pub mod block_device;
pub mod disk;
pub mod filesystem;
pub mod memory;
pub mod tests;
pub mod utils;


use indexmap::IndexMap;
use log::debug;
use lru::LruCache;
use std::collections::HashMap;
use std::ffi::OsString;
use std::num::NonZeroUsize;
use std::sync::atomic::AtomicU64;
use std::sync::Arc;
use std::time::Duration;

use crate::disk::block::{DirectoryEntry, InodeBlock, SuperBlock};
use crate::memory::cached_block::BlockCache;
use block_device::{BlockDevice, BLOCK_SIZE};
use disk::bitmap::Bitmap;
use disk::block::DataBlock;
use disk::inode::INODE_SIZE;
use users::{get_current_gid, get_current_uid};

const TTL: Duration = Duration::new(0, 0);
const INODE_PER_BLOCK: usize = BLOCK_SIZE / INODE_SIZE;

/// The design of MyFS is rather simple:
/// +-------------------+
/// | Super Block       |
/// +-------------------+
/// | Inode Bitmap      |
/// +-------------------+
/// | ...               |
/// +-------------------+
/// | Data Block Bitmap |
/// +-------------------+
/// | ...               |
/// +-------------------+
/// | Inode Block       |
/// +-------------------+
/// | ...               |
/// +-------------------+
/// | Data Block        |
/// +-------------------+
/// With each block 4KiB, each Inode entry 128B

#[repr(C)]
pub struct AyaFS {
    device: Arc<dyn BlockDevice>,
    data_bitmap: Bitmap,
    inode_bitmap: Bitmap,
    inode_start_block: usize,
    data_start_block: usize,

    next_file_handle: AtomicU64,
    // file descriptor -> (inode index, read, write)
    file_handle_map: HashMap<u64, (usize, bool, bool)>,

    // inode index -> (index aware) hashmap that maps dir entry name to inode index
    dir_entry_map: LruCache<usize, IndexMap<OsString, DirectoryEntry>>,

    cached_inodes: BlockCache<InodeBlock>,
    cached_blocks: BlockCache<DataBlock>,

    super_block: SuperBlock,
}

impl AyaFS {
    pub fn new(device: Arc<dyn BlockDevice>, total_block_number: usize) -> Self {
        let max_inode_number: usize = 16384; // TODO: remove hard-coded magic number
        let inode_block_number = max_inode_number / INODE_PER_BLOCK; // == 128
        let inode_bitmap_block_number = (inode_block_number + BLOCK_SIZE - 1) / BLOCK_SIZE;

        let blocks_remaining =
            total_block_number - inode_block_number - inode_bitmap_block_number - 1;
        // let number of data blocks be x, the remaining block number be C,
        // the corresponding data bitmap length should be ceil(x / BLK_SIZE),
        // thus we have BLK_SIZE * (C-1) / (BLK_SIZE+1) <= x <= BLK_SIZE * C / (BLK_SIZE+1)
        // the difference of the two bounds is less than 1,
        // meaning only 1 integer could be in between.
        // Thus we have x = floor(BLK_SIZE * C / (BLK_SIZE + 1))
        let data_block_number = BLOCK_SIZE * blocks_remaining / (BLOCK_SIZE + 1);
        let data_bitmap_block_number = blocks_remaining - data_block_number;
        debug!("data_bitmap_block_number: {}", data_bitmap_block_number);
        debug!("inode_bitmap_block_number: {}", inode_bitmap_block_number);
        debug!("inode_block_number:  {}", inode_block_number);
        debug!("data_block_number:  {}", data_block_number);
        debug!(
            "sum:  {}",
            1 + data_bitmap_block_number
                + inode_bitmap_block_number
                + inode_block_number
                + data_block_number
        );

        let super_block = SuperBlock::new(
            data_bitmap_block_number,
            inode_bitmap_block_number,
            inode_block_number,
            data_block_number,
        );

        let mut data_bitmap = Bitmap::new(1, data_bitmap_block_number, device.clone());
        let _ = data_bitmap.allocate().unwrap(); // data block 0 is not usable
        let mut inode_bitmap = Bitmap::new(
            data_bitmap_block_number + 1,
            inode_bitmap_block_number,
            device.clone(),
        );
        let _ = inode_bitmap.allocate().unwrap(); // inode block 0 is not usable

        let mut fs = Self {
            device: device.clone(),
            data_bitmap,
            inode_bitmap,
            inode_start_block: data_bitmap_block_number + inode_bitmap_block_number + 1,
            data_start_block: data_bitmap_block_number
                + inode_bitmap_block_number
                + inode_block_number
                + 1,

            next_file_handle: AtomicU64::new(3), // 0,1,2 are stdin, stdout and stderr
            file_handle_map: HashMap::new(),

            dir_entry_map: LruCache::new(NonZeroUsize::new(1024).unwrap()),

            cached_inodes: BlockCache::new(device.clone(), 1024),
            cached_blocks: BlockCache::new(device.clone(), 8192),

            super_block,
        };

        fs.create_directory(0o755, get_current_uid(), get_current_gid(), 0, None);

        fs
    }
}