// ldr_image.c - PE32+ loader and export resolver
#include <stdint.h>
#include <string.h>
#include <ldr_image.h>
#include <boot_info.h>
#include <mm_virt.h>
#include <ke_debug.h>

// ---------------------------------------------------------------------------
// PE32+ structures (just what we need)
// ---------------------------------------------------------------------------
#define PE_SIGNATURE        0x00004550UL   // 'PE\0\0'
#define IMAGE_FILE_MACHINE_AMD64  0x8664

#pragma pack(push, 1)
typedef struct {
    uint16_t Magic;
    uint8_t  MajorLinkerVersion;
    uint8_t  MinorLinkerVersion;
    uint32_t SizeOfCode;
    uint32_t SizeOfInitializedData;
    uint32_t SizeOfUninitializedData;
    uint32_t AddressOfEntryPoint;
    uint32_t BaseOfCode;
    uint64_t ImageBase;
    uint32_t SectionAlignment;
    uint32_t FileAlignment;
    uint16_t MajorOSVersion;
    uint16_t MinorOSVersion;
    uint16_t MajorImageVersion;
    uint16_t MinorImageVersion;
    uint16_t MajorSubsystemVersion;
    uint16_t MinorSubsystemVersion;
    uint32_t Win32VersionValue;
    uint32_t SizeOfImage;
    uint32_t SizeOfHeaders;
    uint32_t CheckSum;
    uint16_t Subsystem;
    uint16_t DllCharacteristics;
    uint64_t SizeOfStackReserve;
    uint64_t SizeOfStackCommit;
    uint64_t SizeOfHeapReserve;
    uint64_t SizeOfHeapCommit;
    uint32_t LoaderFlags;
    uint32_t NumberOfRvaAndSizes;
    struct { uint32_t VirtualAddress; uint32_t Size; } DataDirectory[16];
} OPT_HEADER64;

typedef struct {
    uint32_t Signature;
    uint16_t Machine;
    uint16_t NumberOfSections;
    uint32_t TimeDateStamp;
    uint32_t PointerToSymbolTable;
    uint32_t NumberOfSymbols;
    uint16_t SizeOfOptionalHeader;
    uint16_t Characteristics;
    OPT_HEADER64 OptionalHeader;
} PE_HEADER;

typedef struct {
    char     Name[8];
    uint32_t VirtualSize;
    uint32_t VirtualAddress;
    uint32_t SizeOfRawData;
    uint32_t PointerToRawData;
    uint32_t PointerToRelocations;
    uint32_t PointerToLinenumbers;
    uint16_t NumberOfRelocations;
    uint16_t NumberOfLinenumbers;
    uint32_t Characteristics;
} SECTION_HEADER;

typedef struct {
    uint32_t Characteristics;
    uint32_t TimeDateStamp;
    uint16_t MajorVersion;
    uint16_t MinorVersion;
    uint32_t Name;
    uint32_t Base;
    uint32_t NumberOfFunctions;
    uint32_t NumberOfNames;
    uint32_t AddressOfFunctions;
    uint32_t AddressOfNames;
    uint32_t AddressOfNameOrdinals;
} EXPORT_DIR;

typedef struct {
    uint32_t OriginalFirstThunk;
    uint32_t TimeDateStamp;
    uint32_t ForwarderChain;
    uint32_t Name;
    uint32_t FirstThunk;
} IMPORT_DESC;

typedef struct {
    uint32_t VirtualAddress;
    uint32_t SizeOfBlock;
} BASE_RELOC;
#pragma pack(pop)

#define IMAGE_REL_BASED_DIR64 10

// ---------------------------------------------------------------------------
// Module registry
// ---------------------------------------------------------------------------
#define MAX_MODULES  32

typedef struct {
    char      Name[32];
    uintptr_t Base;
} MODULE_ENTRY;

static MODULE_ENTRY gModules[MAX_MODULES];
static int          gModuleCount = 0;

void LdrRegisterModulesFromBootInfo(const BOOT_INFO* bootInfo) {
    for (uint32_t i = 0; i < bootInfo->ModuleCount && i < MAX_MODULES; i++) {
        strncpy(gModules[gModuleCount].Name, bootInfo->Modules[i].Name, 31);
        gModules[gModuleCount].Base = bootInfo->Modules[i].VirtBase;
        gModuleCount++;
    }
}

void LdrRegisterModule(const char* name, uintptr_t base) {
    if (gModuleCount < MAX_MODULES) {
        strncpy(gModules[gModuleCount].Name, name, 31);
        gModules[gModuleCount].Base = base;
        gModuleCount++;
    }
}

static uintptr_t FindModuleBase(const char* name) {
    for (int i = 0; i < gModuleCount; i++) {
        if (_stricmp(gModules[i].Name, name) == 0) return gModules[i].Base;
    }
    return 0;
}

