import NfcManager, { Ndef, NfcTech } from "react-native-nfc-manager";
import { NdefTagInfo } from "../types/NdefTypes";

/**
 * Class which provides methods for reading and writing ndef tags
 */
export default class NdefTools {
  /**
   * Method for cancelling the current listener
   */
  cancelRequest: () => void;
  constructor() {
    this.cancelRequest = () => NfcManager.cancelTechnologyRequest();
  }

  /**
   * Function which listens until a Ndef tag is detected in the device's NFC reader. Then returns the id of the
   * Ndef tag and its decoded payload (as "content")
   *
   * @return { Promise<NdefTagInfo | undefined> } An object containing the id and the decoded payload of the NFC tag or undefined in case there was an error reading the tag (The error will be logged).
   */
  async readTag(): Promise<NdefTagInfo | undefined> {
    try {
      await NfcManager.requestTechnology(NfcTech.Ndef); // Request the hardware to listen for a specific technology
      const tag = await NfcManager.getTag(); // Opening the event listener to look for a NFC card to be read

      if (tag && tag.id) {
        return {
          id: tag.id,
          content: Ndef.uri
            .decodePayload(tag.ndefMessage[0].payload as unknown as Uint8Array)
            .replace("https://www.en", ""), // Decoding the payload since is a buffer and we want to return the decoded payload
        };
      } else {
        throw new Error("Reading the tag was not possible.");
      }
    } catch (err) {
      throw err;
    } finally {
      this.cancelRequest(); // Cancel the NFC request at the end of the operation
    }
  }

  /**
   * Function that writes a value as the payload of a Ndef tag and returns a boolean wether the card was written
   * successfully
   *
   * @param value The value that will be written to the Ndef card
   *
   * @returns A boolean wether the card was written successfully or not
   */
  async writeTag(value: string): Promise<boolean> {
    try {
      await NfcManager.requestTechnology(NfcTech.Ndef);

      const bytes = Ndef.encodeMessage([Ndef.textRecord(value)]); // Encoding as buffer the string we recieved

      if (bytes) {
        await NfcManager.ndefHandler.writeNdefMessage(bytes); // Writing the buffer in the Ndef tag
        return true;
      }

      return false;
    } catch (err) {
      throw err;
    } finally {
      this.cancelRequest();
    }
  }
}