use core::{
    ops::{Deref, DerefMut},
    sync::atomic::{AtomicU32, Ordering},
};

use alloc::sync::{Arc, Weak};
use hashbrown::HashMap;
use system_error::SystemError;

use super::block_device::{BlockDevice, BlockId, GeneralBlockRange, LBA_SIZE};

#[derive(Debug)]
pub struct GenDisk {
    bdev: Weak<dyn BlockDevice>,
    range: GeneralBlockRange,
    block_size_log2: u8,
    idx: Option<u32>,
}

impl GenDisk {
    /// 如果gendisk是整个磁盘，则idx为u32::MAX
    pub const ENTIRE_DISK_IDX: u32 = u32::MAX;

    pub fn new(
        bdev: Weak<dyn BlockDevice>,
        range: GeneralBlockRange,
        idx: Option<u32>,
    ) -> Arc<Self> {
        let bsizelog2 = bdev.upgrade().unwrap().blk_size_log2();

        return Arc::new(GenDisk {
            bdev,
            range,
            block_size_log2: bsizelog2,
            idx,
        });
    }

    pub fn block_device(&self) -> Arc<dyn BlockDevice> {
        return self.bdev.upgrade().unwrap();
    }

    /// # read_at
    ///
    /// 读取分区内的数据
    ///
    /// ## 参数
    ///
    /// - buf: 输出缓冲区，大小必须为LBA_SIZE的整数倍，否则返回EINVAL
    /// - start_block_offset: 分区内的块号
    pub fn read_at(
        &self,
        buf: &mut [u8],
        start_block_offset: BlockId,
    ) -> Result<usize, SystemError> {
        if (buf.len() & (LBA_SIZE - 1)) > 0 {
            return Err(SystemError::EINVAL);
        }

        let blocks = buf.len() / (1 << self.block_size_log2 as usize);
        let lba = self.block_offset_2_disk_blkid(start_block_offset);

        return self.block_device().read_at(lba, blocks, buf);
    }

    /// # read_at_bytes
    ///
    /// 按字节偏移量从分区中读取数据
    ///
    /// ## 参数
    ///
    /// - buf: 输出缓冲区
    /// - bytes_offset: 分区内的字节偏移量
    pub fn read_at_bytes(&self, buf: &mut [u8], bytes_offset: usize) -> Result<usize, SystemError> {
        let start_lba = self.range.lba_start;
        let bytes_offset = self.disk_blkid_2_bytes(start_lba) + bytes_offset;
        return self
            .block_device()
            .read_at_bytes(bytes_offset, buf.len(), buf);
    }

    /// # 分区内的字节偏移量转换为磁盘上的字节偏移量
    pub fn disk_bytes_offset(&self, bytes_offset: usize) -> usize {
        let start_lba = self.range.lba_start;
        return self.disk_blkid_2_bytes(start_lba) + bytes_offset;
    }

    /// # write_at_bytes
    ///
    /// 按字节偏移量向分区写入数据
    ///
    /// ## 参数
    ///
    /// - buf: 输入缓冲区
    /// - bytes_offset: 分区内的字节偏移量
    pub fn write_at_bytes(&self, buf: &[u8], bytes_offset: usize) -> Result<usize, SystemError> {
        let start_lba = self.range.lba_start;
        let bytes_offset = self.disk_blkid_2_bytes(start_lba) + bytes_offset;
        return self
            .block_device()
            .write_at_bytes(bytes_offset, buf.len(), buf);
    }

    /// # write_at
    ///
    /// 向分区内写入数据
    ///
    /// ## 参数
    ///
    /// - buf: 输入缓冲区，大小必须为LBA_SIZE的整数倍，否则返回EINVAL
    /// - start_block_offset: 分区内的块号
    pub fn write_at(&self, buf: &[u8], start_block_offset: BlockId) -> Result<usize, SystemError> {
        if (buf.len() & (LBA_SIZE - 1)) > 0 {
            return Err(SystemError::EINVAL);
        }

        let blocks = buf.len() / (1 << self.block_size_log2 as usize);
        let lba = self.block_offset_2_disk_blkid(start_block_offset);
        return self.block_device().write_at(lba, blocks, buf);
    }

    #[inline]
    fn block_offset_2_disk_blkid(&self, block_offset: BlockId) -> BlockId {
        self.range.lba_start + block_offset
    }

    #[inline]
    fn disk_blkid_2_bytes(&self, disk_blkid: BlockId) -> usize {
        disk_blkid * LBA_SIZE
    }

    #[inline]
    pub fn idx(&self) -> u32 {
        self.idx.unwrap_or(Self::ENTIRE_DISK_IDX)
    }

    #[inline]
    pub fn range(&self) -> &GeneralBlockRange {
        &self.range
    }

    /// # sync
    /// 同步磁盘
    pub fn sync(&self) -> Result<(), SystemError> {
        self.block_device().sync()
    }
}

#[derive(Default)]
pub struct GenDiskMap {
    data: HashMap<u32, Arc<GenDisk>>,
    max_idx: AtomicU32,
}

impl GenDiskMap {
    pub fn new() -> Self {
        GenDiskMap {
            data: HashMap::new(),
            max_idx: AtomicU32::new(1),
        }
    }

    #[inline]
    #[allow(dead_code)]
    pub fn max_idx(&self) -> u32 {
        self.max_idx.load(Ordering::SeqCst)
    }

    #[inline]
    pub fn alloc_idx(&self) -> u32 {
        self.max_idx.fetch_add(1, Ordering::SeqCst)
    }

    pub fn intersects(&self, range: &GeneralBlockRange) -> bool {
        for (_, v) in self.iter() {
            if range.intersects_with(&v.range).is_some() {
                return true;
            }
        }
        return false;
    }
}

impl Deref for GenDiskMap {
    type Target = HashMap<u32, Arc<GenDisk>>;

    fn deref(&self) -> &Self::Target {
        &self.data
    }
}

impl DerefMut for GenDiskMap {
    fn deref_mut(&mut self) -> &mut Self::Target {
        &mut self.data
    }
}