# All files Script.ts

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     import { bigToBufLE } from '@node-dlc/bufio';
    import { encodeVarInt } from '@node-dlc/bufio';
    import { BufferReader } from '@node-dlc/bufio';
    import { StreamReader } from '@node-dlc/bufio';
    import { hash160, isDERSig, sha256, validPublicKey } from '@node-dlc/crypto';

    import { BitcoinError } from './BitcoinError';
    import { BitcoinErrorCode } from './BitcoinErrorCode';
    import { ICloneable } from './ICloneable';
    import { OpCode } from './OpCodes';
    import { ScriptCmd } from './ScriptCmd';
    import { isSigHashTypeValid } from './SigHashType';
    import { Stack } from './Stack';

    function asssertValidSig(sig: Buffer) {
      const der = sig.slice(0, sig.length - 1);
      const hashtype = sig[sig.length - 1];

      if (!isDERSig(der)) {
        throw new BitcoinError(BitcoinErrorCode.SigEncodingInvalid);
      }

      if (!isSigHashTypeValid(hashtype)) {
        throw new BitcoinError(BitcoinErrorCode.SigHashTypeInvalid, hashtype);
      }
    }

    function assertValidPubKey(pubkey: Buffer) {
      if (!validPublicKey(pubkey)) {
        throw new BitcoinError(BitcoinErrorCode.PubKeyInvalid);
      }
    }

    /**
     * Bitcoin Script
     */
    export class Script implements ICloneable<Script> {
      /**
       *
       * @param val
       */
      public static number(val: number | bigint): ScriptCmd {
        // Zero is encoded as OP_0
        if (val === 0 || val === BigInt(0)) {
          return OpCode.OP_0;
        }

        // 1-16 is encoded as OP_1 to OP_16
        if (val >= 1 && val <= 16) {
          return 0x50 + Number(val);
        }

        // anything else is encoded as signed-magnitude value
        // and added to the script as raw push bytes
        return Stack.encodeNum(val);
      }

      /**
       * Creates a standard (though no longer used) pay-to-pubkey
       * scriptPubKey using the provided pubkey.
       *
       * P2PK format:
       *      <pubkey> OP_CHECKSIG
       *
       * @param pubkey 33-byte compressed or 65-byte uncompressed SEC
       * encoded pubkey
       */
      public static p2pkLock(pubkey: Buffer): Script {
        assertValidPubKey(pubkey);
        return new Script(pubkey, OpCode.OP_CHECKSIG);
      }

      /**
       * Creates a standard (though no longer used) pay-to-pubkey
       * scriptSig using the provided signature.
       *
       * P2PK format:
       *      <sig>
       *
       * @param sig DER encoded signature + 1-byte sighash type
       */
      public static p2pkUnlock(sig: Buffer): Script {
        asssertValidSig(sig);
        return new Script(sig);
      }

      /**
       * Creates a standard Pay-to-Public-Key-Hash scriptPubKey by accepting a
       * hash of a public key as input and generating the script in the standard
       * P2PKH script format:
       *   OP_DUP OP_HASH160 <hash160pubkey> OP_EQUALVERIFY OP_CHECKSIG
       *
       * @param value either the 20-byte hash160 of a pubkey or an SEC
       * encoded compressed or uncompressed pubkey
       */
      public static p2pkhLock(value: Buffer): Script {
        // if not a hash160, then it must be a valid pubkey
        if (value.length !== 20) {
          assertValidPubKey(value);
        }

        // either the hash value or a valid pubkey that needs to be hashed
        const hash160PubKey = value.length === 20 ? value : hash160(value);

        return new Script(
          OpCode.OP_DUP,
          OpCode.OP_HASH160,
          hash160PubKey,
          OpCode.OP_EQUALVERIFY,
          OpCode.OP_CHECKSIG,
        );
      }

