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

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

/** A JavaScript function, compiled into bytecode */
class JSFunction extends JS implements ByteCodes, Tokens, org.xwt.Scheduler.Task {


    // Fields and Accessors ///////////////////////////////////////////////

    int numFormalArgs = 0;         ///< the number of formal arguments

    String sourceName;             ///< the source code file that this block was drawn from
    private int firstLine = -1;    ///< the first line of this script

    int[] line = new int[10];      ///< the line numbers
    int[] op = new int[10];        ///< the instructions
    Object[] arg = new Object[10]; ///< the arguments to the instructions
    int size = 0;                  ///< the number of instruction/argument pairs

    JSScope parentScope;           ///< the default scope to use as a parent scope when executing this


    // Public //////////////////////////////////////////////////////////////////////////////

    // FEATURE: make sure that this can only be called from the Scheduler...
    /** if you enqueue a function, it gets invoked in its own pauseable context */
    public void perform() throws JSExn {
        Interpreter i = new Interpreter(this, true, new JSArray());
        int oldpausecount = i.pausecount;
        i.resume();
    }

    /** parse and compile a function */
    public static JSFunction _fromReader(String sourceName, int firstLine, Reader sourceCode) throws IOException {
        JSFunction ret = new JSFunction(sourceName, firstLine, null);
        if (sourceCode == null) return ret;
        Parser p = new Parser(sourceCode, sourceName, firstLine);
        while(true) {
            int s = ret.size;
            p.parseStatement(ret, null);
            if (s == ret.size) break;
        }
        ret.add(-1, LITERAL, null); 
        ret.add(-1, RETURN);
        return ret;
    }

    public JSFunction _cloneWithNewParentScope(JSScope s) {
        JSFunction ret = new JSFunction(sourceName, firstLine, s);
        // Reuse the same op, arg, line, and size variables for the new "instance" of the function
        // NOTE: Neither *this* function nor the new function should be modified after this call
        ret.op = this.op;
        ret.arg = this.arg;
        ret.line = this.line;
        ret.size = this.size;
        ret.numFormalArgs = this.numFormalArgs;
        return ret;
    }

    /** Note: code gets run in an <i>unpauseable</i> context. */
    public Object call(Object a0, Object a1, Object a2, Object[] rest, int nargs) throws JSExn {
        JSArray args = new JSArray();
        if (nargs > 0) args.addElement(a0);
        if (nargs > 1) args.addElement(a1);
        if (nargs > 2) args.addElement(a2);
        for(int i=3; i<nargs; i++) args.addElement(rest[i-3]);
        Interpreter cx = new Interpreter(this, false, args);
        return cx.resume();
    }

    public JSScope getParentScope() { return parentScope; }

    // Adding and Altering Bytecodes ///////////////////////////////////////////////////

    JSFunction(String sourceName, int firstLine, JSScope parentScope) {
        this.sourceName = sourceName;
        this.firstLine = firstLine;
        this.parentScope = parentScope;
    }

    int get(int pos) { return op[pos]; }
    Object getArg(int pos) { return arg[pos]; }
    void set(int pos, int op_, Object arg_) { op[pos] = op_; arg[pos] = arg_; }
    void set(int pos, Object arg_) { arg[pos] = arg_; }
    int pop() { size--; arg[size] = null; return op[size]; }
    void paste(JSFunction other) { for(int i=0; i<other.size; i++) add(other.line[i], other.op[i], other.arg[i]); }
    JSFunction add(int line, int op_) { return add(line, op_, null); }
    JSFunction add(int line, int op_, Object arg_) {
        if (size == op.length - 1) {
            int[] line2 = new int[op.length * 2]; System.arraycopy(this.line, 0, line2, 0, op.length); this.line = line2;
            Object[] arg2 = new Object[op.length * 2]; System.arraycopy(arg, 0, arg2, 0, arg.length); arg = arg2;
            int[] op2 = new int[op.length * 2]; System.arraycopy(op, 0, op2, 0, op.length); op = op2;
        }
        this.line[size] = line;
        op[size] = op_;
        arg[size] = arg_;
        size++;
        return this;
    }
    

    // Debugging //////////////////////////////////////////////////////////////////////

    public String toString() { return "JSFunction [" + sourceName + ":" + firstLine + "]"; }

    public String dump() {
        StringBuffer sb = new StringBuffer(1024);
        sb.append("\n" + sourceName + ": " + firstLine + "\n");
        for (int i=0; i < size; i++) {
            sb.append(i);
            sb.append(": ");
            if (op[i] < 0) sb.append(bytecodeToString[-op[i]]);
            else sb.append(codeToString[op[i]]);
            sb.append(" ");
            sb.append(arg[i] == null ? "(no arg)" : arg[i]);
            if((op[i] == JF || op[i] == JT || op[i] == JMP) && arg[i] != null && arg[i] instanceof Number) {
                sb.append(" jump to ").append(i+((Number) arg[i]).intValue());
            } else  if(op[i] == TRY) {
                int[] jmps = (int[]) arg[i];
                sb.append(" catch: ").append(jmps[0] < 0 ? "No catch block" : ""+(i+jmps[0]));
                sb.append(" finally: ").append(jmps[1] < 0 ? "No finally block" : ""+(i+jmps[1]));
            }
            sb.append("\n");
        }
        return sb.toString();
    } 


}