// Licensed to the Apache Software Foundation (ASF) under one
// or more contributor license agreements.  See the NOTICE file
// distributed with this work for additional information
// regarding copyright ownership.  The ASF licenses this file
// to you under the Apache License, Version 2.0 (the
// "License"); you may not use this file except in compliance
// with the License.  You may obtain a copy of the License at
//
//   http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing,
// software distributed under the License is distributed on an
// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, either express or implied.  See the License for the
// specific language governing permissions and limitations
// under the License.

//! Retry layer implementation for Apache OpenDAL.

#![cfg_attr(docsrs, feature(doc_cfg))]
#![deny(missing_docs)]

use std::fmt::Debug;
use std::sync::Arc;

use backon::BlockingRetryable;
use backon::ExponentialBuilder;
use backon::Retryable;
use opendal_core::raw::*;
use opendal_core::*;

/// Add retry for temporary failed operations.
///
/// # Notes
///
/// This layer will retry failed operations when [`Error::is_temporary`]
/// returns true. If operation still failed, this layer will set error to
/// `Persistent` which means error has been retried.
///
/// # Stateful operation bodies
///
/// While retrying stateful operation bodies, please make sure either:
///
/// - All futures generated by the body methods are resolved to `Ready`.
/// - Or, no methods on the same body are called after retry returns a final error.
///
/// Otherwise, `RetryLayer` can lose the inner body state and fail subsequent calls with an
/// `Unexpected` error.
///
/// For example, while composing `RetryLayer` with `TimeoutLayer`. The order of layer is sensitive.
///
/// ```no_run
/// # use std::time::Duration;
/// #
/// # use opendal_core::services;
/// # use opendal_core::Operator;
/// # use opendal_core::Result;
/// # use opendal_layer_retry::RetryLayer;
/// # use opendal_layer_timeout::TimeoutLayer;
/// #
/// # fn main() -> Result<()> {
/// let op = Operator::new(services::Memory::default())?
///     // This is fine, since timeout happens during retry.
///     .layer(TimeoutLayer::default().with_io_timeout(Duration::from_nanos(1)))
///     .layer(RetryLayer::default())
///     // This is wrong. Timeout layer can drop the retry future before it restores body state.
///     .layer(TimeoutLayer::default().with_io_timeout(Duration::from_nanos(1)));
/// # Ok(())
/// # }
/// ```
///
/// # Examples
///
/// ```no_run
/// # use opendal_core::services;
/// # use opendal_core::Operator;
/// # use opendal_core::Result;
/// # use opendal_layer_retry::RetryLayer;
/// #
/// # fn main() -> Result<()> {
/// let _ = Operator::new(services::Memory::default())?
///     .layer(RetryLayer::default());
/// # Ok(())
/// # }
/// ```
///
/// ## Customize retry interceptor
///
/// RetryLayer accepts [`RetryInterceptor`] to allow users to customize
/// their own retry interceptor logic.
///
/// ```no_run
/// # use std::time::Duration;
/// #
/// # use opendal_core::services;
/// # use opendal_core::Error;
/// # use opendal_core::Operator;
/// # use opendal_core::Result;
/// # use opendal_layer_retry::RetryEvent;
/// # use opendal_layer_retry::RetryInterceptor;
/// # use opendal_layer_retry::RetryLayer;
/// #
/// struct MyRetryInterceptor;
///
/// impl RetryInterceptor for MyRetryInterceptor {
///     fn intercept(&self, event: RetryEvent<'_>) {
///         // do something with event.op, event.err, event.retry_after, event.attempt
///     }
/// }
///
/// # fn main() -> Result<()> {
/// let _ = Operator::new(services::Memory::default())?
///     .layer(RetryLayer::default().with_notify(MyRetryInterceptor));
/// # Ok(())
/// # }
/// ```
pub struct RetryLayer<I: RetryInterceptor = DefaultRetryInterceptor> {
    builder: ExponentialBuilder,
    notify: Arc<I>,
}

impl<I: RetryInterceptor> Debug for RetryLayer<I> {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.debug_struct("RetryLayer")
            .field("builder", &self.builder)
            .finish_non_exhaustive()
    }
}

