// Copyright 2004 Adam Megacz, see the COPYING file for licensing [GPL] 
package org.xwt.js; 

import org.xwt.util.*; 
import org.xwt.*; 
import java.io.*;
import java.util.*;

/** The minimum set of functionality required for objects which are manipulated by JavaScript */
public class JS extends org.xwt.util.BalancedTree { 

    public static final Object METHOD = new Object();
    public final JS unclone() { return _unclone(); }
    public Enumeration keys() throws JSExn { return entries == null ? emptyEnumeration : entries.keys(); }
    public Object get(Object key) throws JSExn { return entries == null ? null : entries.get(key, null); }
    public void put(Object key, Object val) throws JSExn { (entries==null?entries=new Hash():entries).put(key,null,val); }
    public Object callMethod(Object method, Object a0, Object a1, Object a2, Object[] rest, int nargs) throws JSExn {
        throw new JSExn("attempted to call the null value (method "+method+")");
    }    
    public Object call(Object a0, Object a1, Object a2, Object[] rest, int nargs) throws JSExn {
        throw new JSExn("you cannot call this object (class=" + this.getClass().getName() +")");
    }

    JS _unclone() { return this; }
    public static class Cloneable extends JS {
        public Cloneable() { }
        public Object jsclone() throws JSExn {
            throw new JSExn("cloning not yet implemented");
        }
    }

    public static class Clone extends JS.Cloneable {
        protected JS.Cloneable clonee = null;
        JS _unclone() { return clonee.unclone(); }
        public JS.Cloneable getClonee() { return clonee; }
        public Clone(JS.Cloneable clonee) { this.clonee = clonee; }
        public boolean equals(Object o) {
            if (!(o instanceof JS)) return false;
            return unclone() == ((JS)o).unclone();
        }
        public Enumeration keys() throws JSExn { return clonee.keys(); }
        public Object get(Object key) throws JSExn { return clonee.get(key); }
        public void put(Object key, Object val) throws JSExn { clonee.put(key, val); }
        public Object callMethod(Object method, Object a0, Object a1, Object a2, Object[] rest, int nargs) throws JSExn {
            return clonee.callMethod(method, a0, a1, a2, rest, nargs);
        }    
        public Object call(Object a0, Object a1, Object a2, Object[] rest, int nargs) throws JSExn {
            return clonee.call(a0, a1, a2, rest, nargs);
        }
    }

    // Static Interpreter Control Methods ///////////////////////////////////////////////////////////////

    /** log a message with the current JavaScript sourceName/line */
    public static void log(Object message) { info(message); }
    public static void debug(Object message) { Log.debug(Interpreter.getSourceName() + ":" + Interpreter.getLine(), message); }
    public static void info(Object message) { Log.info(Interpreter.getSourceName() + ":" + Interpreter.getLine(), message); }
    public static void warn(Object message) { Log.warn(Interpreter.getSourceName() + ":" + Interpreter.getLine(), message); }
    public static void error(Object message) { Log.error(Interpreter.getSourceName() + ":" + Interpreter.getLine(), message); }

    public static class NotPauseableException extends Exception { NotPauseableException() { } }

    /** returns a callback which will restart the context; expects a value to be pushed onto the stack when unpaused */
    public static UnpauseCallback pause() throws NotPauseableException {
        Interpreter i = Interpreter.current();
        if (i.pausecount == -1) throw new NotPauseableException();
        i.pausecount++;
        return new JS.UnpauseCallback(i);
    }

    public static class UnpauseCallback implements Scheduler.Task {
        Interpreter i;
        UnpauseCallback(Interpreter i) { this.i = i; }
        public void perform() throws JSExn { unpause(null); }
        public void unpause(Object o) throws JSExn {
            // FIXME: if o instanceof JSExn, throw it into the JSworld
            i.stack.push(o);
            i.resume();
        }
    }



    // Static Helper Methods ///////////////////////////////////////////////////////////////////////////////////

    /** coerce an object to a Boolean */
    public static boolean toBoolean(Object o) {
        if (o == null) return false;
        if (o instanceof Boolean) return ((Boolean)o).booleanValue();
        if (o instanceof Long) return ((Long)o).longValue() != 0;
        if (o instanceof Integer) return ((Integer)o).intValue() != 0;
        if (o instanceof Number) {
            double d = ((Number) o).doubleValue();
            // NOTE: d == d is a test for NaN. It should be faster than Double.isNaN()
            return d != 0.0 && d == d;
        }
        if (o instanceof String) return ((String)o).length() != 0;
        return true;
    }

    /** coerce an object to a Long */
    public static long toLong(Object o) { return toNumber(o).longValue(); }

    /** coerce an object to an Int */
    public static int toInt(Object o) { return toNumber(o).intValue(); }

    /** coerce an object to a Double */
    public static double toDouble(Object o) { return toNumber(o).doubleValue(); }

    /** coerce an object to a Number */
    public static Number toNumber(Object o) {
        if (o == null) return ZERO;
        if (o instanceof Number) return ((Number)o);

