/*
 * Copyright (c) 2018 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 <switch.h>
#include <stdarg.h>
#include <stratosphere.hpp>

#include "dmnt_cheat_types.hpp"

enum CheatVmOpcodeType : u32 {
    CheatVmOpcodeType_StoreStatic = 0,
    CheatVmOpcodeType_BeginConditionalBlock = 1,
    CheatVmOpcodeType_EndConditionalBlock = 2,
    CheatVmOpcodeType_ControlLoop = 3,
    CheatVmOpcodeType_LoadRegisterStatic = 4,
    CheatVmOpcodeType_LoadRegisterMemory = 5,
    CheatVmOpcodeType_StoreStaticToAddress = 6,
    CheatVmOpcodeType_PerformArithmeticStatic = 7,
    CheatVmOpcodeType_BeginKeypressConditionalBlock = 8,
    
    /* These are not implemented by Gateway's VM. */
    CheatVmOpcodeType_PerformArithmeticRegister = 9,
    CheatVmOpcodeType_StoreRegisterToAddress = 10,
    CheatVmOpcodeType_Reserved11 = 11,
    
    /* This is a meta entry, and not a real opcode. */
    /* This is to facilitate multi-nybble instruction decoding. */
    CheatVmOpcodeType_ExtendedWidth = 12,
    
    /* Extended width opcodes. */
    CheatVmOpcodeType_BeginRegisterConditionalBlock = 0xC0,
};

enum MemoryAccessType : u32 {
    MemoryAccessType_MainNso = 0,
    MemoryAccessType_Heap = 1,
};

enum ConditionalComparisonType : u32 {
    ConditionalComparisonType_GT = 1,
    ConditionalComparisonType_GE = 2,
    ConditionalComparisonType_LT = 3,
    ConditionalComparisonType_LE = 4,
    ConditionalComparisonType_EQ = 5,
    ConditionalComparisonType_NE = 6,
};

enum RegisterArithmeticType : u32 {
    RegisterArithmeticType_Addition = 0,
    RegisterArithmeticType_Subtraction = 1,
    RegisterArithmeticType_Multiplication = 2,
    RegisterArithmeticType_LeftShift = 3,
    RegisterArithmeticType_RightShift = 4,
    
    /* These are not supported by Gateway's VM. */
    RegisterArithmeticType_LogicalAnd = 5,
    RegisterArithmeticType_LogicalOr = 6,
    RegisterArithmeticType_LogicalNot = 7,
    RegisterArithmeticType_LogicalXor = 8,
    
    RegisterArithmeticType_None = 9,
};

enum StoreRegisterOffsetType : u32 {
    StoreRegisterOffsetType_None = 0,
    StoreRegisterOffsetType_Reg = 1,
    StoreRegisterOffsetType_Imm = 2,
};

enum CompareRegisterValueType : u32 {
    CompareRegisterValueType_MemoryRelAddr = 0,
    CompareRegisterValueType_MemoryOfsReg = 1,
    CompareRegisterValueType_RegisterRelAddr = 2,
    CompareRegisterValueType_RegisterOfsReg = 3,
    CompareRegisterValueType_StaticValue = 4,
    CompareRegisterValueType_OtherRegister = 5,
};

union VmInt {
    u8  bit8;
    u16 bit16;
    u32 bit32;
    u64 bit64;
};

struct StoreStaticOpcode {
    u32 bit_width;
    MemoryAccessType mem_type;
    u32 offset_register;
    u64 rel_address;
    VmInt value;
};

struct BeginConditionalOpcode {
    u32 bit_width;
    MemoryAccessType mem_type;
    ConditionalComparisonType cond_type;
    u64 rel_address;
    VmInt value;
};

struct EndConditionalOpcode {};

struct ControlLoopOpcode {
    bool start_loop;
    u32 reg_index;
    u32 num_iters;
};

