// SPDX-FileCopyrightText: Copyright 2022 yuzu Emulator Project
// SPDX-FileCopyrightText: Copyright 2013 Dolphin Emulator Project / 2015 Citra Emulator Project
// SPDX-License-Identifier: GPL-2.0-or-later

#include <array>
#include <cstring>
#include <fstream>
#include <iterator>
#include <optional>
#include <string_view>
#include <thread>
#include <vector>
#include "common/bit_util.h"
#include "common/common_types.h"
#include "common/logging/log.h"
#include "common/x64/cpu_detect.h"

#ifdef _WIN32
#include <windows.h>
#endif

#ifdef _MSC_VER
#include <intrin.h>

static inline u64 xgetbv(u32 index) {
    return _xgetbv(index);
}
#else

#if defined(__DragonFly__) || defined(__FreeBSD__)
// clang-format off
#include <sys/types.h>
#include <machine/cpufunc.h>
// clang-format on
#endif

static inline void __cpuidex(int info[4], u32 function_id, u32 subfunction_id) {
#if defined(__DragonFly__) || defined(__FreeBSD__)
    // Despite the name, this is just do_cpuid() with ECX as second input.
    cpuid_count((u_int)function_id, (u_int)subfunction_id, (u_int*)info);
#else
    info[0] = function_id;    // eax
    info[2] = subfunction_id; // ecx
    __asm__("cpuid"
            : "=a"(info[0]), "=b"(info[1]), "=c"(info[2]), "=d"(info[3])
            : "a"(function_id), "c"(subfunction_id));
#endif
}

static inline void __cpuid(int info[4], u32 function_id) {
    return __cpuidex(info, function_id, 0);
}

#define _XCR_XFEATURE_ENABLED_MASK 0
static inline u64 xgetbv(u32 index) {
    u32 eax, edx;
    __asm__ __volatile__("xgetbv" : "=a"(eax), "=d"(edx) : "c"(index));
    return ((u64)edx << 32) | eax;
}
#endif // _MSC_VER

namespace Common {

CPUCaps::Manufacturer CPUCaps::ParseManufacturer(std::string_view brand_string) {
    if (brand_string == "GenuineIntel") {
        return Manufacturer::Intel;
    } else if (brand_string == "AuthenticAMD") {
        return Manufacturer::AMD;
    } else if (brand_string == "HygonGenuine") {
        return Manufacturer::Hygon;
    }
    return Manufacturer::Unknown;
}

// Detects the various CPU features
static CPUCaps Detect() {
    CPUCaps caps = {};

    // Assumes the CPU supports the CPUID instruction. Those that don't would likely not support
    // yuzu at all anyway

    int cpu_id[4];

    // Detect CPU's CPUID capabilities and grab manufacturer string
    __cpuid(cpu_id, 0x00000000);
    const u32 max_std_fn = cpu_id[0]; // EAX

    std::memset(caps.brand_string, 0, std::size(caps.brand_string));
    std::memcpy(&caps.brand_string[0], &cpu_id[1], sizeof(u32));
    std::memcpy(&caps.brand_string[4], &cpu_id[3], sizeof(u32));
    std::memcpy(&caps.brand_string[8], &cpu_id[2], sizeof(u32));

    caps.manufacturer = CPUCaps::ParseManufacturer(caps.brand_string);

    // Set reasonable default cpu string even if brand string not available
    std::strncpy(caps.cpu_string, caps.brand_string, std::size(caps.brand_string));

    __cpuid(cpu_id, 0x80000000);

    const u32 max_ex_fn = cpu_id[0];

    // Detect family and other miscellaneous features
    if (max_std_fn >= 1) {
        __cpuid(cpu_id, 0x00000001);
        caps.sse = Common::Bit<25>(cpu_id[3]);
        caps.sse2 = Common::Bit<26>(cpu_id[3]);
        caps.sse3 = Common::Bit<0>(cpu_id[2]);
        caps.pclmulqdq = Common::Bit<1>(cpu_id[2]);
        caps.ssse3 = Common::Bit<9>(cpu_id[2]);
        caps.sse4_1 = Common::Bit<19>(cpu_id[2]);
        caps.sse4_2 = Common::Bit<20>(cpu_id[2]);
        caps.movbe = Common::Bit<22>(cpu_id[2]);
        caps.popcnt = Common::Bit<23>(cpu_id[2]);
        caps.aes = Common::Bit<25>(cpu_id[2]);
        caps.f16c = Common::Bit<29>(cpu_id[2]);

