import { buildRuntimeAuthHeaders } from './runtime-auth';
import { getRuntimeUrlResolver, type RuntimeUrlQuery } from './runtime-url';

export interface RuntimeFetchOptions extends RequestInit {
  query?: RuntimeUrlQuery;
}

const shouldResolveApiPath = (input: string): boolean => {
  return input.startsWith('/api/') || input === '/api' || input.startsWith('/auth/') || input === '/auth' || input === '/health';
};

const getCurrentOrigin = (): string => {
  if (typeof window === 'undefined') return '';
  return window.location.origin || '';
};

const isCurrentWindowUrl = (url: URL): boolean => {
  if (typeof window === 'undefined') return false;
  const currentOrigin = getCurrentOrigin();
  if (currentOrigin && url.origin === currentOrigin) return true;
  try {
    const current = new URL(window.location.href || currentOrigin);
    return url.protocol === current.protocol && url.host === current.host;
  } catch {
    return false;
  }
};

const isAbsoluteUrl = (value: string): boolean => /^[a-z][a-z\d+.-]*:\/\//i.test(value);

const appendRuntimeQuery = (url: URL, query?: RuntimeUrlQuery): void => {
  if (!query) return;
  const entries = query instanceof URLSearchParams ? Array.from(query.entries()) : Object.entries(query);
  for (const [key, value] of entries) {
    if (value === null || value === undefined) continue;
    url.searchParams.set(key, String(value));
  }
};

const isActiveRuntimeServiceUrl = (url: URL): boolean => {
  try {
    const apiBase = getRuntimeUrlResolver().api('/api');
    if (!/^[a-z][a-z\d+.-]*:\/\//i.test(apiBase)) return false;
    const base = new URL(apiBase);
    if (url.origin !== base.origin) return false;
    return shouldResolveApiPath(url.pathname);
  } catch {
    return false;
  }
};

const shouldResolveFetchInput = (input: string): boolean => {
  if (shouldResolveApiPath(input)) return true;
  if (!/^[a-z][a-z\d+.-]*:\/\//i.test(input)) return false;
  try {
    const url = new URL(input);
    return isCurrentWindowUrl(url) && shouldResolveApiPath(url.pathname);
  } catch {
    return false;
  }
};

const buildRuntimeFetchUrlFromAbsolute = (input: string, query?: RuntimeUrlQuery): string => {
  try {
    const url = new URL(input);
    if (!isCurrentWindowUrl(url)) return input;
    const rewritten = buildRuntimeFetchUrl(`${url.pathname}${url.search}`, query);
    if (!isAbsoluteUrl(rewritten) && (url.protocol === 'http:' || url.protocol === 'https:')) {
      appendRuntimeQuery(url, query);
      return url.toString();
    }
    return url.hash ? `${rewritten}${url.hash}` : rewritten;
  } catch {
    return input;
  }
};

export const buildRuntimeFetchUrl = (input: string, query?: RuntimeUrlQuery): string => {
  if (input === '/health') return getRuntimeUrlResolver().health(query);
  if (input.startsWith('/auth/') || input === '/auth') return getRuntimeUrlResolver().auth(input, query);
  if (shouldResolveApiPath(input)) return getRuntimeUrlResolver().api(input, query);
  if (/^[a-z][a-z\d+.-]*:\/\//i.test(input)) return buildRuntimeFetchUrlFromAbsolute(input, query);
  return input;
};

const shouldAttachRuntimeAuth = (input: string | URL | Request): boolean => {
  const raw = input instanceof Request ? input.url : input.toString();
  if (!isAbsoluteUrl(raw)) {
    return shouldResolveApiPath(raw);
  }

  try {
    return isActiveRuntimeServiceUrl(new URL(raw));
  } catch {
    return false;
  }
};

const mergeHeaders = async (inputHeaders?: HeadersInit, initHeaders?: HeadersInit, attachAuth = true): Promise<Headers> => {
  const headers = new Headers(inputHeaders);
  if (initHeaders) {
    new Headers(initHeaders).forEach((value, key) => headers.set(key, value));
  }
  if (!attachAuth) {
    return headers;
  }
  return buildRuntimeAuthHeaders(headers);
};

const resolveRuntimeFetchInput = (input: string | URL | Request, query?: RuntimeUrlQuery): string | URL | Request => {
  if (typeof input === 'string') {
    return buildRuntimeFetchUrl(input, query);
  }

  if (input instanceof URL) {
    return buildRuntimeFetchUrl(input.toString(), query);
  }

  const target = buildRuntimeFetchUrl(input.url, query);
  return target === input.url ? input : new Request(target, input);
};

export const runtimeFetch = async (input: string | URL | Request, init: RuntimeFetchOptions = {}): Promise<Response> => {
  const { query, ...requestInit } = init;
  const resolvedInput = resolveRuntimeFetchInput(input, query);
  const inputHeaders = resolvedInput instanceof Request ? resolvedInput.headers : undefined;
  const headers = await mergeHeaders(inputHeaders, requestInit.headers, shouldAttachRuntimeAuth(resolvedInput));

  if (resolvedInput instanceof Request) {
    return fetch(new Request(resolvedInput, { ...requestInit, headers }));
  }

  return fetch(resolvedInput, {
    ...requestInit,
    headers,
  });
};

let runtimeFetchBridgeInstalled = false;

export const installRuntimeFetchBridge = (): void => {
  if (runtimeFetchBridgeInstalled || typeof window === 'undefined') return;
  runtimeFetchBridgeInstalled = true;

  const nativeFetch = window.fetch.bind(window);
  window.fetch = async (input: RequestInfo | URL, init?: RequestInit): Promise<Response> => {
    if (typeof input === 'string') {
      if (!shouldResolveFetchInput(input)) {
        try {
          const url = new URL(input);
          if (isActiveRuntimeServiceUrl(url)) {
            const headers = await mergeHeaders(undefined, init?.headers);
            return nativeFetch(input, { ...init, headers });
          }
        } catch {
          // Non-URL fetch inputs should fall through unchanged.
        }
        return nativeFetch(input, init);
      }
      const headers = await mergeHeaders(undefined, init?.headers);
      return nativeFetch(buildRuntimeFetchUrl(input), { ...init, headers });
    }

    if (input instanceof URL) {
      const raw = input.toString();
      if (!shouldResolveFetchInput(raw)) {
        if (isActiveRuntimeServiceUrl(input)) {
          const headers = await mergeHeaders(undefined, init?.headers);
          return nativeFetch(input, { ...init, headers });
        }
        return nativeFetch(input, init);
      }
      const headers = await mergeHeaders(undefined, init?.headers);
      return nativeFetch(buildRuntimeFetchUrl(raw), { ...init, headers });
    }

    if (input instanceof Request) {
      if (!shouldResolveFetchInput(input.url)) {
        try {
          const url = new URL(input.url);
          if (isActiveRuntimeServiceUrl(url)) {
            const headers = await mergeHeaders(input.headers, init?.headers);
            return nativeFetch(new Request(input, { ...init, headers }));
          }
        } catch {
          // Non-URL request inputs should fall through unchanged.
        }
        return nativeFetch(input, init);
      }
      const headers = await mergeHeaders(input.headers, init?.headers);
      const target = buildRuntimeFetchUrl(input.url);
      const request = target === input.url ? input : new Request(target, input);
      return nativeFetch(new Request(request, { ...init, headers }));
    }

    return nativeFetch(input, init);
  };
};