/*
 * JBoss, Home of Professional Open Source.
 * Copyright 2014 Red Hat, Inc., and individual contributors
 * as indicated by the @author tags.
 *
 * 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 io.undertow.server.handlers;

import io.undertow.conduits.HeadStreamSinkConduit;
import io.undertow.conduits.RangeStreamSinkConduit;
import io.undertow.server.ConduitWrapper;
import io.undertow.server.HandlerWrapper;
import io.undertow.server.HttpHandler;
import io.undertow.server.HttpServerExchange;
import io.undertow.server.ResponseCommitListener;
import io.undertow.server.handlers.builder.HandlerBuilder;
import io.undertow.util.ByteRange;
import io.undertow.util.ConduitFactory;
import io.undertow.util.DateUtils;
import io.undertow.util.Headers;
import io.undertow.util.Methods;
import io.undertow.util.StatusCodes;
import org.xnio.conduits.StreamSinkConduit;

import java.util.Collections;
import java.util.HashMap;
import java.util.Map;
import java.util.Set;

Handler for Range requests. This is a generic handler that can handle range requests to any resource
of a fixed content length i.e. any resource where the content-length header has been set.
Note that this is not necessarily the most efficient way to handle range requests, as the full content
will be generated and then discarded.
At present this handler can only handle simple (i.e. single range) requests. If multiple ranges are requested the
Range header will be ignored.
Author:
Stuart Douglas/**
 * Handler for Range requests. This is a generic handler that can handle range requests to any resource
 * of a fixed content length i.e. any resource where the content-length header has been set.
 *
 * Note that this is not necessarily the most efficient way to handle range requests, as the full content
 * will be generated and then discarded.
 *
 * At present this handler can only handle simple (i.e. single range) requests. If multiple ranges are requested the
 * Range header will be ignored.
 *
 * @author Stuart Douglas
 */
public class ByteRangeHandler implements HttpHandler {

    private final HttpHandler next;
    private final boolean sendAcceptRanges;

    private static final ResponseCommitListener ACCEPT_RANGE_LISTENER = new ResponseCommitListener() {
        @Override
        public void beforeCommit(HttpServerExchange exchange) {
            if(!exchange.getResponseHeaders().contains(Headers.ACCEPT_RANGES)) {
                if (exchange.getResponseHeaders().contains(Headers.CONTENT_LENGTH)) {
                    exchange.getResponseHeaders().put(Headers.ACCEPT_RANGES, "bytes");
                } else {
                    exchange.getResponseHeaders().put(Headers.ACCEPT_RANGES, "none");
                }
            }
        }

    };

    public ByteRangeHandler(HttpHandler next, boolean sendAcceptRanges) {
        this.next = next;
        this.sendAcceptRanges = sendAcceptRanges;
    }


    @Override
    public void handleRequest(HttpServerExchange exchange) throws Exception {
        //range requests are only support for GET requests as per the RFC
        if(!Methods.GET.equals(exchange.getRequestMethod()) && !Methods.HEAD.equals(exchange.getRequestMethod())) {
            next.handleRequest(exchange);
            return;
        }
        if (sendAcceptRanges) {
            exchange.addResponseCommitListener(ACCEPT_RANGE_LISTENER);
        }
        final ByteRange range = ByteRange.parse(exchange.getRequestHeaders().getFirst(Headers.RANGE));
        if (range != null && range.getRanges() == 1) {
            exchange.addResponseWrapper(new ConduitWrapper<StreamSinkConduit>() {
                @Override
                public StreamSinkConduit wrap(ConduitFactory<StreamSinkConduit> factory, HttpServerExchange exchange) {
                    if(exchange.getStatusCode() != StatusCodes.OK ) {
                        return factory.create();
                    }
                    String length = exchange.getResponseHeaders().getFirst(Headers.CONTENT_LENGTH);
                    if (length == null) {
                        return factory.create();
                    }
                    long responseLength = Long.parseLong(length);
                    String lastModified = exchange.getResponseHeaders().getFirst(Headers.LAST_MODIFIED);
                    ByteRange.RangeResponseResult rangeResponse = range.getResponseResult(responseLength, exchange.getRequestHeaders().getFirst(Headers.IF_RANGE), lastModified == null ? null : DateUtils.parseDate(lastModified), exchange.getResponseHeaders().getFirst(Headers.ETAG));
                    if(rangeResponse != null){
                        long start = rangeResponse.getStart();
                        long end = rangeResponse.getEnd();
                        exchange.setStatusCode(rangeResponse.getStatusCode());
                        exchange.getResponseHeaders().put(Headers.CONTENT_RANGE, rangeResponse.getContentRange());
                        exchange.setResponseContentLength(rangeResponse.getContentLength());
                        if(rangeResponse.getStatusCode() == StatusCodes.REQUEST_RANGE_NOT_SATISFIABLE) {
                            return new HeadStreamSinkConduit(factory.create(), null, true);
                        }
                        return new RangeStreamSinkConduit(factory.create(), start, end, responseLength);
                    } else {
                        return factory.create();
                    }
                }
            });
        }
        next.handleRequest(exchange);

    }

    public static class Wrapper implements HandlerWrapper {

        private final boolean sendAcceptRanges;

        public Wrapper(boolean sendAcceptRanges) {
            this.sendAcceptRanges = sendAcceptRanges;
        }

        @Override
        public HttpHandler wrap(HttpHandler handler) {
            return new ByteRangeHandler(handler, sendAcceptRanges);
        }
    }

    public static class Builder implements HandlerBuilder {

        @Override
        public String name() {
            return "byte-range";
        }

        @Override
        public Map<String, Class<?>> parameters() {
            Map<String, Class<?>> params = new HashMap<>();
            params.put("send-accept-ranges", boolean.class);
            return params;
        }

        @Override
        public Set<String> requiredParameters() {
            return Collections.emptySet();
        }

        @Override
        public String defaultParameter() {
            return "send-accept-ranges";
        }

        @Override
        public HandlerWrapper build(Map<String, Object> config) {
            Boolean send = (Boolean) config.get("send-accept-ranges");
            return new Wrapper(send != null && send);
        }
    }


}