/***** BEGIN LICENSE BLOCK *****
 * Version: CPL 1.0/GPL 2.0/LGPL 2.1
 *
 * The contents of this file are subject to the Common Public
 * License Version 1.0 (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.eclipse.org/legal/cpl-v10.html
 *
 * Software distributed under the License is distributed on an "AS
 * IS" basis, WITHOUT WARRANTY OF ANY KIND, either express or
 * implied. See the License for the specific language governing
 * rights and limitations under the License.
 *
 * Copyright (C) 2006 Thomas E Enebo <enebo@acm.org>
 * 
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 * either of the GNU General Public License Version 2 or later (the "GPL"),
 * or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
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package org.jruby.parser;

import java.io.Serializable;

import org.jruby.ast.AssignableNode;
import org.jruby.ast.Node;
import org.jruby.lexer.yacc.ISourcePosition;

public abstract class StaticScope implements Serializable {
    private static final long serialVersionUID = 4843861446986961013L;
    
    private StaticScope enclosingScope;
    
    // Our name holder (offsets are assigned as variables are added
    private String[] variableNames;
    
    protected StaticScope(StaticScope enclosingScope) {
        this.enclosingScope = enclosingScope;
    }
    
    public int addVariable(String name) {
        int slot = isDefined(name); 

        if (slot >= 0) {
            return slot;
        }
            
        // This is perhaps innefficient timewise?  Optimal spacewise
        if (variableNames == null) {
            variableNames = new String[1];
            variableNames[0] = name;
        } else {
            String[] newVariableNames = new String[variableNames.length + 1];
            System.arraycopy(variableNames, 0, newVariableNames, 0, variableNames.length);
            variableNames = newVariableNames;
            variableNames[variableNames.length - 1] = name;
        }
        
        // Returns slot of variable
        return variableNames.length - 1;
    }
    
    public String[] getVariables() {
        return variableNames;
    }
    
    public int getNumberOfVariables() {
        return variableNames == null ? 0 : variableNames.length;
    }
    
    public void setVariables(String[] names) {
        if (names == null) {
            return;
        }
        
        variableNames = new String[names.length];
        System.arraycopy(names, 0, variableNames, 0, names.length);
    }
    
    /**
     * Next outer most scope in list of scopes.  An enclosing scope may have no direct scoping
     * relationship to its child.  If I am in a localScope and then I enter something which
     * creates another localScope the enclosing scope will be the first scope, but there are
     * no valid scoping relationships between the two.  Methods which walk the enclosing scopes
     * are responsible for enforcing appropriate scoping relationships.
     * 
     * @return the parent scope
     */
    public StaticScope getEnclosingScope() {
        return enclosingScope;
    }
    
    /**
     * Does the variable exist?
     * 
     * @param name of the variable to find
     * @return index of variable or -1 if it does not exist
     */
    public int exists(String name) {
        if (variableNames != null) {
            for (int i = 0; i < variableNames.length; i++) {
                if (name == variableNames[i] || name.equals(variableNames[i])) {
                    return i;
                }   
            }
        }
        
        return -1;        
    }
    
    /**
     * Is this name in the visible to the current scope
     * 
     * @param name to be looked for
     * @return a location where the left-most 16 bits of number of scopes down it is and the
     *   right-most 16 bits represents its index in that scope
     */
    public int isDefined(String name) {
        return isDefined(name, 0);
    }
    
    /**
     * Make a DASgn or LocalAsgn node based on scope logic
     * 
     * @param position
     * @param name
     * @param value
     * @return
     */
    public AssignableNode assign(ISourcePosition position, String name, Node value) {
        return assign(position, name, value, this, 0);
    }
    
    /**
     * Get all visible variables that we can see from this scope
     * 
     * @return a list of all names (sans $~ and $_ which are special names)
     */
    public abstract String[] getAllNamesInScope();
    
    protected abstract int isDefined(String name, int depth);
    protected abstract AssignableNode assign(ISourcePosition position, String name, Node value, 
            StaticScope topScope, int depth);
    protected abstract Node declare(ISourcePosition position, String name, int depth);
    
    /**
     * Make a DVar or LocalVar node based on scoping logic
     * 
     * @param position the location that in the source that the new node will come from
     * @param name of the variable to be created is named
     * @return a DVarNode or LocalVarNode
     */
    public Node declare(ISourcePosition position, String name) {
        return declare(position, name, 0);
    }

    /**
     * Gets the Local Scope relative to the current Scope.  For LocalScopes this will be itself.
     * Blocks will contain the LocalScope it contains.
     * 
     * @return localScope
     */
    public abstract StaticScope getLocalScope();
}