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package com.github.alexvictoor.livereload;

import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.ChannelFuture;
import io.netty.channel.ChannelFutureListener;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.SimpleChannelInboundHandler;
import io.netty.channel.group.ChannelGroup;
import io.netty.handler.codec.http.DefaultFullHttpResponse;
import io.netty.handler.codec.http.FullHttpRequest;
import io.netty.handler.codec.http.FullHttpResponse;
import io.netty.handler.codec.http.HttpHeaders;
import io.netty.handler.codec.http.websocketx.*;
import io.netty.util.CharsetUtil;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.nio.charset.Charset;

import static io.netty.handler.codec.http.HttpHeaders.Names.CONTENT_TYPE;
import static io.netty.handler.codec.http.HttpHeaders.Names.HOST;
import static io.netty.handler.codec.http.HttpMethod.GET;
import static io.netty.handler.codec.http.HttpResponseStatus.*;
import static io.netty.handler.codec.http.HttpVersion.HTTP_1_1;

/**
 * Copy/paste from Netty websocket example
 */
public class WebSocketServerHandler extends SimpleChannelInboundHandler {

    public static final Logger logger = LoggerFactory.getLogger(WebSocketServerHandler.class);

    private static final String WEBSOCKET_PATH = "/livereload";
    public static final String HELLO_MSG = "{\"command\":\"hello\",\"protocols\":[\"http:\\/\\/livereload.com\\/protocols\\/official-7\"],\"serverName\":\"netty-livereload\"}";

    private final ChannelGroup allChannels;
    private final String jsContent;
    private WebSocketServerHandshaker handshaker;

    public WebSocketServerHandler(ChannelGroup allChannels, String jsContent) {
        this.allChannels = allChannels;
        this.jsContent = jsContent;
    }

    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
        allChannels.add(ctx.channel());
        super.channelActive(ctx);
    }

    @Override
    public void channelInactive(ChannelHandlerContext ctx) throws Exception {
        allChannels.remove(ctx.channel());
        super.channelInactive(ctx);
    }

    @Override
    public void channelRead0(ChannelHandlerContext ctx, Object msg) {
        if (msg instanceof FullHttpRequest) {
            handleHttpRequest(ctx, (FullHttpRequest) msg);
        } else if (msg instanceof WebSocketFrame) {
            handleWebSocketFrame(ctx, (WebSocketFrame) msg);
        }
    }

    @Override
    public void channelReadComplete(ChannelHandlerContext ctx) {
        ctx.flush();
    }

    private void handleHttpRequest(ChannelHandlerContext ctx, FullHttpRequest req) {
        // Handle a bad request.
        if (!req.getDecoderResult().isSuccess()) {
            sendHttpResponse(ctx, req, new DefaultFullHttpResponse(HTTP_1_1, BAD_REQUEST));
            return;
        }

        // Allow only GET methods.
        if (req.getMethod() != GET) {
            sendHttpResponse(ctx, req, new DefaultFullHttpResponse(HTTP_1_1, FORBIDDEN));
            return;
        }

        // Send the demo page and favicon.ico
        if (req.getUri().startsWith("/livereload.js")) {

            ByteBuf content = Unpooled.copiedBuffer(jsContent, Charset.defaultCharset());
            FullHttpResponse res = new DefaultFullHttpResponse(HTTP_1_1, OK, content);

            res.headers().set(CONTENT_TYPE, "text/javascript");
            HttpHeaders.setContentLength(res, content.readableBytes());

            sendHttpResponse(ctx, req, res);
            return;
        }
        if ("/favicon.ico".equals(req.getUri())) {
            FullHttpResponse res = new DefaultFullHttpResponse(HTTP_1_1, NOT_FOUND);
            sendHttpResponse(ctx, req, res);
            return;
        }

        // Handshake
        WebSocketServerHandshakerFactory wsFactory = new WebSocketServerHandshakerFactory(
                getWebSocketLocation(req), null, true);
        handshaker = wsFactory.newHandshaker(req);
        if (handshaker == null) {
            WebSocketServerHandshakerFactory.sendUnsupportedVersionResponse(ctx.channel());
        } else {
            handshaker.handshake(ctx.channel(), req);
        }
    }

    private void handleWebSocketFrame(ChannelHandlerContext ctx, WebSocketFrame frame) {

        // Check for closing frame
        if (frame instanceof CloseWebSocketFrame) {
            handshaker.close(ctx.channel(), (CloseWebSocketFrame) frame.retain());
            return;
        }
        if (frame instanceof PingWebSocketFrame) {
            ctx.channel().write(new PongWebSocketFrame(frame.content().retain()));
            return;
        }
        if (!(frame instanceof TextWebSocketFrame)) {
            throw new UnsupportedOperationException(String.format("%s frame types not supported", frame.getClass()
                    .getName()));
        }

        // Send the uppercase string back.
        String request = ((TextWebSocketFrame) frame).text();
        logger.debug("{} received {}", ctx.channel(), request);
        if (request.contains("hello")) {
            logger.info("Saying hello back");
            ctx.channel().write(new TextWebSocketFrame(HELLO_MSG));
        }
    }

    private static void sendHttpResponse(
            ChannelHandlerContext ctx, FullHttpRequest req, FullHttpResponse res) {
        // Generate an error page if response getStatus code is not OK (200).
        if (res.getStatus().code() != 200) {
            ByteBuf buf = Unpooled.copiedBuffer(res.getStatus().toString(), CharsetUtil.UTF_8);
            res.content().writeBytes(buf);
            buf.release();
            HttpHeaders.setContentLength(res, res.content().readableBytes());
        }

        // Send the response and close the connection if necessary.
        ChannelFuture f = ctx.channel().writeAndFlush(res);
        if (!HttpHeaders.isKeepAlive(req) || res.getStatus().code() != 200) {
            f.addListener(ChannelFutureListener.CLOSE);
        }
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
        cause.printStackTrace();
        ctx.close();
    }

    private static String getWebSocketLocation(FullHttpRequest req) {
        String location =  req.headers().get(HOST) + WEBSOCKET_PATH;
        return "ws://" + location;
    }
}