package com.mailserver.service;

import com.mailserver.domain.User;
import com.mailserver.repository.UserRepository;
import org.springframework.r2dbc.core.DatabaseClient;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;
import reactor.core.publisher.Flux;
import reactor.core.publisher.Mono;

import java.util.Collection;
import java.util.Locale;

/**
 * Several mailboxes for one login (V7): own, shared ones it is a MEMBER of, ATTACHED ones (by their password).
 * One rule for the web client, SMTP and IMAP; in mail programs another mailbox is
 * {@code mailbox*login} with the login's password (the Dovecot "master user" form).
 */
@Service
public class MailboxAccess {

    public static final String MEMBER = "MEMBER";
    public static final String ATTACHED = "ATTACHED";

    /** @param kind OWN, MEMBER or ATTACHED; unread — INBOX and own folders (not Spam/Trash/Sent/Drafts) */
    public record Entry(String email, String displayName, String kind, boolean shared, long unread) {
    }

    private final DatabaseClient db;
    private final UserRepository users;
    private final UserService userService;

    public MailboxAccess(DatabaseClient db, UserRepository users, UserService userService) {
        this.db = db;
        this.users = users;
        this.userService = userService;
    }

    /**
     * Login for SMTP / IMAP: {@code login} or {@code mailbox*login} + the login's password → the mailbox the
     * session works with, or null. A shared mailbox never logs in by itself.
     */
    public User login(String username, String password) {
        String name = username.trim().toLowerCase(Locale.ROOT);
        int star = name.indexOf('*');
        String mailbox = star < 0 ? name : name.substring(0, star);
        String login = star < 0 ? name : name.substring(star + 1);
        User user = users.findByEmail(login).block();
        if (user == null || !user.isActive() || user.isShared() || !userService.checkPassword(user, password)) {
            return null;
        }
        if (mailbox.equals(login)) {
            return user;
        }
        User target = users.findByEmail(mailbox).block();
        return target != null && target.isActive() && Boolean.TRUE.equals(has(target.getId(), user.getId()).block())
                ? target : null;
    }

    /** The login may open this mailbox (own or by access). */
    public Mono<Boolean> has(Long mailboxId, Long userId) {
        if (mailboxId.equals(userId)) {
            return Mono.just(true);
        }
        return db.sql("SELECT 1 FROM mailbox_access WHERE mailbox_id = :m AND user_id = :u")
                .bind("m", mailboxId).bind("u", userId).map((row, meta) -> true).one().defaultIfEmpty(false);
    }

    /** Own mailbox first, then the others by address. */
    public Flux<Entry> mailboxes(User login) {
        Mono<Entry> own = unread(login.getId()).map(n -> new Entry(login.getEmail(), login.getDisplayName(), "OWN", false, n));
        Flux<Entry> others = db.sql("SELECT u.id, u.email, u.display_name, u.is_shared, a.kind FROM mailbox_access a "
                        + "JOIN users u ON u.id = a.mailbox_id WHERE a.user_id = :u AND u.is_active ORDER BY u.email")
                .bind("u", login.getId())
                .map((row, meta) -> new Object[]{row.get("id", Long.class), row.get("email", String.class),
                        row.get("display_name", String.class), Boolean.TRUE.equals(row.get("is_shared", Boolean.class)),
                        row.get("kind", String.class)})
                .all()
                .concatMap(r -> unread((Long) r[0]).map(n -> new Entry((String) r[1], (String) r[2], (String) r[4], (Boolean) r[3], n)));
        return own.flux().concatWith(others);
    }

    public Mono<Long> unread(Long mailboxId) {
        return db.sql("SELECT COUNT(*) AS n FROM messages m JOIN folders f ON f.id = m.folder_id "
                        + "WHERE f.user_id = :u AND NOT m.is_read AND NOT m.is_deleted AND (NOT f.is_system OR f.name = 'INBOX')")
                .bind("u", mailboxId).map((row, meta) -> row.get("n", Long.class)).one().defaultIfEmpty(0L);
    }

    public Mono<Void> grant(Long mailboxId, Long userId, String kind) {
        return db.sql("INSERT INTO mailbox_access (mailbox_id, user_id, kind) VALUES (:m, :u, :k) "
                        + "ON CONFLICT (mailbox_id, user_id) DO NOTHING")
                .bind("m", mailboxId).bind("u", userId).bind("k", kind).then();
    }

    public Mono<Boolean> revoke(Long mailboxId, Long userId) {
        return db.sql("DELETE FROM mailbox_access WHERE mailbox_id = :m AND user_id = :u")
                .bind("m", mailboxId).bind("u", userId).fetch().rowsUpdated().map(n -> n > 0);
    }

    /** Exactly these MEMBERs (ATTACHED ones stay — they know the password). */
    @Transactional
    public Mono<Void> setMembers(Long mailboxId, Collection<Long> memberIds) {
        return db.sql("DELETE FROM mailbox_access WHERE mailbox_id = :m AND kind = :k").bind("m", mailboxId).bind("k", MEMBER).then()
                .thenMany(Flux.fromIterable(memberIds).distinct().filter(id -> !id.equals(mailboxId))
                        .concatMap(id -> db.sql("INSERT INTO mailbox_access (mailbox_id, user_id, kind) VALUES (:m, :u, :k) "
                                        + "ON CONFLICT (mailbox_id, user_id) DO UPDATE SET kind = EXCLUDED.kind")
                                .bind("m", mailboxId).bind("u", id).bind("k", MEMBER).then()))
                .then();
    }

    public Flux<String> members(Long mailboxId) {
        return db.sql("SELECT u.email FROM mailbox_access a JOIN users u ON u.id = a.user_id "
                        + "WHERE a.mailbox_id = :m AND a.kind = :k ORDER BY u.email")
                .bind("m", mailboxId).bind("k", MEMBER).map((row, meta) -> row.get("email", String.class)).all();
    }

    /** The login loses every MEMBER access (role removed in Jambotron); ATTACHED stays with the mailbox owner's say. */
    public Mono<Long> removeEverywhere(Long userId) {
        return db.sql("DELETE FROM mailbox_access WHERE user_id = :u AND kind = :k").bind("u", userId).bind("k", MEMBER)
                .fetch().rowsUpdated();
    }

    /** Reply from the web client: the original is answered, and by whom. */
    public Mono<Void> markAnswered(Long messageId, Long mailboxId, String by) {
        return db.sql("UPDATE messages SET is_answered = TRUE, answered_by = :b WHERE id = :id "
                        + "AND folder_id IN (SELECT id FROM folders WHERE user_id = :u)")
                .bind("b", by).bind("id", messageId).bind("u", mailboxId).then();
    }
}