// /composables/useLocalizedCollection.ts
import type { Collections } from "@nuxt/content";

export type UseLocalizedOptions = {
  /** 默认 locale -> suffix 映射 */
  localeMap?: Record<string, string>;
  /** 回退 locale 的 suffix（例如 'en'） */
  fallbackSuffix?: string;
  /** 当找不到内容时是否抛错，默认 true */
  throwOnMissing?: boolean;
  /** useAsyncData 的 key 前缀（默认等于 baseName） */
  keyPrefix?: string;
};

function asCollectionKey(key: string) {
  return key as keyof Collections;
}

/**
 * 带类型安全的多语言内容加载器
 * @example
 * const { data: page } = await useLocalizedCollection('index')
 */
export function useLocalizedCollection<
  B extends string, // 基础名称
>(baseName: B, opts: UseLocalizedOptions = {}) {
  const { locale } = useI18n();

  const localeMap = opts.localeMap ?? { en: "en", "zh-CN": "zh" };
  const fallbackSuffix = opts.fallbackSuffix ?? "en";
  const keyPrefix = opts.keyPrefix ?? baseName;
  const throwOnMissing = opts.throwOnMissing ?? true;

  // 🔥 自动推断对应集合类型
  type LocalizedKey = keyof {
    [K in keyof Collections as K extends `${B}_${string}` ? K : never]: any;
  };
  type Schema = Collections[LocalizedKey];

  return useAsyncData<Schema | null>(
    `${keyPrefix}-${locale.value}`,
    async () => {
      const suffix =
        localeMap[locale.value] ?? locale.value.split("-")[0] ?? "en";
      const key = asCollectionKey(`${baseName}_${suffix}`);
      let content = (await queryCollection(key).first()) as Schema | null;

      if (!content && suffix !== fallbackSuffix) {
        const fallbackKey = asCollectionKey(`${baseName}_${fallbackSuffix}`);
        content = (await queryCollection(fallbackKey).first()) as Schema | null;
      }

      return content;
    },
    { watch: [locale] }
  ).then((res) => {
    if (throwOnMissing && res && !res.data?.value) {
      throw createError({
        statusCode: 404,
        statusMessage: `Page not found: ${baseName} for locale ${locale.value}`,
        fatal: true,
      });
    }
    return res;
  });
}