/*
 * 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/>.
 */
#pragma once
#include <vapours.hpp>
#include <stratosphere/fs/fs_substorage.hpp>

namespace ams::fssystem {

    class BucketTree {
        NON_COPYABLE(BucketTree);
        NON_MOVEABLE(BucketTree);
        public:
            static constexpr u32 Magic   = util::FourCC<'B','K','T','R'>::Code;
            static constexpr u32 Version = 1;

            static constexpr size_t NodeSizeMin = 1_KB;
            static constexpr size_t NodeSizeMax = 512_KB;
        public:
            class Visitor;

            struct Header {
                u32 magic;
                u32 version;
                s32 entry_count;
                s32 reserved;

                void Format(s32 entry_count);
                Result Verify() const;
            };
            static_assert(util::is_pod<Header>::value);
            static_assert(sizeof(Header) == 0x10);

            struct NodeHeader {
                s32 index;
                s32 count;
                s64 offset;

                Result Verify(s32 node_index, size_t node_size, size_t entry_size) const;
            };
            static_assert(util::is_pod<NodeHeader>::value);
            static_assert(sizeof(NodeHeader) == 0x10);

            struct Offsets {
                s64 start_offset;
                s64 end_offset;

                constexpr bool IsInclude(s64 offset) const {
                    return this->start_offset <= offset & offset < this->end_offset;
                }

                constexpr bool IsInclude(s64 offset, s64 size) const {
                    return size > 0 && this->start_offset <= offset && size <= (this->end_offset - offset);
                }
            };
            static_assert(util::is_pod<Offsets>::value);
            static_assert(sizeof(Offsets) == 0x10);

            struct OffsetCache {
                Offsets offsets;
                os::SdkMutex mutex;
                bool is_initialized;

                constexpr OffsetCache() : offsets{ -1, -1 }, mutex(), is_initialized(false) { /* ... */ }
            };

            class ContinuousReadingInfo {
                private:
                    size_t m_read_size;
                    s32 m_skip_count;
                    bool m_done;
                public:
                    constexpr ContinuousReadingInfo() : m_read_size(), m_skip_count(), m_done() { /* ... */ }

                    constexpr void Reset() { m_read_size = 0; m_skip_count = 0; m_done = false; }

                    constexpr void SetSkipCount(s32 count) { AMS_ASSERT(count >= 0); m_skip_count = count; }
                    constexpr s32 GetSkipCount() const { return m_skip_count; }
                    constexpr bool CheckNeedScan() { return (--m_skip_count) <= 0; }

                    constexpr void Done() { m_read_size = 0; m_done = true; }
                    constexpr bool IsDone() const { return m_done; }

                    constexpr void SetReadSize(size_t size) { m_read_size = size; }
                    constexpr size_t GetReadSize() const { return m_read_size; }
                    constexpr bool CanDo() const { return m_read_size > 0; }
            };

            using IAllocator = MemoryResource;
        private:
            class NodeBuffer {
                NON_COPYABLE(NodeBuffer);
                private:
                    IAllocator *m_allocator;
                    void *m_header;
                public:
                    NodeBuffer() : m_allocator(), m_header() { /* ... */ }

                    ~NodeBuffer() {
                        AMS_ASSERT(m_header == nullptr);
                    }

                    NodeBuffer(NodeBuffer &&rhs) : m_allocator(rhs.m_allocator), m_header(rhs.m_allocator) {
                        rhs.m_allocator = nullptr;
                        rhs.m_header = nullptr;
                    }

                    NodeBuffer &operator=(NodeBuffer &&rhs) {
                        if (this != std::addressof(rhs)) {
                            AMS_ASSERT(m_header == nullptr);

                            m_allocator = rhs.m_allocator;
                            m_header    = rhs.m_header;

                            rhs.m_allocator   = nullptr;
                            rhs.m_header      = nullptr;
                        }
                        return *this;
                    }

                    bool Allocate(IAllocator *allocator, size_t node_size) {
                        AMS_ASSERT(m_header == nullptr);

                        m_allocator = allocator;
                        m_header    = allocator->Allocate(node_size, sizeof(s64));

                        AMS_ASSERT(util::IsAligned(m_header, sizeof(s64)));

