BigInt to string

BigIntToString.swift

import Foundation
import BigInt

extension BigUInt {
    func string(decimals: Int) -> String {
        "\(self)".bigIntToString(decimals: decimals)
    }
}

extension BigInt {
    func bigIntToString(decimals: Int) -> String {
        "\(self)".bigIntToString(decimals: decimals)
    }
}

extension String {
    
    func bigIntToString(decimals: Int) -> String {
        var amount = self.components(separatedBy: ".").first ?? "0"
        if self == "0" || decimals == 0 {
            return amount
        }
        let dt = (decimals + 1) - amount.count
        if dt > 0 {
            for _ in 0..<dt {
                amount.insert("0", at: amount.startIndex)
            }
        }
        var offset = amount.count - decimals
        if offset == 0 {
            offset = 1
        }
        let left = amount[0..<offset]
        let right = amount[offset..<offset + min(amount.count - left.count, 6)]
        let formattedAmount = left + "." + right
        return formattedAmount.trimmingZeroDecimal
    }
    
    func bigInt(decimals: Int) -> BigInt {
        guard decimals >= 0 else {
            return 0
        }
        var numbers = self.components(separatedBy: ".")
        if numbers.count == 1 {
            var number = numbers[0]
            number += String(repeating: "0", count: decimals)
            return BigInt(stringLiteral: number)
        } else if numbers.count == 2 {
            var head = numbers[0]
            var tail = numbers[1]
            if tail.count > decimals {
                tail = tail[0..<decimals]
                let number = head + tail
                return BigInt(stringLiteral: number)
            } else {
                let offset = decimals - tail.count
                var number = head + tail
                number += String(repeating: "0", count: offset)
                return BigInt(stringLiteral: number)
            }
        }
        return 0
    }
    
}