// ke_syscall.c - system call dispatcher
//
// KeSyscallEntry (ke_syscall.asm) handles the INT 0x40 ring-3 -> ring-0
// transition, re-orders the arguments to match MS x64, and calls
// KeSyscallDispatch with:
//
//   nr            = original RAX  (syscall number)
//   a0 .. a5      = RCX, RDX, R8, R9, R10, R11  (user arguments)
//
// Every handler receives the same (a0..a5) signature even if it uses fewer
// arguments; unused parameters are silently ignored.
//
// Return value (RAX) is a KSTATUS code *or* an arbitrary 64-bit datum
// (pointer, size, tick count, etc.) depending on the call; conventions are
// documented in syscall_nr.h.
//
// ---------------------------------------------------------------------------
// Unified handle design
// ---------------------------------------------------------------------------
// All kernel objects (FILE_OBJECT, MUTEX, SEMAPHORE, EVENT, QUEUE) are
// reference-counted OBJECTs stored in the per-process handle table.
// SYS_CLOSE_HANDLE is the single close path for every type:
//
//   KeCloseHandle(proc, handle)
//     -> ObDereferenceObject(obj)
//       -> obj->Destroy(obj)   [type-specific cleanup, e.g. FileDestroy]
//       -> MmFreePool(obj)
//
// There is no separate SyscallCloseFile.  Removing that stub was the right
// call: the object model already handled it; the dedicated syscall was only
// adding a footgun where callers could bypass the unified refcount path.

#include "ke_thread.h"
#include "ke_sched.h"
#include "ke_process.h"
#include "ke_mutex.h"
#include "ke_semaphore.h"
#include "ke_event.h"
#include "ke_queue.h"
#include "ke_debug.h"
#include "mm_virt.h"
#include "ldr_image.h"
#include "syscall_nr.h"
#include "hal_api.h"
#include "io_file.h"
#include <stdint.h>
#include <stdbool.h>
#include <string.h>

// ---------------------------------------------------------------------------
// HAL pointer - set once at boot by KeSyscallSetHal()
// ---------------------------------------------------------------------------
static const HAL_API* gHal;

void KeSyscallSetHal(const HAL_API* hal) { gHal = hal; }

// ---------------------------------------------------------------------------
// Helper: get the current process, or NULL if unavailable.
// ---------------------------------------------------------------------------
static inline PROCESS* CurrentProcess(void) {
    THREAD* t = KeCurrentThread();
    return t ? t->Owner : NULL;
}

// ---------------------------------------------------------------------------
// Helper: look up a handle and type-check it in one call.
// Bumps the refcount on success; caller must ObDereferenceObject when done.
// Returns NULL if the handle is invalid or the type does not match.
// ---------------------------------------------------------------------------
static OBJECT* HandleToObject(uint32_t handle, OBJECT_TYPE expected) {
    PROCESS* proc = CurrentProcess();
    if (!proc) return NULL;
    OBJECT* obj = KeLookupHandle(proc, handle);        // bumps refcount
    if (!obj) return NULL;
    if (obj->Type != expected) {
        ObDereferenceObject(obj);                       // undo the bump
        return NULL;
    }
    return obj;
}

// ---------------------------------------------------------------------------
// Helper: allocate a handle in the current process's table for 'obj'.
// Takes one reference on behalf of the handle slot.
// On failure, drops the reference it would have stored.
// ---------------------------------------------------------------------------
static KSTATUS AllocHandleForCurrent(OBJECT* obj, uint32_t* handleOut) {
    PROCESS* proc = CurrentProcess();
    if (!proc) return STATUS_FAILURE;
    KSTATUS s = KeAllocateHandle(proc, obj, handleOut);
    if (!KSUCCESS(s)) ObDereferenceObject(obj);
    return s;
}

// ===========================================================================
// Individual syscall handlers
// ===========================================================================

// ---------------------------------------------------------------------------
// SYS_EXIT_PROCESS (0)  a0 = exitCode
// ---------------------------------------------------------------------------
static uint64_t SyscallExitProcess(uint64_t a0, uint64_t a1, uint64_t a2,
                                    uint64_t a3, uint64_t a4, uint64_t a5) {
    (void)a1; (void)a2; (void)a3; (void)a4; (void)a5;
    THREAD*  t    = KeCurrentThread();
    PROCESS* proc = t ? t->Owner : NULL;
    if (proc) KeExitProcess(proc, (int)a0);
    if (t)    KeExitThread(t, (int)a0);
    for (;;) ; // unreachable - KeExitThread does not return
}

// ---------------------------------------------------------------------------
// SYS_EXIT_THREAD (1)  a0 = exitCode
// ---------------------------------------------------------------------------
static uint64_t SyscallExitThread(uint64_t a0, uint64_t a1, uint64_t a2,
                                   uint64_t a3, uint64_t a4, uint64_t a5) {
    (void)a1; (void)a2; (void)a3; (void)a4; (void)a5;
    THREAD* t = KeCurrentThread();
    if (t) KeExitThread(t, (int)a0);
    for (;;) ;
}

