package com.mydreamjob.application;

import com.mydreamjob.application.dto.CompanyResumeFile;
import com.mydreamjob.common.exception.BusinessException;
import com.mydreamjob.common.exception.ErrorCode;
import com.mydreamjob.profile.StudentProfile;
import com.mydreamjob.profile.StudentProfileRepository;
import com.mydreamjob.profile.storage.ResumeFilenameSanitizer;
import com.mydreamjob.profile.storage.ResumeStorageService;
import com.mydreamjob.profile.storage.ResumeOwnershipVerifier;
import lombok.RequiredArgsConstructor;
import lombok.extern.slf4j.Slf4j;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

import java.util.Set;

/**
 * S03-B 企业读取候选人简历文件。
 *
 * <p>本类只负责「授权已通过之后」的文件读取与响应构建：
 * 授权全部由 {@link CompanyResumeAccessPolicy} 完成，**任何拒绝路径都不会走到
 * {@link ResumeStorageService#read}</strong>。</p>
 *
 * <p>简历正文、存储路径、原始文件名与学生标识都不写入日志、审计或异常。</p>
 */
@Slf4j
@Service
@RequiredArgsConstructor
public class CompanyResumeService {

    /** Content-Type 白名单：只能来自上传时已校验的三种简历类型。 */
    static final Set<String> ALLOWED_CONTENT_TYPES = Set.of(
            "application/pdf",
            "application/msword",
            "application/vnd.openxmlformats-officedocument.wordprocessingml.document");

    static final String FALLBACK_CONTENT_TYPE = "application/octet-stream";

    private final CompanyResumeAccessPolicy accessPolicy;
    private final StudentProfileRepository profileRepository;
    private final ResumeStorageService resumeStorageService;
    private final ResumeOwnershipVerifier resumeOwnership;

    /**
     * 读取该投递对应候选人的简历。
     *
     * @throws BusinessException 授权失败（{@code FORBIDDEN} / {@code APPLICATION_NOT_FOUND}），
     *                           或授权通过但学生没有简历（{@code PROFILE_NOT_FOUND}）
     */
    @Transactional(readOnly = true)
    public CompanyResumeFile load(Long companyUserId, Long applicationId) {
        // 先授权，后读文件：拒绝路径绝不触碰存储。
        CompanyResumeAccessPolicy.Decision decision =
                accessPolicy.authorizeForDownload(companyUserId, applicationId);

        StudentProfile profile = profileRepository.findByUserId(decision.studentUserId())
                .orElseThrow(() -> new BusinessException(ErrorCode.PROFILE_NOT_FOUND));

        String storagePath = profile.getResumeUrl();
        if (storagePath == null || storagePath.isBlank()) {
            throw new BusinessException(ErrorCode.PROFILE_NOT_FOUND);
        }

        // 企业获得的是该候选人的读取授权，不能将历史污染引用当作文件归属证明。
        resumeOwnership.assertOwnedBy(storagePath, decision.studentUserId());
        byte[] content = resumeStorageService.read(storagePath);
        String filename = ResumeFilenameSanitizer.forDownload(profile.getResumeOriginalName(), "resume");
        String contentType = resolveContentType(profile.getResumeContentType());
        return new CompanyResumeFile(content, filename, contentType);
    }

    private String resolveContentType(String stored) {
        return (stored != null && ALLOWED_CONTENT_TYPES.contains(stored)) ? stored : FALLBACK_CONTENT_TYPE;
    }
}