                        return m_header != nullptr;
                    }

                    void Free(size_t node_size) {
                        if (m_header) {
                            m_allocator->Deallocate(m_header, node_size);
                            m_header = nullptr;
                        }
                        m_allocator = nullptr;
                    }

                    void FillZero(size_t node_size) const {
                        if (m_header) {
                            std::memset(m_header, 0, node_size);
                        }
                    }

                    NodeHeader *Get() const {
                        return reinterpret_cast<NodeHeader *>(m_header);
                    }

                    NodeHeader *operator->() const { return this->Get(); }

                    template<typename T>
                    T *Get() const {
                        static_assert(util::is_pod<T>::value);
                        static_assert(sizeof(T) == sizeof(NodeHeader));
                        return reinterpret_cast<T *>(m_header);
                    }

                    IAllocator *GetAllocator() const {
                        return m_allocator;
                    }
            };
        private:
            static constexpr s32 GetEntryCount(size_t node_size, size_t entry_size) {
                return static_cast<s32>((node_size - sizeof(NodeHeader)) / entry_size);
            }

            static constexpr s32 GetOffsetCount(size_t node_size) {
                return static_cast<s32>((node_size - sizeof(NodeHeader)) / sizeof(s64));
            }

            static constexpr s32 GetEntrySetCount(size_t node_size, size_t entry_size, s32 entry_count) {
                const s32 entry_count_per_node = GetEntryCount(node_size, entry_size);
                return util::DivideUp(entry_count, entry_count_per_node);
            }

            static constexpr s32 GetNodeL2Count(size_t node_size, size_t entry_size, s32 entry_count) {
                const s32 offset_count_per_node = GetOffsetCount(node_size);
                const s32 entry_set_count       = GetEntrySetCount(node_size, entry_size, entry_count);

                if (entry_set_count <= offset_count_per_node) {
                    return 0;
                }

                const s32 node_l2_count = util::DivideUp(entry_set_count, offset_count_per_node);
                AMS_ABORT_UNLESS(node_l2_count <= offset_count_per_node);

                return util::DivideUp(entry_set_count - (offset_count_per_node - (node_l2_count - 1)), offset_count_per_node);
            }
        public:
            static constexpr s64 QueryHeaderStorageSize() { return sizeof(Header); }

            static constexpr s64 QueryNodeStorageSize(size_t node_size, size_t entry_size, s32 entry_count) {
                AMS_ASSERT(entry_size >= sizeof(s64));
                AMS_ASSERT(node_size >= entry_size + sizeof(NodeHeader));
                AMS_ASSERT(NodeSizeMin <= node_size && node_size <= NodeSizeMax);
                AMS_ASSERT(util::IsPowerOfTwo(node_size));
                AMS_ASSERT(entry_count >= 0);

                if (entry_count <= 0) {
                    return 0;
                }
                return (1 + GetNodeL2Count(node_size, entry_size, entry_count)) * static_cast<s64>(node_size);
            }

            static constexpr s64 QueryEntryStorageSize(size_t node_size, size_t entry_size, s32 entry_count) {
                AMS_ASSERT(entry_size >= sizeof(s64));
                AMS_ASSERT(node_size >= entry_size + sizeof(NodeHeader));
                AMS_ASSERT(NodeSizeMin <= node_size && node_size <= NodeSizeMax);
                AMS_ASSERT(util::IsPowerOfTwo(node_size));
                AMS_ASSERT(entry_count >= 0);

                if (entry_count <= 0) {
                    return 0;
                }
                return GetEntrySetCount(node_size, entry_size, entry_count) * static_cast<s64>(node_size);
            }
        private:
            mutable fs::SubStorage m_node_storage;
            mutable fs::SubStorage m_entry_storage;
            NodeBuffer m_node_l1;
            size_t m_node_size;
            size_t m_entry_size;
            s32 m_entry_count;
            s32 m_offset_count;
            s32 m_entry_set_count;
            OffsetCache m_offset_cache;
        public:
            BucketTree() : m_node_storage(), m_entry_storage(), m_node_l1(), m_node_size(), m_entry_size(), m_entry_count(), m_offset_count(), m_entry_set_count(), m_offset_cache() { /* ... */ }
            ~BucketTree() { this->Finalize(); }