// ---------------------------------------------------------------------------
// SYS_CREATE_THREAD (2)  a0=entry a1=arg a2=priority a3=*tidOut
// ---------------------------------------------------------------------------
static uint64_t SyscallCreateThread(uint64_t a0, uint64_t a1, uint64_t a2,
                                     uint64_t a3, uint64_t a4, uint64_t a5) {
    (void)a4; (void)a5;
    PROCESS* proc = CurrentProcess();
    if (!proc) return STATUS_FAILURE;
    if (a2 >= PriorityCount) return STATUS_INVALID_PARAMETER;

    THREAD* newt = NULL;
    KSTATUS s = KeCreateThread(proc, (uintptr_t)a0, (uintptr_t)a1,
                                (THREAD_PRIORITY)a2, &newt);
    if (!KSUCCESS(s)) return s;
    if (a3) *(uint32_t*)(uintptr_t)a3 = newt->ThreadId;
    return STATUS_SUCCESS;
}

// ---------------------------------------------------------------------------
// SYS_GET_CURRENT_TID (3)
// ---------------------------------------------------------------------------
static uint64_t SyscallGetCurrentTid(uint64_t a0, uint64_t a1, uint64_t a2,
                                      uint64_t a3, uint64_t a4, uint64_t a5) {
    (void)a0; (void)a1; (void)a2; (void)a3; (void)a4; (void)a5;
    THREAD* t = KeCurrentThread();
    return t ? t->ThreadId : 0;
}

// ---------------------------------------------------------------------------
// SYS_GET_CURRENT_PID (4)
// ---------------------------------------------------------------------------
static uint64_t SyscallGetCurrentPid(uint64_t a0, uint64_t a1, uint64_t a2,
                                      uint64_t a3, uint64_t a4, uint64_t a5) {
    (void)a0; (void)a1; (void)a2; (void)a3; (void)a4; (void)a5;
    PROCESS* p = CurrentProcess();
    return p ? p->ProcessId : 0;
}

// ---------------------------------------------------------------------------
// SYS_YIELD (5)
// ---------------------------------------------------------------------------
static uint64_t SyscallYield(uint64_t a0, uint64_t a1, uint64_t a2,
                              uint64_t a3, uint64_t a4, uint64_t a5) {
    (void)a0; (void)a1; (void)a2; (void)a3; (void)a4; (void)a5;
    KeYield();
    return STATUS_SUCCESS;
}

// ---------------------------------------------------------------------------
// SYS_SLEEP (6)  a0 = milliseconds
// ---------------------------------------------------------------------------
static uint64_t SyscallSleep(uint64_t a0, uint64_t a1, uint64_t a2,
                              uint64_t a3, uint64_t a4, uint64_t a5) {
    (void)a1; (void)a2; (void)a3; (void)a4; (void)a5;
    if (!gHal) return STATUS_FAILURE;
    uint64_t deadline = gHal->Timer.QueryTicks() + (uint64_t)a0;
    while (gHal->Timer.QueryTicks() < deadline)
        KeYield();
    return STATUS_SUCCESS;
}

// ---------------------------------------------------------------------------
// SYS_SET_THREAD_PRIORITY (7)  a0 = priority
// ---------------------------------------------------------------------------
static uint64_t SyscallSetThreadPriority(uint64_t a0, uint64_t a1, uint64_t a2,
                                          uint64_t a3, uint64_t a4, uint64_t a5) {
    (void)a1; (void)a2; (void)a3; (void)a4; (void)a5;
    if (a0 >= PriorityCount) return STATUS_INVALID_PARAMETER;
    THREAD* t = KeCurrentThread();
    if (!t) return STATUS_FAILURE;
    t->Priority = (THREAD_PRIORITY)a0;
    return STATUS_SUCCESS;
}

// ---------------------------------------------------------------------------
// SYS_ALLOC (8)  a0 = size  -> void*
// ---------------------------------------------------------------------------
static uint64_t SyscallAlloc(uint64_t a0, uint64_t a1, uint64_t a2,
                              uint64_t a3, uint64_t a4, uint64_t a5) {
    (void)a1; (void)a2; (void)a3; (void)a4; (void)a5;
    if (!a0) return 0;
    return (uint64_t)(uintptr_t)MmAllocateUserMemory((size_t)a0);
}

// ---------------------------------------------------------------------------
// SYS_FREE (9)  a0 = ptr, a1 = size
// ---------------------------------------------------------------------------
static uint64_t SyscallFree(uint64_t a0, uint64_t a1, uint64_t a2,
                             uint64_t a3, uint64_t a4, uint64_t a5) {
    (void)a2; (void)a3; (void)a4; (void)a5;
    if (a0) MmFreeUserMemory((void*)(uintptr_t)a0, (size_t)a1);
    return STATUS_SUCCESS;
}

