/**
 * 後端 envelope code / data.message → 語言包。
 * 顯示時一律用目前 UI 語系，不直接秀後端英文。
 */

import { useCallback } from "react";
import { useI18n } from "../i18n/I18nContext";
import { translate } from "./i18n/messages";
import { loadUiPrefs } from "./i18n/prefs";
import type { AppLocale } from "./i18n/types";

/** 與 backend internal/response + middleware 對齊 */
export const API_CODES = {
  SUCCESS: 102000,
  BAD_REQUEST: 400001,
  WEAK_PASSWORD: 400003,
  INVALID_CODE: 400004,
  SELF_SUSPEND: 400020,
  LAST_ADMIN: 400021,
  MISSING_AUTH: 401001,
  INVALID_TOKEN: 401002,
  MEMBER_NOT_FOUND_AUTH: 401003,
  BAD_PASSWORD: 401010,
  SUSPENDED: 403001,
  ADMIN_REQUIRED: 403002,
  NOT_FOUND: 404001,
  EMAIL_NOT_REGISTERED: 404002,
  EMAIL_TAKEN: 409001,
  SERVER: 500000,
  NOT_IMPLEMENTED: 501000,
  NETWORK: 0,
} as const;

/** code → messages.ts 的 key */
export const API_ERROR_I18N_KEY: Record<number, string> = {
  [API_CODES.BAD_REQUEST]: "api.err.400001",
  [API_CODES.WEAK_PASSWORD]: "api.err.400003",
  [API_CODES.INVALID_CODE]: "api.err.400004",
  [API_CODES.SELF_SUSPEND]: "api.err.400020",
  [API_CODES.LAST_ADMIN]: "api.err.400021",
  [API_CODES.MISSING_AUTH]: "api.err.401001",
  [API_CODES.INVALID_TOKEN]: "api.err.401002",
  [API_CODES.MEMBER_NOT_FOUND_AUTH]: "api.err.401003",
  [API_CODES.BAD_PASSWORD]: "api.err.401010",
  [API_CODES.SUSPENDED]: "api.err.403001",
  [API_CODES.ADMIN_REQUIRED]: "api.err.403002",
  [API_CODES.NOT_FOUND]: "api.err.404001",
  [API_CODES.EMAIL_NOT_REGISTERED]: "api.err.404002",
  [API_CODES.EMAIL_TAKEN]: "api.err.409001",
  [API_CODES.SERVER]: "api.err.500000",
  [API_CODES.NOT_IMPLEMENTED]: "api.err.501000",
  [API_CODES.NETWORK]: "api.err.network",
};

export function i18nKeyForApiCode(code: number): string | undefined {
  return API_ERROR_I18N_KEY[code];
}

/**
 * 後端 data.message（英文固定字）→ 語言包 key。
 * 對齊 apps/backend internal/logic/** 回傳的 Message 字串。
 */
const API_OK_MESSAGE_KEY: Record<string, string> = {
  "verification code sent": "api.ok.verifySent",
  "verification code issued": "api.ok.verifyIssued",
  "reset code sent": "api.ok.resetSent",
  "password updated": "api.ok.passwordUpdated",
  "logged out": "api.ok.loggedOut",
  "unbound": "api.ok.unbound",
  // 舊文案相容
  "if the account exists, a reset code was issued": "api.ok.resetSent",
};

export function i18nKeyForApiOkMessage(raw: string): string | undefined {
  const k = raw.trim().toLowerCase();
  if (!k) return undefined;
  // exact
  if (API_OK_MESSAGE_KEY[raw.trim()]) return API_OK_MESSAGE_KEY[raw.trim()];
  if (API_OK_MESSAGE_KEY[k]) return API_OK_MESSAGE_KEY[k];
  // case-insensitive scan
  for (const [en, key] of Object.entries(API_OK_MESSAGE_KEY)) {
    if (en.toLowerCase() === k) return key;
  }
  return undefined;
}

/** 成功 data.message → 目前語系文案；未知則回原文或 fallbackKey */
export function messageForApiOk(
  raw: string | undefined | null,
  fallbackKey = "common.success",
  locale?: AppLocale,
): string {
  const loc = locale ?? currentLocale();
  const text = (raw || "").trim();
  if (!text) return translate(loc, fallbackKey);
  const key = i18nKeyForApiOkMessage(text);
  if (key) return translate(loc, key);
  return text;
}

function currentLocale(): AppLocale {
  try {
    return loadUiPrefs().locale;
  } catch {
    return "zh-TW";
  }
}

/**
 * 依業務碼 + 目前語系取文案（給非 React 層，如 http client）。
 * 已知 code 只用語言包；未知才回 fallback 或 api.err.unknown。
 */
export function messageForApiCode(
  code: number,
  _fallback?: string,
  locale?: AppLocale,
): string {
  const loc = locale ?? currentLocale();
  const key = i18nKeyForApiCode(code);
  if (key) return translate(loc, key);
  return translate(loc, "api.err.unknown");
}

type ErrLike = {
  code?: number;
  message?: string;
  name?: string;
};

/** 從 thrown value 取可顯示字串（依目前語言包） */
export function formatThrownError(err: unknown, fallbackKey = "common.error"): string {
  const loc = currentLocale();
  const e = err as ErrLike | null;
  if (e && typeof e === "object" && e.code != null && !Number.isNaN(Number(e.code))) {
    const code = Number(e.code);
    const key = i18nKeyForApiCode(code);
    if (key) return translate(loc, key);
    // 未知業務碼：不顯示後端英文，改通用錯誤
    return translate(loc, "api.err.unknown");
  }
  // mock 前端 throw 的中文 Error，或無 code 的例外
  if (err instanceof Error && err.message && err.name !== "ApiError") {
    return err.message;
  }
  if (err instanceof Error && err.name === "ApiError") {
    // 有 ApiError 但沒 code 時
    return translate(loc, "api.err.unknown");
  }
  return translate(loc, fallbackKey);
}

/**
 * React hook：用目前 I18n 語言包（t / locale）格式化錯誤。
 * 頁面 catch 請用這個，確保跟 UI 語系完全一致。
 */
export function useFormatApiError() {
  const { t, locale } = useI18n();
  return useCallback(
    (err: unknown, fallbackKey = "common.error"): string => {
      const e = err as ErrLike | null;
      if (e && typeof e === "object" && e.code != null && !Number.isNaN(Number(e.code))) {
        const key = i18nKeyForApiCode(Number(e.code));
        if (key) return t(key);
        return t("api.err.unknown");
      }
      if (err instanceof Error && err.message && err.name !== "ApiError") {
        return err.message;
      }
      return t(fallbackKey);
    },
    [t, locale],
  );
}

/**
 * React hook：後端成功 message → 目前語言包。
 * 例：verification code sent → 「驗證碼已寄出」
 */
export function useFormatApiOk() {
  const { t, locale } = useI18n();
  return useCallback(
    (raw: string | undefined | null, fallbackKey = "common.success"): string => {
      const text = (raw || "").trim();
      if (!text) return t(fallbackKey);
      const key = i18nKeyForApiOkMessage(text);
      if (key) return t(key);
      return text;
    },
    [t, locale],
  );
}