/*!
 * common.js - common script functions for bcoin
 * Copyright (c) 2014-2015, Fedor Indutny (MIT License)
 * Copyright (c) 2014-2017, Christopher Jeffrey (MIT License).
 * https://github.com/bcoin-org/bcoin
 */

'use strict';

/**
 * @module script/common
 */

const assert = require('assert');
const util = require('../utils/util');
const secp256k1 = require('../crypto/secp256k1');
const ScriptNum = require('./scriptnum');

/**
 * Script opcodes.
 * @enum {Number}
 * @default
 */

exports.opcodes = {
  // Push
  OP_0: 0x00,

  OP_PUSHDATA1: 0x4c,
  OP_PUSHDATA2: 0x4d,
  OP_PUSHDATA4: 0x4e,

  OP_1NEGATE: 0x4f,

  OP_RESERVED: 0x50,

  OP_1: 0x51,
  OP_2: 0x52,
  OP_3: 0x53,
  OP_4: 0x54,
  OP_5: 0x55,
  OP_6: 0x56,
  OP_7: 0x57,
  OP_8: 0x58,
  OP_9: 0x59,
  OP_10: 0x5a,
  OP_11: 0x5b,
  OP_12: 0x5c,
  OP_13: 0x5d,
  OP_14: 0x5e,
  OP_15: 0x5f,
  OP_16: 0x60,

  // Control
  OP_NOP: 0x61,
  OP_VER: 0x62,
  OP_IF: 0x63,
  OP_NOTIF: 0x64,
  OP_VERIF: 0x65,
  OP_VERNOTIF: 0x66,
  OP_ELSE: 0x67,
  OP_ENDIF: 0x68,
  OP_VERIFY: 0x69,
  OP_RETURN: 0x6a,

  // Stack
  OP_TOALTSTACK: 0x6b,
  OP_FROMALTSTACK: 0x6c,
  OP_2DROP: 0x6d,
  OP_2DUP: 0x6e,
  OP_3DUP: 0x6f,
  OP_2OVER: 0x70,
  OP_2ROT: 0x71,
  OP_2SWAP: 0x72,
  OP_IFDUP: 0x73,
  OP_DEPTH: 0x74,
  OP_DROP: 0x75,
  OP_DUP: 0x76,
  OP_NIP: 0x77,
  OP_OVER: 0x78,
  OP_PICK: 0x79,
  OP_ROLL: 0x7a,
  OP_ROT: 0x7b,
  OP_SWAP: 0x7c,
  OP_TUCK: 0x7d,

  // Splice
  OP_CAT: 0x7e,
  OP_SUBSTR: 0x7f,
  OP_LEFT: 0x80,
  OP_RIGHT: 0x81,
  OP_SIZE: 0x82,

  // Bit
  OP_INVERT: 0x83,
  OP_AND: 0x84,
  OP_OR: 0x85,
  OP_XOR: 0x86,
  OP_EQUAL: 0x87,
  OP_EQUALVERIFY: 0x88,
  OP_RESERVED1: 0x89,
  OP_RESERVED2: 0x8a,

  // Numeric
  OP_1ADD: 0x8b,
  OP_1SUB: 0x8c,
  OP_2MUL: 0x8d,
  OP_2DIV: 0x8e,
  OP_NEGATE: 0x8f,
  OP_ABS: 0x90,
  OP_NOT: 0x91,
  OP_0NOTEQUAL: 0x92,
  OP_ADD: 0x93,
  OP_SUB: 0x94,
  OP_MUL: 0x95,
  OP_DIV: 0x96,
  OP_MOD: 0x97,
  OP_LSHIFT: 0x98,
  OP_RSHIFT: 0x99,
  OP_BOOLAND: 0x9a,
  OP_BOOLOR: 0x9b,
  OP_NUMEQUAL: 0x9c,
  OP_NUMEQUALVERIFY: 0x9d,
  OP_NUMNOTEQUAL: 0x9e,
  OP_LESSTHAN: 0x9f,
  OP_GREATERTHAN: 0xa0,
  OP_LESSTHANOREQUAL: 0xa1,
  OP_GREATERTHANOREQUAL: 0xa2,
  OP_MIN: 0xa3,
  OP_MAX: 0xa4,
  OP_WITHIN: 0xa5,