impl<I: RetryInterceptor> Clone for RetryLayer<I> {
    fn clone(&self) -> Self {
        Self {
            builder: self.builder,
            notify: self.notify.clone(),
        }
    }
}

impl Default for RetryLayer {
    fn default() -> Self {
        Self {
            builder: ExponentialBuilder::default(),
            notify: Arc::new(DefaultRetryInterceptor),
        }
    }
}

impl RetryLayer {
    /// Create a new [`RetryLayer`].
    pub fn new() -> RetryLayer {
        Self::default()
    }
}

impl<I: RetryInterceptor> RetryLayer<I> {
    /// Set the retry interceptor as new notify.
    ///
    /// ```no_run
    /// use opendal_core::services;
    /// use opendal_core::Operator;
    /// use opendal_layer_retry::RetryLayer;
    ///
    /// fn notify(_event: opendal_layer_retry::RetryEvent<'_>) {}
    ///
    /// let _ = Operator::new(services::Memory::default())
    ///     .expect("must init")
    ///     .layer(RetryLayer::default().with_notify(notify));
    /// ```
    pub fn with_notify<NI: RetryInterceptor>(self, notify: NI) -> RetryLayer<NI> {
        RetryLayer {
            builder: self.builder,
            notify: Arc::new(notify),
        }
    }

    /// Set jitter of current backoff.
    ///
    /// If jitter is enabled, ExponentialBackoff will add a random jitter in `[0, min_delay)
    /// to current delay.
    pub fn with_jitter(mut self) -> Self {
        self.builder = self.builder.with_jitter();
        self
    }

    /// Set factor of current backoff.
    ///
    /// # Panics
    ///
    /// This function will panic if input factor smaller than `1.0`.
    pub fn with_factor(mut self, factor: f32) -> Self {
        self.builder = self.builder.with_factor(factor);
        self
    }

    /// Set min_delay of current backoff.
    pub fn with_min_delay(mut self, min_delay: Duration) -> Self {
        self.builder = self.builder.with_min_delay(min_delay);
        self
    }

    /// Set max_delay of current backoff.
    ///
    /// Delay will not increase if current delay is larger than max_delay.
    pub fn with_max_delay(mut self, max_delay: Duration) -> Self {
        self.builder = self.builder.with_max_delay(max_delay);
        self
    }

    /// Set max_times of current backoff.
    ///
    /// Backoff will return `None` if max times is reaching.
    pub fn with_max_times(mut self, max_times: usize) -> Self {
        self.builder = self.builder.with_max_times(max_times);
        self
    }
}

impl<I: RetryInterceptor> Layer for RetryLayer<I> {
    fn apply_service(&self, inner: Servicer) -> Servicer {
        Arc::new(self.layer(inner))
    }
}

impl<I: RetryInterceptor> RetryLayer<I> {
    fn layer(&self, inner: Servicer) -> RetryService<I> {
        RetryService {
            inner,
            notify: self.notify.clone(),
            builder: self.builder,
        }
    }
}

/// Context passed to [`RetryInterceptor`] before each retry sleep.
#[non_exhaustive]
#[derive(Debug)]
pub struct RetryEvent<'a> {
    /// The operation being retried.
    pub op: Operation,
    /// The error that triggered the retry.
    pub err: &'a Error,
    /// The duration to wait before the next retry attempt.
    pub retry_after: Duration,
    /// 1-based retry attempt number.
    pub attempt: u32,
}

/// RetryInterceptor observes retry attempts before the retry sleep.
pub trait RetryInterceptor: Send + Sync + 'static {
    /// Called before each retry sleep.
    ///
    /// # Notes
    ///
    /// The intercept must be quick and non-blocking. No heavy IO is
    /// allowed. Otherwise, the retry will be blocked.
    fn intercept(&self, event: RetryEvent<'_>);
}

impl<F> RetryInterceptor for F
where
    F: for<'a> Fn(RetryEvent<'a>) + Send + Sync + 'static,
{
    fn intercept(&self, event: RetryEvent<'_>) {
        self(event);
    }
}