// ---------------------------------------------------------------------------
// SYS_REALLOC (10)  a0 = ptr, a1 = newSize  -> void*
// ---------------------------------------------------------------------------
static uint64_t SyscallRealloc(uint64_t a0, uint64_t a1, uint64_t a2,
                                uint64_t a3, uint64_t a4, uint64_t a5) {
    (void)a2; (void)a3; (void)a4; (void)a5;
    return (uint64_t)(uintptr_t)MmReallocateUserMemory(
        (void*)(uintptr_t)a0, (size_t)a1);
}

// ---------------------------------------------------------------------------
// SYS_MUTEX_CREATE (11)  a0 = *handleOut
// ---------------------------------------------------------------------------
static uint64_t SyscallMutexCreate(uint64_t a0, uint64_t a1, uint64_t a2,
                                    uint64_t a3, uint64_t a4, uint64_t a5) {
    (void)a1; (void)a2; (void)a3; (void)a4; (void)a5;
    if (!a0) return STATUS_INVALID_PARAMETER;
    MUTEX* mx = NULL;
    KSTATUS s = MutexCreate(&mx);
    if (!KSUCCESS(s)) return s;
    uint32_t h = 0;
    s = AllocHandleForCurrent(&mx->Header, &h);  // takes ownership of the ref
    if (!KSUCCESS(s)) return s;
    *(uint32_t*)(uintptr_t)a0 = h;
    return STATUS_SUCCESS;
}

// ---------------------------------------------------------------------------
// SYS_MUTEX_ACQUIRE (12)  a0 = handle
// ---------------------------------------------------------------------------
static uint64_t SyscallMutexAcquire(uint64_t a0, uint64_t a1, uint64_t a2,
                                     uint64_t a3, uint64_t a4, uint64_t a5) {
    (void)a1; (void)a2; (void)a3; (void)a4; (void)a5;
    MUTEX* mx = (MUTEX*)HandleToObject((uint32_t)a0, ObjectTypeMutex);
    if (!mx) return STATUS_NOT_FOUND;
    KSTATUS s = KeAcquireMutex(mx);
    ObDereferenceObject(&mx->Header);
    return s;
}

// ---------------------------------------------------------------------------
// SYS_MUTEX_TRY_ACQUIRE (13)  a0 = handle
// ---------------------------------------------------------------------------
static uint64_t SyscallMutexTryAcquire(uint64_t a0, uint64_t a1, uint64_t a2,
                                        uint64_t a3, uint64_t a4, uint64_t a5) {
    (void)a1; (void)a2; (void)a3; (void)a4; (void)a5;
    MUTEX* mx = (MUTEX*)HandleToObject((uint32_t)a0, ObjectTypeMutex);
    if (!mx) return STATUS_NOT_FOUND;
    KSTATUS s = KeTryAcquireMutex(mx);
    ObDereferenceObject(&mx->Header);
    return s;
}

// ---------------------------------------------------------------------------
// SYS_MUTEX_RELEASE (14)  a0 = handle
// ---------------------------------------------------------------------------
static uint64_t SyscallMutexRelease(uint64_t a0, uint64_t a1, uint64_t a2,
                                     uint64_t a3, uint64_t a4, uint64_t a5) {
    (void)a1; (void)a2; (void)a3; (void)a4; (void)a5;
    MUTEX* mx = (MUTEX*)HandleToObject((uint32_t)a0, ObjectTypeMutex);
    if (!mx) return STATUS_NOT_FOUND;
    KeReleaseMutex(mx);
    ObDereferenceObject(&mx->Header);
    return STATUS_SUCCESS;
}

// ---------------------------------------------------------------------------
// SYS_SEM_CREATE (15)  a0=initial a1=max a2=*handleOut
// ---------------------------------------------------------------------------
static uint64_t SyscallSemCreate(uint64_t a0, uint64_t a1, uint64_t a2,
                                  uint64_t a3, uint64_t a4, uint64_t a5) {
    (void)a3; (void)a4; (void)a5;
    if (!a2) return STATUS_INVALID_PARAMETER;
    SEMAPHORE* sem = NULL;
    KSTATUS s = SemaphoreCreate((int32_t)a0, (int32_t)a1, &sem);
    if (!KSUCCESS(s)) return s;
    uint32_t h = 0;
    s = AllocHandleForCurrent(&sem->Header, &h);
    if (!KSUCCESS(s)) return s;
    *(uint32_t*)(uintptr_t)a2 = h;
    return STATUS_SUCCESS;
}

// ---------------------------------------------------------------------------
// SYS_SEM_WAIT (16)  a0 = handle
// ---------------------------------------------------------------------------
static uint64_t SyscallSemWait(uint64_t a0, uint64_t a1, uint64_t a2,
                                uint64_t a3, uint64_t a4, uint64_t a5) {
    (void)a1; (void)a2; (void)a3; (void)a4; (void)a5;
    SEMAPHORE* sem = (SEMAPHORE*)HandleToObject((uint32_t)a0, ObjectTypeSemaphore);
    if (!sem) return STATUS_NOT_FOUND;
    KSTATUS s = KeWaitSemaphore(sem);
    ObDereferenceObject(&sem->Header);
    return s;
}

