/*
 * Copyright 2005 the original author or authors.
 * 
 * Licensed under the Apache License, Version 2.0 (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.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */ 
package org.wamblee.photos.model;

import java.io.Serializable;

/**
 * Represents a path to a photo. 
 *
 */
public class Path implements Serializable {

	static final long serialVersionUID = 1287597039089552731L;
	
    /**
     * The parts of the path.
     */
	private String[] _path; 
	
    /**
     * Constructs an empty path. 
     *
     */
	public Path() {
		_path = new String[0];
	}

    /**
     * Construcst the path based on a path string. 
     * @param aPath Path, must start with a / 
     */
	public Path(String aPath) {
		if ( aPath == null ) {
			throw new IllegalArgumentException("path is null"); 
		}
		if ( !aPath.startsWith("/")) {
			throw new IllegalArgumentException("path must start with / '" + aPath + "'");
		}
		if ( aPath.length() == 1 ) { 
			_path = new String[0];
			return;
		}
		_path = aPath.substring(1).split("/");
	}
	
    /**
     * Constructs the path based on an array of the parts. 
     * @param aPath Path. 
     */
	private Path(String[] aPath) {
		_path = aPath; 
	}
	
    /**
     * Returns the child of a path by appending a part. 
     * @param aId Id to append.  
     * @return Child. 
     * @throws IllegalArgumentException In case the id contains a / 
     */
	public Path child(String aId) {
        if ( aId.matches("/")) { 
            throw new IllegalArgumentException("Id '" + aId + "' contains a /");
        }
	    String[] newpath = new String[_path.length + 1];
	    System.arraycopy(_path, 0, newpath, 0, _path.length); 
	    newpath[_path.length] = aId; 
	    return new Path(newpath);
	}
	
    /**
     * Checks if the path is the root path. 
     * @return True if the path is the root. 
     */
	public boolean isRoot() {
		return _path.length == 0; 
	}
	
    /**
     * Gets the parent of the path. 
     * @return Parent of the path or the root if the path is already at the root. 
     */
	public Path parent() {
		if ( isRoot() ) {
			return this;
		}
		String[] newpath = new String[_path.length -1];
		System.arraycopy(_path, 0, newpath, 0, _path.length - 1);
		return new Path(newpath);
	}
	
    /**
     * Converts the path to a regular path.
     * @return A path, always starting with a /
     */
	public String toString() {
		if ( _path.length == 0 ) {
			return "/";
		}
		String result = "";
		for (String part: _path) {
			result += "/" + part; 
		}
        return result; 
	}

    /**
     * Gets the id (last part) of the path. 
     * @return Id or null if the path has no parts (root)
     */
	public String getId() {
		if ( _path.length == 0 ) {
			return null; 
		}
		return _path[_path.length -1];
	}

    /**
     * Returns the number of components in the path. 
     * @return Size. 
     */
    public int size() { 
        return _path.length; 
    }
   
    /**
     * Returns a part of the path. 
     * @param aPart Part number (starts at 0).
     * @return Part. 
     */
    public String getPart(int aPart) { 
        return _path[aPart];
    }
    
    /**
     * Strips the first part of the path and returns the remainder.
     * @return Remainder.
     */
    public Path remainder() { 
        if ( _path.length == 0 ) { 
            return null; 
        }
        String[] result = new String[_path.length-1];
        for (int i = 0; i < _path.length-1; i++) { 
            result[i] = _path[i+1]; 
        }
        return new Path(result);
    }
}