#pragma once
/// \file paging.h
/// Page table structure and related definitions
#include <stdint.h>
#include <uefi/boot_services.h>
#include "kernel_args.h"

namespace boot {
namespace paging {

/// Struct to allow easy accessing of a memory page being used as a page table.
struct page_table
{
	uint64_t entries[512];

	inline page_table * get(int i, uint16_t *flags = nullptr) const {
		uint64_t entry = entries[i];
		if ((entry & 1) == 0) return nullptr;
		if (flags) *flags = entry & 0xfff;
		return reinterpret_cast<page_table *>(entry & ~0xfffull);
	}

	inline void set(int i, void *p, uint16_t flags) {
		entries[i] = reinterpret_cast<uint64_t>(p) | (flags & 0xfff);
	}
};

/// Allocate memory to be used for initial page tables. Initial offset-mapped
/// page tables are pre-filled. All pages are saved as a module in kernel args
/// and kernel args' `page_table_cache` and `num_free_tables` are updated with
/// the leftover space.
/// \arg args    The kernel args struct, used for the page table cache and pml4
void allocate_tables(
	kernel::init::args *args,
	uefi::boot_services *bs);

/// Copy existing page table entries to a new page table. Does not do a deep
/// copy - the new PML4 is updated to point to the existing next-level page
/// tables in the current PML4.
/// \arg new_pml4  The new PML4 to copy into
void add_current_mappings(page_table *new_pml4);

/// Map physical memory pages to virtual addresses in the given page tables.
/// \arg args       The kernel args struct, used for the page table cache and pml4
/// \arg phys       The physical address of the pages to map
/// \arg virt       The virtual address at which to map the pages
/// \arg count      The number of pages to map
/// \arg write_flag If true, mark the pages writeable
/// \arg exe_flag   If true, mark the pages executable
void map_pages(
	kernel::init::args *args,
	uintptr_t phys, uintptr_t virt,
	size_t count, bool write_flag, bool exe_flag);

/// Map a program section in physical memory to its virtual address in the
/// given page tables.
/// \arg args    The kernel args struct, used for the page table cache and pml4
/// \arg section The program section to load
void map_section(
	kernel::init::args *args,
	const kernel::init::program_section &section);


} // namespace paging
} // namespace boot