import {
  API_RESPONSE_ENVELOPE_HEADER,
  API_RESPONSE_ENVELOPE_VERSION,
  API_VERSION,
  type ApiErrorPayload,
  type ApiMeta,
  parseApiErrorMessage,
  unwrapApiResponse,
} from '../../packages/shared/src/http';

const ACCESS_TOKEN_KEY = 'genarrative.auth.access-token.v1';
const AUTO_AUTH_USERNAME_KEY = 'genarrative.auth.auto-username.v1';
const AUTO_AUTH_PASSWORD_KEY = 'genarrative.auth.auto-password.v1';
export const AUTH_STATE_EVENT = 'genarrative-auth-state-changed';
const REQUEST_ID_HEADER = 'x-request-id';
const API_VERSION_HEADER = 'x-api-version';
const ROUTE_VERSION_HEADER = 'x-route-version';
const DEFAULT_RETRYABLE_STATUS_CODES = [408, 425, 429, 502, 503, 504];
const DEFAULT_SAFE_RETRY_METHODS = new Set(['GET', 'HEAD', 'OPTIONS']);

export type ApiRetryOptions = {
  maxRetries?: number;
  baseDelayMs?: number;
  maxDelayMs?: number;
  retryableStatusCodes?: number[];
  retryUnsafeMethods?: boolean;
  allowRetryMethods?: string[];
};

export type ApiRequestOptions = {
  retry?: ApiRetryOptions;
  skipAuth?: boolean;
  omitEnvelopeHeader?: boolean;
  skipRefresh?: boolean;
};

type ResolvedRetryOptions = {
  maxRetries: number;
  baseDelayMs: number;
  maxDelayMs: number;
  retryableStatusCodes: Set<number>;
  retryUnsafeMethods: boolean;
  allowRetryMethods: Set<string>;
  method: string;
};

type ParsedApiErrorShape = {
  code: string;
  details: Record<string, unknown> | null;
  meta: Partial<ApiMeta>;
};

type RefreshTokenResponse = {
  token: string;
};

function isRecord(value: unknown): value is Record<string, unknown> {
  return typeof value === 'object' && value !== null;
}

function normalizeHeaders(headers?: HeadersInit) {
  const nextHeaders: Record<string, string> = {};

  if (typeof Headers !== 'undefined' && headers instanceof Headers) {
    headers.forEach((value, key) => {
      nextHeaders[key] = value;
    });
    return nextHeaders;
  }

  if (Array.isArray(headers)) {
    for (const [key, value] of headers) {
      nextHeaders[key] = value;
    }
    return nextHeaders;
  }

  if (headers) {
    Object.assign(nextHeaders, headers);
  }

  return nextHeaders;
}

function coerceMeta(value: unknown): Partial<ApiMeta> {
  if (!isRecord(value)) {
    return {};
  }

  return {
    apiVersion:
      typeof value.apiVersion === 'string' && value.apiVersion.trim()
        ? value.apiVersion.trim()
        : undefined,
    requestId:
      typeof value.requestId === 'string' && value.requestId.trim()
        ? value.requestId.trim()
        : undefined,
    routeVersion:
      typeof value.routeVersion === 'string' && value.routeVersion.trim()
        ? value.routeVersion.trim()
        : undefined,
    operation:
      typeof value.operation === 'string' && value.operation.trim()
        ? value.operation.trim()
        : value.operation === null
          ? null
          : undefined,
    latencyMs:
      typeof value.latencyMs === 'number' && Number.isFinite(value.latencyMs)
        ? value.latencyMs
        : undefined,
    timestamp:
      typeof value.timestamp === 'string' && value.timestamp.trim()
        ? value.timestamp.trim()
        : undefined,
  };
}

function parseApiErrorShape(rawText: string): ParsedApiErrorShape | null {
  if (!rawText.trim()) {
    return null;
  }

  try {
    const parsed = JSON.parse(rawText) as
      | {
          error?: ApiErrorPayload;
          meta?: Partial<ApiMeta>;
          code?: string;
          details?: Record<string, unknown> | null;
        }
      | Record<string, unknown>;