      /**
       * Creates a standard Pay-to-Public-Key-Hash scriptSig
       * @param sig BIP66 compliant DER encoded signuture + hash byte
       * @param pubkey SEC encoded public key
       */
      public static p2pkhUnlock(sig: Buffer, pubkey: Buffer): Script {
        asssertValidSig(sig);
        assertValidPubKey(pubkey);
        return new Script(sig, pubkey);
      }

      /**
       * Creates a standard Pay-to-MultiSig scriptPubKey by accepting m of n
       * public keys as inputs in the format:
       *   OP_<m> <pubkey1> <pubkey2> <pubkey..m> OP_<n> OP_CHECKMULTISIG
       */
      public static p2msLock(m: number, ...pubkeys: Buffer[]): Script {
        // assert all public keys are valid
        for (const pubkey of pubkeys) {
          assertValidPubKey(pubkey);
        }

        // ensure proper number of keys
        if (
          m < 1 ||
          m > pubkeys.length ||
          pubkeys.length === 0 ||
          pubkeys.length > 20
        ) {
          throw new BitcoinError(BitcoinErrorCode.MultiSigSetupInvalid);
        }

        return new Script(
                Script.number(m),
                ...pubkeys,
                Script.number(pubkeys.length),
                OpCode.OP_CHECKMULTISIG,
            ); // prettier-ignore
      }

      /**
       * Creates a standard Pay-to-MultiSig scripSig using the provided
       * signatures. The signatures must be in the order of the pub keys
       * used in the lock script. This function also correctly adds OP_0
       * as the first element on the stack to ensure the p2ms off-by-one
       * error is correctly accounted for.
       *
       * Each signature must be DER encoded using BIP66 and
       * include a 1-byte sighash type at the end. The builder validates
       * the signatures. As such they will be 10 to 74 bytes.
       *
       * @param pubkeys
       */
      public static p2msUnlock(...sigs: Buffer[]): Script {
        // assert all signatures
        for (const sig of sigs) {
          asssertValidSig(sig);
        }
        return new Script(
                OpCode.OP_0,
                ...sigs
            ); // prettier-ignore
      }

      /**
       * Creates a standard Pay-to-Script-Hash scriptPubKey by accepting a hash of
       * the redeem script as input and generating the P2SH script:
       *   OP_HASH160 <hashScript> OP_EQUAL
       *
       * Accepts the redeem script either as a Script object or as the
       * hash160 of the redeem script. When the hash160 Buffer is provided
       * it will throw if the Buffer is not 20-bytes.
       *
       * @param value can be either the redeem script as a Script type or
       * the hash160 as a 20-byte buffer
       */
      public static p2shLock(value: Script | Buffer): Script {
        const scriptHash160 = value instanceof Script ? value.hash160() : value;

        if (scriptHash160.length !== 20) {
          throw new BitcoinError(BitcoinErrorCode.Hash160Invalid, {
            got: scriptHash160.length,
            expected: 20,
          });
        }

        return new Script(
                OpCode.OP_HASH160,
                scriptHash160,
                OpCode.OP_EQUAL,
            ); // prettier-ignore
      }

      /**
       * Creates a p2sh unlock script for use in a transaction input
       * scriptSig value. The redeem script, which is the preimage of the
       * of the script hash used to lock the p2sh output, must be provided
       * along with any additional data required to unlock the script.
       *
       * @param redeemScript preimage of the script hash
       * @param data script commands will be added as unlock data
       */
      public static p2shUnlock(redeemScript: Script, data: Script): Script;

      /**
       * Creates a p2sh unlock script for use in a transaction input
       * scriptSig value. The redeem script, which is the preimage of the
       * of the script hash used to lock the p2sh output, must be provided
       * along with any additional data required to unlock the script.
       *
       * @param redeemScript preimage of the script hash
       * @param data ScriptCmd data used to unlock the script
       */
      public static p2shUnlock(redeemScript: Script, ...data: ScriptCmd[]): Script;

      public static p2shUnlock(
        redeemScript: Script,
        ...data: Script[] | ScriptCmd[]
      ): Script {
        if (data[0] instanceof Script) {
          return new Script(...data[0].cmds, redeemScript.serializeCmds());
        } else {
          return new Script(...(data as ScriptCmd[]), redeemScript.serializeCmds());
        }
      }

