package com.mydreamjob.application;

import com.mydreamjob.common.exception.BusinessException;
import com.mydreamjob.common.exception.ErrorCode;
import com.mydreamjob.company.Company;
import com.mydreamjob.company.CompanyRepository;
import com.mydreamjob.job.Job;
import com.mydreamjob.job.JobRepository;
import com.mydreamjob.privacy.ResumeVisibility;
import com.mydreamjob.privacy.StudentPrivacySettings;
import com.mydreamjob.privacy.StudentPrivacySettingsRepository;
import lombok.RequiredArgsConstructor;
import org.springframework.stereotype.Component;

import java.util.Set;

/**
 * S03-B 企业简历访问授权（失败关闭）。
 *
 * <p>授权顺序严格按设计 §4.2：当前 COMPANY 用户 → 当前 Company → Application+Job →
 * Job.companyId → Student → privacy setting。归属信息全部由服务端推导，
 * <strong>不信任任何客户端传入的 companyId / studentUserId</strong>。</p>
 *
 * <p>决策表（设计 §4.3）：</p>
 * <ul>
 *   <li>无设置记录 / null / PRIVATE：拒绝（按 PRIVATE 处理）</li>
 *   <li>APPLIED_COMPANIES：岗位必须属于当前企业，且投递状态为
 *       SUBMITTED/VIEWED/INTERVIEW/HIRED；WITHDRAWN/REJECTED 拒绝</li>
 *   <li>VERIFIED_COMPANIES：当前企业 {@code verified=true} <strong>且</strong>拥有该投递岗位；
 *       投递状态不额外限制</li>
 * </ul>
 *
 * <p>本类修复了此前 {@code PrivacySettingsService.canCompanyViewResume} 只校验学生与状态、
 * 不校验企业归属的缺陷。</p>
 */
@Component
@RequiredArgsConstructor
public class CompanyResumeAccessPolicy {

    /**
     * {@code APPLIED_COMPANIES} 允许的投递状态：**严格白名单**。
     *
     * <p>不得改为「不是拒绝状态就允许」的黑名单逻辑 —— 那会让 {@code null}、空白、
     * 未知状态或大小写变体（如 {@code "submitted"}）失败开放。状态比较区分大小写。</p>
     */
    static final Set<String> APPLIED_COMPANY_VISIBLE_STATUSES =
            Set.of("SUBMITTED", "VIEWED", "INTERVIEW", "HIRED");

    private final CompanyRepository companyRepository;
    private final ApplicationRepository applicationRepository;
    private final JobRepository jobRepository;
    private final StudentPrivacySettingsRepository privacyRepository;

    /** 授权通过后返回候选人用户 ID；这是后续读取简历的唯一依据。 */
    public record Decision(Long studentUserId) {
    }

    /**
     * 企业下载接口使用的授权入口：仅凭当前登录公司用户与路径中的 applicationId 完成全部判定。
     *
     * @throws BusinessException 未拥有企业资料 / 跨企业 / 隐私拒绝 → {@code FORBIDDEN(2002)}；
     *                           投递不存在 → {@code APPLICATION_NOT_FOUND(8002)}
     */
    public Decision authorizeForDownload(Long companyUserId, Long applicationId) {
        if (companyUserId == null || applicationId == null) {
            throw new BusinessException(ErrorCode.FORBIDDEN);
        }
        Company company = companyRepository.findByOwnerUserId(companyUserId).orElse(null);
        if (company == null) {
            throw new BusinessException(ErrorCode.FORBIDDEN);
        }
        Application application = applicationRepository.findById(applicationId)
                .orElseThrow(() -> new BusinessException(ErrorCode.APPLICATION_NOT_FOUND));

        if (!isVisibleToCompanyInternal(application, company.getId())) {
            throw new BusinessException(ErrorCode.FORBIDDEN);
        }
        return new Decision(application.getStudentUserId());
    }

    /**
     * 既有布尔语义的授权判定（供 {@code PrivacySettingsService} 委托）。
     *
     * <p>调用方提供的 {@code studentUserId} 只用于一致性校验：必须与投递记录一致，
     * 否则视为不可信并拒绝。</p>
     */
    public boolean isVisible(Long studentUserId, Long companyId, Long applicationId) {
        if (studentUserId == null || companyId == null || applicationId == null) {
            return false;
        }
        Application application = applicationRepository.findById(applicationId).orElse(null);
        if (application == null || !studentUserId.equals(application.getStudentUserId())) {
            return false;
        }
        return isVisibleToCompanyInternal(application, companyId);
    }

    /**
     * 核心判定：投递所属岗位必须属于该企业，再按学生隐私设置决定可见性。
     */
    private boolean isVisibleToCompanyInternal(Application application, Long companyId) {
        Job job = jobRepository.findById(application.getJobId()).orElse(null);
        if (job == null || !companyId.equals(job.getCompanyId())) {
            // 岗位不存在或不属于当前企业：一律拒绝（含跨企业投递）。
            return false;
        }

        ResumeVisibility visibility = visibilityOf(application.getStudentUserId());
        switch (visibility) {
            case APPLIED_COMPANIES:
                // 白名单判定（失败关闭）：null / 空白 / 未知 / 大小写变体一律拒绝。
                // 先做 null 判断，避免 Set.of(...).contains(null) 抛 NPE。
                return application.getStatus() != null
                        && APPLIED_COMPANY_VISIBLE_STATUSES.contains(application.getStatus());
            case VERIFIED_COMPANIES:
                Company company = companyRepository.findById(companyId).orElse(null);
                return company != null && Boolean.TRUE.equals(company.getVerified());
            case PRIVATE:
            default:
                // 无设置记录、null 或 PRIVATE：按 PRIVATE 处理。
                return false;
        }
    }

    private ResumeVisibility visibilityOf(Long studentUserId) {
        StudentPrivacySettings settings = privacyRepository.findByStudentUserId(studentUserId).orElse(null);
        if (settings == null || settings.getResumeVisibility() == null) {
            return ResumeVisibility.PRIVATE;
        }
        return settings.getResumeVisibility();
    }
}