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 * regarding copyright ownership.  The ASF licenses this file   *
 * to you under the Apache License, Version 2.0 (the            *
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package org.apache.james.jmap.jwt;

import javax.inject.Inject;
import javax.inject.Named;

import org.apache.james.core.Username;
import org.apache.james.jmap.exceptions.UnauthorizedException;
import org.apache.james.jmap.http.AuthenticationChallenge;
import org.apache.james.jmap.http.AuthenticationScheme;
import org.apache.james.jmap.http.AuthenticationStrategy;
import org.apache.james.jwt.JwtTokenVerifier;
import org.apache.james.mailbox.MailboxManager;
import org.apache.james.mailbox.MailboxSession;
import org.apache.james.user.api.UsersRepository;
import org.apache.james.user.api.UsersRepositoryException;

import com.google.common.annotations.VisibleForTesting;
import com.google.common.collect.ImmutableMap;

import reactor.core.publisher.Mono;
import reactor.core.scheduler.Schedulers;
import reactor.netty.http.server.HttpServerRequest;

public class JWTAuthenticationStrategy implements AuthenticationStrategy {

    @VisibleForTesting
    public static final String AUTHORIZATION_HEADER_PREFIX = "Bearer ";
    private final JwtTokenVerifier tokenManager;
    private final MailboxManager mailboxManager;
    private final UsersRepository usersRepository;

    @Inject
    @VisibleForTesting
    public JWTAuthenticationStrategy(@Named("jmap") JwtTokenVerifier tokenManager,
                                     MailboxManager mailboxManager,
                                     UsersRepository usersRepository) {
        this.tokenManager = tokenManager;
        this.mailboxManager = mailboxManager;
        this.usersRepository = usersRepository;
    }

    @Override
    public Mono<MailboxSession> createMailboxSession(HttpServerRequest httpRequest) {
        return Mono.fromCallable(() -> authHeaders(httpRequest))
            .filter(header -> header.startsWith(AUTHORIZATION_HEADER_PREFIX))
            .map(header -> header.substring(AUTHORIZATION_HEADER_PREFIX.length()))
            .flatMap(userJWTToken -> Mono.fromCallable(() -> {
                if (!tokenManager.verify(userJWTToken)) {
                    throw new UnauthorizedException("Failed Jwt verification");
                }

                Username username = Username.of(tokenManager.extractLogin(userJWTToken));
                try {
                    usersRepository.assertValid(username);
                } catch (UsersRepositoryException e) {
                    throw new UnauthorizedException("Invalid username", e);
                }

                return username;
            }).subscribeOn(Schedulers.elastic()))
            .map(mailboxManager::createSystemSession);
    }

    @Override
    public AuthenticationChallenge correspondingChallenge() {
        return AuthenticationChallenge.of(
            AuthenticationScheme.of("Bearer"),
            ImmutableMap.of("realm", "JWT"));
    }
}