      /**
       * Create a standard Pay-to-Witness-PubKey-Hash scriptPubKey by accepting
       * the hash160 of a compressed public key point as input. It is of the
       * format:
       *   OP_0 <hash160_pubkey>
       *
       * @param value either a 20-byte pubkeyhash or a valid pubkey
       */
      public static p2wpkhLock(value: Buffer): Script {
        // if not a hash160, then it must be a valid pubkey
        if (value.length !== 20) {
          assertValidPubKey(value);
        }

        // either the hash value or a valid pubkey that needs to be hashed
        const hash160PubKey = value.length === 20 ? value : hash160(value);

        return new Script(
                OpCode.OP_0,
                hash160PubKey,
            ); // prettier-ignore
      }

      /**
       * Create a standard Pay-to-Witness-Script-Hash scriptPubKey by accepting
       * the sha256 of the witness script as input. It is of the format:
       *   OP_0 <sha256_redeem_script>
       */
      public static p2wshLock(value: Buffer | Script): Script {
        const sha256Script =
          value instanceof Buffer ? value : sha256(value.serializeCmds());

        if (sha256Script.length !== 32) {
          throw new BitcoinError(BitcoinErrorCode.Hash256Invalid);
        }

        return new Script(
                OpCode.OP_0,
                sha256Script,
            ); // prettier-ignore
      }

      /**
       * Parses a stream of bytes representing a Script. The stream must start
       * with a Varint length of Script data. The Script data is then parsed into
       * data blocks or op_codes depending on the meaning of the bytes
       * @param stream
       */
      public static parse(reader: StreamReader): Script {
        // read the length
        const len = reader.readVarInt();

        // read the length of bytes occupied by the script and then pass it
        // through the command parser.
        const buf = reader.readBytes(Number(len));
        const cmds = Script.parseCmds(buf);

        // return the script object with the commands
        return new Script(...cmds);
      }

      /**
       * When supplied with a Buffer of cmds this method will parse the commands
       * into data blocks or op_codes depending on the meaning of the bytes
       * @param buf
       */
      public static parseCmds(buf: Buffer): ScriptCmd[] {
        const br = new BufferReader(buf);

        // commands that were read off the stack
        const cmds: ScriptCmd[] = [];

        // loop until all bytes have been read
        while (!br.eof) {
          // read the current command from the stream
          const op = br.readUInt8();

          // data range between 1-75 bytes is OP_PUSHBYTES_xx and we simple
          // read the xx number of bytes off the script
          if (op >= 0x01 && op <= 0x4b) {
            const n = op;
            const bytes = br.readBytes(n);
            cmds.push(bytes);
          }

          // data range between 76 and 255 bytes uses OP_PUSHDATA1 and uses
          // the format with a single byte length and then the n bytes are
          // read from the script
          else if (op === OpCode.OP_PUSHDATA1) {
            const n = br.readUInt8();
            cmds.push(br.readBytes(n));
          }

          // data range between 256 and 520 uses OP_PUSHDATA2 and uses the
          // format with two bytes little-endian to determine the n bytes of
          // data of data that need to be read.
          else if (op === OpCode.OP_PUSHDATA2) {
            const n = br.readUInt16LE();
            cmds.push(br.readBytes(n));
          }

          // otherwise the value is an opcode that should be added to the cmds
          else {
            cmds.push(op);
          }
        }

        return cmds;
      }

      /**
       * Commands belonging to the script
       */
      public readonly cmds: ScriptCmd[];

      /**
       * Constructs a Script with the supplied ScriptCmd values
       * @param cmds
       */
      constructor(...cmds: ScriptCmd[]) {
        this.cmds = cmds;
      }