// ---------------------------------------------------------------------------
// SYS_SEM_TRY_WAIT (17)  a0 = handle
// ---------------------------------------------------------------------------
static uint64_t SyscallSemTryWait(uint64_t a0, uint64_t a1, uint64_t a2,
                                   uint64_t a3, uint64_t a4, uint64_t a5) {
    (void)a1; (void)a2; (void)a3; (void)a4; (void)a5;
    SEMAPHORE* sem = (SEMAPHORE*)HandleToObject((uint32_t)a0, ObjectTypeSemaphore);
    if (!sem) return STATUS_NOT_FOUND;
    KSTATUS s = KeTrySemaphore(sem);
    ObDereferenceObject(&sem->Header);
    return s;
}

// ---------------------------------------------------------------------------
// SYS_SEM_SIGNAL (18)  a0 = handle
// ---------------------------------------------------------------------------
static uint64_t SyscallSemSignal(uint64_t a0, uint64_t a1, uint64_t a2,
                                  uint64_t a3, uint64_t a4, uint64_t a5) {
    (void)a1; (void)a2; (void)a3; (void)a4; (void)a5;
    SEMAPHORE* sem = (SEMAPHORE*)HandleToObject((uint32_t)a0, ObjectTypeSemaphore);
    if (!sem) return STATUS_NOT_FOUND;
    KeSignalSemaphore(sem);
    ObDereferenceObject(&sem->Header);
    return STATUS_SUCCESS;
}

// ---------------------------------------------------------------------------
// SYS_EVENT_CREATE (19)  a0=type a1=initialState a2=*handleOut
// ---------------------------------------------------------------------------
static uint64_t SyscallEventCreate(uint64_t a0, uint64_t a1, uint64_t a2,
                                    uint64_t a3, uint64_t a4, uint64_t a5) {
    (void)a3; (void)a4; (void)a5;
    if (!a2 || a0 > EventManualReset) return STATUS_INVALID_PARAMETER;
    EVENT* ev = NULL;
    KSTATUS s = KeEventCreate((EVENT_TYPE)a0, (uint32_t)a1, &ev);
    if (!KSUCCESS(s)) return s;
    uint32_t h = 0;
    s = AllocHandleForCurrent(&ev->Header, &h);
    if (!KSUCCESS(s)) return s;
    *(uint32_t*)(uintptr_t)a2 = h;
    return STATUS_SUCCESS;
}

// ---------------------------------------------------------------------------
// SYS_EVENT_SIGNAL (20)  a0 = handle
// ---------------------------------------------------------------------------
static uint64_t SyscallEventSignal(uint64_t a0, uint64_t a1, uint64_t a2,
                                    uint64_t a3, uint64_t a4, uint64_t a5) {
    (void)a1; (void)a2; (void)a3; (void)a4; (void)a5;
    EVENT* ev = (EVENT*)HandleToObject((uint32_t)a0, ObjectTypeEvent);
    if (!ev) return STATUS_NOT_FOUND;
    KeSignalEvent(ev);
    ObDereferenceObject(&ev->Header);
    return STATUS_SUCCESS;
}

// ---------------------------------------------------------------------------
// SYS_EVENT_CLEAR (21)  a0 = handle
// ---------------------------------------------------------------------------
static uint64_t SyscallEventClear(uint64_t a0, uint64_t a1, uint64_t a2,
                                   uint64_t a3, uint64_t a4, uint64_t a5) {
    (void)a1; (void)a2; (void)a3; (void)a4; (void)a5;
    EVENT* ev = (EVENT*)HandleToObject((uint32_t)a0, ObjectTypeEvent);
    if (!ev) return STATUS_NOT_FOUND;
    KeClearEvent(ev);
    ObDereferenceObject(&ev->Header);
    return STATUS_SUCCESS;
}

// ---------------------------------------------------------------------------
// SYS_EVENT_WAIT (22)  a0 = handle
// ---------------------------------------------------------------------------
static uint64_t SyscallEventWait(uint64_t a0, uint64_t a1, uint64_t a2,
                                  uint64_t a3, uint64_t a4, uint64_t a5) {
    (void)a1; (void)a2; (void)a3; (void)a4; (void)a5;
    EVENT* ev = (EVENT*)HandleToObject((uint32_t)a0, ObjectTypeEvent);
    if (!ev) return STATUS_NOT_FOUND;
    KSTATUS s = KeWaitForEvent(ev);
    ObDereferenceObject(&ev->Header);
    return s;
}

// ---------------------------------------------------------------------------
// SYS_QUEUE_CREATE (23)  a0 = *handleOut
// ---------------------------------------------------------------------------
static uint64_t SyscallQueueCreate(uint64_t a0, uint64_t a1, uint64_t a2,
                                    uint64_t a3, uint64_t a4, uint64_t a5) {
    (void)a1; (void)a2; (void)a3; (void)a4; (void)a5;
    if (!a0) return STATUS_INVALID_PARAMETER;
    QUEUE* q = NULL;
    KSTATUS s = QueueCreate(&q);
    if (!KSUCCESS(s)) return s;
    uint32_t h = 0;
    s = AllocHandleForCurrent(&q->Header, &h);
    if (!KSUCCESS(s)) return s;
    *(uint32_t*)(uintptr_t)a0 = h;
    return STATUS_SUCCESS;
}

