/*******************************************************************************
 * Copyright 2011 See AUTHORS file.
 * 
 * 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 com.badlogic.gdx.graphics.g3d;

import com.badlogic.gdx.utils.Array;

/** Extend this class to implement a material attribute. Register the attribute type by statically calling the
 * {@link #register(String)} method, whose return value should be used to instantiate the attribute. A class can implement
 * multiple types
 * @author Xoppa */
public abstract class Attribute implements Comparable<Attribute> {
	/** The registered type aliases */
	private final static Array<String> types = new Array<String>();

	/** @return The ID of the specified attribute type, or zero if not available */
	public final static long getAttributeType (final String alias) {
		for (int i = 0; i < types.size; i++)
			if (types.get(i).compareTo(alias) == 0) return 1L << i;
		return 0;
	}

	/** @return The alias of the specified attribute type, or null if not available. */
	public final static String getAttributeAlias (final long type) {
		int idx = -1;
		while (type != 0 && ++idx < 63 && (((type >> idx) & 1) == 0))
			;
		return (idx >= 0 && idx < types.size) ? types.get(idx) : null;
	}

	/** Call this method to register a custom attribute type, see the wiki for an example. If the alias already exists, then that ID
	 * will be reused. The alias should be unambiguously and will by default be returned by the call to {@link #toString()}.
	 * @param alias The alias of the type to register, must be different for each dirrect type, will be used for debugging
	 * @return the ID of the newly registered type, or the ID of the existing type if the alias was already registered */
	protected final static long register (final String alias) {
		long result = getAttributeType(alias);
		if (result > 0) return result;
		types.add(alias);
		return 1L << (types.size - 1);
	}

	/** The type of this attribute */
	public final long type;

	private final int typeBit;

	protected Attribute (final long type) {
		this.type = type;
		this.typeBit = Long.numberOfTrailingZeros(type);
	}

	/** @return An exact copy of this attribute */
	public abstract Attribute copy ();

	protected boolean equals (Attribute other) {
		return other.hashCode() == hashCode();
	}

	@Override
	public boolean equals (Object obj) {
		if (obj == null) return false;
		if (obj == this) return true;
		if (!(obj instanceof Attribute)) return false;
		final Attribute other = (Attribute)obj;
		if (this.type != other.type) return false;
		return equals(other);
	}

	@Override
	public String toString () {
		return getAttributeAlias(type);
	}

	@Override
	public int hashCode () {
		return 7489 * typeBit;
	}
}