Path.java

package cn.liutils.ripple;

/**
 * Path for script objects (functions and values).
 * @author acaly
 *
 */
public final class Path {

    public static final String pathRegex = "\\w+(.\\w+)*";
    
    /**
     * The string value of this path.
     * Allows null. When path is null, it represents the root namespace. 
     */
    public final String path;
    
    public Path(String path) {
        this.path = path;
        if (!isValid(this.path))
            throw new RippleException("Invalid path");
    }
    
    public Path(Path parent, String sub) {
        if (parent.path == null) {
            this.path = sub;
        } else {
            this.path = parent.path + '.' + sub;
        }
        if (!isValid(this.path))
            throw new RippleException("Invalid path");
    }
    
    public Path(Path parent, Path sub) {
        if (parent.path == null) {
            this.path = sub.path;
        } else {
            this.path = parent.path + '.' + sub.path;
        }
        if (!isValid(this.path))
            throw new RippleException("Invalid path");
    }
    
    public boolean hasParent() {
        return path != null;
    }
    
    public Path getParent() {
        if (!hasParent()) {
            throw new RuntimeException("Try to get parent of the root namespace");
        }
        int id = path.lastIndexOf('.');
        if (id == -1) {
            return new Path(null);
        }
        return new Path(path.substring(0, id));
    }
    
    public static boolean isValid(String path) {
        return path == null || path.matches(pathRegex);
    }
    
    public static Path concatenate(Path a, Path b) {
        if (b.path == null) {
            throw new RuntimeException("Try to concatenate null paths");
        }
        if (a.path == null) {
            return b;
        }
        String matchA = '.' + a.path + '.';
        int indexInB = b.path.indexOf('.');
        if (indexInB == -1) {
            return b;
        }
        String matchB = b.path.substring(0, indexInB);
        int matching = matchA.indexOf('.' + matchB + '.');
        if (matching == -1) {
            return b;
        }
        return new Path(a.path.substring(0, matching) + b.path);
    }
    
    @Override
    public String toString() {
        return path;
    }
}