struct LoadRegisterStaticOpcode {
    u32 reg_index;
    u64 value;
};

struct LoadRegisterMemoryOpcode {
    u32 bit_width;
    MemoryAccessType mem_type;
    u32 reg_index;
    bool load_from_reg;
    u64 rel_address;
};

struct StoreStaticToAddressOpcode {
    u32 bit_width;
    u32 reg_index;
    bool increment_reg;
    bool add_offset_reg;
    u32 offset_reg_index;
    u64 value;
};

struct PerformArithmeticStaticOpcode {
    u32 bit_width;
    u32 reg_index;
    RegisterArithmeticType math_type;
    u32 value;
};

struct BeginKeypressConditionalOpcode {
    u32 key_mask;
};

struct PerformArithmeticRegisterOpcode {
    u32 bit_width;
    RegisterArithmeticType math_type;
    u32 dst_reg_index;
    u32 src_reg_1_index;
    u32 src_reg_2_index;
    bool has_immediate;
    VmInt value;
};

struct StoreRegisterToAddressOpcode {
    u32 bit_width;
    u32 str_reg_index;
    u32 addr_reg_index;
    bool increment_reg;
    StoreRegisterOffsetType ofs_type;
    u32 ofs_reg_index;
    u64 rel_address;
};

struct BeginRegisterConditionalOpcode {
    u32 bit_width;
    ConditionalComparisonType cond_type;
    u32 val_reg_index;
    CompareRegisterValueType comp_type;
    MemoryAccessType mem_type;
    u32 addr_reg_index;
    u32 other_reg_index;
    u32 ofs_reg_index;
    u64 rel_address;
    VmInt value;
};


struct CheatVmOpcode {
    CheatVmOpcodeType opcode;
    bool begin_conditional_block;
    union {
        StoreStaticOpcode store_static;
        BeginConditionalOpcode begin_cond;
        EndConditionalOpcode end_cond;
        ControlLoopOpcode ctrl_loop;
        LoadRegisterStaticOpcode ldr_static;
        LoadRegisterMemoryOpcode ldr_memory;
        StoreStaticToAddressOpcode str_static;
        PerformArithmeticStaticOpcode perform_math_static;
        BeginKeypressConditionalOpcode begin_keypress_cond;
        PerformArithmeticRegisterOpcode perform_math_reg;
        StoreRegisterToAddressOpcode str_register;
        BeginRegisterConditionalOpcode begin_reg_cond;
    };
};

class DmntCheatVm {
    public:
        constexpr static size_t MaximumProgramOpcodeCount = 0x400;
        constexpr static size_t NumRegisters = 0x10;
    private:
        size_t num_opcodes = 0;
        size_t instruction_ptr = 0;
        size_t condition_depth = 0;
        bool decode_success = false;
        u32 program[MaximumProgramOpcodeCount] = {0};
        u64 registers[NumRegisters] = {0};
        size_t loop_tops[NumRegisters] = {0};
    private:
        bool DecodeNextOpcode(CheatVmOpcode *out);
        void SkipConditionalBlock();
        void ResetState();
        
        /* For debugging. These will be IFDEF'd out normally. */
        void OpenDebugLogFile();
        void CloseDebugLogFile();
        void LogToDebugFile(const char *format, ...);
        void LogOpcode(const CheatVmOpcode *opcode);
        
        static u64 GetVmInt(VmInt value, u32 bit_width);
        static u64 GetCheatProcessAddress(const CheatProcessMetadata* metadata, MemoryAccessType mem_type, u64 rel_address);
    public:
        DmntCheatVm() { }
        
        size_t GetProgramSize() {
            return this->num_opcodes;
        }
        
        bool LoadProgram(const CheatEntry *cheats, size_t num_cheats);
        void Execute(const CheatProcessMetadata *metadata);
#ifdef DMNT_CHEAT_VM_DEBUG_LOG
    private:
        FILE *debug_log_file = NULL;
#endif
};