use std::fs::{OpenOptions, Permissions};
use std::io::{Read, Seek, SeekFrom};
use std::mem;
use std::os::unix::prelude::*;
use std::sync::Arc;
use std::time::Duration;

use futures::channel::oneshot;
use futures::future::join_all;
use futures::{select_biased, FutureExt};
use tokio::task::{self, LocalSet};
use tokio::time::delay_for;

use assert_matches::assert_matches;
use helpers::*;
use linux_aio_tokio::{
    aio_context, local_aio_context, AioCommandError, LockedBuf, ReadFlags, WriteFlags,
};
use linux_aio_tokio::{AioOpenOptionsExt, File};
use std::cell::RefCell;
use std::rc::Rc;

pub mod helpers;

const FILE_SIZE: usize = 1024 * 512;
const BUF_CAPACITY: usize = 8192;

#[tokio::test]
async fn local_context() {
    let (dir, path) = create_filled_tempfile(FILE_SIZE);

    let (_aio, aio_handle, aio_background) = local_aio_context(10, true).unwrap();

    let buffer = Rc::new(RefCell::new(LockedBuf::with_size(BUF_CAPACITY).unwrap()));

    LocalSet::new()
        .run_until({
            let buffer = buffer.clone();

            async move {
                task::spawn_local(aio_background);

                let file = File::open(&path, false).await.unwrap();

                file.read_at(
                    &aio_handle,
                    0,
                    &mut *buffer.borrow_mut(),
                    BUF_CAPACITY as _,
                    ReadFlags::empty(),
                )
                .await
                .unwrap();
            }
        })
        .await;

    assert!(validate_block((&*buffer.borrow()).as_ref()));

    dir.close().unwrap();
}

#[tokio::test]
async fn not_use_semaphore() {
    let (dir, path) = create_filled_tempfile(FILE_SIZE);

    // Single kernel thread and sequential requests may work without semaphore
    let (_aio, aio_handle, aio_background) = local_aio_context(1, false).unwrap();

    let buffer = Rc::new(RefCell::new(LockedBuf::with_size(BUF_CAPACITY).unwrap()));

    LocalSet::new()
        .run_until({
            let buffer = buffer.clone();

            async move {
                task::spawn_local(aio_background);

                let file = File::open(&path, false).await.unwrap();

                for _ in 0..10 {
                    file.read_at(
                        &aio_handle,
                        0,
                        &mut *buffer.borrow_mut(),
                        BUF_CAPACITY as _,
                        ReadFlags::empty(),
                    )
                    .await
                    .unwrap();
                }

                task::spawn_local({
                    let aio_handle = aio_handle.clone();
                    let path = path.clone();

                    async move {
                        let file = File::open(&path, false).await.unwrap();
                        let mut buffer = LockedBuf::with_size(BUF_CAPACITY).unwrap();

                        file.read_at(
                            &aio_handle,
                            0,
                            &mut buffer,
                            BUF_CAPACITY as _,
                            ReadFlags::empty(),
                        )
                        .await
                        .unwrap();
                    }
                });

                task::yield_now().await;

                let _ = task::spawn_local(async move {
                    let file = File::open(&path, false).await.unwrap();
                    let mut buffer = LockedBuf::with_size(BUF_CAPACITY).unwrap();

                    let err = file
                        .read_at(
                            &aio_handle,
                            0,
                            &mut buffer,
                            BUF_CAPACITY as _,
                            ReadFlags::empty(),
                        )
                        .await
                        .unwrap_err();

                    assert_matches!(err, AioCommandError::CapacityExceeded);
                })
                .await;
            }
        })
        .await;

    assert!(validate_block((&*buffer.borrow()).as_ref()));

    dir.close().unwrap();
}

#[tokio::test]
async fn aio_close() {
    let (dir, path) = create_filled_tempfile(FILE_SIZE);

    let (aio, aio_handle) = aio_context(10, true).unwrap();
    let file = File::open(&path, false).await.unwrap();

    let mut buffer = LockedBuf::with_size(BUF_CAPACITY).unwrap();

    aio.close().await;

    assert_matches!(
        file.read_at(
            &aio_handle,
            0,
            &mut buffer,
            BUF_CAPACITY as _,
            ReadFlags::empty()
        )
        .await
        .err()
        .unwrap(),
        AioCommandError::AioStopped
    );