/// The DefaultRetryInterceptor logs each retry error at warn level.
pub struct DefaultRetryInterceptor;

impl RetryInterceptor for DefaultRetryInterceptor {
    fn intercept(&self, event: RetryEvent<'_>) {
        log::warn!(
            target: "opendal::layers::retry",
            "will retry {:?} (attempt {}) after {}s because: {:?}",
            event.op, event.attempt, event.retry_after.as_secs_f64(), event.err
        );
    }
}

#[doc(hidden)]
pub struct RetryService<I: RetryInterceptor> {
    inner: Servicer,
    notify: Arc<I>,
    builder: ExponentialBuilder,
}

impl<I: RetryInterceptor> Debug for RetryService<I> {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.debug_struct("RetryService")
            .field("inner", &self.inner)
            .finish_non_exhaustive()
    }
}

impl<I: RetryInterceptor> Service for RetryService<I> {
    type Reader = RetryReader<oio::Reader, I>;
    type Writer = RetryWrapper<oio::Writer, I>;
    type Lister = RetryWrapper<oio::Lister, I>;
    type Deleter = RetryWrapper<oio::Deleter, I>;
    type Copier = RetryWrapper<oio::Copier, I>;

    fn info(&self) -> ServiceInfo {
        self.inner.info()
    }

    fn capability(&self) -> Capability {
        self.inner.capability()
    }

    async fn create_dir(
        &self,
        ctx: &OperationContext,
        path: &str,
        args: OpCreateDir,
    ) -> Result<RpCreateDir> {
        let mut attempt: u32 = 0;
        { || self.inner.create_dir(ctx, path, args.clone()) }
            .retry(self.builder)
            .when(|e| e.is_temporary())
            .notify(|err, dur| {
                attempt += 1;
                self.notify.intercept(RetryEvent {
                    op: Operation::CreateDir,
                    err,
                    retry_after: dur,
                    attempt,
                })
            })
            .await
            .map_err(|err| err.set_persistent())
    }

    fn read(&self, ctx: &OperationContext, path: &str, args: OpRead) -> Result<Self::Reader> {
        let mut attempt: u32 = 0;
        let reader = { || self.inner.read(ctx, path, args.clone()) }
            .retry(self.builder)
            .when(|e| e.is_temporary())
            .notify(|err, dur| {
                attempt += 1;
                self.notify.intercept(RetryEvent {
                    op: Operation::Read,
                    err,
                    retry_after: dur,
                    attempt,
                })
            })
            .call()
            .map_err(|err| err.set_persistent())?;

        Ok(RetryReader::new(reader, self.notify.clone(), self.builder))
    }

    fn write(&self, ctx: &OperationContext, path: &str, args: OpWrite) -> Result<Self::Writer> {
        let mut attempt: u32 = 0;
        let writer = { || self.inner.write(ctx, path, args.clone()) }
            .retry(self.builder)
            .when(|e| e.is_temporary())
            .notify(|err, dur| {
                attempt += 1;
                self.notify.intercept(RetryEvent {
                    op: Operation::Write,
                    err,
                    retry_after: dur,
                    attempt,
                })
            })
            .call()
            .map_err(|err| err.set_persistent())?;

        Ok(RetryWrapper::new(writer, self.notify.clone(), self.builder))
    }

    async fn stat(&self, ctx: &OperationContext, path: &str, args: OpStat) -> Result<RpStat> {
        let mut attempt: u32 = 0;
        { || self.inner.stat(ctx, path, args.clone()) }
            .retry(self.builder)
            .when(|e| e.is_temporary())
            .notify(|err, dur| {
                attempt += 1;
                self.notify.intercept(RetryEvent {
                    op: Operation::Stat,
                    err,
                    retry_after: dur,
                    attempt,
                })
            })
            .await
            .map_err(|err| err.set_persistent())
    }

    fn delete(&self, ctx: &OperationContext) -> Result<Self::Deleter> {
        let mut attempt: u32 = 0;
        let deleter = { || self.inner.delete(ctx) }
            .retry(self.builder)
            .when(|e| e.is_temporary())
            .notify(|err, dur| {
                attempt += 1;
                self.notify.intercept(RetryEvent {
                    op: Operation::Delete,
                    err,
                    retry_after: dur,
                    attempt,
                })
            })
            .call()
            .map_err(|err| err.set_persistent())?;

