/*
 * Copyright 2002-2011 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.springframework.web.servlet.mvc.condition;

import javax.servlet.http.HttpServletRequest;

/**
 * Supports "name=value" style expressions as described in: 
 * {@link org.springframework.web.bind.annotation.RequestMapping#params()} and 
 * {@link org.springframework.web.bind.annotation.RequestMapping#headers()}.
 *
 * @author Rossen Stoyanchev
 * @author Arjen Poutsma
 * @since 3.1
 */
abstract class AbstractNameValueExpression<T> implements NameValueExpression<T> {

	protected final String name;

	protected final T value;

	protected final boolean isNegated;

	AbstractNameValueExpression(String expression) {
		int separator = expression.indexOf('=');
		if (separator == -1) {
			this.isNegated = expression.startsWith("!");
			this.name = isNegated ? expression.substring(1) : expression;
			this.value = null;
		}
		else {
			this.isNegated = (separator > 0) && (expression.charAt(separator - 1) == '!');
			this.name = isNegated ? expression.substring(0, separator - 1) : expression.substring(0, separator);
			this.value = parseValue(expression.substring(separator + 1));
		}
	}
	
	public String getName() {
		return this.name;
	}

	public T getValue() {
		return this.value;
	}

	public boolean isNegated() {
		return this.isNegated;
	}

	protected abstract T parseValue(String valueExpression);

	public final boolean match(HttpServletRequest request) {
		boolean isMatch;
		if (this.value != null) {
			isMatch = matchValue(request);
		}
		else {
			isMatch = matchName(request);
		}
		return isNegated ? !isMatch : isMatch;
	}

	protected abstract boolean matchName(HttpServletRequest request);

	protected abstract boolean matchValue(HttpServletRequest request);

	@Override
	public boolean equals(Object obj) {
		if (this == obj) {
			return true;
		}
		if (obj != null && obj instanceof AbstractNameValueExpression) {
			AbstractNameValueExpression<?> other = (AbstractNameValueExpression<?>) obj;
			return ((this.name.equalsIgnoreCase(other.name)) &&
					(this.value != null ? this.value.equals(other.value) : other.value == null) &&
					this.isNegated == other.isNegated);
		}
		return false;
	}

	@Override
	public int hashCode() {
		int result = name.hashCode();
		result = 31 * result + (value != null ? value.hashCode() : 0);
		result = 31 * result + (isNegated ? 1 : 0);
		return result;
	}

	@Override
	public String toString() {
		StringBuilder builder = new StringBuilder();
		if (value != null) {
			builder.append(name);
			if (isNegated) {
				builder.append('!');
			}
			builder.append('=');
			builder.append(value);
		}
		else {
			if (isNegated) {
				builder.append('!');
			}
			builder.append(name);
		}
		return builder.toString();
	}
}
