/*
 * 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(@Nullable 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 : "") + "\"]");
        }

}