// ---------------------------------------------------------------------------
// SYS_QUEUE_SEND (24)  a0=handle a1=*msg a2=blocking
// ---------------------------------------------------------------------------
static uint64_t SyscallQueueSend(uint64_t a0, uint64_t a1, uint64_t a2,
                                  uint64_t a3, uint64_t a4, uint64_t a5) {
    (void)a3; (void)a4; (void)a5;
    if (!a1) return STATUS_INVALID_PARAMETER;
    QUEUE* q = (QUEUE*)HandleToObject((uint32_t)a0, ObjectTypeQueue);
    if (!q) return STATUS_NOT_FOUND;
    KSTATUS s = KeSendMessage(q, (const QUEUE_MESSAGE*)(uintptr_t)a1, (bool)a2);
    ObDereferenceObject(&q->Header);
    return s;
}

// ---------------------------------------------------------------------------
// SYS_QUEUE_RECV (25)  a0=handle a1=*msg a2=blocking
// ---------------------------------------------------------------------------
static uint64_t SyscallQueueRecv(uint64_t a0, uint64_t a1, uint64_t a2,
                                  uint64_t a3, uint64_t a4, uint64_t a5) {
    (void)a3; (void)a4; (void)a5;
    if (!a1) return STATUS_INVALID_PARAMETER;
    QUEUE* q = (QUEUE*)HandleToObject((uint32_t)a0, ObjectTypeQueue);
    if (!q) return STATUS_NOT_FOUND;
    KSTATUS s = KeReceiveMessage(q, (QUEUE_MESSAGE*)(uintptr_t)a1, (bool)a2);
    ObDereferenceObject(&q->Header);
    return s;
}

// ---------------------------------------------------------------------------
// SYS_CLOSE_HANDLE (26)  a0 = handle
//
// The one and only close path.  KeCloseHandle drops the handle-table reference
// on 'obj'.  If that was the last reference, ObDereferenceObject runs the
// type-specific Destroy callback (FileDestroy, etc.) and frees the pool memory.
// No per-type close syscall needed or wanted.
// ---------------------------------------------------------------------------
static uint64_t SyscallCloseHandle(uint64_t a0, uint64_t a1, uint64_t a2,
                                    uint64_t a3, uint64_t a4, uint64_t a5) {
    (void)a1; (void)a2; (void)a3; (void)a4; (void)a5;
    PROCESS* proc = CurrentProcess();
    if (!proc) return STATUS_FAILURE;
    KeCloseHandle(proc, (uint32_t)a0);
    return STATUS_SUCCESS;
}

// ---------------------------------------------------------------------------
// SYS_OPEN_FILE (27)  a0=*path a1=*handleOut
// ---------------------------------------------------------------------------
static uint64_t SyscallOpenFile(uint64_t a0, uint64_t a1, uint64_t a2,
                                 uint64_t a3, uint64_t a4, uint64_t a5) {
    (void)a2; (void)a3; (void)a4; (void)a5;
    if (!a0 || !a1) return STATUS_INVALID_PARAMETER;
    FILE_OBJECT* file = NULL;
    KSTATUS s = IoOpenFile((const char*)(uintptr_t)a0, &file);
    if (!KSUCCESS(s)) return s;
    uint32_t h = 0;
    s = AllocHandleForCurrent(&file->Header, &h);
    if (!KSUCCESS(s)) {
        // AllocHandleForCurrent already dropped the ref on failure;
        // the refcount is now 0, so ObDereferenceObject will run FileDestroy.
        ObDereferenceObject(&file->Header);
        return s;
    }
    *(uint32_t*)(uintptr_t)a1 = h;
    return STATUS_SUCCESS;
}

// ---------------------------------------------------------------------------
// SYS_READ_FILE (28)  a0=handle a1=buf a2=size a3=*bytesReadOut
// ---------------------------------------------------------------------------
static uint64_t SyscallReadFile(uint64_t a0, uint64_t a1, uint64_t a2,
                                 uint64_t a3, uint64_t a4, uint64_t a5) {
    (void)a4; (void)a5;
    if (!a1) return STATUS_INVALID_PARAMETER;
    FILE_OBJECT* file = (FILE_OBJECT*)HandleToObject((uint32_t)a0, ObjectTypeFile);
    if (!file) return STATUS_NOT_FOUND;
    size_t got = 0;
    KSTATUS s = IoReadFile(file, (void*)(uintptr_t)a1, (size_t)a2, &got);
    if (a3) *(size_t*)(uintptr_t)a3 = got;
    ObDereferenceObject(&file->Header);
    return s;
}

