package com.tcm.training.admin.upload;

import org.springframework.stereotype.Service;
import org.springframework.util.StringUtils;
import org.springframework.web.multipart.MultipartFile;

import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.time.LocalDate;
import java.time.format.DateTimeFormatter;
import java.util.UUID;

/**
 * 安装包本地存储服务。
 */
@Service
public class LocalAppPackageStorageService {

    private static final DateTimeFormatter DATE_FORMATTER = DateTimeFormatter.ofPattern("yyyy/MM/dd");

    private final LocalUploadProperties localUploadProperties;

    public LocalAppPackageStorageService(LocalUploadProperties localUploadProperties) {
        this.localUploadProperties = localUploadProperties;
    }

    /**
     * 将安装包写入服务器本地目录，并返回可下载地址。
     */
    public UploadFileResult store(MultipartFile file, String platform) throws IOException {
        validateConfig();
        String originalName = file.getOriginalFilename();
        String extension = resolveExtension(originalName);
        String relativePath = buildRelativePath(platform, extension);
        Path targetPath = resolveTargetPath(relativePath);
        Files.createDirectories(targetPath.getParent());
        file.transferTo(targetPath.toFile());
        return new UploadFileResult(buildPublicUrl(relativePath), originalName, relativePath);
    }

    /**
     * 解析安装包最终写入路径。
     */
    Path resolveTargetPath(String relativePath) {
        Path uploadRoot = resolveUploadRoot();
        String normalizedRelativePath = relativePath.replace("/", java.io.File.separator);
        return uploadRoot.resolve(normalizedRelativePath).normalize();
    }

    /**
     * 生成对外下载地址。
     */
    String buildPublicUrl(String relativePath) {
        String baseUrl = trimTrailingSlash(localUploadProperties.getPublicBaseUrl());
        String pathPrefix = ensureLeadingSlash(trimTrailingSlash(localUploadProperties.getPathPrefix()));
        return baseUrl + pathPrefix + "/" + relativePath;
    }

    /**
     * 组装安装包相对路径。
     */
    String buildRelativePath(String platform, String extension) {
        String datePath = LocalDate.now().format(DATE_FORMATTER);
        String fileName = UUID.randomUUID().toString().replace("-", "") + extension;
        return normalizePackageDir() + "/" + platform.toLowerCase() + "/" + datePath + "/" + fileName;
    }

    private Path resolveUploadRoot() {
        String uploadDir = localUploadProperties.getDir();
        if (!StringUtils.hasText(uploadDir)) {
            throw new IllegalArgumentException("本地上传根目录未配置");
        }
        Path uploadRoot = Paths.get(uploadDir).toAbsolutePath().normalize();
        Path storageRoot = uploadRoot.resolve(normalizePackageDir()).normalize();
        if (!storageRoot.startsWith(uploadRoot)) {
            throw new IllegalArgumentException("安装包存储目录必须位于上传根目录下");
        }
        return uploadRoot;
    }

    private void validateConfig() {
        if (!StringUtils.hasText(localUploadProperties.getPublicBaseUrl())) {
            throw new IllegalArgumentException("安装包公网下载地址未配置");
        }
        normalizePackageDir();
        resolveUploadRoot();
    }

    private String normalizePackageDir() {
        String appPackageDir = localUploadProperties.getAppPackageDir();
        if (!StringUtils.hasText(appPackageDir)) {
            throw new IllegalArgumentException("安装包存储目录未配置");
        }
        String normalized = trimSlash(appPackageDir.replace("\\", "/"));
        if (!StringUtils.hasText(normalized)) {
            throw new IllegalArgumentException("安装包存储目录未配置");
        }
        if (normalized.startsWith("..") || normalized.contains("/../")) {
            throw new IllegalArgumentException("安装包存储目录不合法");
        }
        return normalized;
    }

    private String resolveExtension(String originalName) {
        if (!StringUtils.hasText(originalName) || !originalName.contains(".")) {
            return "";
        }
        return originalName.substring(originalName.lastIndexOf(".")).toLowerCase();
    }

    private String trimTrailingSlash(String value) {
        String normalized = value == null ? "" : value.trim();
        while (normalized.endsWith("/")) {
            normalized = normalized.substring(0, normalized.length() - 1);
        }
        return normalized;
    }

    private String ensureLeadingSlash(String value) {
        return value.startsWith("/") ? value : "/" + value;
    }

    private String trimSlash(String value) {
        String normalized = value == null ? "" : value.trim();
        while (normalized.startsWith("/")) {
            normalized = normalized.substring(1);
        }
        while (normalized.endsWith("/")) {
            normalized = normalized.substring(0, normalized.length() - 1);
        }
        return normalized;
    }
}