    if (isRecord(parsed.error)) {
      return {
        code:
          typeof parsed.error.code === 'string' && parsed.error.code.trim()
            ? parsed.error.code.trim()
            : 'HTTP_ERROR',
        details:
          isRecord(parsed.error.details) || parsed.error.details === null
            ? (parsed.error.details as Record<string, unknown> | null)
            : null,
        meta: coerceMeta(parsed.meta),
      };
    }

    if (typeof parsed.code === 'string' && parsed.code.trim()) {
      return {
        code: parsed.code.trim(),
        details:
          isRecord(parsed.details) || parsed.details === null
            ? (parsed.details as Record<string, unknown> | null)
            : null,
        meta: coerceMeta(parsed.meta),
      };
    }
  } catch {
    // Ignore malformed json responses.
  }

  return null;
}

function createAbortError() {
  if (typeof DOMException !== 'undefined') {
    return new DOMException('The operation was aborted.', 'AbortError');
  }

  const error = new Error('The operation was aborted.');
  error.name = 'AbortError';
  return error;
}

async function waitForRetry(ms: number, signal?: AbortSignal) {
  if (ms <= 0) {
    return;
  }

  await new Promise<void>((resolve, reject) => {
    const timeoutId = setTimeout(() => {
      cleanup();
      resolve();
    }, ms);

    const onAbort = () => {
      cleanup();
      reject(signal?.reason ?? createAbortError());
    };

    const cleanup = () => {
      clearTimeout(timeoutId);
      signal?.removeEventListener('abort', onAbort);
    };

    if (signal?.aborted) {
      cleanup();
      reject(signal.reason ?? createAbortError());
      return;
    }

    signal?.addEventListener('abort', onAbort, { once: true });
  });
}

function resolveRetryOptions(
  method: string,
  retry?: ApiRetryOptions,
): ResolvedRetryOptions {
  const normalizedMethod = method.toUpperCase();
  const defaultMaxRetries = DEFAULT_SAFE_RETRY_METHODS.has(normalizedMethod)
    ? 1
    : 0;

  return {
    maxRetries:
      typeof retry?.maxRetries === 'number' && retry.maxRetries >= 0
        ? Math.floor(retry.maxRetries)
        : defaultMaxRetries,
    baseDelayMs:
      typeof retry?.baseDelayMs === 'number' && retry.baseDelayMs > 0
        ? retry.baseDelayMs
        : 250,
    maxDelayMs:
      typeof retry?.maxDelayMs === 'number' && retry.maxDelayMs > 0
        ? retry.maxDelayMs
        : 1500,
    retryableStatusCodes: new Set(
      retry?.retryableStatusCodes?.length
        ? retry.retryableStatusCodes
        : DEFAULT_RETRYABLE_STATUS_CODES,
    ),
    retryUnsafeMethods: retry?.retryUnsafeMethods === true,
    allowRetryMethods: new Set(
      (retry?.allowRetryMethods ?? []).map((value) => value.toUpperCase()),
    ),
    method: normalizedMethod,
  };
}

function shouldRetryResponse(
  status: number,
  attempt: number,
  retry: ResolvedRetryOptions,
) {
  if (attempt >= retry.maxRetries) {
    return false;
  }

  if (!retry.retryableStatusCodes.has(status)) {
    return false;
  }

  return (
    retry.retryUnsafeMethods ||
    DEFAULT_SAFE_RETRY_METHODS.has(retry.method) ||
    retry.allowRetryMethods.has(retry.method)
  );
}

export function isAbortError(error: unknown) {
  return (
    error instanceof Error &&
    (error.name === 'AbortError' ||
      (typeof DOMException !== 'undefined' &&
        error instanceof DOMException &&
        error.name === 'AbortError'))
  );
}

function shouldRetryError(error: unknown, attempt: number, retry: ResolvedRetryOptions) {
  if (attempt >= retry.maxRetries || isAbortError(error)) {
    return false;
  }