      /**
       * Returns true if other script is an exact match of the current script.
       * This requires all data element sto be exact matches and all operations
       * to be exact matches.
       * @param other
       */
      public equals(other: Script): boolean {
        if (this.cmds.length !== other.cmds.length) return false;
        for (let i = 0; i < this.cmds.length; i++) {
          const l = this.cmds[i];
          const r = other.cmds[i];
          if (Buffer.isBuffer(l) && Buffer.isBuffer(r)) {
            if (!l.equals(r)) return false;
          } else {
            if (l !== r) return false;
          }
        }
        return true;
      }

      /**
       * Returns a string with the friendly name of the opcode. For data,
       * it returns the value in hexadecimal format.
       */
      public toString(): string {
        return this.cmds
          .map((cmd) => {
            if (Buffer.isBuffer(cmd)) {
              return cmd.toString('hex');
            } else {
              return OpCode[cmd as OpCode];
            }
          })
          .join(' ');
      }

      /**
       * Returns a JSON serialization of the Script.
       */
      public toJSON(): string {
        return this.toString();
      }

      /**
       * Serializes the Script to a Buffer by serializing the cmds prefixed with
       * the overall length as a varint. Therefore the format of this method is
       * the format used when encoding a Script and is:
       *
       * [varint]: length
       * [length]: script_cmds
       */
      public serialize(): Buffer {
        // first obtain the length of all commands in the script
        const cmdBuf = this.serializeCmds();

        // capture the length of cmd buffer
        const len = encodeVarInt(cmdBuf.length);

        // return combined buffer
        return Buffer.concat([len, cmdBuf]);
      }

      /**
       * Serializes the commands to a buffer. This information is the raw
       * serialization and can be directly parsed with the `parseCmds` method.
       */
      public serializeCmds(): Buffer {
        const results: Buffer[] = [];
        for (const op of this.cmds) {
          // OP_CODES are just an integers and can just be pushed directly onto
          // the byte array after being converted into a single byte buffer
          if (typeof op === 'number') {
            const opBuf = Buffer.from([op]);
            results.push(opBuf);
          }

          // elements will be represented as a buffer of information and we will
          // use the length to determine how to encode it
          else if (op instanceof Buffer) {
            // between 1 and 75 bytes are OP_PUSHBYTES_XX
            // there is no op_code for these. We first need to push
            // the length of the buffer array though as the operation
            if (op.length >= 1 && op.length <= 75) {
              results.push(Buffer.from([op.length]));
              results.push(op);
            }

            // between 76 and 255 uses OP_PUSHDATA1
            // this requires us to push the op_code, a single byte length
            // and finally push the 76-255 bytes of data
            else if (op.length >= 76 && op.length <= 255) {
              results.push(Buffer.from([OpCode.OP_PUSHDATA1])); // op_pushdata1
              results.push(Buffer.from([op.length])); // single-byte
              results.push(op);
            }

            // between 256 and 520 uses OP_PUSHDATA2
            // this requires us to push the op_code, a two-byte little-endian number
            // and finally push the 256-520 bytes of data
            else if (op.length >= 256 && op.length <= 520) {
              results.push(Buffer.from([OpCode.OP_PUSHDATA2])); // op_pushdata2
              results.push(bigToBufLE(BigInt(op.length), 2)); // two-bytes little-endian
              results.push(op);
            }

            // data longer than 520 is not supported
            else {
              throw new Error('Data too long');
            }
          }
        }

        // combine all parts of data
        return Buffer.concat(results);
      }

      /**
       * Clone via deep copy
       */
      public clone(): Script {
        return new Script(
          ...this.cmds.map((cmd) => {
            if (Buffer.isBuffer(cmd)) {
              return Buffer.from(cmd);
            } else {
              return cmd;
            }
          }),
        );
      }

      /**
       * Performs a hash160 on the serialized commands. This is useful for
       * turning a script into a P2SH redeem script.
       */
      public hash160(): Buffer {
        return hash160(this.serializeCmds());
      }

      /**
       * Performs a sha256 hash on the serialized commands. This is useful
       * fro turning a script into a P2WSH lock script.
       */
      public sha256(): Buffer {
        return sha256(this.serializeCmds());
      }
    }