// ---------------------------------------------------------------------------
// SYS_SEEK_FILE (29)  a0=handle a1=offset
// ---------------------------------------------------------------------------
static uint64_t SyscallSeekFile(uint64_t a0, uint64_t a1, uint64_t a2,
                                 uint64_t a3, uint64_t a4, uint64_t a5) {
    (void)a2; (void)a3; (void)a4; (void)a5;
    FILE_OBJECT* file = (FILE_OBJECT*)HandleToObject((uint32_t)a0, ObjectTypeFile);
    if (!file) return STATUS_NOT_FOUND;
    KSTATUS s = IoSeekFile(file, (uint64_t)a1);
    ObDereferenceObject(&file->Header);
    return s;
}

// ---------------------------------------------------------------------------
// SYS_GET_FILE_SIZE (30)  a0=handle  -> uint64_t
// ---------------------------------------------------------------------------
static uint64_t SyscallGetFileSize(uint64_t a0, uint64_t a1, uint64_t a2,
                                    uint64_t a3, uint64_t a4, uint64_t a5) {
    (void)a1; (void)a2; (void)a3; (void)a4; (void)a5;
    FILE_OBJECT* file = (FILE_OBJECT*)HandleToObject((uint32_t)a0, ObjectTypeFile);
    if (!file) return 0;
    uint64_t sz = IoGetFileSize(file);
    ObDereferenceObject(&file->Header);
    return sz;
}

// ---------------------------------------------------------------------------
// SYS_SCREEN_BLIT (31)  a0=x a1=y a2=w a3=h a4=*pixels
// ---------------------------------------------------------------------------
static uint64_t SyscallScreenBlit(uint64_t a0, uint64_t a1, uint64_t a2,
                                   uint64_t a3, uint64_t a4, uint64_t a5) {
    (void)a5;
    if (!gHal || !a4) return STATUS_FAILURE;
    gHal->Screen.Blit((int)a0, (int)a1, (int)a2, (int)a3,
                      (const uint32_t*)(uintptr_t)a4);
    return STATUS_SUCCESS;
}

// ---------------------------------------------------------------------------
// SYS_SCREEN_CLEAR (32)  a0=color
// ---------------------------------------------------------------------------
static uint64_t SyscallScreenClear(uint64_t a0, uint64_t a1, uint64_t a2,
                                    uint64_t a3, uint64_t a4, uint64_t a5) {
    (void)a1; (void)a2; (void)a3; (void)a4; (void)a5;
    if (!gHal) return STATUS_FAILURE;
    gHal->Screen.Clear((uint32_t)a0);
    return STATUS_SUCCESS;
}

// ---------------------------------------------------------------------------
// SYS_SCREEN_GET_SIZE (33)  a0=*widthOut a1=*heightOut
// ---------------------------------------------------------------------------
static uint64_t SyscallScreenGetSize(uint64_t a0, uint64_t a1, uint64_t a2,
                                      uint64_t a3, uint64_t a4, uint64_t a5) {
    (void)a2; (void)a3; (void)a4; (void)a5;
    if (!gHal) return STATUS_FAILURE;
    int w = 0, h = 0;
    gHal->Screen.GetSize(&w, &h);
    if (a0) *(int*)(uintptr_t)a0 = w;
    if (a1) *(int*)(uintptr_t)a1 = h;
    return STATUS_SUCCESS;
}

// ---------------------------------------------------------------------------
// SYS_SCREEN_PUT_CHAR (34)  a0=c a1=x a2=y a3=fg a4=bg
// ---------------------------------------------------------------------------
static uint64_t SyscallScreenPutChar(uint64_t a0, uint64_t a1, uint64_t a2,
                                      uint64_t a3, uint64_t a4, uint64_t a5) {
    (void)a5;
    if (!gHal) return STATUS_FAILURE;
    gHal->Screen.PutChar((char)a0, (int)a1, (int)a2,
                         (uint32_t)a3, (uint32_t)a4);
    return STATUS_SUCCESS;
}

// ---------------------------------------------------------------------------
// SYS_KB_POLL (35)  -> 1 or 0
// ---------------------------------------------------------------------------
static uint64_t SyscallKbPoll(uint64_t a0, uint64_t a1, uint64_t a2,
                               uint64_t a3, uint64_t a4, uint64_t a5) {
    (void)a0; (void)a1; (void)a2; (void)a3; (void)a4; (void)a5;
    if (!gHal) return 0;
    return gHal->Keyboard.Poll() ? 1u : 0u;
}

// ---------------------------------------------------------------------------
// SYS_KB_READ_CHAR (36)  -> char  (blocks, yields while waiting)
// ---------------------------------------------------------------------------
static uint64_t SyscallKbReadChar(uint64_t a0, uint64_t a1, uint64_t a2,
                                   uint64_t a3, uint64_t a4, uint64_t a5) {
    (void)a0; (void)a1; (void)a2; (void)a3; (void)a4; (void)a5;
    if (!gHal) return 0;
    while (!gHal->Keyboard.Poll()) KeYield();
    return (uint64_t)(uint8_t)gHal->Keyboard.ReadChar();
}