        Ok(RetryWrapper::new(
            deleter,
            self.notify.clone(),
            self.builder,
        ))
    }

    fn copy(
        &self,
        ctx: &OperationContext,
        from: &str,
        to: &str,
        args: OpCopy,
        opts: OpCopier,
    ) -> Result<Self::Copier> {
        let mut attempt: u32 = 0;
        let copier = { || self.inner.copy(ctx, from, to, args.clone(), opts.clone()) }
            .retry(self.builder)
            .when(|e| e.is_temporary())
            .notify(|err, dur| {
                attempt += 1;
                self.notify.intercept(RetryEvent {
                    op: Operation::Copy,
                    err,
                    retry_after: dur,
                    attempt,
                })
            })
            .call()
            .map_err(|err| err.set_persistent())?;

        Ok(RetryWrapper::new(copier, self.notify.clone(), self.builder))
    }

    async fn rename(
        &self,
        ctx: &OperationContext,
        from: &str,
        to: &str,
        args: OpRename,
    ) -> Result<RpRename> {
        let mut attempt: u32 = 0;
        { || self.inner.rename(ctx, from, to, args.clone()) }
            .retry(self.builder)
            .when(|e| e.is_temporary())
            .notify(|err, dur| {
                attempt += 1;
                self.notify.intercept(RetryEvent {
                    op: Operation::Rename,
                    err,
                    retry_after: dur,
                    attempt,
                })
            })
            .await
            .map_err(|err| err.set_persistent())
    }

    fn list(&self, ctx: &OperationContext, path: &str, args: OpList) -> Result<Self::Lister> {
        let mut attempt: u32 = 0;
        let lister = { || self.inner.list(ctx, path, args.clone()) }
            .retry(self.builder)
            .when(|e| e.is_temporary())
            .notify(|err, dur| {
                attempt += 1;
                self.notify.intercept(RetryEvent {
                    op: Operation::List,
                    err,
                    retry_after: dur,
                    attempt,
                })
            })
            .call()
            .map_err(|err| err.set_persistent())?;

        Ok(RetryWrapper::new(lister, self.notify.clone(), self.builder))
    }

    async fn presign(
        &self,
        ctx: &OperationContext,
        path: &str,
        args: OpPresign,
    ) -> Result<RpPresign> {
        let mut attempt: u32 = 0;
        { || self.inner.presign(ctx, path, args.clone()) }
            .retry(self.builder)
            .when(|e| e.is_temporary())
            .notify(|err, dur| {
                attempt += 1;
                self.notify.intercept(RetryEvent {
                    op: Operation::Presign,
                    err,
                    retry_after: dur,
                    attempt,
                })
            })
            .await
            .map_err(|err| err.set_persistent())
    }
}

#[doc(hidden)]
pub struct RetryReader<R, I> {
    inner: Arc<R>,
    notify: Arc<I>,
    builder: ExponentialBuilder,
}

impl<R, I> RetryReader<R, I> {
    fn new(inner: R, notify: Arc<I>, builder: ExponentialBuilder) -> Self {
        Self {
            inner: Arc::new(inner),
            notify,
            builder,
        }
    }
}

impl<R: oio::Read + 'static, I: RetryInterceptor> oio::Read for RetryReader<R, I> {
    async fn open(&self, range: BytesRange) -> Result<(RpRead, Box<dyn oio::ReadStreamDyn>)> {
        use backon::Retryable;

        let mut attempt: u32 = 0;
        let (rp, stream) = { || self.inner.open(range) }
            .retry(self.builder)
            .when(|e| e.is_temporary())
            .notify(|err, dur| {
                attempt += 1;
                self.notify.intercept(RetryEvent {
                    op: Operation::Read,
                    err,
                    retry_after: dur,
                    attempt,
                })
            })
            .await
            .map_err(|e| e.set_persistent())?;

