import {toBufferLE, toBigIntLE, toBufferBE, toBigIntBE} from "bigint-buffer";

type Endianness = "le" | "be";

const hexByByte: string[] = [];
export function toHexString(bytes: Uint8Array): string {
  let hex = "0x";
  for (const byte of bytes) {
    if (!hexByByte[byte]) {
      hexByByte[byte] = byte < 16 ? "0" + byte.toString(16) : byte.toString(16);
    }
    hex += hexByByte[byte];
  }
  return hex;
}

/**
 * Return a byte array from a number or BigInt
 */
export function intToBytes(value: bigint | number, length: number, endianness: Endianness = "le"): Buffer {
  return bigIntToBytes(BigInt(value), length, endianness);
}

/**
 * Convert byte array in LE to integer.
 */
export function bytesToInt(value: Uint8Array, endianness: Endianness = "le"): number {
  return Number(bytesToBigInt(value, endianness));
}

export function bigIntToBytes(value: bigint, length: number, endianness: Endianness = "le"): Buffer {
  if (endianness === "le") {
    return toBufferLE(value, length);
  } else if (endianness === "be") {
    return toBufferBE(value, length);
  }
  throw new Error("endianness must be either 'le' or 'be'");
}

export function bytesToBigInt(value: Uint8Array, endianness: Endianness = "le"): bigint {
  if (endianness === "le") {
    return toBigIntLE(value as Buffer);
  } else if (endianness === "be") {
    return toBigIntBE(value as Buffer);
  }
  throw new Error("endianness must be either 'le' or 'be'");
}

export function toHex(buffer: Uint8Array | Parameters<typeof Buffer.from>[0]): string {
  if (Buffer.isBuffer(buffer)) {
    return "0x" + buffer.toString("hex");
  } else if (buffer instanceof Uint8Array) {
    return "0x" + Buffer.from(buffer.buffer, buffer.byteOffset, buffer.length).toString("hex");
  } else {
    return "0x" + Buffer.from(buffer).toString("hex");
  }
}

export function fromHex(hex: string): Uint8Array {
  const b = Buffer.from(hex.replace("0x", ""), "hex");
  return new Uint8Array(b.buffer, b.byteOffset, b.length);
}