/*
 * Copyright (c) Atmosphère-NX
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms and conditions of the GNU General Public License,
 * version 2, as published by the Free Software Foundation.
 *
 * This program is distributed in the hope it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 * more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
#include <stratosphere.hpp>

namespace ams::hos {

    namespace {

        constinit os::SdkMutex g_hos_init_lock;
        constinit hos::Version g_hos_version;
        constinit bool g_set_hos_version;

        Result GetExosphereApiInfo(exosphere::ApiInfo *out) {
            u64 exosphere_cfg;
            R_TRY_CATCH(spl::impl::GetConfig(std::addressof(exosphere_cfg), spl::ConfigItem::ExosphereApiVersion)) {
                R_CATCH_RETHROW(spl::ResultSecureMonitorNotInitialized)
            } R_END_TRY_CATCH_WITH_ABORT_UNLESS;

            *out = { exosphere_cfg };
            return ResultSuccess();
        }

        Result GetApproximateExosphereApiInfo(exosphere::ApiInfo *out) {
            u64 exosphere_cfg;

            R_TRY_CATCH(spl::impl::GetConfig(std::addressof(exosphere_cfg), spl::ConfigItem::ExosphereApproximateApiVersion)) {
                R_CATCH_RETHROW(spl::ResultSecureMonitorBusy)
            } R_END_TRY_CATCH_WITH_ABORT_UNLESS;

            *out = { exosphere_cfg };
            return ResultSuccess();
        }

        exosphere::ApiInfo GetExosphereApiInfo(bool allow_approximate) {
            exosphere::ApiInfo info;
            while (true) {
                if (R_SUCCEEDED(GetExosphereApiInfo(std::addressof(info)))) {
                    return info;
                }

                if (allow_approximate && R_SUCCEEDED(GetApproximateExosphereApiInfo(std::addressof(info)))) {
                    return info;
                }

                svc::SleepThread(TimeSpan::FromMilliSeconds(25).GetNanoSeconds());
            }
        }

        settings::FirmwareVersion GetSettingsFirmwareVersion() {
            /* Mount the system version title. */
            R_ABORT_UNLESS(ams::fs::MountSystemData("sysver", ncm::SystemDataId::SystemVersion));
            ON_SCOPE_EXIT { ams::fs::Unmount("sysver"); };

            /* Read the firmware version file. */
            ams::fs::FileHandle file;
            R_ABORT_UNLESS(ams::fs::OpenFile(std::addressof(file), "sysver:/file", fs::OpenMode_Read));
            ON_SCOPE_EXIT { ams::fs::CloseFile(file); };

            /* Must be possible to read firmware version from file. */
            settings::FirmwareVersion firmware_version;
            R_ABORT_UNLESS(ams::fs::ReadFile(file, 0, std::addressof(firmware_version), sizeof(firmware_version)));

            return firmware_version;
        }

    }

    void InitializeVersionInternal(bool allow_approximate) {
        /* Get the current (and previous approximation of) target firmware. */
        hos::Version prev, current;
        bool has_prev = false;
        {
            /* Acquire exclusive access to set hos version. */
            std::scoped_lock lk(g_hos_init_lock);

            /* Save the previous value of g_hos_version. */
            prev     = g_hos_version;
            has_prev = g_set_hos_version;

            /* Set hos version = exosphere api version target firmware. */
            g_hos_version = static_cast<hos::Version>(GetExosphereApiInfo(allow_approximate).GetTargetFirmware());

            /* Save the current value of g_hos_version. */
            current = g_hos_version;

            /* Note that we've set a previous hos version. */
            g_set_hos_version = true;
        }

        /* Ensure that this is a hos version we can sanely *try* to run. */
        /* To be friendly, we will only require that we recognize the major and minor versions. */
        /* We can consider only recognizing major in the future, but micro seems safe to ignore as */
        /* there are no breaking IPC changes in minor updates. */
        {
            constexpr u32 MaxMajor = (static_cast<u32>(hos::Version_Max) >> 24) & 0xFF;
            constexpr u32 MaxMinor = (static_cast<u32>(hos::Version_Max) >> 16) & 0xFF;

            const u32 major = (static_cast<u32>(current) >> 24) & 0xFF;
            const u32 minor = (static_cast<u32>(current) >> 16) & 0xFF;

            const bool is_safely_tryable_version = (current <= hos::Version_Max) || (major == MaxMajor && minor <= MaxMinor);
            AMS_ABORT_UNLESS(is_safely_tryable_version);
        }

        /* Ensure that this is a hos version compatible with previous approximations. */
        if (has_prev) {
            AMS_ABORT_UNLESS(current >= prev);

            const u32 current_major = (static_cast<u32>(current) >> 24) & 0xFF;
            const u32 prev_major    = (static_cast<u32>(prev) >> 24) & 0xFF;

            AMS_ABORT_UNLESS(current_major == prev_major);
        }

        /* Set the version for libnx. */
        {
            const u32 major = (static_cast<u32>(current) >> 24) & 0xFF;
            const u32 minor = (static_cast<u32>(current) >> 16) & 0xFF;
            const u32 micro = (static_cast<u32>(current) >>  8) & 0xFF;
            hosversionSet((BIT(31)) | (MAKEHOSVERSION(major, minor, micro)));
        }
    }

    void SetNonApproximateVersionInternal() {
        /* Get the settings . */
        const auto firmware_version = GetSettingsFirmwareVersion();

        /* Set the exosphere api version. */
        R_ABORT_UNLESS(spl::SetConfig(spl::ConfigItem::ExosphereApiVersion, (static_cast<u32>(firmware_version.major) << 24) | (static_cast<u32>(firmware_version.minor) << 16) | (static_cast<u32>(firmware_version.micro) <<  8)));

        /* Update our own version value. */
        InitializeVersionInternal(false);
    }

    ::ams::hos::Version GetVersion() {
        return g_hos_version;
    }

}