import type {
  APIGatewayProxyEvent,
  APIGatewayProxyEventV2,
  APIGatewayProxyResult,
  APIGatewayProxyStructuredResultV2,
  Context as APIGWContext,
} from 'aws-lambda';
import type { AnyRouter, inferRouterContext } from '../../core';
import { TRPCError } from '../../error/TRPCError';
import type { HTTPHeaders, ResponseMetaFn } from '../../http/internals/types';
import type { OnErrorFunction } from '../../internals/types';

export type APIGatewayEvent = APIGatewayProxyEvent | APIGatewayProxyEventV2;
export type APIGatewayResult =
  | APIGatewayProxyResult
  | APIGatewayProxyStructuredResultV2;

export type CreateAWSLambdaContextOptions<TEvent extends APIGatewayEvent> = {
  event: TEvent;
  context: APIGWContext;
};
export type AWSLambdaCreateContextFn<
  TRouter extends AnyRouter,
  TEvent extends APIGatewayEvent,
> = ({
  event,
  context,
}: CreateAWSLambdaContextOptions<TEvent>) =>
  | inferRouterContext<TRouter>
  | Promise<inferRouterContext<TRouter>>;

export type AWSLambdaOptions<
  TRouter extends AnyRouter,
  TEvent extends APIGatewayEvent,
> =
  | {
      router: TRouter;
      batching?: {
        enabled: boolean;
      };
      onError?: OnErrorFunction<TRouter, TEvent>;
      responseMeta?: ResponseMetaFn<TRouter>;
    } & (
      | {
          /**
           * @link https://trpc.io/docs/context
           **/
          createContext: AWSLambdaCreateContextFn<TRouter, TEvent>;
        }
      | {
          /**
           * @link https://trpc.io/docs/context
           **/
          createContext?: AWSLambdaCreateContextFn<TRouter, TEvent>;
        }
    );

export function isPayloadV1(
  event: APIGatewayEvent,
): event is APIGatewayProxyEvent {
  return determinePayloadFormat(event) == '1.0';
}
export function isPayloadV2(
  event: APIGatewayEvent,
): event is APIGatewayProxyEventV2 {
  return determinePayloadFormat(event) == '2.0';
}

function determinePayloadFormat(
  event: APIGatewayEvent,
): APIGatewayPayloadFormatVersion {
  // https://docs.aws.amazon.com/apigateway/latest/developerguide/http-api-develop-integrations-lambda.html
  // According to AWS support, version is is extracted from the version property in the event.
  // If there is no version property, then the version is implied as 1.0
  const unknownEvent = event as { version?: string };
  if (typeof unknownEvent.version === 'undefined') {
    return '1.0';
  } else {
    if (['1.0', '2.0'].includes(unknownEvent.version)) {
      return unknownEvent.version as APIGatewayPayloadFormatVersion;
    } else {
      return 'custom';
    }
  }
}

export function getHTTPMethod(event: APIGatewayEvent) {
  if (isPayloadV1(event)) {
    return event.httpMethod;
  }
  if (isPayloadV2(event)) {
    return event.requestContext.http.method;
  }
  throw new TRPCError({
    code: 'INTERNAL_SERVER_ERROR',
    message: UNKNOWN_PAYLOAD_FORMAT_VERSION_ERROR_MESSAGE,
  });
}

export function getPath(event: APIGatewayEvent) {
  if (isPayloadV1(event)) {
    if (!event.pathParameters) {
      // Then this event was not triggered by a resource denoted with {proxy+}
      return event.path.split('/').pop() ?? '';
    }
    const matches = event.resource.matchAll(/\{(.*?)\}/g);
    for (const match of matches) {
      // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
      const group = match[1]!;
      if (group.includes('+') && event.pathParameters) {
        return event.pathParameters[group.replace('+', '')] ?? '';
      }
    }
    return event.path.slice(1);
  }
  if (isPayloadV2(event)) {
    const matches = event.routeKey.matchAll(/\{(.*?)\}/g);
    for (const match of matches) {
      // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
      const group = match[1]!;
      if (group.includes('+') && event.pathParameters) {
        return event.pathParameters[group.replace('+', '')] ?? '';
      }
    }
    return event.rawPath.slice(1);
  }
  throw new TRPCError({
    code: 'INTERNAL_SERVER_ERROR',
    message: UNKNOWN_PAYLOAD_FORMAT_VERSION_ERROR_MESSAGE,
  });
}

export function transformHeaders(
  headers: HTTPHeaders,
): APIGatewayResult['headers'] {
  const obj: APIGatewayResult['headers'] = {};

  for (const [key, value] of Object.entries(headers)) {
    if (typeof value === 'undefined') {
      continue;
    }
    obj[key] = Array.isArray(value) ? value.join(',') : value;
  }
  return obj;
}

export type DefinedAPIGatewayPayloadFormats = '1.0' | '2.0';
export type APIGatewayPayloadFormatVersion =
  | DefinedAPIGatewayPayloadFormats
  | 'custom';

export const UNKNOWN_PAYLOAD_FORMAT_VERSION_ERROR_MESSAGE =
  'Custom payload format version not handled by this adapter. Please use either 1.0 or 2.0. More information here' +
  'https://docs.aws.amazon.com/apigateway/latest/developerguide/http-api-develop-integrations-lambda.html';