        // NOTE: There are about 3 pages of rules in ecma262 about string to number conversions
        //       We aren't even close to following all those rules.  We probably never will be.
        if (o instanceof String) try { return N((String)o); } catch (NumberFormatException e) { return N(Double.NaN); }
        if (o instanceof Boolean) return ((Boolean)o).booleanValue() ? N(1) : ZERO;
        throw new Error("toNumber() got object of type " + o.getClass().getName() + " which we don't know how to handle");
    }

    /** coerce an object to a String */
    public static String toString(Object o) {
        if(o == null) return "null";
        if(o instanceof String) return (String) o;
        if(o instanceof Integer || o instanceof Long || o instanceof Boolean) return o.toString();
        if(o instanceof JSArray) return o.toString();
        if(o instanceof JSDate) return o.toString();
        if(o instanceof Double || o instanceof Float) {
            double d = ((Number)o).doubleValue();
            if((int)d == d) return Integer.toString((int)d);
            return o.toString();
        }
        throw new RuntimeException("can't coerce that!");
    }

    // Instance Methods ////////////////////////////////////////////////////////////////////

    public static final Integer ZERO = new Integer(0);
 
    // this gets around a wierd fluke in the Java type checking rules for ?..:
    public static final Object T = Boolean.TRUE;
    public static final Object F = Boolean.FALSE;

    public static final Boolean B(boolean b) { return b ? Boolean.TRUE : Boolean.FALSE; }
    public static final Boolean B(int i) { return i==0 ? Boolean.FALSE : Boolean.TRUE; }
    public static final Number N(String s) { return s.indexOf('.') == -1 ? N(Integer.parseInt(s)) : new Double(s); }
    public static final Number N(double d) { return (int)d == d ? N((int)d) : new Double(d); }
    public static final Number N(long l) { return N((int)l); }

    private static final Integer[] smallIntCache = new Integer[65535 / 4];
    private static final Integer[] largeIntCache = new Integer[65535 / 4];
    public static final Number N(int i) {
        Integer ret = null;
        int idx = i + smallIntCache.length / 2;
        if (idx < smallIntCache.length && idx > 0) {
            ret = smallIntCache[idx];
            if (ret != null) return ret;
        }
        else ret = largeIntCache[Math.abs(idx % largeIntCache.length)];
        if (ret == null || ret.intValue() != i) {
            ret = new Integer(i);
            if (idx < smallIntCache.length && idx > 0) smallIntCache[idx] = ret;
            else largeIntCache[Math.abs(idx % largeIntCache.length)] = ret;
        }
        return ret;
    }
    
    private static Enumeration emptyEnumeration = new Enumeration() {
            public boolean hasMoreElements() { return false; }
            public Object nextElement() { throw new NoSuchElementException(); }
        };
    
    private Hash entries = null;

    public static JS fromReader(String sourceName, int firstLine, Reader sourceCode) throws IOException {
        return JSFunction._fromReader(sourceName, firstLine, sourceCode);
    }

    // HACK: caller can't know if the argument is a JSFunction or not...
    public static JS cloneWithNewParentScope(JS j, JSScope s) {
        return ((JSFunction)j)._cloneWithNewParentScope(s);
    }


    // Trap support //////////////////////////////////////////////////////////////////////////////

    /** override and return true to allow placing traps on this object.
     *  if isRead true, this is a read trap, otherwise write trap
     **/
    protected boolean isTrappable(Object name, boolean isRead) { return true; }

    /** performs a put, triggering traps if present; traps are run in an unpauseable interpreter */
    public void putAndTriggerTraps(Object key, Object value) throws JSExn {
        Trap t = getTrap(key);
        if (t != null) t.invoke(value);
        else put(key, value);
    }

    /** performs a get, triggering traps if present; traps are run in an unpauseable interpreter */
    public Object getAndTriggerTraps(Object key) throws JSExn {
        Trap t = getTrap(key);
        if (t != null) return t.invoke();
        else return get(key);
    }

    /** retrieve a trap from the entries hash */
    protected final Trap getTrap(Object key) {
        return entries == null ? null : (Trap)entries.get(key, Trap.class);
    }

    /** retrieve a trap from the entries hash */
    protected final void putTrap(Object key, Trap value) {
        if (entries == null) entries = new Hash();
        entries.put(key, Trap.class, value);
    }

    /** adds a trap, avoiding duplicates */
    protected final void addTrap(Object name, JSFunction f) throws JSExn {
        if (f.numFormalArgs > 1) throw new JSExn("traps must take either one argument (write) or no arguments (read)");
        boolean isRead = f.numFormalArgs == 0;
        if (!isTrappable(name, isRead)) throw new JSExn("not allowed "+(isRead?"read":"write")+" trap on property: "+name);
        for(Trap t = getTrap(name); t != null; t = t.next) if (t.f == f) return;
        putTrap(name, new Trap(this, name.toString(), f, (Trap)getTrap(name)));
    }

    /** deletes a trap, if present */
    protected final void delTrap(Object name, JSFunction f) {
        Trap t = (Trap)getTrap(name);
        if (t == null) return;
        if (t.f == f) { putTrap(t.name, t.next); return; }
        for(; t.next != null; t = t.next) if (t.next.f == f) { t.next = t.next.next; return; }
    }


}