AuroraRuntime/Source/RNG/RandomDevice.cpp

/***
    Copyright (C) 2021 J Reece Wilson (a/k/a "Reece"). All rights reserved.

    File: RandomDevice.cpp
    Date: 2021-9-3
    Author: Reece
***/
#include <AuroraRuntime.hpp>
#include <Source/RNG/WELL.hpp>
#include "RandomDevice.hpp"

namespace Aurora::RNG
{
    class RandomDevice : public IRandomDevice
    {
    public:
        void     Read(void *in, AuUInt32 length) override;

        AuString NextString(AuUInt32 length, ERngStringCharacters type) override;
        void     NextString(char *string, AuUInt32 length, ERngStringCharacters type) override;
        AuUInt8  NextByte() override;
        bool     NextBoolean() override;
        AuUInt32 NextU32() override;
        AuUInt64 NextU64() override;
        AuInt32  NextInt(AuInt32 min, AuInt32 max) override;
        AuUInt32 NextU32(AuUInt32 min, AuUInt32 max)    override;
        double   NextDecimal() override;
        float    NextNumber(float min, float max) override;
        AuUInt32 NextIndex(AuUInt32 count /* = max + 1*/) override;

        void Init(const RandomDef &def);
    
    private:
        RandomDef def_;
        WELLRand fast_;
    };

    void RandomDevice::Init(const RandomDef &def)
    {
        this->def_ = def;
        if (!def.secure)
        {
            if (def.seed)
            {
                this->fast_ = WELL_SeedRand(def.seed.value());
            }
            else if (def.seed64)
            {
                this->fast_ = WELL_SeedRand64(def.seed64.value());
            }
            else if (def.seedMassive)
            {
                this->fast_ = WELL_SeedRandBig64(def.seedMassive.value());
            }
            else
            {
                this->fast_ = {};
                RNG::RngFillArray<false>(this->fast_.state);
            }
        }
        // secure rng requires no init -> we just passthrough to the global ReadSecureRNG function
    }

    void     RandomDevice::Read(void *in, AuUInt32 length)
    {
        if (this->def_.secure)
        {
            ReadSecureRNG(in, length);
        }
        else
        {
            WELL_NextBytes(&this->fast_, in, length);
        }
    }

    AuString RandomDevice::NextString(AuUInt32 length, ERngStringCharacters type)
    {
        AuString ret(length, '\00');
        NextString(ret.data(), AuUInt32(ret.size()), type);
        return ret;
    }

    void     RandomDevice::NextString(char *string, AuUInt32 length, ERngStringCharacters type)
    {
        static AuPair<const char *, int> rngSequence[static_cast<int>(ERngStringCharacters::eEnumCount)] =
        {
            {"abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ", 52},
            {"abcdefghijklmnopqrstuvwxyz", 26},
            {"ABCDEFGHIJKLMNOPQRSTUVWXYZ", 26},
            {"1234567890", 10},
            {"abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890", 62},
            {"abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890=-+!$%^*.[];:", 75}
        };

        ReadSecureRNG(string, length);

        if (!ERngStringCharactersIsValid(type))
        {
            SysPushErrorArg("NextString was called with an invalid ERngStringCharacters {}", (AuUInt)type);
            type = ERngStringCharacters::eAlphaNumericCharacters; // guess we cant just return false
        }

        const auto &pair = rngSequence[static_cast<int>(type)];

        for (auto i = 0u; i < length; i++)
        {
            string[i] = pair.first[reinterpret_cast<const AuUInt8 *>(string)[i] % static_cast<int>(pair.second)];
        }
    }

    AuUInt8  RandomDevice::NextByte()
    {
        return NextFillTmpl<AuUInt8>();
    }

    bool     RandomDevice::NextBoolean()
    {
        return NextByte() > 127;
    }
    
    AuUInt32 RandomDevice::NextU32()
    {
        return NextFillTmpl<AuUInt32>();
    }
    
    AuUInt64 RandomDevice::NextU64()
    {
        return NextFillTmpl<AuUInt64>();
    }
    
    AuInt32 RandomDevice::NextInt(AuInt32 min, AuInt32 max)
    {
        auto range = max - min;
        return (NextU64() % range) + min;
    }

    AuUInt32 RandomDevice::NextU32(AuUInt32 min, AuUInt32 max)
    {
        auto range = max - min;
        return (NextU64() % range) + min;
    }

    double   RandomDevice::NextDecimal() 
    {
        return double(NextU32()) * (double(1.0) / double(AuNumericLimits<AuUInt32>::max()));
    }

    AuUInt32 RandomDevice::NextIndex(AuUInt32 count /* = max + 1*/)
    {
        return NextU32() % count;
    }
    
    float    RandomDevice::NextNumber(float min, float max)
    {
        auto range = max - min;
        return NextDecimal() * range + min;
    }
    
    AUKN_SYM IRandomDevice *RandomNew(const Aurora::RNG::RandomDef &def)
    {
        auto device = _new RandomDevice();
        if (!device)
        {
            return nullptr;
        }

        device->Init(def);
        
        return device;
    }

    AUKN_SYM void RandomRelease(IRandomDevice *stream)
    {
        AuSafeDelete<RandomDevice*>(stream);
    }
}