/**
 * This file is part of Graylog.
 *
 * Graylog is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * Graylog 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 for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with Graylog.  If not, see <http://www.gnu.org/licenses/>.
 */
package org.graylog2.rest;

import com.google.common.base.Strings;
import org.glassfish.grizzly.http.server.Request;
import org.glassfish.jersey.server.model.Resource;
import org.graylog2.shared.security.ShiroPrincipal;
import org.graylog2.shared.security.ShiroSecurityContext;
import org.jboss.netty.handler.ipfilter.IpSubnet;

import javax.annotation.Nullable;
import javax.validation.constraints.NotNull;
import javax.ws.rs.container.ContainerRequestContext;
import javax.ws.rs.core.HttpHeaders;
import javax.ws.rs.core.SecurityContext;
import java.net.URI;
import java.net.URISyntaxException;
import java.net.UnknownHostException;
import java.security.Principal;
import java.util.List;
import java.util.Optional;
import java.util.Set;

public class RestTools {
    @Nullable
    public static String getUserNameFromRequest(ContainerRequestContext requestContext) {
        final SecurityContext securityContext = requestContext.getSecurityContext();

        if (!(securityContext instanceof ShiroSecurityContext)) {
            return null;
        }

        final ShiroSecurityContext shiroSecurityContext = (ShiroSecurityContext) securityContext;
        final Principal userPrincipal = shiroSecurityContext.getUserPrincipal();

        if (!(userPrincipal instanceof ShiroPrincipal)) {
            return null;
        }

        final ShiroPrincipal shiroPrincipal = (ShiroPrincipal) userPrincipal;

        return shiroPrincipal.getName();
    }

    /**
     * If X-Forwarded-For request header is set, and the request came from a trusted source,
     * return the value of X-Forwarded-For. Otherwise return {@link Request#getRemoteAddr()}.
     */
    public static String getRemoteAddrFromRequest(Request request, Set<IpSubnet> trustedSubnets) {
        final String remoteAddr = request.getRemoteAddr();
        final String XForwardedFor = request.getHeader("X-Forwarded-For");
        if (XForwardedFor != null) {
            for (IpSubnet s : trustedSubnets) {
                try {
                    if (s.contains(remoteAddr)) {
                        // Request came from trusted source, trust X-Forwarded-For and return it
                        return XForwardedFor;
                    }
                } catch (UnknownHostException e) {
                    // ignore silently, probably not worth logging
                }
            }
        }

        // Request did not come from a trusted source, or the X-Forwarded-For header was not set
        return remoteAddr;
    }

    public static String buildEndpointUri(@NotNull HttpHeaders httpHeaders, @NotNull URI defaultEndpointUri) {
        Optional<String> endpointUri = Optional.empty();
        final List<String> headers = httpHeaders.getRequestHeader("X-Graylog-Server-URL");
        if (headers != null && !headers.isEmpty()) {
            endpointUri = headers.stream().filter(s -> {
                try {
                    if (Strings.isNullOrEmpty(s)) {
                        return false;
                    }
                    final URI uri = new URI(s);
                    if (!uri.isAbsolute()) {
                        return true;
                    }
                    switch (uri.getScheme()) {
                        case "http":
                        case "https":
                            return true;
                    }
                    return false;
                } catch (URISyntaxException e) {
                    return false;
                }
            }).findFirst();
        }

        return endpointUri.orElse(defaultEndpointUri.toString());
    }

    public static String getPathFromResource(Resource resource) {
        String path = resource.getPath();
        Resource parent = resource.getParent();

        while (parent != null) {
            if (!path.startsWith("/")) {
                path = "/" + path;
            }

            path = parent.getPath() + path;
            parent = parent.getParent();
        }

        return path;

    }
}