/*

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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 */

package jdk.internal.net.http;

import java.io.IOException;

import java.io.UncheckedIOException;

import java.net.URI;

import java.net.http.HttpClient;

import java.net.http.HttpHeaders;

import jdk.internal.net.http.common.Log;

import jdk.internal.net.http.common.Utils;

class RedirectFilter implements HeaderFilter {

    HttpRequestImpl request;

    HttpClientImpl client;

    HttpClient.Redirect policy;

    String method;

    MultiExchange<?> exchange;

    static final int DEFAULT_MAX_REDIRECTS = 5;

    URI uri;

    /*

     * NOT_MODIFIED status code results from a conditional GET where

     * the server does not (must not) return a response body because

     * the condition specified in the request disallows it

     */

    static final int HTTP_NOT_MODIFIED = 304;

    static final int max_redirects = Utils.getIntegerNetProperty(

            "jdk.httpclient.redirects.retrylimit", DEFAULT_MAX_REDIRECTS

    );

    // A public no-arg constructor is required by FilterFactory

    public RedirectFilter() {}

    @Override

    public synchronized void request(HttpRequestImpl r, MultiExchange<?> e) throws IOException {

        this.request = r;

        this.client = e.client();

        this.policy = client.followRedirects();

        this.method = r.method();

        this.uri = r.uri();

        this.exchange = e;

    }

    @Override

    public synchronized HttpRequestImpl response(Response r) throws IOException {

        return handleResponse(r);

    }

    private static String redirectedMethod(int statusCode, String orig) {

        switch (statusCode) {

            case 301:

            case 302:

                return orig.equals("POST") ? "GET" : orig;

            case 303:

                return "GET";

            case 307:

            case 308:

                return orig;

            default:

                // unexpected but return orig

                return orig;

        }

    }

    /**

     * Checks to see if a new request is needed and returns it.

     * Null means response is ok to return to user.

     */

    private HttpRequestImpl handleResponse(Response r) {

        int rcode = r.statusCode();

        if (rcode == 200 || policy == HttpClient.Redirect.NEVER) {

            return null;

        }

        if (rcode == HTTP_NOT_MODIFIED)

            return null;

            URI redir = getRedirectedURI(r.headers());

            String newMethod = redirectedMethod(rcode, method);

            Log.logTrace("response code: {0}, redirected URI: {1}", rcode, redir);

            if (canRedirect(redir) && ++exchange.numberOfRedirects < max_redirects) {

                Log.logTrace("redirect to: {0} with method: {1}", redir, newMethod);

            } else {

                Log.logTrace("not redirecting");

                return null;

            }

        }

        return null;

    }

    private URI getRedirectedURI(HttpHeaders headers) {

        URI redirectedURI;

        redirectedURI = headers.firstValue("Location")

                .map(URI::create)

                .orElseThrow(() -> new UncheckedIOException(

                        new IOException("Invalid redirection")));

        // redirect could be relative to original URL, but if not

        // then redirect is used.

        redirectedURI = uri.resolve(redirectedURI);

        return redirectedURI;

    }

    private boolean canRedirect(URI redir) {

        String newScheme = redir.getScheme();

        String oldScheme = uri.getScheme();

        switch (policy) {

            case ALWAYS:

                return true;

            case NEVER:

                return false;

            case NORMAL:

                return newScheme.equalsIgnoreCase(oldScheme)

                        || newScheme.equalsIgnoreCase("https");

            default:

                throw new InternalError();

        }

    }

}