# All files / lib/messages FundingInput.ts

86.14% Statements 87/101
74.36% Branches 29/39
88.89% Functions 8/9
86% Lines 86/100

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     import { Sequence, Tx } from '@node-dlc/bitcoin';
    import { BufferReader, BufferWriter, StreamReader } from '@node-dlc/bufio';

    import { MessageType } from '../MessageType';
    import { bigIntToNumber, toBigInt } from '../util';
    import { DlcInput } from './DlcInput';
    import { IDlcMessage } from './DlcMessage';

    /**
     * FundingInput contains information about a specific input to be used
     * in a funding transaction, as well as its corresponding on-chain UTXO.
     * Matches rust-dlc FundingInput struct.
     */
    export class FundingInput implements IDlcMessage {
      public static type = MessageType.FundingInput;

      /**
       * Creates a FundingInput from JSON data (e.g., from test vectors)
       * @param json JSON object representing funding input
       */
      // eslint-disable-next-line @typescript-eslint/explicit-module-boundary-types, @typescript-eslint/no-explicit-any
      public static fromJSON(json: any): FundingInput {
        const instance = new FundingInput();

        instance.inputSerialId = toBigInt(
          json.inputSerialId || json.input_serial_id,
        );

        // Parse previous transaction
        const prevTxHex = json.prevTx || json.prev_tx;
        Eif (prevTxHex) {
          instance.prevTx = Tx.decode(
            StreamReader.fromBuffer(Buffer.from(prevTxHex, 'hex')),
          );
        } else {
          // Create a minimal transaction for test purposes
          // TODO: This should be properly implemented when full test vector support is needed
          const writer = new BufferWriter();
          writer.writeUInt32BE(2); // version
          writer.writeUInt8(0); // input count
          writer.writeUInt8(1); // output count
          writer.writeUInt64BE(BigInt(100000000)); // output value
          writer.writeUInt8(25); // script length
          writer.writeBytes(Buffer.alloc(25)); // script
          writer.writeUInt32BE(0); // locktime

          const txBytes = writer.toBuffer();
          instance.prevTx = Tx.decode(StreamReader.fromBuffer(txBytes));
        }

        instance.prevTxVout = json.prevTxVout || json.prev_tx_vout || 0;
        instance.sequence = new Sequence(json.sequence || 0xffffffff);
        instance.maxWitnessLen = json.maxWitnessLen || json.max_witness_len || 108;

        const redeemScript = json.redeemScript || json.redeem_script || '';
        instance.redeemScript = Buffer.from(redeemScript, 'hex');

        // Parse optional DLC input
        const dlcInput = json.dlcInput || json.dlc_input;
        if (dlcInput) {
          instance.dlcInput = DlcInput.fromJSON(dlcInput);
        }

        return instance;
      }

      /**
       * Deserializes a funding_input message
       * @param buf
       */
      public static deserialize(buf: Buffer): FundingInput {
        const instance = new FundingInput();
        const reader = new BufferReader(buf);

        reader.readBigSize(); // read type
        instance.length = reader.readBigSize();
        instance.inputSerialId = reader.readUInt64BE();
        const prevTxLen = reader.readUInt16BE();
        instance.prevTx = Tx.decode(
          StreamReader.fromBuffer(reader.readBytes(prevTxLen)),
        );
        instance.prevTxVout = reader.readUInt32BE();
        instance.sequence = new Sequence(reader.readUInt32BE());
        instance.maxWitnessLen = reader.readUInt16BE();
        const redeemScriptLen = reader.readUInt16BE();
        instance.redeemScript = reader.readBytes(redeemScriptLen);

        // Read optional DLC input using rust-dlc Optional format (0x00/0x01 prefix)
        if (reader.position < reader.buffer.length) {
          const dlcInputData = reader.readOptional();
          if (dlcInputData) {
            instance.dlcInput = DlcInput.deserializeBody(dlcInputData);
          }
        }

        return instance;
      }

      /**
       * Deserializes a funding_input message without TLV wrapper (for use in DlcOffer)
       * This matches rust-dlc behavior where FundingInput is in a vector without individual TLV wrappers
       * @param buf
       */
      public static deserializeBody(buf: Buffer): FundingInput {
        const instance = new FundingInput();
        const reader = new BufferReader(buf);

        // No TLV type/length to read - funding input body is serialized directly
        instance.inputSerialId = reader.readUInt64BE();

