reactive-mail-server/backend/src/main/java/com/mailserver/controller/MailboxesController.java

package com.mailserver.controller;

import com.mailserver.domain.User;
import com.mailserver.dto.LoginResponse;
import com.mailserver.security.Actor;
import com.mailserver.security.LoginGuard;
import com.mailserver.service.MailboxAccess;
import com.mailserver.service.UserService;
import com.mailserver.util.JwtUtils;
import jakarta.validation.constraints.NotBlank;
import jakarta.validation.constraints.Size;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.http.HttpStatus;
import org.springframework.http.server.reactive.ServerHttpRequest;
import org.springframework.security.core.Authentication;
import org.springframework.web.bind.annotation.DeleteMapping;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseStatus;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.server.ResponseStatusException;
import reactor.core.publisher.Flux;
import reactor.core.publisher.Mono;

import java.time.Duration;
import java.util.Locale;

/**
 * The mailboxes of the logged-in user (left menu): own, shared ones it is a member of, attached ones.
 * Always works for the LOGIN behind the session, also when a shared mailbox is open.
 */
@RestController
@RequestMapping("/api/mailboxes")
public class MailboxesController {

    private static final Logger log = LoggerFactory.getLogger(MailboxesController.class);

    public record AttachRequest(@NotBlank @Size(max = 254) String email, @NotBlank @Size(max = 200) String password) {
    }

    private final MailboxAccess access;
    private final UserService users;
    private final JwtUtils jwt;
    private final LoginGuard guard;

    public MailboxesController(MailboxAccess access, UserService users, JwtUtils jwt, LoginGuard guard) {
        this.access = access;
        this.users = users;
        this.jwt = jwt;
        this.guard = guard;
    }

    @GetMapping
    public Flux<MailboxAccess.Entry> mine(Mono<Authentication> auth) {
        return login(auth).flatMapMany(access::mailboxes);
    }

    /** A session of this mailbox for the login (switch in the left menu). */
    @PostMapping("/{email}/session")
    public Mono<LoginResponse> session(Mono<Authentication> auth, @PathVariable String email) {
        return login(auth).flatMap(me -> mailbox(email).flatMap(target -> access.has(target.getId(), me.getId())
                .flatMap(allowed -> {
                    if (!allowed) {
                        return Mono.error(new ResponseStatusException(HttpStatus.FORBIDDEN, "No access to this mailbox"));
                    }
                    LoginResponse response = new LoginResponse();
                    boolean own = target.getId().equals(me.getId());
                    response.setToken(own ? jwt.generateToken(me.getEmail()) : jwt.generateToken(target.getEmail(), me.getEmail()));
                    response.setEmail(target.getEmail());
                    return Mono.just(response);
                })));
    }

    /** Adds another mailbox the user knows the password of. The password is checked like a login (LoginGuard). */
    @PostMapping("/attach")
    @ResponseStatus(HttpStatus.CREATED)
    public Mono<MailboxAccess.Entry> attach(Mono<Authentication> auth, @RequestBody Mono<AttachRequest> body, ServerHttpRequest http) {
        String ip = AuthenticationController.clientIp(http);
        return login(auth).zipWith(body).flatMap(pair -> {
            User me = pair.getT1();
            String email = pair.getT2().email().trim().toLowerCase(Locale.ROOT);
            Duration wait = guard.retryAfter(ip, email);
            if (!wait.isZero()) {
                return Mono.error(new ResponseStatusException(HttpStatus.TOO_MANY_REQUESTS,
                        "Too many failed attempts, try again in " + LoginGuard.human(wait)));
            }
            return users.findOptional(email)
                    .filter(target -> target.isActive() && !target.isShared() && users.checkPassword(target, pair.getT2().password()))
                    .switchIfEmpty(Mono.defer(() -> {
                        guard.failure(ip, email);
                        log.warn("WEB {}: {} failed to attach {}", ip, me.getEmail(), email);
                        return Mono.error(new ResponseStatusException(HttpStatus.BAD_REQUEST, "Wrong address or password"));
                    }))
                    .flatMap(target -> {
                        if (target.getId().equals(me.getId())) {
                            return Mono.error(new ResponseStatusException(HttpStatus.BAD_REQUEST, "This is your own mailbox"));
                        }
                        guard.success(ip, email);
                        log.info("{} attached mailbox {}", me.getEmail(), email);
                        return access.grant(target.getId(), me.getId(), MailboxAccess.ATTACHED)
                                .then(access.unread(target.getId()))
                                .map(n -> new MailboxAccess.Entry(target.getEmail(), target.getDisplayName(), MailboxAccess.ATTACHED, false, n));
                    });
        });
    }

    /** Removes the mailbox from the user's menu (attached or shared). */
    @DeleteMapping("/{email}")
    @ResponseStatus(HttpStatus.NO_CONTENT)
    public Mono<Void> leave(Mono<Authentication> auth, @PathVariable String email) {
        return login(auth).flatMap(me -> mailbox(email).flatMap(target -> access.revoke(target.getId(), me.getId())
                .flatMap(done -> done ? Mono.<Void>empty()
                        : Mono.error(new ResponseStatusException(HttpStatus.NOT_FOUND, "Not in your mailboxes")))));
    }

    private Mono<User> login(Mono<Authentication> auth) {
        return auth.switchIfEmpty(Mono.error(new ResponseStatusException(HttpStatus.UNAUTHORIZED)))
                .flatMap(a -> users.findOptional(Actor.login(a)))
                .switchIfEmpty(Mono.error(new ResponseStatusException(HttpStatus.UNAUTHORIZED)));
    }

    private Mono<User> mailbox(String email) {
        return users.findOptional(email)
                .switchIfEmpty(Mono.error(new ResponseStatusException(HttpStatus.NOT_FOUND, "No such mailbox")));
    }
}