/*
 * Copyright (c) 2018-2020 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/>.
 */
#pragma once
#include <mesosphere/kern_common.hpp>
#include <mesosphere/kern_k_thread.hpp>
#include <mesosphere/kern_select_page_table.hpp>
#include <mesosphere/kern_svc.hpp>

namespace ams::kern {

    class KCapabilities {
        private:
            static constexpr size_t SvcFlagCount = svc::NumSupervisorCalls / BITSIZEOF(u8);
            static constexpr size_t IrqFlagCount = /* TODO */0x80;

            enum class CapabilityType : u32 {
                CorePriority  = (1u <<  3) - 1,
                SyscallMask   = (1u <<  4) - 1,
                MapRange      = (1u <<  6) - 1,
                MapIoPage     = (1u <<  7) - 1,
                MapRegion     = (1u << 10) - 1,
                InterruptPair = (1u << 11) - 1,
                ProgramType   = (1u << 13) - 1,
                KernelVersion = (1u << 14) - 1,
                HandleTable   = (1u << 15) - 1,
                DebugFlags    = (1u << 16) - 1,

                Invalid       = 0u,
                Padding       = ~0u,
            };

            using RawCapabilityValue = util::BitPack32::Field<0, BITSIZEOF(util::BitPack32), u32>;

            static constexpr CapabilityType GetCapabilityType(const util::BitPack32 cap) {
                const u32 value = cap.Get<RawCapabilityValue>();
                return static_cast<CapabilityType>((~value & (value + 1)) - 1);
            }

            static constexpr u32 GetCapabilityFlag(CapabilityType type) {
                return static_cast<u32>(type) + 1;
            }

            static constexpr u32 CountTrailingZero(u32 flag) {
                for (u32 i = 0; i < BITSIZEOF(u32); i++) {
                    if (flag & (1u << i)) {
                        return i;
                    }
                }
                return BITSIZEOF(u32);
            }

            static constexpr u32 GetCapabilityId(CapabilityType type) {
                const u32 flag = GetCapabilityFlag(type);
                if (true /* C++20: std::is_constant_evaluated() */) {
                    return CountTrailingZero(flag);
                } else {
                    return static_cast<u32>(__builtin_ctz(flag));
                }
            }

            template<size_t Index, size_t Count, typename T = u32>
            using Field = util::BitPack32::Field<Index, Count, T>;

            #define DEFINE_FIELD(name, prev, ...) using name = Field<prev::Next, __VA_ARGS__>

            template<CapabilityType Type>
            static constexpr inline u32 CapabilityFlag = []() -> u32 {
                return static_cast<u32>(Type) + 1;
            }();

            template<CapabilityType Type>
            static constexpr inline u32 CapabilityId = []() -> u32 {
                const u32 flag = static_cast<u32>(Type) + 1;
                if (true /* C++20: std::is_constant_evaluated() */) {
                    for (u32 i = 0; i < BITSIZEOF(u32); i++) {
                        if (flag & (1u << i)) {
                            return i;
                        }
                    }
                    return BITSIZEOF(u32);
                } else {
                    return __builtin_ctz(flag);
                }
            }();

            struct CorePriority {
                using IdBits = Field<0, CapabilityId<CapabilityType::CorePriority> + 1>;

                DEFINE_FIELD(LowestThreadPriority,  IdBits,                6);
                DEFINE_FIELD(HighestThreadPriority, LowestThreadPriority,  6);
                DEFINE_FIELD(MinimumCoreId,         HighestThreadPriority, 8);
                DEFINE_FIELD(MaximumCoreId,         MinimumCoreId,         8);
            };

            struct SyscallMask {
                using IdBits = Field<0, CapabilityId<CapabilityType::SyscallMask> + 1>;

                DEFINE_FIELD(Mask,  IdBits, 24);
                DEFINE_FIELD(Index, Mask,    3);
            };

            static constexpr u64 PhysicalMapAllowedMask = (1ul << 36) - 1;

            struct MapRange {
                using IdBits = Field<0, CapabilityId<CapabilityType::MapRange> + 1>;

                DEFINE_FIELD(Address,  IdBits,  24);
                DEFINE_FIELD(ReadOnly, Address,  1, bool);
            };

            struct MapRangeSize {
                using IdBits = Field<0, CapabilityId<CapabilityType::MapRange> + 1>;

                DEFINE_FIELD(Pages,    IdBits,   20);
                DEFINE_FIELD(Reserved, Pages,     4);
                DEFINE_FIELD(Normal,   Reserved,  1, bool);
            };

            struct MapIoPage {
                using IdBits = Field<0, CapabilityId<CapabilityType::MapIoPage> + 1>;

                DEFINE_FIELD(Address, IdBits, 24);
            };

            enum class RegionType : u32 {
                None              = 0,
                KernelTraceBuffer = 1,
                OnMemoryBootImage = 2,
                DTB               = 3,
            };

            struct MapRegion {
                using IdBits = Field<0, CapabilityId<CapabilityType::MapRegion> + 1>;

                DEFINE_FIELD(Region0,   IdBits,      6, RegionType);
                DEFINE_FIELD(ReadOnly0, Region0,     1, bool);
                DEFINE_FIELD(Region1,   ReadOnly0,   6, RegionType);
                DEFINE_FIELD(ReadOnly1, Region1,     1, bool);
                DEFINE_FIELD(Region2,   ReadOnly1,   6, RegionType);
                DEFINE_FIELD(ReadOnly2, Region2,     1, bool);
            };

            static const u32 PaddingInterruptId = 0x3FF;

            struct InterruptPair {
                using IdBits = Field<0, CapabilityId<CapabilityType::InterruptPair> + 1>;