        Ok((
            rp,
            Box::new(RetryReadStream::new(
                self.inner.clone(),
                stream,
                range,
                self.notify.clone(),
                self.builder,
            )) as Box<dyn oio::ReadStreamDyn>,
        ))
    }

    async fn read(&self, range: BytesRange) -> Result<(RpRead, Buffer)> {
        use backon::Retryable;

        let mut attempt: u32 = 0;
        { || self.inner.read(range) }
            .retry(self.builder)
            .when(|e| e.is_temporary())
            .notify(|err, dur| {
                attempt += 1;
                self.notify.intercept(RetryEvent {
                    op: Operation::Read,
                    err,
                    retry_after: dur,
                    attempt,
                })
            })
            .await
            .map_err(|e| e.set_persistent())
    }
}

#[doc(hidden)]
pub struct RetryReadStream<R, I> {
    reader: Arc<R>,
    stream: Option<Box<dyn oio::ReadStreamDyn>>,
    range: BytesRange,
    read: u64,
    notify: Arc<I>,
    builder: ExponentialBuilder,
}

impl<R, I> RetryReadStream<R, I> {
    fn new(
        reader: Arc<R>,
        stream: Box<dyn oio::ReadStreamDyn>,
        range: BytesRange,
        notify: Arc<I>,
        builder: ExponentialBuilder,
    ) -> Self {
        Self {
            reader,
            stream: Some(stream),
            range,
            read: 0,
            notify,
            builder,
        }
    }
}

impl<R: oio::Read, I: RetryInterceptor> oio::ReadStream for RetryReadStream<R, I> {
    async fn read(&mut self) -> Result<Buffer> {
        use backon::RetryableWithContext;

        let reader = self.reader.clone();
        let stream = self.stream.take();
        let range = self.range;
        let read = self.read;
        let mut attempt: u32 = 0;

        let ((stream, range, read), res) = {
            |(stream, mut range, mut read): (
                Option<Box<dyn oio::ReadStreamDyn>>,
                BytesRange,
                u64,
            )| {
                let reader = reader.clone();
                async move {
                    let mut stream = match stream {
                        Some(stream) => stream,
                        None => {
                            range.advance(read);
                            read = 0;

                            match reader.open(range).await {
                                Ok((_, stream)) => stream,
                                Err(err) => return ((None, range, read), Err(err)),
                            }
                        }
                    };

                    let res = match stream.read().await {
                        Ok(buf) => {
                            if !buf.is_empty() {
                                read += buf.len() as u64;
                            }
                            (Some(stream), Ok(buf))
                        }
                        Err(err) => (None, Err(err)),
                    };

                    ((res.0, range, read), res.1)
                }
            }
        }
        .retry(self.builder)
        .when(|e| e.is_temporary())
        .context((stream, range, read))
        .notify(|err, dur| {
            attempt += 1;
            self.notify.intercept(RetryEvent {
                op: Operation::Read,
                err,
                retry_after: dur,
                attempt,
            })
        })
        .await;

        self.stream = stream;
        self.range = range;
        self.read = read;

        res.map_err(|err| err.set_persistent())
    }
}

#[doc(hidden)]
pub struct RetryWrapper<R, I> {
    inner: Option<R>,
    notify: Arc<I>,

    builder: ExponentialBuilder,
}

impl<R, I> RetryWrapper<R, I> {
    fn new(inner: R, notify: Arc<I>, backoff: ExponentialBuilder) -> Self {
        Self {
            inner: Some(inner),
            notify,
            builder: backoff,
        }
    }

    fn take_inner(&mut self) -> Result<R> {
        self.inner.take().ok_or_else(|| {
            Error::new(
                ErrorKind::Unexpected,
                "retry layer is in bad state, please make sure future not dropped before ready",
            )
        })
    }
}

impl<R: oio::ReadStream, I: RetryInterceptor> oio::ReadStream for RetryWrapper<R, I> {
    async fn read(&mut self) -> Result<Buffer> {
        use backon::RetryableWithContext;

        let inner = self.take_inner()?;
        let mut attempt: u32 = 0;

        let (inner, res) = {
            |mut r: R| async move {
                let res = r.read().await;