    dir.close().unwrap();
}

#[tokio::test]
async fn file_open_and_meta() {
    let (dir, path) = create_filled_tempfile(FILE_SIZE);

    let file = File::open(&path, false).await.unwrap();

    let mut buffer = LockedBuf::with_size(BUF_CAPACITY).unwrap();

    let (_aio, aio_handle) = aio_context(10, true).unwrap();

    file.read_at(
        &aio_handle,
        0,
        &mut buffer,
        BUF_CAPACITY as _,
        ReadFlags::empty(),
    )
    .await
    .unwrap();
    assert!(validate_block(buffer.as_ref()));

    assert!(file
        .write_at(
            &aio_handle,
            0,
            &mut buffer,
            BUF_CAPACITY as _,
            WriteFlags::empty()
        )
        .await
        .is_err());

    file.metadata().await.unwrap();
    file.set_permissions(Permissions::from_mode(0o644))
        .await
        .unwrap();

    dir.close().unwrap();
}

#[tokio::test]
async fn file_create_and_set_len() {
    let (dir, path) = create_filled_tempfile(FILE_SIZE);

    let mut file = File::create(&path, false).await.unwrap();

    file.set_len(BUF_CAPACITY as u64).await.unwrap();

    let mut buffer = LockedBuf::with_size(BUF_CAPACITY).unwrap();

    let (_aio, aio_handle) = aio_context(10, true).unwrap();

    file.write_at(
        &aio_handle,
        0,
        &buffer,
        BUF_CAPACITY as _,
        WriteFlags::empty(),
    )
    .await
    .unwrap();

    assert!(file
        .read_at(
            &aio_handle,
            0,
            &mut buffer,
            BUF_CAPACITY as _,
            ReadFlags::empty()
        )
        .await
        .is_err());

    dir.close().unwrap();
}

#[tokio::test(threaded_scheduler)]
async fn read_block_mt() {
    let (dir, path) = create_filled_tempfile(FILE_SIZE);

    let mut open_options = OpenOptions::new();
    open_options.read(true).write(true);

    let file = Arc::new(open_options.aio_open(path.clone(), true).await.unwrap());

    let mut buffer = LockedBuf::with_size(BUF_CAPACITY * 2).unwrap();

    let (aio, aio_handle) = aio_context(10, true).unwrap();

    let read_bytes = file
        .read_at(
            &aio_handle,
            0,
            &mut buffer,
            BUF_CAPACITY as _,
            ReadFlags::empty(),
        )
        .await
        .unwrap();

    assert_eq!(read_bytes, BUF_CAPACITY as u64);

    assert!(validate_block(&buffer.as_ref()[..BUF_CAPACITY]));

    assert_eq!(10, aio.available_slots().unwrap());

    dir.close().unwrap();
}

#[tokio::test]
#[should_panic]
async fn panic_on_wrong_len() {
    let (dir, path) = create_filled_tempfile(FILE_SIZE);

    {
        let mut open_options = OpenOptions::new();
        open_options.read(true).write(true);

        let file = open_options.aio_open(path.clone(), true).await.unwrap();

        let mut buffer = LockedBuf::with_size(BUF_CAPACITY).unwrap();

        let (_aio, aio_handle) = aio_context(1, true).unwrap();

        file.read_at(
            &aio_handle,
            0,
            &mut buffer,
            (BUF_CAPACITY + 1) as _,
            ReadFlags::empty(),
        )
        .await
        .unwrap();
    }

    dir.close().unwrap();
}

#[tokio::test(threaded_scheduler)]
async fn write_block_mt() {
    let (dir, path) = create_filled_tempfile(FILE_SIZE);

    {
        let mut open_options = OpenOptions::new();
        open_options.read(true).write(true);

        let file = Arc::new(open_options.aio_open(path.clone(), true).await.unwrap());

        let (_aio, aio_handle) = aio_context(2, true).unwrap();

        {
            let mut buffer = LockedBuf::with_size(BUF_CAPACITY * 2).unwrap();
            fill_pattern(65u8, buffer.as_mut());
            let wrote_bytes = file
                .write_at(
                    &aio_handle,
                    16384,
                    &buffer,
                    BUF_CAPACITY as _,
                    WriteFlags::DSYNC,
                )
                .await
                .unwrap();

            assert_eq!(BUF_CAPACITY, wrote_bytes as usize);
        }

        {
            let mut buffer = LockedBuf::with_size(BUF_CAPACITY).unwrap();
            fill_pattern(66u8, buffer.as_mut());
            file.write_at(
                &aio_handle,
                32768,
                &buffer,
                BUF_CAPACITY as _,
                WriteFlags::empty(),
            )
            .await
            .unwrap();
        }