  return error instanceof TypeError;
}

function buildRetryDelayMs(attempt: number, retry: ResolvedRetryOptions) {
  return Math.min(retry.maxDelayMs, retry.baseDelayMs * Math.max(1, attempt));
}

export class ApiClientError extends Error {
  status: number;
  code: string;
  details: Record<string, unknown> | null;
  meta: ApiMeta;
  responseText: string;

  constructor(params: {
    message: string;
    status: number;
    code: string;
    details?: Record<string, unknown> | null;
    meta?: Partial<ApiMeta>;
    responseText?: string;
  }) {
    super(params.message);
    this.name = 'ApiClientError';
    this.status = params.status;
    this.code = params.code;
    this.details = params.details ?? null;
    this.meta = {
      apiVersion: params.meta?.apiVersion ?? API_VERSION,
      requestId: params.meta?.requestId,
      routeVersion: params.meta?.routeVersion,
      operation: params.meta?.operation,
      latencyMs: params.meta?.latencyMs,
      timestamp: params.meta?.timestamp,
    };
    this.responseText = params.responseText ?? '';
  }
}

function canUseLocalStorage() {
  return typeof window !== 'undefined' && typeof window.localStorage !== 'undefined';
}

function emitAuthStateChange() {
  if (typeof window === 'undefined') {
    return;
  }

  if (typeof CustomEvent === 'function') {
    window.dispatchEvent(new CustomEvent(AUTH_STATE_EVENT));
    return;
  }

  if (typeof Event === 'function') {
    window.dispatchEvent(new Event(AUTH_STATE_EVENT));
  }
}

export function getStoredAccessToken() {
  if (!canUseLocalStorage()) {
    return '';
  }

  return window.localStorage.getItem(ACCESS_TOKEN_KEY)?.trim() || '';
}

export function setStoredAccessToken(
  token: string,
  options: {
    emit?: boolean;
  } = {},
) {
  if (!canUseLocalStorage()) {
    return;
  }

  const nextToken = token.trim();
  if (nextToken) {
    window.localStorage.setItem(ACCESS_TOKEN_KEY, nextToken);
  } else {
    window.localStorage.removeItem(ACCESS_TOKEN_KEY);
  }
  if (options.emit !== false) {
    emitAuthStateChange();
  }
}

export function clearStoredAccessToken(
  options: {
    emit?: boolean;
  } = {},
) {
  if (!canUseLocalStorage()) {
    return;
  }

  window.localStorage.removeItem(ACCESS_TOKEN_KEY);
  if (options.emit !== false) {
    emitAuthStateChange();
  }
}

export function getStoredAutoAuthCredentials() {
  if (!canUseLocalStorage()) {
    return null;
  }

  const username = window.localStorage.getItem(AUTO_AUTH_USERNAME_KEY)?.trim() || '';
  const password = window.localStorage.getItem(AUTO_AUTH_PASSWORD_KEY)?.trim() || '';

  if (!username || !password) {
    return null;
  }

  return {
    username,
    password,
  };
}

export function setStoredAutoAuthCredentials(credentials: {
  username: string;
  password: string;
}) {
  if (!canUseLocalStorage()) {
    return;
  }

  window.localStorage.setItem(AUTO_AUTH_USERNAME_KEY, credentials.username.trim());
  window.localStorage.setItem(AUTO_AUTH_PASSWORD_KEY, credentials.password.trim());
}

export function clearStoredAutoAuthCredentials() {
  if (!canUseLocalStorage()) {
    return;
  }

  window.localStorage.removeItem(AUTO_AUTH_USERNAME_KEY);
  window.localStorage.removeItem(AUTO_AUTH_PASSWORD_KEY);
  emitAuthStateChange();
}

function withAuthorizationHeaders(
  headers?: HeadersInit,
  options: Pick<ApiRequestOptions, 'omitEnvelopeHeader' | 'skipAuth'> = {},
) {
  const nextHeaders = normalizeHeaders(headers);
  const token = getStoredAccessToken();
  if (token && !options.skipAuth) {
    nextHeaders.Authorization = `Bearer ${token}`;
  }
  if (!options.omitEnvelopeHeader) {
    nextHeaders[API_RESPONSE_ENVELOPE_HEADER] = API_RESPONSE_ENVELOPE_VERSION;
  }
  return nextHeaders;
}

