//
//  SeqNum.h
//  libraries/networking/src/udt
//
//  Created by Clement on 7/23/15.
//  Copyright 2015 High Fidelity, Inc.
//
//  Distributed under the Apache License, Version 2.0.
//  See the accompanying file LICENSE or http://www.apache.org/licenses/LICENSE-2.0.html
//

#ifndef hifi_SeqNum_h
#define hifi_SeqNum_h

#include <functional>

#include <glm/detail/func_common.hpp>

namespace udt {

class SeqNum {
public:
    // Base type of sequence numbers
    using Type = uint32_t;
    
    // Values are for 29 bit SeqNum
    static const Type THRESHOLD = 0x0FFFFFFF; // threshold for comparing sequence numbers
    static const Type MAX = 0x1FFFFFFF; // maximum sequence number used in UDT
    
    SeqNum() = default;
    SeqNum(const SeqNum& other) : _value(other._value) {}
    
    // Only explicit conversions
    explicit SeqNum(char* value) { _value = (*reinterpret_cast<int32_t*>(value)) & MAX; }
    explicit SeqNum(Type value) { _value = (value <= MAX) ? value : MAX; }
    explicit operator Type() { return _value; }
    
    inline SeqNum& operator++() {
        _value = (_value == MAX) ? 0 : ++_value;
        return *this;
    }
    inline SeqNum& operator--() {
        _value = (_value == 0) ? MAX : --_value;
        return *this;
    }
    inline SeqNum operator++(int) {
        SeqNum before = *this;
        (*this)++;
        return before;
    }
    inline SeqNum operator--(int) {
        SeqNum before = *this;
        (*this)--;
        return before;
    }
    
    inline SeqNum& operator=(const SeqNum& other) {
        _value = other._value;
        return *this;
    }
    inline SeqNum& operator+=(Type inc) {
        _value = (_value + inc > MAX) ? _value + inc - (MAX + 1) : _value + inc;
        return *this;
    }
    inline SeqNum& operator-=(Type dec) {
        _value = (_value < dec) ? MAX - (dec - _value + 1) : _value - dec;
        return *this;
    }
    
    inline bool operator==(const SeqNum& other) const {
        return _value == other._value;
    }
    inline bool operator!=(const SeqNum& other) const {
         return _value != other._value;
    }
    
    friend bool operator<(const SeqNum&  a, const SeqNum& b);
    friend bool operator>(const SeqNum&  a, const SeqNum& b);
    friend bool operator<=(const SeqNum&  a, const SeqNum& b);
    friend bool operator>=(const SeqNum&  a, const SeqNum& b);
    
    friend SeqNum operator+(const SeqNum a, const Type& b);
    friend SeqNum operator+(const Type& a, const SeqNum b);
    friend SeqNum operator-(const SeqNum a, const Type& b);
    friend SeqNum operator-(const Type& a, const SeqNum b);
    
    friend int seqlen(const SeqNum& seq1, const SeqNum& seq2);
    friend int seqoff(const SeqNum& seq1, const SeqNum& seq2);
    
private:
    Type _value { 0 };
    
    friend struct std::hash<SeqNum>;
};
    
    
inline bool operator<(const SeqNum&  a, const SeqNum& b) {
    return (glm::abs(a._value - b._value) < SeqNum::THRESHOLD) ? a._value < b._value : b._value < a._value;
}

inline bool operator>(const SeqNum&  a, const SeqNum& b) {
    return (glm::abs(a._value - b._value) < SeqNum::THRESHOLD) ? a._value > b._value : b._value > a._value;
}

inline bool operator<=(const SeqNum&  a, const SeqNum& b) {
    return (glm::abs(a._value - b._value) < SeqNum::THRESHOLD) ? a._value <= b._value : b._value <= a._value;
}

inline bool operator>=(const SeqNum&  a, const SeqNum& b) {
    return (glm::abs(a._value - b._value) < SeqNum::THRESHOLD) ? a._value >= b._value : b._value >= a._value;
}
    
    
inline SeqNum operator+(SeqNum a, const SeqNum::Type& b) {
    a += b;
    return a;
}

inline SeqNum operator+(const SeqNum::Type& a, SeqNum b) {
    b += a;
    return b;
}

inline SeqNum operator-(SeqNum a, const SeqNum::Type& b) {
    a -= b;
    return a;
}

inline SeqNum operator-(const SeqNum::Type& a, SeqNum b) {
    b -= a;
    return b;
}
    
int seqlen(const SeqNum& seq1, const SeqNum& seq2);
int seqoff(const SeqNum& seq1, const SeqNum& seq2);
    
}

template<> struct std::hash<udt::SeqNum> {
    size_t operator()(const udt::SeqNum& seqNum) const {
        return std::hash<unsigned long>()(seqNum._value);
    }
};

#endif // hifi_SeqNum_h