package org.grothoff;

import java.lang.reflect.Field;
import java.util.Enumeration;
import java.util.WeakHashMap;

/**
 * Obtain line number information for any JTB node.  Note that
 * "any" really means any -- we use reflection to overcome the
 * problem that we do not know the full name of the AST root
 * (in particular, there maybe multiple AST hierarchies in the
 * project with multiple root "Node" classes).<p>
 * 
 * Essentially, pass a JTB node to the static "get" method
 * and (if it is a JTB node and there is source corresponding
 * to it), a LineNumberInfo object with the scope of the 
 * subtree is returned.  Otherwise null.<p>
 * 
 *
 * Minimal example:
 * <code>
 * void semanticError(String message, Node n) {
 *   throw new Error(message + " at " + LineNumberInfo.get(n));
 * }
 * </code>
 *<p>
 *
 * This code is dual licensed under both BSD and LGPL.
 * 
 * @author Christian Grothoff
 */
public class LineNumberInfo {

    private static final Object NULL = new Object();
    private static final Object SELF = new Object();
    private static final WeakHashMap<Object, Object> cacheF_ = new WeakHashMap<Object,Object>();
    private static final WeakHashMap<Object, Object> cacheL_ = new WeakHashMap<Object,Object>();
    
    public final int lineStart;
    public final int lineEnd;
    public final int colStart;
    public final int colEnd;
    
    public LineNumberInfo(int s, int e, int cs, int ce) {
        lineStart = s;
        lineEnd = e;
        colStart = cs;
        colEnd = ce;
    }
    
    public String toString() {
        return "["+lineStart+":"+colStart+","+lineEnd+":"+colEnd+"]";
    }

    /**
     * Compute line number information for the given JTB node.
     * 
     * @param o any JTB node (the type should be node, but since this
     *  code handles any JTB AST we cannot hardwire the 
     *  type ("Node" -- but which package?)
     * @return
     */
    public static LineNumberInfo get(Object o) {
        if (o == null) 
            return null; // fail!        
        Object p = firstMatch(o);        
        Object q = lastMatch(o);
        try {
            int lstart = ((Integer)p.getClass().getField("beginLine").get(p)).intValue();
            int cstart = ((Integer)p.getClass().getField("beginColumn").get(p)).intValue();
            int lend = ((Integer)p.getClass().getField("endLine").get(q)).intValue();
            int cend = ((Integer)p.getClass().getField("endColumn").get(q)).intValue();
            return new LineNumberInfo(lstart, lend, cstart, cend);
        } catch (Throwable t) {
            return null; // failed
        }
    }

    private static Object firstMatch(Object o) {
        synchronized(cacheF_) {
            Object r = cacheF_.get(o);
            if (r != null)
                return (r == SELF) ? o : (r == NULL) ? null : r;
        }
        Object r = firstMatch_(o);
        synchronized(cacheF_) {
            cacheF_.put(o, r == o ? SELF : r == null ? NULL : r);
        }
        return r;
    }

   
    private static Object lastMatch(Object o) {
        synchronized(cacheL_) {
            Object r = cacheL_.get(o);
            if (r != null)
                return (r == SELF) ? o : (r == NULL) ? null : r;
        }
        Object r = lastMatch_(o);
        synchronized(cacheL_) {
            cacheL_.put(o, r == o ? SELF : r == null ? NULL : r);
        }
        return r;
    }

    private static Object firstMatch_(Object o) {        
        if (o == null)
            return null;
        Class c = o.getClass();
        if  (c.getName().endsWith("NodeToken"))
            return o;        
        try {
            int i=0;            
            while (true) {
                Field f = null;                           
                try {
                    f = c.getField("f" + i);
                } catch (Throwable t) {                    
                }
                if ( (f == null) && (i == 0) && (c.getName().endsWith("NodeChoice")) ) {
                    f = c.getField("choice");
                } else if ( (f == null) && (i == 0) && (c.getName().endsWith("NodeOptional")) ) {
                    f = c.getField("node");
                } else if ( (f == null) && (i == 0) ) {                        
                    // special cases: node sequence, etc.
                    Enumeration e = (Enumeration) c.getMethod("elements").invoke(o);
                    while (e.hasMoreElements()) {
                        Object x = firstMatch(e.nextElement());
                        if (x != null)
                            return x;
                    }
                } 
                if (f != null) {
                    Object r = firstMatch(f.get(o));
                    if (r != null)
                        return r;
                } else {
                    return null;
                }
                i++;
            }
        } catch (Throwable t) {
        }
        return null;
    }

    private static Object lastMatch_(Object o) {
        if (o == null)
            return null;
        Class c = o.getClass();
        if  (c.getName().endsWith("NodeToken"))
            return o;

        Object ret = null;
        try {
            int i=0;            
            while (true) {
                Field f = null;                           
                try {
                    f = c.getField("f" + i);
                } catch (Throwable t) {                    
                }
                if ( (f == null) && (i == 0) && (c.getName().endsWith("NodeChoice")) ) {
                    f = c.getField("choice");
                } else if ( (f == null) && (i == 0) && (c.getName().endsWith("NodeOptional")) ) {
                    f = c.getField("node");
                } else if ( (f == null) && (i == 0) ) {                        
                    // special cases: node sequence, etc.
                    Enumeration e = (Enumeration) o.getClass().getMethod("elements").invoke(o);
                    while (e.hasMoreElements()) {
                        Object x = lastMatch(e.nextElement());
                        if (x != null)
                            ret = x;
                    }                    
                    return ret;
                }
                if (f != null) {
                    Object r = lastMatch(f.get(o));
                    if (r != null)
                        ret = r;
                } else {
                    return ret;
                }
                i++;
            }            
        } catch (Throwable t) {
        }        
        return ret;
    }
    
}