// ---------------------------------------------------------------------------
// SYS_KB_READ_SCANCODE (37)  -> uint8_t  (blocks, yields while waiting)
// ---------------------------------------------------------------------------
static uint64_t SyscallKbReadScancode(uint64_t a0, uint64_t a1, uint64_t a2,
                                       uint64_t a3, uint64_t a4, uint64_t a5) {
    (void)a0; (void)a1; (void)a2; (void)a3; (void)a4; (void)a5;
    if (!gHal) return 0;
    while (!gHal->Keyboard.Poll()) KeYield();
    return (uint64_t)gHal->Keyboard.ReadScancode();
}

// ---------------------------------------------------------------------------
// SYS_GET_TICK (38)  -> uint64_t milliseconds
// ---------------------------------------------------------------------------
static uint64_t SyscallGetTick(uint64_t a0, uint64_t a1, uint64_t a2,
                                uint64_t a3, uint64_t a4, uint64_t a5) {
    (void)a0; (void)a1; (void)a2; (void)a3; (void)a4; (void)a5;
    return gHal ? gHal->Timer.QueryTicks() : 0;
}

// ---------------------------------------------------------------------------
// SYS_DEBUG_PRINT (39)  a0=*str
// ---------------------------------------------------------------------------
static uint64_t SyscallDebugPrint(uint64_t a0, uint64_t a1, uint64_t a2,
                                   uint64_t a3, uint64_t a4, uint64_t a5) {
    (void)a1; (void)a2; (void)a3; (void)a4; (void)a5;
    if (a0) DbgPrint("%s", (const char*)(uintptr_t)a0);
    return STATUS_SUCCESS;
}

// ---------------------------------------------------------------------------
// SYS_CREATE_PROCESS (40)  a0=*path  a1=*handleOut
// ---------------------------------------------------------------------------
static uint64_t SyscallCreateProcess(uint64_t a0, uint64_t a1, uint64_t a2,
                                      uint64_t a3, uint64_t a4, uint64_t a5) {
    (void)a2; (void)a3; (void)a4; (void)a5;

    const char* path    = (const char*)(uintptr_t)a0;
    uint32_t*   handleOut = (uint32_t*)(uintptr_t)a1;
    if (!path || !handleOut) return STATUS_INVALID_PARAMETER;

    // Read the executable from disk.
    FILE_OBJECT* f;
    KSTATUS s = IoOpenFile(path, &f);
    if (!KSUCCESS(s)) return s;

    uint64_t size = IoGetFileSize(f);
    void* mem = MmAllocateUserMemory(size);
    if (!mem) { IoCloseFile(f); return STATUS_NO_MEMORY; }

    size_t got;
    s = IoReadFile(f, mem, size, &got);
    IoCloseFile(f);
    if (!KSUCCESS(s)) { MmFreeUserMemory(mem, size); return s; }

    // Create the process object.
    PROCESS* proc;
    s = KeCreateProcess(path, &proc);
    if (!KSUCCESS(s)) { MmFreeUserMemory(mem, size); return s; }

    // Map the PE image into memory.
    uintptr_t imageBase = 0;
    s = LdrLoadImage(mem, size, &imageBase, true);
    MmFreeUserMemory(mem, size);
    if (!KSUCCESS(s)) { ObDereferenceObject(&proc->Header); return s; }

    // Spin up the initial thread at the PE entry point.
    THREAD* thread;
    uintptr_t entryPoint = LdrGetEntryPoint(imageBase);
    s = KeCreateThread(proc, entryPoint, 0, PriorityNormal, &thread);
    if (!KSUCCESS(s)) { ObDereferenceObject(&proc->Header); return s; }

    // Give the caller a handle to the new process so they can wait on it.
    PROCESS* caller = CurrentProcess();
    if (!caller) { ObDereferenceObject(&proc->Header); return STATUS_FAILURE; }

    uint32_t handle;
    s = KeAllocateHandle(caller, &proc->Header, &handle);
    if (!KSUCCESS(s)) { ObDereferenceObject(&proc->Header); return s; }

    *handleOut = handle;
    return STATUS_SUCCESS;
}

// ---------------------------------------------------------------------------
// SYS_WAIT_FOR_PROCESS (41)  a0=handle
// Blocks until the target process signals its ExitEvent.
// ---------------------------------------------------------------------------
static uint64_t SyscallWaitForProcess(uint64_t a0, uint64_t a1, uint64_t a2,
                                       uint64_t a3, uint64_t a4, uint64_t a5) {
    (void)a1; (void)a2; (void)a3; (void)a4; (void)a5;

    PROCESS* proc = (PROCESS*)HandleToObject((uint32_t)a0, ObjectTypeProcess);
    if (!proc) return STATUS_INVALID_HANDLE;

    KSTATUS s = KeWaitForEvent(proc->ExitEvent);
    ObDereferenceObject(&proc->Header);
    return s;
}

// ---------------------------------------------------------------------------
// SYS_GET_PROCESS_EXIT_CODE (42)  a0=handle  a1=*exitCodeOut
// ---------------------------------------------------------------------------
static uint64_t SyscallGetProcessExitCode(uint64_t a0, uint64_t a1, uint64_t a2,
                                           uint64_t a3, uint64_t a4, uint64_t a5) {
    (void)a2; (void)a3; (void)a4; (void)a5;