let refreshAccessTokenPromise: Promise<string> | null = null;

async function refreshAccessToken() {
  if (refreshAccessTokenPromise) {
    return refreshAccessTokenPromise;
  }

  refreshAccessTokenPromise = (async () => {
    const response = await fetch('/api/auth/refresh', {
      method: 'POST',
      credentials: 'same-origin',
      headers: {
        [API_RESPONSE_ENVELOPE_HEADER]: API_RESPONSE_ENVELOPE_VERSION,
      },
    });

    if (!response.ok) {
      clearStoredAccessToken();
      throw await buildApiClientError(response, '刷新登录状态失败');
    }

    const responseText = await response.text();
    const payload = responseText
      ? unwrapApiResponse<RefreshTokenResponse>(
          JSON.parse(responseText) as RefreshTokenResponse,
        )
      : null;

    if (!payload?.token?.trim()) {
      clearStoredAccessToken();
      throw new Error('刷新登录状态失败');
    }

    setStoredAccessToken(payload.token, { emit: false });
    return payload.token;
  })();

  try {
    return await refreshAccessTokenPromise;
  } finally {
    refreshAccessTokenPromise = null;
  }
}

export async function fetchWithApiAuth(
  input: string,
  init: RequestInit = {},
  options: ApiRequestOptions = {},
) {
  const method = (init.method ?? 'GET').toUpperCase();
  const retry = resolveRetryOptions(method, options.retry);
  let attempt = 0;
  let refreshAttempted = false;

  for (;;) {
    try {
      const response = await fetch(input, {
        credentials: 'same-origin',
        ...init,
        headers: withAuthorizationHeaders(init.headers, options),
      });

      if (
        response.status === 401 &&
        !options.skipAuth &&
        !options.skipRefresh &&
        !refreshAttempted
      ) {
        try {
          await refreshAccessToken();
          refreshAttempted = true;
          continue;
        } catch {
          clearStoredAccessToken();
        }
      } else if (response.status === 401) {
        clearStoredAccessToken();
      }

      if (!shouldRetryResponse(response.status, attempt, retry)) {
        return response;
      }
    } catch (error) {
      if (!shouldRetryError(error, attempt, retry)) {
        throw error;
      }
    }

    attempt += 1;
    await waitForRetry(
      buildRetryDelayMs(attempt, retry),
      init.signal ?? undefined,
    );
  }
}

async function buildApiClientError(
  response: Response,
  fallbackMessage: string,
) {
  const responseText = await response.text();
  const parsedError = parseApiErrorShape(responseText);

  return new ApiClientError({
    message: parseApiErrorMessage(responseText, fallbackMessage),
    status: response.status,
    code: parsedError?.code ?? `HTTP_${response.status || 0}`,
    details: parsedError?.details ?? null,
    meta: {
      apiVersion:
        parsedError?.meta.apiVersion ??
        response.headers.get(API_VERSION_HEADER) ??
        API_VERSION,
      requestId:
        parsedError?.meta.requestId ??
        response.headers.get(REQUEST_ID_HEADER) ??
        undefined,
      routeVersion:
        parsedError?.meta.routeVersion ??
        response.headers.get(ROUTE_VERSION_HEADER) ??
        undefined,
      operation: parsedError?.meta.operation,
      latencyMs: parsedError?.meta.latencyMs,
      timestamp: parsedError?.meta.timestamp,
    },
    responseText,
  });
}

export async function requestJson<T>(
  url: string,
  init: RequestInit,
  fallbackMessage: string,
  options: ApiRequestOptions = {},
): Promise<T> {
  const response = await fetchWithApiAuth(url, init, options);

  if (!response.ok) {
    throw await buildApiClientError(response, fallbackMessage);
  }

  const responseText = await response.text();

  return responseText
    ? unwrapApiResponse<T>(JSON.parse(responseText) as T)
    : (null as T);
}