server/protocols/jmap/src/main/java/org/apache/james/jmap/http/XUserAuthenticationStrategy.java

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package org.apache.james.jmap.http;

import java.util.Optional;

import jakarta.inject.Inject;

import org.apache.james.core.Username;
import org.apache.james.jmap.exceptions.UnauthorizedException;
import org.apache.james.mailbox.MailboxManager;
import org.apache.james.mailbox.MailboxSession;
import org.apache.james.user.api.UsersRepository;

import com.google.common.collect.ImmutableMap;

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

public class XUserAuthenticationStrategy implements AuthenticationStrategy {
    private static final String X_USER_HEADER_NAME = "X-User";
    private static final AuthenticationChallenge X_USER_CHALLENGE = AuthenticationChallenge.of(
        AuthenticationScheme.of("XUserHeader"),
        ImmutableMap.of());

    private final UsersRepository usersRepository;
    private final MailboxManager mailboxManager;

    @Inject
    public XUserAuthenticationStrategy(UsersRepository usersRepository, MailboxManager mailboxManager) {
        this.usersRepository = usersRepository;
        this.mailboxManager = mailboxManager;
    }

    @Override
    public Mono<MailboxSession> createMailboxSession(HttpServerRequest httpRequest) {
        return Optional.ofNullable(httpRequest.requestHeaders().get(X_USER_HEADER_NAME))
            .map(String::trim)
            .filter(s -> !s.isEmpty())
            .map(Username::of)
            .map(this::createMailboxSession)
            .orElse(Mono.empty());
    }

    private Mono<MailboxSession> createMailboxSession(Username username) {
        return usersRepository.assertValidReactive(username)
            .onErrorMap(e -> new UnauthorizedException("Invalid username", e))
            .then(Mono.fromCallable(() -> mailboxManager.authenticate(username).withoutDelegation()));
    }

    @Override
    public AuthenticationChallenge correspondingChallenge() {
        return X_USER_CHALLENGE;
    }
}