declare module 'bn.js' {
  import { Buffer } from 'buffer';

  type Endianness = 'le' | 'be';
  type IPrimeName = 'k256' | 'p224' | 'p192' | 'p25519';
  class RedBN {
    redAdd(b: RedBN): RedBN;
    redIAdd(b: RedBN): RedBN;
    redSub(b: RedBN): RedBN;
    redISub(b: RedBN): RedBN;
    redShl(num: number): RedBN;
    redMul(b: RedBN): RedBN;
    redIMul(b: RedBN): RedBN;
    redSqr(): RedBN;
    redISqr(): RedBN;
    /**
       * @description square root modulo reduction context's prime
       */
    redSqrt(): RedBN;
    /**
       * @description  modular inverse of the number
       */
    redInvm(): RedBN;
    redNeg(): RedBN;
    /**
       * @description modular exponentiation
       */
    redPow(b: RedBN): RedBN;
    fromRed(): BN;
  }

  // FIXME: not sure how to specify the reduction context here
  interface IReductionContext {
    m: number;
    prime: object;
    [key: string]: any;
  }

  export default class BN {
    constructor(
      number: number | string | number[] | Buffer | BN,
      base?: number,
      endian?: Endianness
    );
    /**
     * @description  create a reduction context
     */

    static red(reductionContext: BN | IPrimeName): IReductionContext;
    /**
     * @description  create a reduction context  with the Montgomery trick.
     */

    static mont(num: BN): IReductionContext;
    /**
     * @description  Convert number to red
     */

    /**
     * @description returns true if the supplied object is a BN.js instance
     */

    static isBN(b: object): boolean;

    toRed(reductionContext: IReductionContext): RedBN;
    /**
     * @description  clone number
     */

    clone(): BN;

    /**
     * @description  convert to base-string and pad with zeroes
     */

    toString(base?: number, length?: number): string;

    /**
     * @description convert to Javascript Number (limited to 53 bits)
     */

    toNumber(): number;

    /**
     * @description convert to JSON compatible hex string (alias of toString(16))
     */

    toJSON(): string;

    /**
     * @description  convert to byte Array, and optionally zero pad to length, throwing if already exceeding
     */

    toArray(endian?: Endianness, length?: number): number[];

    /**
     * @description convert to an instance of `type`, which must behave like an Array
     */
    toArrayLike(
      ArrayType: Buffer | Array<any>,
      endian?: Endianness,
      length?: number
    ): Buffer | Array<any>;

    /**
     * @description  convert to Node.js Buffer (if available). For compatibility with browserify and similar tools, use this instead: a.toArrayLike(Buffer, endian, length)
     */
    toBuffer(endian?: Endianness, length?: number): Buffer;

    /**
     * @description get number of bits occupied
     */

    bitLength(): number;

    /**
     * @description return number of less-significant consequent zero bits (example: 1010000 has 4 zero bits)
     */

    zeroBits(): number;

    /**
     * @description return number of bytes occupied
     */

    byteLength(): number;

    /**
     * @description  true if the number is negative
     */

    isNeg(): boolean;

    /**
     * @description  no comments
     */

    isEven(): boolean;

    /**
     * @description   no comments
     */

    isOdd(): boolean;

    /**
     * @description   no comments
     */

    isZero(): boolean;

    /**
     * @description compare numbers and return `-1 (a < b)`, `0 (a == b)`, or `1 (a > b)` depending on the comparison result 
     */

    cmp(b: BN): -1 | 0 | 1;

    /**
     * @description compare numbers and return `-1 (a < b)`, `0 (a == b)`, or `1 (a > b)` depending on the comparison result 
     */

    ucmp(b: BN): -1 | 0 | 1;

    /**
     * @description compare numbers and return `-1 (a < b)`, `0 (a == b)`, or `1 (a > b)` depending on the comparison result 
     */

    cmpn(b: number): -1 | 0 | 1;

    /**
     * @description a less than b 
     */

    lt(b: BN): boolean;

    /**
     * @description a less than b 
     */

    ltn(b: number): boolean;

    /**
     * @description a less than or equals b 
     */

    lte(b: BN): boolean;

    /**
     * @description a less than or equals b 
     */

    lten(b: number): boolean;

    /**
     * @description a greater than b
     */

    gt(b: BN): boolean;

    /**
     * @description a greater than b
     */

    gtn(b: number): boolean;

    /**
     * @description a greater than or equals b
     */

    gte(b: BN): boolean;

    /**
     * @description a greater than or equals b
     */

    gten(b: number): boolean;

    /**
     * @description a equals b
     */

    eq(b: BN): boolean;

