import { BadRequestException, NotFoundException } from '@nestjs/common';
import { extname } from 'node:path';

/** 上传文件的最小信息（兼容 multer 的 Express.Multer.File 与测试替身） */
export interface UploadedFileLike {
  originalname: string;
  mimetype: string;
  path: string;
  size: number;
}

/**
 * 修正 multipart 文件名编码。
 *
 * busboy/multer 按 latin1 解出 `originalname`，含中文/日文/emoji 的文件名会变成
 * 乱码（例如 `模型_初音…zip` → `模å_åé³…`）。这里用 latin1 还原原始字节再按
 * UTF-8 解一次；只有当结果不含替换字符、且原文确实含高位字节时才替换，
 * 避免破坏真正的 latin1 文件名。
 */
export function decodeUploadName(rawName: string): string {
  if (![...rawName].some((ch) => ch.charCodeAt(0) > 0x7f)) return rawName;
  const restored = Buffer.from(rawName, 'latin1').toString('utf8');
  if (restored.includes('\uFFFD')) return rawName;
  return restored;
}

export function requireUploadedFile(file: UploadedFileLike | undefined, label = 'file'): UploadedFileLike {
  if (!file) throw new BadRequestException(`缺少上传文件字段 ${label}`);
  if (!file.path) throw new BadRequestException('上传文件未落盘');
  return { ...file, originalname: decodeUploadName(file.originalname) };
}

/** 按扩展名白名单解析格式；不在白名单内一律 422 */
export function resolveFormatByExtension(
  originalName: string,
  map: Record<string, string>,
  kindLabel: string,
): { ext: string; format: string } {
  const ext = extname(originalName).toLowerCase();
  const format = map[ext];
  if (!format) {
    throw new BadRequestException(
      `${kindLabel}格式不支持：${ext || '(无扩展名)'}，允许：${Object.keys(map).join(', ')}`,
    );
  }
  return { ext, format };
}

export function parseOptionalInt(value: unknown, field: string): number | undefined {
  if (value === undefined || value === null || value === '') return undefined;
  const num = Number(value);
  if (!Number.isFinite(num)) throw new BadRequestException(`${field} 必须为数字`);
  return Math.trunc(num);
}

export function parseOptionalNumber(value: unknown, field: string): number | undefined {
  if (value === undefined || value === null || value === '') return undefined;
  const num = Number(value);
  if (!Number.isFinite(num)) throw new BadRequestException(`${field} 必须为数字`);
  return num;
}

export function parseOptionalBool(value: unknown): boolean {
  if (value === undefined || value === null || value === '') return false;
  if (typeof value === 'boolean') return value;
  return value === 'true' || value === '1' || value === 1;
}

export function notFound(what: string, id: number | string): NotFoundException {
  return new NotFoundException(`${what} #${id} 不存在`);
}