use std::fs::read_to_string;

pub unsafe trait VirtualMemoryApi: Sized + Drop {
    type Reservation<'s>: Reservation + 's
    where
        Self: 's;

    fn getPageSize(&self) -> usize;

    fn reserveMemory<'s>(&'s self, pagesCount: usize) -> Option<Self::Reservation<'s>>;

    unsafe fn extendReservation<'s>(
        &'s self,
        base: &Self::Reservation<'s>,
        pagesCount: usize,
    ) -> ExtendResult<Self::Reservation<'s>>;
}

pub unsafe trait Reservation: Sized + Ord + Drop {
    fn getPageSize(&self) -> usize;
    fn pagesCount(&self) -> usize;
    unsafe fn commitPages(&mut self, indexOfFirst: usize, count: usize) -> *mut [u8];
    unsafe fn decommitPages(&mut self, indexOfFirst: usize, count: usize);
    unsafe fn release(self);

    fn isFollowedBy(&self, next: &Self) -> bool;
    fn isPrecededBy(&self, next: &Self) -> bool {
        return next.isFollowedBy(self);
    }
}

pub enum ExtendResult<T> {
    OutOfMemory,
    ContinuationIsBusy,
    Success(T),
}

impl<T> ExtendResult<T> {
    pub fn map<R>(&self, caster: impl FnOnce(&T) -> R) -> ExtendResult<R> {
        match self {
            ExtendResult::Success(v) => {
                return ExtendResult::Success(caster(&v));
            }
            ExtendResult::ContinuationIsBusy => return ExtendResult::ContinuationIsBusy,
            ExtendResult::OutOfMemory => return ExtendResult::OutOfMemory,
        }
    }

    pub fn map_into<R>(self, caster: impl FnOnce(T) -> R) -> ExtendResult<R> {
        match self {
            ExtendResult::Success(v) => {
                return ExtendResult::Success(caster(v));
            }
            ExtendResult::ContinuationIsBusy => return ExtendResult::ContinuationIsBusy,
            ExtendResult::OutOfMemory => return ExtendResult::OutOfMemory,
        }
    }
}