                (r, res)
            }
        }
        .retry(self.builder)
        .when(|e| e.is_temporary())
        .context(inner)
        .notify(|err, dur| {
            attempt += 1;
            self.notify.intercept(RetryEvent {
                op: Operation::Read,
                err,
                retry_after: dur,
                attempt,
            })
        })
        .await;

        self.inner = Some(inner);
        res.map_err(|err| err.set_persistent())
    }
}

impl<R: oio::Write, I: RetryInterceptor> oio::Write for RetryWrapper<R, I> {
    async fn write(&mut self, bs: Buffer) -> Result<()> {
        use backon::RetryableWithContext;

        let inner = self.take_inner()?;
        let mut attempt: u32 = 0;

        let ((inner, _), res) = {
            |(mut r, bs): (R, Buffer)| async move {
                let res = r.write(bs.clone()).await;

                ((r, bs), res)
            }
        }
        .retry(self.builder)
        .when(|e| e.is_temporary())
        .context((inner, bs))
        .notify(|err, dur| {
            attempt += 1;
            self.notify.intercept(RetryEvent {
                op: Operation::Write,
                err,
                retry_after: dur,
                attempt,
            })
        })
        .await;

        self.inner = Some(inner);
        res.map_err(|err| err.set_persistent())
    }

    async fn abort(&mut self) -> Result<()> {
        use backon::RetryableWithContext;

        let inner = self.take_inner()?;
        let mut attempt: u32 = 0;

        let (inner, res) = {
            |mut r: R| async move {
                let res = r.abort().await;

                (r, res)
            }
        }
        .retry(self.builder)
        .when(|e| e.is_temporary())
        .context(inner)
        .notify(|err, dur| {
            attempt += 1;
            self.notify.intercept(RetryEvent {
                op: Operation::Write,
                err,
                retry_after: dur,
                attempt,
            })
        })
        .await;

        self.inner = Some(inner);
        res.map_err(|err| err.set_persistent())
    }

    async fn close(&mut self) -> Result<Metadata> {
        use backon::RetryableWithContext;

        let inner = self.take_inner()?;
        let mut attempt: u32 = 0;

        let (inner, res) = {
            |mut r: R| async move {
                let res = r.close().await;

                (r, res)
            }
        }
        .retry(self.builder)
        .when(|e| e.is_temporary())
        .context(inner)
        .notify(|err, dur| {
            attempt += 1;
            self.notify.intercept(RetryEvent {
                op: Operation::Write,
                err,
                retry_after: dur,
                attempt,
            })
        })
        .await;

        self.inner = Some(inner);
        res.map_err(|err| err.set_persistent())
    }
}

impl<P: oio::List, I: RetryInterceptor> oio::List for RetryWrapper<P, I> {
    async fn next(&mut self) -> Result<Option<oio::Entry>> {
        use backon::RetryableWithContext;

        let inner = self.take_inner()?;
        let mut attempt: u32 = 0;

        let (inner, res) = {
            |mut p: P| async move {
                let res = p.next().await;

                (p, res)
            }
        }
        .retry(self.builder)
        .when(|e| e.is_temporary())
        .context(inner)
        .notify(|err, dur| {
            attempt += 1;
            self.notify.intercept(RetryEvent {
                op: Operation::List,
                err,
                retry_after: dur,
                attempt,
            })
        })
        .await;

        self.inner = Some(inner);
        res.map_err(|err| err.set_persistent())
    }
}

impl<P: oio::Delete, I: RetryInterceptor> oio::Delete for RetryWrapper<P, I> {
    async fn delete(&mut self, path: &str, args: OpDelete) -> Result<()> {
        use backon::RetryableWithContext;

        let inner = self.take_inner()?;
        let path = path.to_string();
        let args_cloned = args.clone();
        let mut attempt: u32 = 0;

        let (inner, res) = {
            |mut p: P| {
                let path = path.clone();
                let args = args_cloned.clone();
                async move {
                    let res = p.delete(&path, args).await;
                    (p, res)
                }
            }
        }
        .retry(self.builder)
        .when(|e| e.is_temporary())
        .context(inner)
        .notify(|err, dur| {
            attempt += 1;
            self.notify.intercept(RetryEvent {
                op: Operation::Delete,
                err,
                retry_after: dur,
                attempt,
            });
        })
        .await;

        self.inner = Some(inner);
        res.map_err(|e| e.set_persistent())
    }

    async fn close(&mut self) -> Result<()> {
        use backon::RetryableWithContext;

        let inner = self.take_inner()?;
        let mut attempt: u32 = 0;

        let (inner, res) = {
            |mut p: P| async move {
                let res = p.close().await;

