//
// Created by rick on 21-02-21.
//

#include <sys/types.h>
#include <attributes.h>

#include <myke/mem/paging.h>
#include <sys/param.h>

#define PAGING_DIR_INDEX(virt) ((virt) >> 22)
#define PAGING_TABLE_INDEX(virt) ((virt) >> 12 & 0x03FF)

#define KERNEL_OFFSET 0xC0000000

// One page table, only 4M
#define PAGING_STATE_EARLY 0
#define PAGING_STATE_FULL 60

page_directory_entry att_aligned(4096) kernel_page_directory[DIRECTORY_SIZE] = {0};

int paging_state = PAGING_STATE_EARLY;

void paging_load_directory(uintptr_t physical_address) {
    asm volatile("mov %%eax, %%cr3" : : "a" (physical_address));
}

uintptr_t paging_get_current_directory_physical() {
    uintptr_t directory_address;
    asm volatile("mov %%cr3, %%eax" : "=a" (directory_address));
    return directory_address;
}

page_directory_entry *paging_get_current() {
    return kernel_page_directory;
}

int paging_map_4m(uintptr_t physical_address, uintptr_t virtual_address, int count, int mode) {
    if (virtual_address & ~PAGING_MASK_4M || physical_address & PAGING_MASK_4M) {
        // address not 4M aligned
        return PAGING_RESULT_ALIGN;
    }
    page_directory_entry *dir = paging_get_current();
    for (int i = 0; i < count; ++i) {
        page_directory_entry current_val = dir[PAGING_DIR_INDEX(virtual_address) + i];
        if (current_val & DIRECTORY_PRESENT_MASK) {
            return PAGING_RESULT_INUSE;
        }
    }
    page_directory_entry mask = DIRECTORY_PAGE_SIZE_MASK;
    if (mode & PAGING_MODE_RW) {
        mask |= DIRECTORY_RW_MASK;
    }
    if (mode & PAGING_MODE_US) {
        mask |= DIRECTORY_US_MASK;
    }
    for (int i = 0; i < count; ++i) {
        dir[PAGING_DIR_INDEX(virtual_address) + i] = physical_address & mask;
    }
    paging_load_directory((uintptr_t) dir);
    return PAGING_RESULT_OK;
}

int paging_map_memory(uintptr_t physical_address, uintptr_t virtual_address, int count, int mode) {
    if (mode & PAGING_MODE_4M) {
        return paging_map_4m(physical_address, virtual_address, count, mode);
    }
    if (paging_state < PAGING_STATE_FULL) {
        // can't allocate 4K pages yet
        if ((virtual_address & ~PAGING_MASK_4M) != (physical_address & ~PAGING_MASK_4M)) {
            return PAGING_RESULT_ERR; // not in same pos in 4M page
        }
        int table_index = PAGING_TABLE_INDEX(virtual_address);
        int pages = DIV_ROUND_UP(table_index + count, 1024);
        return paging_map_4m(physical_address & PAGING_MASK_4M,
                             virtual_address & PAGING_MASK_4M,
                             pages,
                             mode | PAGING_MODE_4M);
    }
    return PAGING_RESULT_ERR;
}