    PROCESS* proc = (PROCESS*)HandleToObject((uint32_t)a0, ObjectTypeProcess);
    if (!proc) return STATUS_INVALID_HANDLE;

    int* exitCodeOut = (int*)(uintptr_t)a1;
    KSTATUS s = KeGetProcessExitCode(proc, exitCodeOut);
    ObDereferenceObject(&proc->Header);
    return s;
}

// ===========================================================================
// Dispatch table  -  index must match SYS_* in syscall_nr.h exactly.
// ===========================================================================
typedef uint64_t (*SYSCALL_HANDLER)(uint64_t, uint64_t, uint64_t,
                                    uint64_t, uint64_t, uint64_t);

static const SYSCALL_HANDLER gSyscallTable[SYS_MAX] = {
    /* 00 SYS_EXIT_PROCESS        */ SyscallExitProcess,
    /* 01 SYS_EXIT_THREAD         */ SyscallExitThread,
    /* 02 SYS_CREATE_THREAD       */ SyscallCreateThread,
    /* 03 SYS_GET_CURRENT_TID     */ SyscallGetCurrentTid,
    /* 04 SYS_GET_CURRENT_PID     */ SyscallGetCurrentPid,
    /* 05 SYS_YIELD               */ SyscallYield,
    /* 06 SYS_SLEEP               */ SyscallSleep,
    /* 07 SYS_SET_THREAD_PRIORITY */ SyscallSetThreadPriority,
    /* 08 SYS_ALLOC               */ SyscallAlloc,
    /* 09 SYS_FREE                */ SyscallFree,
    /* 10 SYS_REALLOC             */ SyscallRealloc,
    /* 11 SYS_MUTEX_CREATE        */ SyscallMutexCreate,
    /* 12 SYS_MUTEX_ACQUIRE       */ SyscallMutexAcquire,
    /* 13 SYS_MUTEX_TRY_ACQUIRE   */ SyscallMutexTryAcquire,
    /* 14 SYS_MUTEX_RELEASE       */ SyscallMutexRelease,
    /* 15 SYS_SEM_CREATE          */ SyscallSemCreate,
    /* 16 SYS_SEM_WAIT            */ SyscallSemWait,
    /* 17 SYS_SEM_TRY_WAIT        */ SyscallSemTryWait,
    /* 18 SYS_SEM_SIGNAL          */ SyscallSemSignal,
    /* 19 SYS_EVENT_CREATE        */ SyscallEventCreate,
    /* 20 SYS_EVENT_SIGNAL        */ SyscallEventSignal,
    /* 21 SYS_EVENT_CLEAR         */ SyscallEventClear,
    /* 22 SYS_EVENT_WAIT          */ SyscallEventWait,
    /* 23 SYS_QUEUE_CREATE        */ SyscallQueueCreate,
    /* 24 SYS_QUEUE_SEND          */ SyscallQueueSend,
    /* 25 SYS_QUEUE_RECV          */ SyscallQueueRecv,
    /* 26 SYS_CLOSE_HANDLE        */ SyscallCloseHandle,
    /* 27 SYS_OPEN_FILE           */ SyscallOpenFile,
    /* 28 SYS_READ_FILE           */ SyscallReadFile,
    /* 29 SYS_SEEK_FILE           */ SyscallSeekFile,
    /* 30 SYS_GET_FILE_SIZE       */ SyscallGetFileSize,
    /* 31 SYS_SCREEN_BLIT         */ SyscallScreenBlit,
    /* 32 SYS_SCREEN_CLEAR        */ SyscallScreenClear,
    /* 33 SYS_SCREEN_GET_SIZE     */ SyscallScreenGetSize,
    /* 34 SYS_SCREEN_PUT_CHAR     */ SyscallScreenPutChar,
    /* 35 SYS_KB_POLL             */ SyscallKbPoll,
    /* 36 SYS_KB_READ_CHAR        */ SyscallKbReadChar,
    /* 37 SYS_KB_READ_SCANCODE    */ SyscallKbReadScancode,
    /* 38 SYS_GET_TICK            */ SyscallGetTick,
    /* 39 SYS_DEBUG_PRINT         */ SyscallDebugPrint,
    /* 40 SYS_CREATE_PROCESS      */ SyscallCreateProcess,
    /* 41 SYS_WAIT_FOR_PROCESS    */ SyscallWaitForProcess,
    /* 42 SYS_GET_PROCESS_EXIT_CODE */ SyscallGetProcessExitCode,
};

// ---------------------------------------------------------------------------
// Entry point - called from ke_syscall.asm after argument re-ordering
// ---------------------------------------------------------------------------
KSTATUS KeSyscallDispatch(uint64_t nr, uint64_t a0, uint64_t a1,
                           uint64_t a2, uint64_t a3, uint64_t a4, uint64_t a5) {
    if (nr >= SYS_MAX || !gSyscallTable[nr]) return STATUS_NOT_SUPPORTED;
    return (KSTATUS)gSyscallTable[nr](a0, a1, a2, a3, a4, a5);
}