// ---------------------------------------------------------------------------
// Export lookup
// ---------------------------------------------------------------------------
void* LdrGetExport(const char* moduleName, const char* functionName) {
    uintptr_t base = FindModuleBase(moduleName);
    if (!base) return (void *)0;

    uint32_t peOffset = *(uint32_t *)(base + 0x3C);
    PE_HEADER* pe = (PE_HEADER *)(base + peOffset);
    if (pe->Signature != PE_SIGNATURE) return (void *)0;

    OPT_HEADER64* opt = &pe->OptionalHeader;
    if (opt->NumberOfRvaAndSizes < 1) return (void *)0;

    uint32_t expRva = opt->DataDirectory[0].VirtualAddress;
    if (!expRva) return (void *)0;

    EXPORT_DIR* exp = (EXPORT_DIR *)(base + expRva);
    uint32_t* names     = (uint32_t *)(base + exp->AddressOfNames);
    uint16_t* ordinals  = (uint16_t *)(base + exp->AddressOfNameOrdinals);
    uint32_t* functions = (uint32_t *)(base + exp->AddressOfFunctions);

    for (uint32_t i = 0; i < exp->NumberOfNames; i++) {
        const char* name = (const char *)(base + names[i]);
        if (strcmp(name, functionName) == 0) {
            uint16_t ord = ordinals[i];
            return (void *)(base + functions[ord]);
        }
    }
    return (void *)0;
}

// ---------------------------------------------------------------------------
// Entry point lookup
// ---------------------------------------------------------------------------
uintptr_t LdrGetEntryPoint(uintptr_t base) {
    uint32_t pe_offset = *(uint32_t*)(base + 0x3C);
    uint32_t entry_rva = *(uint32_t*)(base + pe_offset + 0x28);
    return base + entry_rva;
}

// ---------------------------------------------------------------------------
// Base Relocation
// ---------------------------------------------------------------------------
static KSTATUS LdrApplyRelocations(uintptr_t base, uintptr_t delta) {
    uint32_t peOffset = *(uint32_t *)(base + 0x3C);
    PE_HEADER* pe = (PE_HEADER *)(base + peOffset);
    OPT_HEADER64* opt = &pe->OptionalHeader;

    if (opt->NumberOfRvaAndSizes < 6) return STATUS_SUCCESS;
    uint32_t relocRva = opt->DataDirectory[5].VirtualAddress;
    uint32_t relocSize = opt->DataDirectory[5].Size;
    if (!relocRva || !relocSize) return STATUS_SUCCESS;

    BASE_RELOC* block = (BASE_RELOC *)(base + relocRva);
    uintptr_t end = (uintptr_t)block + relocSize;

    while ((uintptr_t)block < end && block->SizeOfBlock > 0) {
        uint32_t count = (block->SizeOfBlock - sizeof(BASE_RELOC)) / sizeof(uint16_t);
        uint16_t* entries = (uint16_t *)(block + 1);

        for (uint32_t i = 0; i < count; i++) {
            int type = entries[i] >> 12;
            int offset = entries[i] & 0xFFF;

            // For 64-bit PEs, we mostly care about DIR64 (Type 10)
            if (type == IMAGE_REL_BASED_DIR64) {
                uint64_t* ptr = (uint64_t *)(base + block->VirtualAddress + offset);
                *ptr += delta;
            }
        }
        block = (BASE_RELOC *)((uint8_t *)block + block->SizeOfBlock);
    }
    return STATUS_SUCCESS;
}

