# All files / lib/messages OracleAttestation.ts

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74.42% Branches 32/43
69.23% Functions 9/13
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     import { BufferReader, BufferWriter } from '@node-dlc/bufio';
    import { math, verify } from 'bip-schnorr';

    import { MessageType } from '../MessageType';
    import { IDlcMessage } from './DlcMessage';
    import { OracleAnnouncement } from './OracleAnnouncement';

    /**
     * Oracle attestation providing signatures over an outcome value.
     * This represents the oracle's actual attestation to a specific outcome.
     * Updated to match rust-dlc specification with 2-byte count prefixes.
     *
     * An attestation from an oracle providing signatures over an outcome value.
     * This is what the oracle publishes when they want to attest to a specific outcome.
     */
    export class OracleAttestation implements IDlcMessage {
      public static type = MessageType.OracleAttestation;

      /**
       * Deserializes an oracle_attestation message
       * @param buf
       */
      public static deserialize(buf: Buffer): OracleAttestation {
        const instance = new OracleAttestation();
        const reader = new BufferReader(buf);

        reader.readBigSize(); // read type
        instance.length = reader.readBigSize();

        // Detect format: old rust-dlc 0.4.0 (no event_id) vs new rust-dlc (with event_id)
        const currentPos = reader.position;

        try {
          // Try reading as new format (with event_id)
          const eventIdLength = reader.readBigSize();

          // If event ID length is reasonable (0-100 bytes), assume new format
          if (eventIdLength >= BigInt('0') && eventIdLength <= BigInt('100')) {
            if (eventIdLength === BigInt('0')) {
              instance.eventId = '';
            } else {
              const eventIdBuf = reader.readBytes(Number(eventIdLength));
              instance.eventId = eventIdBuf.toString();
            }
            instance.oraclePubkey = reader.readBytes(32);
          } else {
            // Event ID length is unreasonable, probably old format without event_id
            reader.position = currentPos;
            instance.eventId = ''; // Default empty event ID for old format
            instance.oraclePubkey = reader.readBytes(32);
          }
        } catch (error) {
          // If reading fails, assume old format without event_id
          reader.position = currentPos;
          instance.eventId = ''; // Default empty event ID for old format
          instance.oraclePubkey = reader.readBytes(32);
        }

        const numSignatures = reader.readUInt16BE();

        for (let i = 0; i < numSignatures; i++) {
          const signature = reader.readBytes(64);
          instance.signatures.push(signature);
        }

        // Handle both rust-dlc format (with u16 count prefix) and DLCSpecs format (no count prefix)
        // Try to detect format by checking if next 2 bytes look like a reasonable outcome count
        Eif (!reader.eof) {
          const currentPos = reader.position;

          try {
            // Try reading as rust-dlc format (with u16 count prefix)
            const numOutcomes = reader.readUInt16BE();

            // Validate that this looks like a reasonable count
            // If it's > 1000 or the remaining bytes can't accommodate this many outcomes,
            // it's probably not a count prefix
            const remainingBytes = reader.buffer.length - reader.position;

            if (
              numOutcomes > 0 &&
              numOutcomes <= 1000 &&
              remainingBytes >= numOutcomes * 2
            ) {
              // Looks like rust-dlc format with u16 count prefix
              for (let i = 0; i < numOutcomes; i++) {
                const outcomeLen = reader.readBigSize();
                const outcomeBuf = reader.readBytes(Number(outcomeLen));
                instance.outcomes.push(outcomeBuf.toString());
              }
            } else {
              // Reset and try DLCSpecs format (no count prefix)
              reader.position = currentPos;
              while (!reader.eof) {
                const outcomeLen = reader.readBigSize();
                const outcomeBuf = reader.readBytes(Number(outcomeLen));
                instance.outcomes.push(outcomeBuf.toString());
              }
            }
          } catch (error) {
            // If reading as rust-dlc format fails, reset and try DLCSpecs format
            reader.position = currentPos;
            while (!reader.eof) {
              const outcomeLen = reader.readBigSize();
              const outcomeBuf = reader.readBytes(Number(outcomeLen));
              instance.outcomes.push(outcomeBuf.toString());
            }
          }
        }

        return instance;
      }

      /**
       * The type for oracle_attestation message. oracle_attestation = 55400
       */
      public type = OracleAttestation.type;

      public length: bigint;

      /** The identifier of the announcement. */
      public eventId: string;

      /** The public key of the oracle (32 bytes, x-only). */
      public oraclePubkey: Buffer;

      /** The signatures over the event outcome (64 bytes each, Schnorr format). */
      public signatures: Buffer[] = [];

      /** The set of strings representing the outcome value. */
      public outcomes: string[] = [];