            Result Initialize(IAllocator *allocator, fs::SubStorage node_storage, fs::SubStorage entry_storage, size_t node_size, size_t entry_size, s32 entry_count);
            void Initialize(size_t node_size, s64 end_offset);
            void Finalize();

            bool IsInitialized() const { return m_node_size > 0; }
            bool IsEmpty() const { return m_entry_size == 0; }

            Result Find(Visitor *visitor, s64 virtual_address);
            Result InvalidateCache();

            s32 GetEntryCount() const { return m_entry_count; }
            IAllocator *GetAllocator() const { return m_node_l1.GetAllocator(); }

            Result GetOffsets(Offsets *out) {
                /* Ensure we have an offset cache. */
                R_TRY(this->EnsureOffsetCache());

                /* Set the output. */
                *out = m_offset_cache.offsets;
                R_SUCCEED();
            }
        private:
            template<typename EntryType>
            struct ContinuousReadingParam {
                s64 offset;
                size_t size;
                NodeHeader entry_set;
                s32 entry_index;
                Offsets offsets;
                EntryType entry;
            };
        private:
            template<typename EntryType>
            Result ScanContinuousReading(ContinuousReadingInfo *out_info, const ContinuousReadingParam<EntryType> &param) const;

            bool IsExistL2() const { return m_offset_count < m_entry_set_count; }
            bool IsExistOffsetL2OnL1() const { return this->IsExistL2() && m_node_l1->count < m_offset_count; }

            s64 GetEntrySetIndex(s32 node_index, s32 offset_index) const {
                return (m_offset_count - m_node_l1->count) + (m_offset_count * node_index) + offset_index;
            }

            Result EnsureOffsetCache();
    };

    class BucketTree::Visitor {
        NON_COPYABLE(Visitor);
        NON_MOVEABLE(Visitor);
        private:
            friend class BucketTree;

            union EntrySetHeader {
                NodeHeader header;
                struct Info {
                    s32 index;
                    s32 count;
                    s64 end;
                    s64 start;
                } info;
                static_assert(util::is_pod<Info>::value);
            };
            static_assert(util::is_pod<EntrySetHeader>::value);
        private:
            const BucketTree *m_tree;
            BucketTree::Offsets m_offsets;
            void *m_entry;
            s32 m_entry_index;
            s32 m_entry_set_count;
            EntrySetHeader m_entry_set;
        public:
            constexpr Visitor() : m_tree(), m_entry(), m_entry_index(-1), m_entry_set_count(), m_entry_set{} { /* ... */ }
            ~Visitor() {
                if (m_entry != nullptr) {
                    m_tree->GetAllocator()->Deallocate(m_entry, m_tree->m_entry_size);
                    m_tree  = nullptr;
                    m_entry = nullptr;
                }
            }

            bool IsValid() const { return m_entry_index >= 0; }
            bool CanMoveNext() const { return this->IsValid() && (m_entry_index + 1 < m_entry_set.info.count || m_entry_set.info.index + 1 < m_entry_set_count); }
            bool CanMovePrevious() const { return this->IsValid() && (m_entry_index > 0 || m_entry_set.info.index > 0); }

            Result MoveNext();
            Result MovePrevious();

            template<typename EntryType>
            Result ScanContinuousReading(ContinuousReadingInfo *out_info, s64 offset, size_t size) const;

            const void *Get() const { AMS_ASSERT(this->IsValid()); return m_entry; }

            template<typename T>
            const T *Get() const { AMS_ASSERT(this->IsValid()); return reinterpret_cast<const T *>(m_entry); }

            const BucketTree *GetTree() const { return m_tree; }
        private:
            Result Initialize(const BucketTree *tree, const BucketTree::Offsets &offsets);

            Result Find(s64 virtual_address);

            Result FindEntrySet(s32 *out_index, s64 virtual_address, s32 node_index);
            Result FindEntrySetWithBuffer(s32 *out_index, s64 virtual_address, s32 node_index, char *buffer);
            Result FindEntrySetWithoutBuffer(s32 *out_index, s64 virtual_address, s32 node_index);

            Result FindEntry(s64 virtual_address, s32 entry_set_index);
            Result FindEntryWithBuffer(s64 virtual_address, s32 entry_set_index, char *buffer);
            Result FindEntryWithoutBuffer(s64 virtual_address, s32 entry_set_index);
    };

}