use std::cell::RefCell;
use crate::block_device::{BLOCK_SIZE, BlockDevice};

#[repr(C)]
pub struct MemoryDisk {
    /// Emulating a block device with a segment of RAM,
    /// which is 64MiB == 4KiB per block * 16384 blocks
    pub arena: RefCell<Vec<u8>>,
}

impl MemoryDisk {
    pub fn new() -> Self {
        Self {
            arena: RefCell::new(vec![0u8; BLOCK_SIZE * 16384]),
        }
    }

}

impl BlockDevice for MemoryDisk {
    fn read(&self, block_id: usize, buffer: &mut [u8]) {
        let block_front = block_id * BLOCK_SIZE;
        let block_back = block_front + BLOCK_SIZE;
        let arena = self.arena.borrow();
        buffer.copy_from_slice(&arena[block_front..block_back]);
    }

    fn write(&self, block_id: usize, buffer: &[u8]) {
        let block_front = block_id * BLOCK_SIZE;
        let block_back = block_front + BLOCK_SIZE;
        let mut arena = self.arena.borrow_mut();
        arena[block_front..block_back].copy_from_slice(buffer);
    }
}