/*
 * Copyright 2012-2020 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
 *
 *      https://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.boot.env;

import java.util.Random;
import java.util.UUID;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import org.springframework.core.env.ConfigurableEnvironment;
import org.springframework.core.env.PropertySource;
import org.springframework.core.env.StandardEnvironment;
import org.springframework.util.DigestUtils;
import org.springframework.util.StringUtils;

PropertySource that returns a random value for any property that starts with "random.". Where the "unqualified property name" is the portion of the requested property name beyond the "random." prefix, this PropertySource returns: 

When "int", a random Integer value, restricted by an optionally specified range.
When "long", a random Long value, restricted by an optionally specified range.
Otherwise, a byte[].
 The "random.int" and "random.long" properties supports a range suffix whose syntax is: 
 OPEN value (,max) CLOSE where the OPEN,CLOSE are any character and value,max are integers. If max is provided then value is the minimum value and max is the maximum (exclusive). 
Author:
Dave Syer, Matt Benson
Since:
1.0.0/**
 * {@link PropertySource} that returns a random value for any property that starts with
 * {@literal "random."}. Where the "unqualified property name" is the portion of the
 * requested property name beyond the "random." prefix, this {@link PropertySource}
 * returns:
 * <ul>
 * <li>When {@literal "int"}, a random {@link Integer} value, restricted by an optionally
 * specified range.</li>
 * <li>When {@literal "long"}, a random {@link Long} value, restricted by an optionally
 * specified range.</li>
 * <li>Otherwise, a {@code byte[]}.</li>
 * </ul>
 * The {@literal "random.int"} and {@literal "random.long"} properties supports a range
 * suffix whose syntax is:
 * <p>
 * {@code OPEN value (,max) CLOSE} where the {@code OPEN,CLOSE} are any character and
 * {@code value,max} are integers. If {@code max} is provided then {@code value} is the
 * minimum value and {@code max} is the maximum (exclusive).
 *
 * @author Dave Syer
 * @author Matt Benson
 * @since 1.0.0
 */
public class RandomValuePropertySource extends PropertySource<Random> {

	
Name of the random PropertySource. /**
	 * Name of the random {@link PropertySource}.
	 */
	public static final String RANDOM_PROPERTY_SOURCE_NAME = "random";

	private static final String PREFIX = "random.";

	private static final Log logger = LogFactory.getLog(RandomValuePropertySource.class);

	public RandomValuePropertySource() {
		this(RANDOM_PROPERTY_SOURCE_NAME);
	}

	public RandomValuePropertySource(String name) {
		super(name, new Random());
	}

	@Override
	public Object getProperty(String name) {
		if (!name.startsWith(PREFIX)) {
			return null;
		}
		if (logger.isTraceEnabled()) {
			logger.trace("Generating random property for '" + name + "'");
		}
		return getRandomValue(name.substring(PREFIX.length()));
	}

	private Object getRandomValue(String type) {
		if (type.equals("int")) {
			return getSource().nextInt();
		}
		if (type.equals("long")) {
			return getSource().nextLong();
		}
		String range = getRange(type, "int");
		if (range != null) {
			return getNextIntInRange(range);
		}
		range = getRange(type, "long");
		if (range != null) {
			return getNextLongInRange(range);
		}
		if (type.equals("uuid")) {
			return UUID.randomUUID().toString();
		}
		return getRandomBytes();
	}

	private String getRange(String type, String prefix) {
		if (type.startsWith(prefix)) {
			int startIndex = prefix.length() + 1;
			if (type.length() > startIndex) {
				return type.substring(startIndex, type.length() - 1);
			}
		}
		return null;
	}

	private int getNextIntInRange(String range) {
		String[] tokens = StringUtils.commaDelimitedListToStringArray(range);
		int start = Integer.parseInt(tokens[0]);
		if (tokens.length == 1) {
			return getSource().nextInt(start);
		}
		return start + getSource().nextInt(Integer.parseInt(tokens[1]) - start);
	}

	private long getNextLongInRange(String range) {
		String[] tokens = StringUtils.commaDelimitedListToStringArray(range);
		if (tokens.length == 1) {
			return Math.abs(getSource().nextLong() % Long.parseLong(tokens[0]));
		}
		long lowerBound = Long.parseLong(tokens[0]);
		long upperBound = Long.parseLong(tokens[1]) - lowerBound;
		return lowerBound + Math.abs(getSource().nextLong() % upperBound);
	}

	private Object getRandomBytes() {
		byte[] bytes = new byte[32];
		getSource().nextBytes(bytes);
		return DigestUtils.md5DigestAsHex(bytes);
	}

	public static void addToEnvironment(ConfigurableEnvironment environment) {
		environment.getPropertySources().addAfter(StandardEnvironment.SYSTEM_ENVIRONMENT_PROPERTY_SOURCE_NAME,
				new RandomValuePropertySource(RANDOM_PROPERTY_SOURCE_NAME));
		logger.trace("RandomValuePropertySource add to Environment");
	}

}