package vmm

import (
	"github.com/achilleasa/gopher-os/kernel/mem"
	"github.com/achilleasa/gopher-os/kernel/mem/pmm"
)

// PageTableEntryFlag describes a flag that can be applied to a page table entry.
type PageTableEntryFlag uintptr

// pageTableEntry describes a page table entry. These entries encode
// a physical frame address and a set of flags. The actual format
// of the entry and flags is architecture-dependent.
type pageTableEntry uintptr

// HasFlags returns true if this entry has all the input flags set.
func (pte pageTableEntry) HasFlags(flags PageTableEntryFlag) bool {
	return (uintptr(pte) & uintptr(flags)) == uintptr(flags)
}

// HasAnyFlag returns true if this entry has at least one of the input flags set.
func (pte pageTableEntry) HasAnyFlag(flags PageTableEntryFlag) bool {
	return (uintptr(pte) & uintptr(flags)) != 0
}

// SetFlags sets the input list of flags to the page table entry.
func (pte *pageTableEntry) SetFlags(flags PageTableEntryFlag) {
	*pte = (pageTableEntry)(uintptr(*pte) | uintptr(flags))
}

// ClearFlags unsets the input list of flags from the page table entry.
func (pte *pageTableEntry) ClearFlags(flags PageTableEntryFlag) {
	*pte = (pageTableEntry)(uintptr(*pte) &^ uintptr(flags))
}

// Frame returns the physical page frame that this page table entry points to.
func (pte pageTableEntry) Frame() pmm.Frame {
	return pmm.Frame((uintptr(pte) & ptePhysPageMask) >> mem.PageShift)
}

// SetFrame updates the page table entry to point the the given physical frame .
func (pte *pageTableEntry) SetFrame(frame pmm.Frame) {
	*pte = (pageTableEntry)((uintptr(*pte) &^ ptePhysPageMask) | frame.Address())
}