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());
  }
}