import type {
  CloudFrontRequestEvent,
  CloudFrontRequestResult,
  CloudFrontHeaders,
} from "aws-lambda";
import { debug } from "./logger.js";

// @ts-ignore
const index = await (() => import("./middleware.js"))();

export async function handler(
  event: CloudFrontRequestEvent
): Promise<CloudFrontRequestResult> {
  const request = event.Records[0].cf.request;
  const { uri, method, headers, querystring, body } = request;
  debug(uri);
  debug(request);
  debug(request.headers);

  // Convert CloudFront request to Node request
  // @ts-ignore Types has not been added for Node 18 native fetch API
  const requestHeaders = new Headers();
  for (const [key, values] of Object.entries(headers)) {
    for (const { value } of values) {
      if (value) {
        requestHeaders.append(key, value);
      }
    }
  }
  const host = headers["host"][0].value;
  const qs = querystring.length > 0 ? `?${querystring}` : "";
  const url = new URL(`${uri}${qs}`, `https://${host}`);
  // @ts-ignore Types has not been added for Node 18 native fetch API
  const nodeRequest = new Request(url.toString(), {
    method,
    headers: requestHeaders,
    body: body?.data
      ? body.encoding === "base64"
        ? Buffer.from(body.data, "base64").toString()
        : body.data
      : undefined,
  });

  // Process request
  const response = await index.default(nodeRequest, {
    waitUntil: () => {},
  });
  debug("middleware response header", response.headers);

  // WORKAROUND: Pass headers from middleware function to server function (AWS specific) — https://github.com/serverless-stack/open-next#workaround-pass-headers-from-middleware-function-to-server-function-aws-specific
  if (response.headers.get("x-middleware-next") === "1") {
    headers["x-op-middleware-request-headers"] = [
      {
        key: "x-op-middleware-request-headers",
        value: getMiddlewareRequestHeaders(response),
      },
    ];
    headers["x-op-middleware-response-headers"] = [
      {
        key: "x-op-middleware-response-headers",
        value: getMiddlewareResponseHeaders(response),
      },
    ];
    return request;
  }

  return {
    status: response.status,
    body: response.body ? await response.text() : undefined,
    headers: httpHeadersToCfHeaders(response.headers),
  };
}

function getMiddlewareRequestHeaders(response: any) {
  const headers: Record<string, string> = {};
  (response.headers.get("x-middleware-override-headers") || "")
    .split(",")
    .filter(Boolean)
    .forEach((key: string) => {
      headers[key] = response.headers.get(`x-middleware-request-${key}`);
    });
  debug("getMiddlewareRequestHeaders", headers);
  return JSON.stringify(headers);
}

function getMiddlewareResponseHeaders(response: any) {
  const headers: Record<string, string> = {};
  response.headers.forEach((value: string, key: string) => {
    if (!key.startsWith("x-middleware-")) {
      headers[key] = value;
    }
  });
  debug("getMiddlewareResponseHeaders", headers);
  return JSON.stringify(headers);
}

function httpHeadersToCfHeaders(httpHeaders: any) {
  const headers: CloudFrontHeaders = {};
  httpHeaders.forEach((value: string, key: string) => {
    headers[key] = [{ key, value }];
  });
  debug("httpHeadersToCfHeaders", headers);
  return headers;
}