  // Crypto
  OP_RIPEMD160: 0xa6,
  OP_SHA1: 0xa7,
  OP_SHA256: 0xa8,
  OP_HASH160: 0xa9,
  OP_HASH256: 0xaa,
  OP_CODESEPARATOR: 0xab,
  OP_CHECKSIG: 0xac,
  OP_CHECKSIGVERIFY: 0xad,
  OP_CHECKMULTISIG: 0xae,
  OP_CHECKMULTISIGVERIFY: 0xaf,

  // Expansion
  OP_NOP1: 0xb0,
  OP_CHECKLOCKTIMEVERIFY: 0xb1,
  OP_CHECKSEQUENCEVERIFY: 0xb2,
  OP_NOP4: 0xb3,
  OP_NOP5: 0xb4,
  OP_NOP6: 0xb5,
  OP_NOP7: 0xb6,
  OP_NOP8: 0xb7,
  OP_NOP9: 0xb8,
  OP_NOP10: 0xb9,

  // Custom
  OP_INVALIDOPCODE: 0xff
};

/**
 * Opcodes by value.
 * @const {RevMap}
 */

exports.opcodesByVal = util.reverse(exports.opcodes);

/**
 * Small ints (1 indexed, 1==0).
 * @const {Buffer[]}
 */

exports.small = [
  Buffer.from([0x81]),
  Buffer.from([]),
  Buffer.from([0x01]),
  Buffer.from([0x02]),
  Buffer.from([0x03]),
  Buffer.from([0x04]),
  Buffer.from([0x05]),
  Buffer.from([0x06]),
  Buffer.from([0x07]),
  Buffer.from([0x08]),
  Buffer.from([0x09]),
  Buffer.from([0x0a]),
  Buffer.from([0x0b]),
  Buffer.from([0x0c]),
  Buffer.from([0x0d]),
  Buffer.from([0x0e]),
  Buffer.from([0x0f]),
  Buffer.from([0x10])
];

/**
 * Script and locktime flags. See {@link VerifyFlags}.
 * @enum {Number}
 */

exports.flags = {
  VERIFY_NONE: 0,
  VERIFY_P2SH: 1 << 0,
  VERIFY_STRICTENC: 1 << 1,
  VERIFY_DERSIG: 1 << 2,
  VERIFY_LOW_S: 1 << 3,
  VERIFY_NULLDUMMY: 1 << 4,
  VERIFY_SIGPUSHONLY: 1 << 5,
  VERIFY_MINIMALDATA: 1 << 6,
  VERIFY_DISCOURAGE_UPGRADABLE_NOPS: 1 << 7,
  VERIFY_CLEANSTACK: 1 << 8,
  VERIFY_CHECKLOCKTIMEVERIFY: 1 << 9,
  VERIFY_CHECKSEQUENCEVERIFY: 1 << 10,
  VERIFY_WITNESS: 1 << 11,
  VERIFY_DISCOURAGE_UPGRADABLE_WITNESS_PROGRAM: 1 << 12,
  VERIFY_MINIMALIF: 1 << 13,
  VERIFY_NULLFAIL: 1 << 14,
  VERIFY_WITNESS_PUBKEYTYPE: 1 << 15,
  VERIFY_MAST: 1 << 16
};

/**
 * Consensus verify flags (used for block validation).
 * @const {VerifyFlags}
 * @default
 */

exports.flags.MANDATORY_VERIFY_FLAGS = exports.flags.VERIFY_P2SH;