        {
            let mut buffer = LockedBuf::with_size(BUF_CAPACITY).unwrap();
            fill_pattern(67u8, buffer.as_mut());
            file.write_at(
                &aio_handle,
                49152,
                &buffer,
                BUF_CAPACITY as _,
                WriteFlags::SYNC,
            )
            .await
            .unwrap();
        }
    }

    let mut file = std::fs::File::open(&path).unwrap();

    let mut read_buffer: [u8; BUF_CAPACITY] = [0u8; BUF_CAPACITY];

    file.seek(SeekFrom::Start(16384)).unwrap();
    file.read(&mut read_buffer).unwrap();
    assert!(validate_pattern(65u8, &read_buffer));

    file.seek(SeekFrom::Start(32768)).unwrap();
    file.read(&mut read_buffer).unwrap();
    assert!(validate_pattern(66u8, &read_buffer));

    file.seek(SeekFrom::Start(49152)).unwrap();
    file.read(&mut read_buffer).unwrap();
    assert!(validate_pattern(67u8, &read_buffer));

    dir.close().unwrap();
}

#[tokio::test(threaded_scheduler)]
async fn invalid_offset() {
    let (dir, path) = create_filled_tempfile(FILE_SIZE);

    let mut buffer = LockedBuf::with_size(BUF_CAPACITY).unwrap();

    let mut open_options = OpenOptions::new();
    open_options.read(true).write(true);

    let file = Arc::new(open_options.aio_open(path.clone(), false).await.unwrap());

    let (_aio, aio_handle) = aio_context(10, true).unwrap();
    let res = file
        .read_at(
            &aio_handle,
            1000000,
            &mut buffer,
            BUF_CAPACITY as _,
            ReadFlags::empty(),
        )
        .await;

    assert!(res.is_err());

    dir.close().unwrap();
}

#[tokio::test(basic_scheduler)]
async fn future_cancellation() {
    let (dir, path) = create_filled_tempfile(FILE_SIZE);

    let mut buffer = LockedBuf::with_size(BUF_CAPACITY).unwrap();

    let mut open_options = OpenOptions::new();
    open_options.read(true).write(true);

    let file = Arc::new(open_options.aio_open(path.clone(), true).await.unwrap());

    let num_slots = 10;

    let (aio, aio_handle) = aio_context(num_slots, true).unwrap();
    let mut read = Box::pin(
        file.read_at(
            &aio_handle,
            0,
            &mut buffer,
            BUF_CAPACITY as _,
            ReadFlags::empty(),
        )
        .fuse(),
    );

    let (_, immediate) = oneshot::channel::<()>();

    let mut immediate = immediate.fuse();

    select_biased! {
        _ = read => {
            assert!(false);
        },
        _ = immediate => {},
    }

    mem::drop(read);

    while aio.available_slots().unwrap() != num_slots {
        delay_for(Duration::from_millis(50)).await;
    }

    dir.close().unwrap();
}

#[tokio::test(threaded_scheduler)]
async fn mixed_read_write_at() {
    let (dir, path) = create_filled_tempfile(FILE_SIZE);

    let mut open_options = OpenOptions::new();
    open_options.read(true).write(true);

    let file = Arc::new(open_options.aio_open(path.clone(), true).await.unwrap());

    let (_aio, aio_handle) = aio_context(7, true).unwrap();

    let seq1 = {
        let file = file.clone();
        let aio_handle = aio_handle.clone();

        async move {
            let mut buffer = LockedBuf::with_size(BUF_CAPACITY).unwrap();

            file.read_at(
                &aio_handle,
                8192,
                &mut buffer,
                BUF_CAPACITY as _,
                ReadFlags::empty(),
            )
            .await
            .unwrap();
            assert!(validate_block(buffer.as_ref()));

            fill_pattern(0u8, buffer.as_mut());
            file.write_at(
                &aio_handle,
                8192,
                &buffer,
                BUF_CAPACITY as _,
                WriteFlags::DSYNC,
            )
            .await
            .unwrap();

            file.read_at(
                &aio_handle,
                0,
                &mut buffer,
                BUF_CAPACITY as _,
                ReadFlags::empty(),
            )
            .await
            .unwrap();
            assert!(validate_block(buffer.as_ref()));

