#pragma once

#include <string>

namespace bstl {

class BigInteger {
public:
    BigInteger();
    BigInteger(int value);
    BigInteger(long long value);
    BigInteger(unsigned long long value);
    explicit BigInteger(const std::string& value);
    explicit BigInteger(const char* value);
    BigInteger(const BigInteger& other) = default;
    BigInteger& operator=(const BigInteger& other) = default;

    bool isZero() const;
    int sign() const;
    std::string toString() const;

    bool operator==(const BigInteger& other) const;
    bool operator!=(const BigInteger& other) const;
    bool operator<(const BigInteger& other) const;
    bool operator>(const BigInteger& other) const;
    bool operator<=(const BigInteger& other) const;
    bool operator>=(const BigInteger& other) const;

    bool operator==(int value) const;
    bool operator!=(int value) const;
    bool operator<(int value) const;
    bool operator>(int value) const;
    bool operator<=(int value) const;
    bool operator>=(int value) const;

    bool operator==(long long value) const;
    bool operator!=(long long value) const;
    bool operator<(long long value) const;
    bool operator>(long long value) const;
    bool operator<=(long long value) const;
    bool operator>=(long long value) const;

    BigInteger operator+() const;
    BigInteger operator-() const;
    BigInteger& operator+=(const BigInteger& other);
    BigInteger& operator-=(const BigInteger& other);
    BigInteger& operator*=(const BigInteger& other);
    BigInteger& operator/=(const BigInteger& other);

    BigInteger operator+(const BigInteger& other) const;
    BigInteger operator-(const BigInteger& other) const;
    BigInteger operator*(const BigInteger& other) const;
    BigInteger operator/(const BigInteger& other) const;

private:
    std::string digits_;  // 无符号数字，从高位到低位
    int sign_;            // -1, 0, 1

    static std::string trimLeadingZeros(const std::string& value);
    static int compareAbs(const std::string& a, const std::string& b);
    static std::string addAbs(const std::string& a, const std::string& b);
    static std::string subAbs(const std::string& a, const std::string& b);
    static std::string mulAbs(const std::string& a, const std::string& b);
    static std::string divAbs(const std::string& a, const std::string& b);
};

using BitInteger = BigInteger;

} // namespace bstl