/**
 * Standard verify flags (used for mempool validation).
 * @const {VerifyFlags}
 * @default
 */

exports.flags.STANDARD_VERIFY_FLAGS = 0
  | exports.flags.MANDATORY_VERIFY_FLAGS
  | exports.flags.VERIFY_DERSIG
  | exports.flags.VERIFY_STRICTENC
  | exports.flags.VERIFY_MINIMALDATA
  | exports.flags.VERIFY_NULLDUMMY
  | exports.flags.VERIFY_DISCOURAGE_UPGRADABLE_NOPS
  | exports.flags.VERIFY_CLEANSTACK
  | exports.flags.VERIFY_MINIMALIF
  | exports.flags.VERIFY_NULLFAIL
  | exports.flags.VERIFY_CHECKLOCKTIMEVERIFY
  | exports.flags.VERIFY_CHECKSEQUENCEVERIFY
  | exports.flags.VERIFY_LOW_S
  | exports.flags.VERIFY_WITNESS
  | exports.flags.VERIFY_DISCOURAGE_UPGRADABLE_WITNESS_PROGRAM
  | exports.flags.VERIFY_WITNESS_PUBKEYTYPE;

/**
 * Standard flags without mandatory bits.
 * @const {VerifyFlags}
 * @default
 */

exports.flags.ONLY_STANDARD_VERIFY_FLAGS =
  exports.flags.STANDARD_VERIFY_FLAGS & ~exports.flags.MANDATORY_VERIFY_FLAGS;

/**
 * Sighash Types.
 * @enum {SighashType}
 * @default
 */

exports.hashType = {
  /*
   * Sign all outputs.
   */

  ALL: 1,

  /*
   * Do not sign outputs (zero sequences).
   */

  NONE: 2,

  /*
   * Sign output at the same index (zero sequences).
   */

  SINGLE: 3,

  /*
   * Sign only the current input (mask).
   */

  ANYONECANPAY: 0x80,

  /*
   * Omit the Flo TX Comment from the signature
   */

  OMIT_TX_COMMENT: (1 << 6)
};

/**
 * Sighash types by value.
 * @const {RevMap}
 */

exports.hashTypeByVal = util.reverse(exports.hashType);

/**
 * Output script types.
 * @enum {Number}
 */

exports.types = {
  NONSTANDARD: 0,
  PUBKEY: 1,
  PUBKEYHASH: 2,
  SCRIPTHASH: 3,
  MULTISIG: 4,
  NULLDATA: 5,
  WITNESSMALFORMED: 0x80 | 0,
  WITNESSSCRIPTHASH: 0x80 | 1,
  WITNESSPUBKEYHASH: 0x80 | 2,
  WITNESSMASTHASH: 0x80 | 3
};

/**
 * Output script types by value.
 * @const {RevMap}
 */

exports.typesByVal = util.reverse(exports.types);

/**
 * Test a signature to see whether it contains a valid sighash type.
 * @param {Buffer} sig
 * @returns {Boolean}
 */

exports.isHashType = function isHashType(sig) {
  assert(Buffer.isBuffer(sig));

  if (sig.length === 0)
    return false;

  const type = sig[sig.length - 1] & ~exports.hashType.ANYONECANPAY;

  if (!(type >= exports.hashType.ALL && type <= exports.hashType.SINGLE))
    return false;

  return true;
};

/**
 * Test a signature to see whether it contains a low S value.
 * @param {Buffer} sig
 * @returns {Boolean}
 */

exports.isLowDER = function isLowDER(sig) {
  if (!exports.isSignatureEncoding(sig))
    return false;

  return secp256k1.isLowS(sig.slice(0, -1));
};

/**
 * Test whether the data element is a valid key.
 * @param {Buffer} key
 * @returns {Boolean}
 */

exports.isKeyEncoding = function isKeyEncoding(key) {
  assert(Buffer.isBuffer(key));

  if (key.length < 33)
    return false;

  if (key[0] === 0x04) {
    if (key.length !== 65)
      return false;
  } else if (key[0] === 0x02 || key[0] === 0x03) {
    if (key.length !== 33)
      return false;
  } else {
    return false;
  }

  return true;
};