            fill_pattern(1u8, buffer.as_mut());
            file.write_at(
                &aio_handle,
                0,
                &buffer,
                BUF_CAPACITY as _,
                WriteFlags::DSYNC,
            )
            .await
            .unwrap();

            file.read_at(
                &aio_handle,
                8192,
                &mut buffer,
                BUF_CAPACITY as _,
                ReadFlags::empty(),
            )
            .await
            .unwrap();
            assert!(validate_pattern(0u8, buffer.as_ref()));

            file.read_at(
                &aio_handle,
                0,
                &mut buffer,
                BUF_CAPACITY as _,
                ReadFlags::empty(),
            )
            .await
            .unwrap();
            assert!(validate_pattern(1u8, buffer.as_ref()));
        }
    };

    let seq2 = {
        let file = file.clone();
        let aio_handle = aio_handle.clone();

        async move {
            let mut buffer = LockedBuf::with_size(BUF_CAPACITY).unwrap();

            file.read_at(
                &aio_handle,
                16384,
                &mut buffer,
                BUF_CAPACITY as _,
                ReadFlags::empty(),
            )
            .await
            .unwrap();
            assert!(validate_block(buffer.as_ref()));

            fill_pattern(2u8, buffer.as_mut());
            file.write_at(
                &aio_handle,
                16384,
                &buffer,
                BUF_CAPACITY as _,
                WriteFlags::DSYNC,
            )
            .await
            .unwrap();

            file.read_at(
                &aio_handle,
                24576,
                &mut buffer,
                BUF_CAPACITY as _,
                ReadFlags::empty(),
            )
            .await
            .unwrap();
            assert!(validate_block(buffer.as_ref()));

            fill_pattern(3, buffer.as_mut());
            file.write_at(
                &aio_handle,
                24576,
                &buffer,
                BUF_CAPACITY as _,
                WriteFlags::DSYNC,
            )
            .await
            .unwrap();

            file.read_at(
                &aio_handle,
                16384,
                &mut buffer,
                BUF_CAPACITY as _,
                ReadFlags::empty(),
            )
            .await
            .unwrap();
            assert!(validate_pattern(2, buffer.as_ref()));

            file.read_at(
                &aio_handle,
                24576,
                &mut buffer,
                BUF_CAPACITY as _,
                ReadFlags::empty(),
            )
            .await
            .unwrap();
            assert!(validate_pattern(3u8, buffer.as_ref()));
        }
    };

    let seq3 = {
        async move {
            let mut buffer = LockedBuf::with_size(BUF_CAPACITY).unwrap();

            file.read_at(
                &aio_handle,
                40960,
                &mut buffer,
                BUF_CAPACITY as _,
                ReadFlags::empty(),
            )
            .await
            .unwrap();
            assert!(validate_block(buffer.as_ref()));

            fill_pattern(5u8, buffer.as_mut());
            file.write_at(
                &aio_handle,
                40960,
                &buffer,
                BUF_CAPACITY as _,
                WriteFlags::DSYNC,
            )
            .await
            .unwrap();

            file.read_at(
                &aio_handle,
                32768,
                &mut buffer,
                BUF_CAPACITY as _,
                ReadFlags::empty(),
            )
            .await
            .unwrap();
            assert!(validate_block(buffer.as_ref()));

            fill_pattern(6, buffer.as_mut());
            file.write_at(
                &aio_handle,
                32768,
                &buffer,
                BUF_CAPACITY as _,
                WriteFlags::DSYNC,
            )
            .await
            .unwrap();

            file.read_at(
                &aio_handle,
                40960,
                &mut buffer,
                BUF_CAPACITY as _,
                ReadFlags::empty(),
            )
            .await
            .unwrap();
            assert!(validate_pattern(5, buffer.as_ref()));

            file.read_at(
                &aio_handle,
                32768,
                &mut buffer,
                BUF_CAPACITY as _,
                ReadFlags::empty(),
            )
            .await
            .unwrap();
            assert!(validate_pattern(6, buffer.as_ref()));
        }
    };

    join_all(vec![
        tokio::spawn(seq1),
        tokio::spawn(seq2),
        tokio::spawn(seq3),
    ])
    .await
    .into_iter()
    .collect::<Result<Vec<_>, _>>()
    .unwrap();

    dir.close().unwrap();
}