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/*
 * Copyright 2002-2018 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.web.socket.sockjs.frame;

import java.nio.charset.Charset;
import java.nio.charset.StandardCharsets;

import org.springframework.lang.Nullable;
import org.springframework.util.Assert;
import org.springframework.util.StringUtils;

/**
 * Represents a SockJS frame. Provides factory methods to create SockJS frames.
 *
 * @author Rossen Stoyanchev
 * @since 4.0
 */
public class SockJsFrame {

	/**
	 * The charset used by SockJS.
	 */
	public static final Charset CHARSET = StandardCharsets.UTF_8;

	private static final SockJsFrame OPEN_FRAME = new SockJsFrame("o");

	private static final SockJsFrame HEARTBEAT_FRAME = new SockJsFrame("h");

	private static final SockJsFrame CLOSE_GO_AWAY_FRAME = closeFrame(3000, "Go away!");

	private static final SockJsFrame CLOSE_ANOTHER_CONNECTION_OPEN_FRAME =
			closeFrame(2010, "Another connection still open");


	private final SockJsFrameType type;

	private final String content;


	/**
	 * Create a new instance frame with the given frame content.
	 * @param content the content (must be a non-empty and represent a valid SockJS frame)
	 */
	public SockJsFrame(String content) {
		Assert.hasText(content, "Content must not be empty");
		if ("o".equals(content)) {
			this.type = SockJsFrameType.OPEN;
			this.content = content;
		}
		else if ("h".equals(content)) {
			this.type = SockJsFrameType.HEARTBEAT;
			this.content = content;
		}
		else if (content.charAt(0) == 'a') {
			this.type = SockJsFrameType.MESSAGE;
			this.content = (content.length() > 1 ? content : "a[]");
		}
		else if (content.charAt(0) == 'm') {
			this.type = SockJsFrameType.MESSAGE;
			this.content = (content.length() > 1 ? content : "null");
		}
		else if (content.charAt(0) == 'c') {
			this.type = SockJsFrameType.CLOSE;
			this.content = (content.length() > 1 ? content : "c[]");
		}
		else {
			throw new IllegalArgumentException("Unexpected SockJS frame type in content \"" + content + "\"");
		}
	}


	/**
	 * Return the SockJS frame type.
	 */
	public SockJsFrameType getType() {
		return this.type;
	}

	/**
	 * Return the SockJS frame content (never {@code null}).
	 */
	public String getContent() {
		return this.content;
	}

	/**
	 * Return the SockJS frame content as a byte array.
	 */
	public byte[] getContentBytes() {
		return this.content.getBytes(CHARSET);
	}

	/**
	 * Return data contained in a SockJS "message" and "close" frames. Otherwise
	 * for SockJS "open" and "close" frames, which do not contain data, return
	 * {@code null}.
	 */
	@Nullable
	public String getFrameData() {
		if (getType() == SockJsFrameType.OPEN || getType() == SockJsFrameType.HEARTBEAT) {
			return null;
		}
		else {
			return getContent().substring(1);
		}
	}


	@Override
	public boolean equals(Object other) {
		if (this == other) {
			return true;
		}
		if (!(other instanceof SockJsFrame)) {
			return false;
		}
		SockJsFrame otherFrame = (SockJsFrame) other;
		return (this.type.equals(otherFrame.type) && this.content.equals(otherFrame.content));
	}

	@Override
	public int hashCode() {
		return this.content.hashCode();
	}

	@Override
	public String toString() {
		String result = this.content;
		if (result.length() > 80) {
			result = result.substring(0, 80) + "...(truncated)";
		}
		result = StringUtils.replace(result, "\n", "\\n");
		result = StringUtils.replace(result, "\r", "\\r");
		return "SockJsFrame content='" + result + "'";
	}


	public static SockJsFrame openFrame() {
		return OPEN_FRAME;
	}

	public static SockJsFrame heartbeatFrame() {
		return HEARTBEAT_FRAME;
	}

	public static SockJsFrame messageFrame(SockJsMessageCodec codec, String... messages) {
		String encoded = codec.encode(messages);
		return new SockJsFrame(encoded);
	}

	public static SockJsFrame closeFrameGoAway() {
		return CLOSE_GO_AWAY_FRAME;
	}

	public static SockJsFrame closeFrameAnotherConnectionOpen() {
		return CLOSE_ANOTHER_CONNECTION_OPEN_FRAME;
	}

	public static SockJsFrame closeFrame(int code, @Nullable String reason) {
		return new SockJsFrame("c[" + code + ",\"" + (reason != null ? reason : "") + "\"]");
	}

}