#include "uaccess.h"
#include "assert.h"
#include "errno.h"
#include "minmax.h"
#include "mmuContext.h"
#include "paging.h"
#include "process.h"
#include "thread.h"
#include "types.h"

static int bindtoUserContext()
{
    struct thread *currentThread;
    struct mmu_context *ctx;

    currentThread = getCurrentThread();
    assert(NULL != currentThread->process);

    /* Switch to the user's address space */
    ctx = processGetMMUContext(currentThread->process);
    return threadChangeCurrentContext(ctx);
}

static int unbindUserContext()
{
    return threadChangeCurrentContext(NULL);
}

static int memcpyUserMemNoCheck(vaddr_t dest, vaddr_t src, size_t size)
{

    int ret;

    ret = bindtoUserContext();
    if (ret != 0)
        return ret;

    memcpy((void *)dest, (void *)src, size);

    ret = unbindUserContext();
    if (ret != 0)
        return ret;

    return size;
}

int memcpyToUser(uaddr_t to, vaddr_t from, size_t size)
{

    if ((uint)to < PAGING_BASE_USER_ADDRESS)
        return -EPERM;
    if ((uint)to > PAGING_TOP_USER_ADDRESS - size)
        return -EPERM;

    return memcpyUserMemNoCheck(to, from, size);
}

int memcpyFromUser(vaddr_t to, uaddr_t from, size_t size)
{

    if ((uint)from < PAGING_BASE_USER_ADDRESS)
        return -EPERM;
    if ((uint)from > PAGING_TOP_USER_ADDRESS - size)
        return -EPERM;

    return memcpyUserMemNoCheck(to, from, size);
}

static int strzcpyFromUserNoCheck(char *to, char *from, size_t size)
{
    int ret;

    ret = bindtoUserContext();
    if (ret != 0)
        return ret;

    for (unsigned int i = 0; i < size; i++) {
        to[i] = from[i];
        if (from[i] == '\0')
            break;
    }

    if (size > 0)
        to[size - 1] = '\0';

    ret = unbindUserContext();
    if (ret != 0)
        return ret;

    return size;
}

int strzcpyFromUser(vaddr_t *to, uaddr_t *from, size_t size)
{
    if ((uint)from < PAGING_BASE_USER_ADDRESS)
        return -EPERM;
    if ((uint)from > PAGING_TOP_USER_ADDRESS - size)
        return -EPERM;

    return strzcpyFromUserNoCheck((char *)to, (char *)from, size);
}