/**
 * Test whether the data element is a compressed key.
 * @param {Buffer} key
 * @returns {Boolean}
 */

exports.isCompressedEncoding = function isCompressedEncoding(key) {
  assert(Buffer.isBuffer(key));

  if (key.length !== 33)
    return false;

  if (key[0] !== 0x02 && key[0] !== 0x03)
    return false;

  return true;
};

/**
 * Test a signature to see if it abides by BIP66.
 * @see https://github.com/bitcoin/bips/blob/master/bip-0066.mediawiki
 * @param {Buffer} sig
 * @returns {Boolean}
 */

exports.isSignatureEncoding = function isSignatureEncoding(sig) {
  assert(Buffer.isBuffer(sig));

  // Format:
  //   0x30 [total-length] 0x02 [R-length] [R] 0x02 [S-length] [S] [sighash]
  // * total-length: 1-byte length descriptor of everything that follows,
  //   excluding the sighash byte.
  // * R-length: 1-byte length descriptor of the R value that follows.
  // * R: arbitrary-length big-endian encoded R value. It must use the shortest
  //   possible encoding for a positive integers (which means no null bytes at
  //   the start, except a single one when the next byte has its highest bit
  //   set).
  // * S-length: 1-byte length descriptor of the S value that follows.
  // * S: arbitrary-length big-endian encoded S value. The same rules apply.
  // * sighash: 1-byte value indicating what data is hashed (not part of the DER
  //   signature)

  // Minimum and maximum size constraints.
  if (sig.length < 9)
    return false;

  if (sig.length > 73)
    return false;

  // A signature is of type 0x30 (compound).
  if (sig[0] !== 0x30)
    return false;

  // Make sure the length covers the entire signature.
  if (sig[1] !== sig.length - 3)
    return false;

  // Extract the length of the R element.
  const lenR = sig[3];

  // Make sure the length of the S element is still inside the signature.
  if (5 + lenR >= sig.length)
    return false;

  // Extract the length of the S element.
  const lenS = sig[5 + lenR];

  // Verify that the length of the signature matches the sum of the length
  // of the elements.
  if (lenR + lenS + 7 !== sig.length)
    return false;

  // Check whether the R element is an integer.
  if (sig[2] !== 0x02)
    return false;

  // Zero-length integers are not allowed for R.
  if (lenR === 0)
    return false;

  // Negative numbers are not allowed for R.
  if (sig[4] & 0x80)
    return false;

  // Null bytes at the start of R are not allowed, unless R would
  // otherwise be interpreted as a negative number.
  if (lenR > 1 && (sig[4] === 0x00) && !(sig[5] & 0x80))
    return false;

  // Check whether the S element is an integer.
  if (sig[lenR + 4] !== 0x02)
    return false;

  // Zero-length integers are not allowed for S.
  if (lenS === 0)
    return false;

  // Negative numbers are not allowed for S.
  if (sig[lenR + 6] & 0x80)
    return false;

  // Null bytes at the start of S are not allowed, unless S would otherwise be
  // interpreted as a negative number.
  if (lenS > 1 && (sig[lenR + 6] === 0x00) && !(sig[lenR + 7] & 0x80))
    return false;

  return true;
};

/**
 * Format stack item into bitcoind asm format.
 * @param {Buffer} item
 * @param {Boolean?} decode - Attempt to decode hash types.
 * @returns {String} Human-readable string.
 */

exports.toASM = function toASM(item, decode) {
  if (item.length <= 4) {
    const num = ScriptNum.decode(item);
    return num.toString(10);
  }

  if (decode && exports.isSignatureEncoding(item)) {
    const type = item[item.length - 1];

    let symbol = exports.hashTypeByVal[type & 0x1f] || '';

    if (symbol) {
      if (type & exports.hashType.ANYONECANPAY)
        symbol += '|ANYONECANPAY';
      symbol = `[${symbol}]`;
    }

    return item.slice(0, -1).toString('hex') + symbol;
  }

  return item.toString('hex');
};