// ---------------------------------------------------------------------------
// Import resolution
// ---------------------------------------------------------------------------
KSTATUS LdrResolveImports(uintptr_t imageBase) {
    uint32_t peOffset = *(uint32_t *)(imageBase + 0x3C);
    PE_HEADER* pe = (PE_HEADER *)(imageBase + peOffset);
    OPT_HEADER64* opt = &pe->OptionalHeader;

    if (opt->NumberOfRvaAndSizes < 2) return STATUS_SUCCESS; // no imports
    uint32_t impRva = opt->DataDirectory[1].VirtualAddress;
    if (!impRva) return STATUS_SUCCESS;

    IMPORT_DESC* imp = (IMPORT_DESC *)(imageBase + impRva);
    while (imp->Name) {
        const char* dllName = (const char *)(imageBase + imp->Name);
        if (!_stricmp(dllName, "kernel32.dll") || !_stricmp(dllName, "user32.dll")
            || !_stricmp(dllName, "ole32.dll") || !_stricmp(dllName, "winmm.dll"))
            dllName = "win32.dll";
        uint64_t* thunk     = (uint64_t *)(imageBase + imp->FirstThunk);
        uint64_t* origThunk = (uint64_t *)(imageBase + (imp->OriginalFirstThunk
                                                         ? imp->OriginalFirstThunk
                                                         : imp->FirstThunk));
        while (*origThunk) {
            if (*origThunk & (1ULL << 63)) {
                // Import by ordinal - not supported.
                DbgPrint("LdrResolveImports: Ordinal imports not supported! (%s)\n", dllName);
                return STATUS_NOT_SUPPORTED;
            }
            const char* funcName = (const char *)(imageBase + (*origThunk & 0xFFFFFFFF) + 2);
            void* addr = LdrGetExport(dllName, funcName);
            if (!addr) {
                DbgPrint("LdrResolveImports: Function not found! (%s)\n", funcName);
                return STATUS_NOT_FOUND;
            }
            *thunk = (uint64_t)addr;
            thunk++;
            origThunk++;
        }
        imp++;
    }
    return STATUS_SUCCESS;
}

// LdrLoadImage - load a PE from a raw buffer into virtual space.
KSTATUS LdrLoadImage(const void* buffer, size_t size, uintptr_t* baseOut, bool user) {
    if (!buffer || !size || !baseOut) return STATUS_INVALID_PARAMETER;

    uint32_t peOffset = *(uint32_t *)((uint8_t *)buffer + 0x3C);
    PE_HEADER* pe = (PE_HEADER *)((uint8_t *)buffer + peOffset);
    if (pe->Signature != PE_SIGNATURE) return STATUS_FAILURE;

    OPT_HEADER64* opt = &pe->OptionalHeader;
    size_t imageSize = opt->SizeOfImage;

    void* mem = user ? MmAllocateUserMemory(imageSize) : MmAllocatePool(imageSize);
    if (!mem) return STATUS_NO_MEMORY;
    memset(mem, 0, imageSize);

    // Copy headers and sections
    memcpy(mem, buffer, opt->SizeOfHeaders);
    SECTION_HEADER* sec = (SECTION_HEADER *)((uint8_t *)&pe->OptionalHeader + pe->SizeOfOptionalHeader);
    for (int i = 0; i < pe->NumberOfSections; i++) {
        void* dst = (uint8_t *)mem + sec[i].VirtualAddress;
        const void* src = (const uint8_t *)buffer + sec[i].PointerToRawData;
        if (sec[i].SizeOfRawData) {
            memcpy(dst, src, sec[i].SizeOfRawData < sec[i].VirtualSize ? sec[i].SizeOfRawData : sec[i].VirtualSize);
        }
        
        uint64_t prot = PAGE_PRESENT | PAGE_WRITE | (user ? PAGE_USER : 0);
        MmSetPageProtect((uintptr_t)mem + sec[i].VirtualAddress, sec[i].VirtualSize, prot);
    }

    // Apply Relocations
    uintptr_t delta = (uintptr_t)mem - opt->ImageBase;
    if (delta != 0) {
        LdrApplyRelocations((uintptr_t)mem, delta);
    }

    // Resolve Imports
    KSTATUS status = LdrResolveImports((uintptr_t)mem);
    if (status != STATUS_SUCCESS) return status;

    *baseOut = (uintptr_t)mem;
    return STATUS_SUCCESS;
}