AuroraRuntime/Source/RNG/AuRandomDevice.cpp

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

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

namespace Aurora::RNG
{
    void RandomDevice::Init(const RandomDef &def)
    {
        this->def_ = def;

        // Gross...
        if (!def.bSecure)
        {
            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(Memory::MemoryViewWrite view)
    {
        if (!view)
        {
            SysPushErrorArg();
            return;
        }

        if (this->def_.bSecure)
        {
            ReadSecureRNG(view);
        }
        else
        {
            WELL_NextBytes(&this->fast_, view.ptr, AuUInt32(view.length));
        }
    }

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

    void     RandomDevice::NextString(char *pString, AuUInt32 uLength, 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}
        };

        if (!pString)
        {
            SysPushErrorArg();
            return;
        }

        ReadSecureRNG(AuMemoryViewWrite { pString, uLength });

        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 < uLength; i++)
        {
            pString[i] = pair.first[reinterpret_cast<const AuUInt8 *>(pString)[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 uMin, AuInt32 uMax)
    {
        auto range = uMax - uMin;
        return (NextU64() % range) + uMin;
    }

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

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

    AuUInt32 RandomDevice::NextIndex(AuUInt32 uCount /* = max + 1*/)
    {
        return NextU32() % uCount;
    }
    
    float    RandomDevice::NextNumber(float min, float max)
    {
        auto range = max - min;
        return NextDecimal() * range + min;
    }

    AuMemoryViewRead RandomDevice::ToSeed()
    {
        if (this->def_.bSecure)
        {
            return {};
        }

        return this->fast_.state;
    }

    AUKN_SYM IRandomDevice *RandomNew(const Aurora::RNG::RandomDef &def)
    {
        auto pDevice = _new RandomDevice();
        if (!pDevice)
        {
            return nullptr;
        }

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

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