        // Read prev_tx with BigSize length (to match rust-dlc)
        const prevTxLen = Number(reader.readBigSize());
        instance.prevTx = Tx.decode(
          StreamReader.fromBuffer(reader.readBytes(prevTxLen)),
        );

        instance.prevTxVout = reader.readUInt32BE();
        instance.sequence = new Sequence(reader.readUInt32BE());
        instance.maxWitnessLen = reader.readUInt16BE();

        // Test: Read redeem_script with simple u16 length (to match rust-bitcoin ScriptBuf)
        const redeemScriptLen = reader.readUInt16BE();
        instance.redeemScript = reader.readBytes(redeemScriptLen);

        // Read optional DLC input using rust-dlc Optional format (0x00/0x01 prefix)
        Eif (reader.position < reader.buffer.length) {
          const dlcInputData = reader.readOptional();
          if (dlcInputData) {
            instance.dlcInput = DlcInput.deserializeBody(dlcInputData);
          }
        }

        return instance;
      }

      /**
       * The type for funding_input message. funding_input = 42772
       */
      public type = FundingInput.type;

      public length: bigint;

      public inputSerialId: bigint;

      public prevTx: Tx;

      public prevTxVout: number;

      public sequence: Sequence;

      public maxWitnessLen: number;

      public redeemScript: Buffer;

      public dlcInput?: DlcInput;

      public scriptSigLength(): number {
        if (this.redeemScript.length > 0) {
          return 1 + this.redeemScript.length;
        } else {
          return 0;
        }
      }

      /**
       * Validates correctness of all fields
       * @throws Will throw an error if validation fails
       */
      public validate(): void {
        // 1. Type is set automatically in class
        // 2. Ensure inputs are segwit
        if (!this.prevTx.isSegWit) throw new Error('fundingInput must be segwit');
      }

      /**
       * Converts funding_input to JSON (canonical rust-dlc format)
       */
      public toJSON(): IFundingInputJSON {
        const result: IFundingInputJSON = {
          inputSerialId: bigIntToNumber(this.inputSerialId),
          prevTx: this.prevTx.serialize().toString('hex'),
          prevTxVout: this.prevTxVout,
          sequence: this.sequence.value,
          maxWitnessLen: this.maxWitnessLen,
          redeemScript: this.redeemScript.toString('hex'),
        };

        Iif (this.dlcInput) {
          result.dlcInput = this.dlcInput.toJSON();
        }

        return result;
      }

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

        const dataWriter = new BufferWriter();
        dataWriter.writeUInt64BE(this.inputSerialId);
        dataWriter.writeUInt16BE(this.prevTx.serialize().length);
        dataWriter.writeBytes(this.prevTx.serialize());
        dataWriter.writeUInt32BE(this.prevTxVout);
        dataWriter.writeUInt32BE(this.sequence.value);
        dataWriter.writeUInt16BE(this.maxWitnessLen);
        dataWriter.writeUInt16BE(this.redeemScript.length);
        dataWriter.writeBytes(this.redeemScript);

        // Write optional DLC input using rust-dlc Optional format (0x00/0x01 prefix)
        const dlcInputData = this.dlcInput ? this.dlcInput.serializeBody() : null;
        dataWriter.writeOptional(dlcInputData);

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

        return writer.toBuffer();
      }

      public serializeBody(): Buffer {
        // Serialize funding input body without TLV wrapper (for embedding in DlcOffer)
        // This matches rust-dlc behavior where FundingInput.write() doesn't add type_id
        const writer = new BufferWriter();
        writer.writeUInt64BE(this.inputSerialId);

        // Use BigSize for prev_tx length to match rust-dlc (prev_tx, vec)
        writer.writeBigSize(this.prevTx.serialize().length);
        writer.writeBytes(this.prevTx.serialize());

        writer.writeUInt32BE(this.prevTxVout);
        writer.writeUInt32BE(this.sequence.value);
        writer.writeUInt16BE(this.maxWitnessLen);

        // Test: Use simple u16 length for redeem_script to match rust-bitcoin ScriptBuf
        writer.writeUInt16BE(this.redeemScript.length);
        writer.writeBytes(this.redeemScript);

        // Write optional DLC input using rust-dlc Optional format (0x00/0x01 prefix)
        const dlcInputData = this.dlcInput ? this.dlcInput.serializeBody() : null;
        writer.writeOptional(dlcInputData);

        return writer.toBuffer();
      }
    }

    export interface IFundingInputJSON {
      inputSerialId: number;
      prevTx: string;
      prevTxVout: number;
      sequence: number;
      maxWitnessLen: number;
      redeemScript: string;
      dlcInput?: {
        localFundPubkey: string;
        remoteFundPubkey: string;
        contractId: string;
      };
    }