    /**
     * @description a equals b
     */

    eqn(b: number): boolean;

    /**
     * @description convert to two's complement representation, where width is bit width
     */

    toTwos(width: number): BN;

    /**
     * @description  convert from two's complement representation, where width is the bit width
     */

    fromTwos(width: number): BN;

    /**
     * @description negate sign
     */

    neg(): BN;

    /**
     * @description negate sign
     */

    ineg(): BN;

    /**
     * @description absolute value
     */

    abs(): BN;

    /**
     * @description absolute value
     */

    iabs(): BN;

    /**
     * @description addition
     */

    add(b: BN): BN;
    /**
     * @description  addition
     */

    iadd(b: BN): BN;
    addition;
    /**
     * @description addition
     */

    addn(b: number): BN;
    /**
     * @description addition
     */

    iaddn(b: number): BN;

    /**
     * @description subtraction
     */

    sub(b: BN): BN;
    /**
     * @description subtraction
     */

    isub(b: BN): BN;
    /**
     * @description subtraction
     */

    subn(b: number): BN;
    /**
     * @description subtraction
     */

    isubn(b: number): BN;

    /**
     * @description multiply
     */

    mul(b: BN): BN;
    /**
     * @description multiply
     */

    imul(b: BN): BN;
    /**
     * @description multiply
     */

    muln(b: number): BN;
    /**
     * @description multiply
     */

    imuln(b: number): BN;

    /**
     * @description square
     */
    sqr(): BN;
    /**
     * @description square
     */
    isqr(): BN;

    /**
     * @description raise `a` to the power of `b`
     */

    pow(b: BN): BN;

    /**
     * @description divide
     */
    div(b: BN): BN;
    /**
     * @description divide
     */
    divn(b: number): BN;
    /**
     * @description divide
     */
    idivn(b: number): BN;

    /**
     * @description reduct
     */

    mod(b: BN): BN;
    /**
     * @description reduct
     */

    umod(b: BN): BN;
    /**
     * @description reduct
     */

    modn(b: number): BN;

    /**
     * @description  rounded division
     */

    divRound(b: BN): BN;

    /**
     * @description or
     */

    or(b: BN): BN;
    /**
     * @description or
     */

    ior(b: BN): BN;
    /**
     * @description or
     */

    uor(b: BN): BN;
    /**
     * @description or
     */

    iuor(b: BN): BN;

    /**
     * @description and
     */

    and(b: BN): BN;
    /**
     * @description and
     */

    iand(b: BN): BN;
    /**
     * @description and
     */

    uand(b: BN): BN;
    /**
     * @description and
     */

    iuand(b: BN): BN;
    /**
     * @description and (NOTE: `andln` is going to be replaced with `andn` in future)
     */

    andln(b: number): BN;
    /**
     * @description xor
     */

    xor(b: BN): BN;

    /**
     * @description xor
     */

    ixor(b: BN): BN;
    /**
     * @description xor
     */

    uxor(b: BN): BN;
    /**
     * @description xor
     */

    iuxor(b: BN): BN;
    /**
     * @description set specified bit to 1
     */

    setn(b: number): BN;
    /**
     * @description shift left
     */

    shln(b: number): BN;
    /**
     * @description shift left
     */

    ishln(b: number): BN;
    /**
     * @description shift left
     */

    ushln(b: number): BN;
    /**
     * @description shift left
     */

    iushln(b: number): BN;
    /**
     * @description shift right
     */

    shrn(b: number): BN;

    /**
     * @description shift right
     */

    ishrn(b: number): BN;
    /**
     * @description shift right
     */

    ushrn(b: number): BN;
    /**
     * @description shift right
     */

    iushrn(b: number): BN;
    /**
     * @description  test if specified bit is set
     */

    testn(b: number): boolean;
    /**
     * @description clear bits with indexes higher or equal to `b`
     */

    maskn(b: number): BN;
    /**
     * @description clear bits with indexes higher or equal to `b`
     */

    imaskn(b: number): BN;
    /**
     * @description add `1 << b` to the number
     */

    bincn(b: number): BN;
    /**
     * @description not (for the width specified by `w`) 
     */

    notn(w: number): BN;
    /**
     * @description not (for the width specified by `w`) 
     */

    inotn(w: number): BN;

    /**
     * @description GCD
     */

    gcd(b: BN): BN;
    /**
     * @description Extended GCD results `({ a: ..., b: ..., gcd: ... })`
     */

    egcd(b: BN): { a: BN; b: BN; gcd: BN };
    /**
     * @description inverse `a` modulo `b`
     */

    invm(b: BN): BN;
  }
}