      /**
       * Validates the oracle attestation according to rust-dlc specification.
       * This includes validating signatures and ensuring consistency with announcement.
       * @param announcement The corresponding oracle announcement for validation (optional)
       * @throws Will throw an error if validation fails
       */
      public validate(announcement?: OracleAnnouncement): void {
        // Basic structure validation
        Iif (this.signatures.length !== this.outcomes.length) {
          throw new Error('Number of signatures must match number of outcomes');
        }

        Iif (this.signatures.length === 0) {
          throw new Error('Must have at least one signature and outcome');
        }

        // Validate event ID
        Iif (!this.eventId || this.eventId.length === 0) {
          throw new Error('Event ID cannot be empty');
        }

        // Validate oracle public key format
        Iif (!this.oraclePubkey || this.oraclePubkey.length !== 32) {
          throw new Error('Oracle public key must be 32 bytes (x-only format)');
        }

        // Validate signature formats
        this.signatures.forEach((sig, index) => {
          Iif (!sig || sig.length !== 64) {
            throw new Error(
              `Signature at index ${index} must be 64 bytes (Schnorr format)`,
            );
          }
        });

        // Validate outcomes are not empty
        this.outcomes.forEach((outcome, index) => {
          Iif (!outcome || outcome.length === 0) {
            throw new Error(`Outcome at index ${index} cannot be empty`);
          }
        });

        // Verify signatures over outcomes using tagged hash
        this.signatures.forEach((sig, index) => {
          const outcome = this.outcomes[index];
          try {
            const msg = math.taggedHash('DLC/oracle/attestation/v0', outcome);
            verify(this.oraclePubkey, msg, sig);
          } catch (error) {
            throw new Error(
              `Invalid signature for outcome "${outcome}" at index ${index}: ${error.message}`,
            );
          }
        });

        // If announcement is provided, validate consistency
        if (announcement) {
          this.validateAgainstAnnouncement(announcement);
        }
      }

      /**
       * Validates the attestation against the corresponding oracle announcement.
       * This ensures the attestation is consistent with the original announcement.
       * @param announcement The oracle announcement to validate against
       * @throws Will throw an error if validation fails
       */
      private validateAgainstAnnouncement(announcement: OracleAnnouncement): void {
        // Validate oracle public key matches announcement
        Iif (!this.oraclePubkey.equals(announcement.oraclePubkey)) {
          throw new Error('Oracle public key must match announcement');
        }

        // Validate event ID matches
        Iif (this.eventId !== announcement.getEventId()) {
          throw new Error('Event ID must match announcement');
        }

        // Validate that the number of signatures matches the number of nonces in announcement
        const announcementNonces = announcement.getNonces();
        Iif (this.signatures.length !== announcementNonces.length) {
          throw new Error(
            'Number of signatures must match number of nonces in announcement',
          );
        }

        // Extract nonces from signatures (first 32 bytes) and compare with announcement nonces
        // This validates that the signatures were created using the committed nonces
        this.signatures.forEach((sig, index) => {
          const nonceFromSig = sig.slice(0, 32);
          const expectedNonce = announcementNonces[index];

          Iif (!nonceFromSig.equals(expectedNonce)) {
            throw new Error(
              `Signature nonce mismatch at index ${index}: signature was not created with announced nonce`,
            );
          }
        });
      }

      /**
       * Returns the nonces used by the oracle to sign the event outcome.
       * This is used for finding the matching oracle announcement.
       * The nonce is extracted from the first 32 bytes of each signature.
       */
      public getNonces(): Buffer[] {
        return this.signatures.map((sig) => sig.slice(0, 32));
      }

      /**
       * Converts oracle_attestation to JSON
       */
      public toJSON(): OracleAttestationJSON {
        return {
          type: this.type,
          eventId: this.eventId,
          oraclePubkey: this.oraclePubkey.toString('hex'),
          signatures: this.signatures.map((sig) => sig.toString('hex')),
          outcomes: this.outcomes,
        };
      }

      /**
       * Serializes the oracle_attestation message into a Buffer
       */
      public serialize(): Buffer {
        const writer = new BufferWriter();
        writer.writeBigSize(this.type);

        const dataWriter = new BufferWriter();
        dataWriter.writeBigSize(this.eventId.length);
        dataWriter.writeBytes(Buffer.from(this.eventId));
        dataWriter.writeBytes(this.oraclePubkey);
        dataWriter.writeUInt16BE(this.signatures.length);

        for (const signature of this.signatures) {
          dataWriter.writeBytes(signature);
        }

        // Write outcomes with u16 count prefix (matching rust-dlc format)
        dataWriter.writeUInt16BE(this.outcomes.length);
        for (const outcome of this.outcomes) {
          dataWriter.writeBigSize(outcome.length);
          dataWriter.writeBytes(Buffer.from(outcome));
        }

        writer.writeBigSize(dataWriter.size);
        writer.writeBytes(dataWriter.toBuffer());

        return writer.toBuffer();
      }
    }

    export interface OracleAttestationJSON {
      type: number;
      eventId: string;
      oraclePubkey: string;
      signatures: string[];
      outcomes: string[];
    }