package com.labelsys.backend.service;

import com.labelsys.backend.context.LoginUser;
import com.labelsys.backend.enums.UserRole;
import java.util.List;
import java.util.function.Function;
import java.util.stream.Collectors;
import org.springframework.stereotype.Service;

@Service
public class DataPermissionService {

    public boolean canAccessCreator(LoginUser currentUser, Long creatorId, UserRole creatorRole) {
        return switch (currentUser.role()) {
            case EMPLOYEE -> currentUser.userId().equals(creatorId);
            case MANAGER -> creatorRole == UserRole.EMPLOYEE || creatorRole == UserRole.MANAGER;
            case ENGINEER -> true;
        };
    }

    /**
     * Generic in-memory role-based data filter for records already loaded in memory.
     */
    public <T> List<T> filterByRole(
            LoginUser currentUser,
            List<T> allRecords,
            Function<T, UserRole> roleExtractor,
            Function<T, Long> ownerIdExtractor) {

        if (allRecords == null || allRecords.isEmpty()) {
            return List.of();
        }

        UserRole currentRole = currentUser.role();
        Long currentUserId = currentUser.userId();

        return allRecords.stream()
                .filter(record -> {
                    UserRole recordRole = roleExtractor.apply(record);
                    Long recordOwnerId = ownerIdExtractor.apply(record);

                    return switch (currentRole) {
                        case EMPLOYEE -> currentUserId.equals(recordOwnerId);
                        case MANAGER -> recordRole == UserRole.EMPLOYEE || recordRole == UserRole.MANAGER;
                        case ENGINEER -> true;
                    };
                })
                .collect(Collectors.toList());
    }

    /**
     * Returns the creator roles visible to the current user for SQL-side filtering.
     */
    public List<String> getAllowedRoles(LoginUser currentUser) {
        return switch (currentUser.role()) {
            case EMPLOYEE -> List.of();
            case MANAGER -> List.of("EMPLOYEE", "MANAGER");
            case ENGINEER -> List.of("EMPLOYEE", "MANAGER", "ENGINEER");
        };
    }

    /**
     * Whether SQL queries should additionally restrict by creator/user id.
     */
    public boolean shouldFilterByUserId(LoginUser currentUser) {
        return currentUser.role() == UserRole.EMPLOYEE;
    }
}