hash-wallet/lib/core/lightning_invoice_service.dart

import 'dart:convert';

import 'package:cw_core/utils/proxy_wrapper.dart';

Future<String?> getBolt11FromLightingAddress(String lightningAddress, {int amount = 0}) async {
  try {
    final uri = getURlOfLightningAddress(lightningAddress);

    var response = await ProxyWrapper().get(clearnetUri: uri);
    final responseBody =
        _LNURLPResponseDTO.fromJson(jsonDecode(response.body) as Map<String, dynamic>);

    response =
        await ProxyWrapper().get(clearnetUri: Uri.parse("${responseBody.callback}?amount=$amount"));

    final callbackResponseBody =
        _LNURLPCallbackResponseDTO.fromJson(jsonDecode(response.body) as Map<String, dynamic>);

    return callbackResponseBody.pr;
  } catch (e) {
    return null;
  }
}

Uri getURlOfLightningAddress(String lightningAddress) {
  final parts = lightningAddress.split("@");

  final name = parts.first;
  final domain = parts.last;
  return Uri.parse("https://$domain/.well-known/lnurlp/$name");
}

class _LNURLPResponseDTO {
  final String callback;
  final int maxSendable;
  final int minSendable;
  final String tag;
  final String metadata;

  const _LNURLPResponseDTO(
      this.callback, this.maxSendable, this.minSendable, this.tag, this.metadata);

  static _LNURLPResponseDTO fromJson(Map<String, dynamic> map) => _LNURLPResponseDTO(
      map["callback"] as String,
      map["maxSendable"] as int,
      map["minSendable"] as int,
      map["tag"] as String,
      map["metadata"] as String);
}

class _LNURLPCallbackResponseDTO {
  final String pr;

  const _LNURLPCallbackResponseDTO(this.pr);

  static _LNURLPCallbackResponseDTO fromJson(Map<String, dynamic> map) =>
      _LNURLPCallbackResponseDTO(map["pr"] as String);
}