import type { DiagramDocument } from '../types';
import type { HostAdapter } from './HostAdapter';

/**
 * postMessage handshake with the Bitrix bridge script (see
 * docs/bitrix-integration.md for the PHP side). `targetOrigin` is always a
 * concrete origin, never '*' — matches the security requirement from the
 * original design doc.
 */
const READY_MESSAGE = 'diagram:ready';
const INIT_MESSAGE = 'diagram:init';
const CHANGE_MESSAGE = 'diagram:change';

function getBitrixOrigin(): string {
  const origin = import.meta.env.VITE_BITRIX_ORIGIN;
  if (!origin) {
    throw new Error(
      'VITE_BITRIX_ORIGIN is not set. The bridge needs a concrete parent origin — postMessage must never target "*".',
    );
  }
  return origin;
}

export function createBitrixAdapter(): HostAdapter {
  const targetOrigin = getBitrixOrigin();

  return {
    onReady(callback) {
      let delivered = false;

      function onMessage(event: MessageEvent) {
        if (event.origin !== targetOrigin || event.source !== window.parent) return;
        if (delivered || event.data?.type !== INIT_MESSAGE) return;
        delivered = true;
        window.removeEventListener('message', onMessage);

        const payload = event.data.payload as string | null | undefined;
        if (!payload) {
          callback(null);
          return;
        }
        try {
          callback(JSON.parse(payload) as DiagramDocument);
        } catch {
          callback(null);
        }
      }

      window.addEventListener('message', onMessage);
      window.parent.postMessage({ type: READY_MESSAGE }, targetOrigin);
    },
    onChange(doc) {
      window.parent.postMessage({ type: CHANGE_MESSAGE, payload: JSON.stringify(doc) }, targetOrigin);
    },
  };
}