use crate::memory::{
    PhysAddr, RandomAccessMemory,
    ram::{NUM_PAGES, Page},
};

pub struct PreAllocStore {
    heap: Box<[u8; NUM_PAGES * 4096]>,
}

unsafe impl Send for PreAllocStore {}
impl PreAllocStore {
    pub fn new() -> Self {
        Self {
            heap: unsafe { Box::new_zeroed().assume_init() },
        }
    }
}

impl RandomAccessMemory for PreAllocStore {
    #[inline(always)]
    fn read_word(&self, addr: PhysAddr) -> u32 {
        unsafe { (self.heap.as_ptr().add(addr as usize) as *const u32).read() }
    }

    #[inline(always)]
    fn read_byte(&self, addr: PhysAddr) -> u8 {
        self.heap[addr as usize]
    }

    #[inline(always)]
    fn read_page(&self, addr: PhysAddr) -> &Page {
        debug_assert_eq!(addr % 4096, 0);
        unsafe { (self.heap.as_ptr().add(addr as usize) as *const Page).as_ref_unchecked() }
    }

    #[inline(always)]
    fn write_byte(&mut self, addr: PhysAddr, value: u8) {
        self.heap[addr as usize] = value;
    }

    #[inline(always)]
    fn write_word(&mut self, addr: PhysAddr, value: u32) {
        unsafe { (self.heap.as_ptr().add(addr as usize) as *mut u32).write(value) };
    }

    #[inline(always)]
    fn write_page(&mut self, addr: PhysAddr, value: &Page) {
        self.heap[addr as usize..addr as usize + 4096].copy_from_slice(value);
    }
}