        // AVX support requires 3 separate checks:
        //  - Is the AVX bit set in CPUID?
        //  - Is the XSAVE bit set in CPUID?
        //  - XGETBV result has the XCR bit set.
        if (Common::Bit<28>(cpu_id[2]) && Common::Bit<27>(cpu_id[2])) {
            if ((xgetbv(_XCR_XFEATURE_ENABLED_MASK) & 0x6) == 0x6) {
                caps.avx = true;
                if (Common::Bit<12>(cpu_id[2]))
                    caps.fma = true;
            }
        }

        if (max_std_fn >= 7) {
            __cpuidex(cpu_id, 0x00000007, 0x00000000);
            // Can't enable AVX{2,512} unless the XSAVE/XGETBV checks above passed
            if (caps.avx) {
                caps.avx2 = Common::Bit<5>(cpu_id[1]);
                caps.avx512f = Common::Bit<16>(cpu_id[1]);
                caps.avx512dq = Common::Bit<17>(cpu_id[1]);
                caps.avx512cd = Common::Bit<28>(cpu_id[1]);
                caps.avx512bw = Common::Bit<30>(cpu_id[1]);
                caps.avx512vl = Common::Bit<31>(cpu_id[1]);
                caps.avx512vbmi = Common::Bit<1>(cpu_id[2]);
                caps.avx512bitalg = Common::Bit<12>(cpu_id[2]);
            }

            caps.bmi1 = Common::Bit<3>(cpu_id[1]);
            caps.bmi2 = Common::Bit<8>(cpu_id[1]);
            caps.sha = Common::Bit<29>(cpu_id[1]);

            caps.waitpkg = Common::Bit<5>(cpu_id[2]);
            caps.gfni = Common::Bit<8>(cpu_id[2]);

            __cpuidex(cpu_id, 0x00000007, 0x00000001);
            caps.avx_vnni = caps.avx && Common::Bit<4>(cpu_id[0]);
        }
    }

    if (max_ex_fn >= 0x80000004) {
        // Extract CPU model string
        __cpuid(cpu_id, 0x80000002);
        std::memcpy(caps.cpu_string, cpu_id, sizeof(cpu_id));
        __cpuid(cpu_id, 0x80000003);
        std::memcpy(caps.cpu_string + 16, cpu_id, sizeof(cpu_id));
        __cpuid(cpu_id, 0x80000004);
        std::memcpy(caps.cpu_string + 32, cpu_id, sizeof(cpu_id));
    }

    if (max_ex_fn >= 0x80000001) {
        // Check for more features
        __cpuid(cpu_id, 0x80000001);
        caps.lzcnt = Common::Bit<5>(cpu_id[2]);
        caps.fma4 = Common::Bit<16>(cpu_id[2]);
    }

    if (max_ex_fn >= 0x80000007) {
        __cpuid(cpu_id, 0x80000007);
        caps.invariant_tsc = Common::Bit<8>(cpu_id[3]);
    }

    if (max_std_fn >= 0x15) {
        __cpuid(cpu_id, 0x15);
        caps.tsc_crystal_ratio_denominator = cpu_id[0];
        caps.tsc_crystal_ratio_numerator = cpu_id[1];
        caps.crystal_frequency = cpu_id[2];
        // Some CPU models might not return a crystal frequency.
        // The CPU model can be detected to use the values from turbostat
        // https://github.com/torvalds/linux/blob/master/tools/power/x86/turbostat/turbostat.c#L5569
        // but it's easier to just estimate the TSC tick rate for these cases.
        if (caps.tsc_crystal_ratio_denominator) {
            caps.tsc_frequency = static_cast<u64>(caps.crystal_frequency) *
                                 caps.tsc_crystal_ratio_numerator /
                                 caps.tsc_crystal_ratio_denominator;
        }
    }

    if (max_std_fn >= 0x16) {
        __cpuid(cpu_id, 0x16);
        caps.base_frequency = cpu_id[0];
        caps.max_frequency = cpu_id[1];
        caps.bus_frequency = cpu_id[2];
    }

    return caps;
}

const CPUCaps& GetCPUCaps() {
    static CPUCaps caps = Detect();
    return caps;
}

std::optional<int> GetProcessorCount() {
#if defined(_WIN32)
    // Get the buffer length.
    DWORD length = 0;
    GetLogicalProcessorInformation(nullptr, &length);
    if (GetLastError() != ERROR_INSUFFICIENT_BUFFER) {
        LOG_ERROR(Frontend, "Failed to query core count.");
        return std::nullopt;
    }
    std::vector<SYSTEM_LOGICAL_PROCESSOR_INFORMATION> buffer(
        length / sizeof(SYSTEM_LOGICAL_PROCESSOR_INFORMATION));
    // Now query the core count.
    if (!GetLogicalProcessorInformation(buffer.data(), &length)) {
        LOG_ERROR(Frontend, "Failed to query core count.");
        return std::nullopt;
    }
    return static_cast<int>(
        std::count_if(buffer.cbegin(), buffer.cend(), [](const auto& proc_info) {
            return proc_info.Relationship == RelationProcessorCore;
        }));
#elif defined(__unix__)
    const int thread_count = std::thread::hardware_concurrency();
    std::ifstream smt("/sys/devices/system/cpu/smt/active");
    char state = '0';
    if (smt) {
        smt.read(&state, sizeof(state));
    }
    switch (state) {
    case '0':
        return thread_count;
    case '1':
        return thread_count / 2;
    default:
        return std::nullopt;
    }
#else
    // Shame on you
    return std::nullopt;
#endif
}

} // namespace Common
