import { getRuntimePlatform } from './env';
import { ensureJssdkReady } from './jssdk';
import type { WeixinSdkConfig } from './types';

export type ChooseWechatImageOptions = {
  count?: number;
  sourceType?: Array<'album' | 'camera'>;
};

function base64ToFile(base64: string, fileName: string): File {
  const normalized = base64.startsWith('data:')
    ? base64
    : `data:image/jpeg;base64,${base64.replace(/\s/g, '')}`;
  const [header, body] = normalized.split(',');
  const mime = header.match(/:(.*?);/)?.[1] ?? 'image/jpeg';
  const binary = atob(body);
  const bytes = new Uint8Array(binary.length);
  for (let i = 0; i < binary.length; i++) bytes[i] = binary.charCodeAt(i);
  return new File([bytes], fileName, { type: mime });
}

function localIdToFile(localId: string): Promise<File> {
  return new Promise((resolve, reject) => {
    if (!window.wx?.getLocalImgData) {
      reject(new Error('微信 getLocalImgData 不可用'));
      return;
    }
    window.wx.getLocalImgData({
      localId,
      success: (res) => {
        try {
          resolve(base64ToFile(res.localData, `wx-${Date.now()}.jpg`));
        } catch (e) {
          reject(e instanceof Error ? e : new Error('图片解析失败'));
        }
      },
      fail: (err) => reject(new Error(err.errMsg || '读取图片失败')),
    });
  });
}

/** 微信内选图（相册/拍照），返回 File 列表；非微信环境返回 null */
export async function chooseWechatImages(
  config: WeixinSdkConfig,
  options: ChooseWechatImageOptions = {},
): Promise<File[] | null> {
  const platform = getRuntimePlatform();
  if (platform === 'browser') return null;

  const count = options.count ?? 1;
  const sourceType = options.sourceType ?? ['album', 'camera'];

  if (platform === 'wechat-h5') {
    const pageUrl = typeof window !== 'undefined' ? window.location.href.split('#')[0] : '';
    await ensureJssdkReady({
      apiBase: config.apiBase ?? '/api/v1',
      clientApp: config.clientApp,
      getAccessToken: config.getAccessToken,
      url: pageUrl,
      jsApiList: ['chooseImage', 'getLocalImgData'],
    });
    if (!window.wx?.chooseImage) {
      throw new Error('微信选图接口不可用，请刷新页面后重试');
    }

    const localIds = await new Promise<string[]>((resolve, reject) => {
      window.wx!.chooseImage!({
        count,
        sizeType: ['compressed'],
        sourceType,
        success: (res) => resolve(res.localIds ?? []),
        fail: (err) => reject(new Error(err.errMsg || '无法打开相册')),
      });
    });

    const files: File[] = [];
    for (const localId of localIds) {
      files.push(await localIdToFile(localId));
    }
    return files;
  }

  return null;
}

export function canUseWechatChooseImage(): boolean {
  return getRuntimePlatform() !== 'browser';
}