
                    System.err.println(ioe.toString());
                }
                if (quitting) {
                    // The user executed the quit() function.
                    break;
                }
            } while (!hitEOF);
            System.err.println();
        } else {
            FileReader in = null;
            try {
                in = new FileReader(filename);
            }
            catch (FileNotFoundException ex) {
                Context.reportError("Couldn't open file \"" + filename + "\".");
                return;
            }

            try {
                // Here we evalute the entire contents of the file as
                // a script. Text is printed only if the print() function
                // is called.
                cx.evaluateReader(global, in, filename, 1, null);
            }
            catch (WrappedException we) {
                System.err.println(we.getWrappedException().toString());
                we.printStackTrace();
            }
            catch (EvaluatorException ee) {
                System.err.println("js: " + ee.getMessage());
            }
            catch (JavaScriptException jse) {
                System.err.println("js: " + jse.getMessage());
            }
            catch (IOException ioe) {
                System.err.println(ioe.toString());
            }
            finally {
                try {
                    in.close();
                }
                catch (IOException ioe) {
                    System.err.println(ioe.toString());
                }
            }
        }
        System.gc();
    }

    private static void p(String s) {
        System.out.println(s);
    }

    static Shell global;
    static boolean quitting;
}