                DEFINE_FIELD(InterruptId0, IdBits,       10);
                DEFINE_FIELD(InterruptId1, InterruptId0, 10);
            };


            struct ProgramType {
                using IdBits = Field<0, CapabilityId<CapabilityType::ProgramType> + 1>;

                DEFINE_FIELD(Type,     IdBits,  3);
                DEFINE_FIELD(Reserved, Type,   15);
            };

            struct KernelVersion {
                using IdBits = Field<0, CapabilityId<CapabilityType::KernelVersion> + 1>;

                DEFINE_FIELD(MinorVersion, IdBits,        4);
                DEFINE_FIELD(MajorVersion, MinorVersion, 13);
            };

            struct HandleTable {
                using IdBits = Field<0, CapabilityId<CapabilityType::HandleTable> + 1>;

                DEFINE_FIELD(Size,     IdBits, 10);
                DEFINE_FIELD(Reserved, Size,    6);
            };

            struct DebugFlags {
                using IdBits = Field<0, CapabilityId<CapabilityType::DebugFlags> + 1>;

                DEFINE_FIELD(AllowDebug, IdBits,      1, bool);
                DEFINE_FIELD(ForceDebug, AllowDebug,  1, bool);
                DEFINE_FIELD(Reserved,   ForceDebug, 13);
            };

            #undef DEFINE_FIELD

            static constexpr u32 InitializeOnceFlags = CapabilityFlag<CapabilityType::CorePriority>  |
                                                       CapabilityFlag<CapabilityType::ProgramType>   |
                                                       CapabilityFlag<CapabilityType::KernelVersion> |
                                                       CapabilityFlag<CapabilityType::HandleTable>   |
                                                       CapabilityFlag<CapabilityType::DebugFlags>;
        private:
            u8 svc_access_flags[SvcFlagCount]{};
            u8 irq_access_flags[IrqFlagCount]{};
            u64 core_mask{};
            u64 priority_mask{};
            util::BitPack32 debug_capabilities;
            s32 handle_table_size{};
            util::BitPack32 intended_kernel_version;
            u32 program_type{};
        private:
            static constexpr ALWAYS_INLINE void SetSvcAllowedImpl(u8 *data, u32 id) {
                constexpr size_t BitsPerWord = BITSIZEOF(*data);
                MESOSPHERE_ASSERT(id < svc::SvcId_Count);
                data[id / BitsPerWord] |= (1ul << (id % BitsPerWord));
            }

            static constexpr ALWAYS_INLINE void ClearSvcAllowedImpl(u8 *data, u32 id) {
                constexpr size_t BitsPerWord = BITSIZEOF(*data);
                MESOSPHERE_ASSERT(id < svc::SvcId_Count);
                data[id / BitsPerWord] &= ~(1ul << (id % BitsPerWord));
            }

            bool SetSvcAllowed(u32 id) {
                if (id < BITSIZEOF(this->svc_access_flags)) {
                    SetSvcAllowedImpl(this->svc_access_flags, id);
                    return true;
                } else {
                    return false;
                }
            }

            bool SetInterruptAllowed(u32 id) {
                constexpr size_t BitsPerWord = BITSIZEOF(this->irq_access_flags[0]);
                if (id < BITSIZEOF(this->irq_access_flags)) {
                    this->irq_access_flags[id / BitsPerWord] = (1ul << (id % BitsPerWord));
                    return true;
                } else {
                    return false;
                }
            }

            Result SetCorePriorityCapability(const util::BitPack32 cap);
            Result SetSyscallMaskCapability(const util::BitPack32 cap, u32 &set_svc);
            Result MapRange(const util::BitPack32 cap, const util::BitPack32 size_cap, KProcessPageTable *page_table);
            Result MapIoPage(const util::BitPack32 cap, KProcessPageTable *page_table);
            Result MapRegion(const util::BitPack32 cap, KProcessPageTable *page_table);
            Result SetInterruptPairCapability(const util::BitPack32 cap);
            Result SetProgramTypeCapability(const util::BitPack32 cap);
            Result SetKernelVersionCapability(const util::BitPack32 cap);
            Result SetHandleTableCapability(const util::BitPack32 cap);
            Result SetDebugFlagsCapability(const util::BitPack32 cap);

            Result SetCapability(const util::BitPack32 cap, u32 &set_flags, u32 &set_svc, KProcessPageTable *page_table);
            Result SetCapabilities(const u32 *caps, s32 num_caps, KProcessPageTable *page_table);
        public:
            constexpr KCapabilities() : debug_capabilities(0), intended_kernel_version(0) { /* ... */ }

            Result Initialize(const u32 *caps, s32 num_caps, KProcessPageTable *page_table);

            constexpr u64 GetCoreMask() const { return this->core_mask; }
            constexpr u64 GetPriorityMask() const { return this->priority_mask; }
            constexpr s32 GetHandleTableSize() const { return this->handle_table_size; }

            ALWAYS_INLINE void CopySvcPermissionsTo(KThread::StackParameters &sp) const {
                static_assert(sizeof(svc_access_flags) == sizeof(sp.svc_permission));
                std::memcpy(sp.svc_permission, this->svc_access_flags, sizeof(this->svc_access_flags));

                /* Clear specific SVCs based on our state. */
                ClearSvcAllowedImpl(sp.svc_permission, svc::SvcId_ReturnFromException);
                ClearSvcAllowedImpl(sp.svc_permission, svc::SvcId_SynchronizePreemptionState);
                if (sp.is_preemption_state_pinned) {
                    ClearSvcAllowedImpl(sp.svc_permission, svc::SvcId_GetInfo);
                }
            }

            /* TODO: Member functions. */
    };

}