                (p, res)
            }
        }
        .retry(self.builder)
        .when(|e| e.is_temporary())
        .context(inner)
        .notify(|err, dur| {
            attempt += 1;
            self.notify.intercept(RetryEvent {
                op: Operation::Delete,
                err,
                retry_after: dur,
                attempt,
            })
        })
        .await;

        self.inner = Some(inner);
        res.map_err(|err| err.set_persistent())
    }
}

impl<C: oio::Copy, I: RetryInterceptor> oio::Copy for RetryWrapper<C, I> {
    async fn next(&mut self) -> Result<Option<usize>> {
        use backon::RetryableWithContext;

        let inner = self.take_inner()?;
        let mut attempt: u32 = 0;

        let (inner, res) = {
            |mut c: C| async move {
                let res = c.next().await;

                (c, res)
            }
        }
        .retry(self.builder)
        .when(|e| e.is_temporary())
        .context(inner)
        .notify(|err, dur| {
            attempt += 1;
            self.notify.intercept(RetryEvent {
                op: Operation::Copy,
                err,
                retry_after: dur,
                attempt,
            })
        })
        .await;

        self.inner = Some(inner);
        res.map_err(|err| err.set_persistent())
    }

    async fn close(&mut self) -> Result<Metadata> {
        use backon::RetryableWithContext;

        let inner = self.take_inner()?;
        let mut attempt: u32 = 0;

        let (inner, res) = {
            |mut c: C| async move {
                let res = c.close().await;

                (c, res)
            }
        }
        .retry(self.builder)
        .when(|e| e.is_temporary())
        .context(inner)
        .notify(|err, dur| {
            attempt += 1;
            self.notify.intercept(RetryEvent {
                op: Operation::Copy,
                err,
                retry_after: dur,
                attempt,
            })
        })
        .await;

        self.inner = Some(inner);
        res.map_err(|err| err.set_persistent())
    }

    async fn abort(&mut self) -> Result<()> {
        use backon::RetryableWithContext;

        let inner = self.take_inner()?;
        let mut attempt: u32 = 0;

        let (inner, res) = {
            |mut c: C| async move {
                let res = c.abort().await;

                (c, res)
            }
        }
        .retry(self.builder)
        .when(|e| e.is_temporary())
        .context(inner)
        .notify(|err, dur| {
            attempt += 1;
            self.notify.intercept(RetryEvent {
                op: Operation::Copy,
                err,
                retry_after: dur,
                attempt,
            })
        })
        .await;

        self.inner = Some(inner);
        res.map_err(|err| err.set_persistent())
    }
}

#[cfg(test)]
mod tests {
    use std::sync::Mutex;

    use bytes::Bytes;
    use futures::TryStreamExt;
    use futures::stream;
    use logforth::append::Testing;
    use logforth::filter::rustlog::RustLogFilterBuilder;
    use logforth::layout::TextLayout;
    use opendal_layer_logging::LoggingLayer;

    use super::*;

    #[derive(Default, Clone)]
    struct MockBuilder {
        attempt: Arc<Mutex<usize>>,
    }

    impl Builder for MockBuilder {
        type Config = ();

        fn build(self) -> Result<impl Service> {
            Ok(MockService {
                attempt: self.attempt,
            })
        }
    }

    #[derive(Debug, Clone, Default)]
    struct MockService {
        attempt: Arc<Mutex<usize>>,
    }

    /// Reader returned by this backend.
    pub struct MockReader {
        backend: MockService,
    }

    impl MockReader {
        fn new(backend: MockService, _: &str, _: OpRead) -> Self {
            Self { backend }
        }
    }

    impl oio::StreamRead for MockReader {
        async fn open(&self, range: BytesRange) -> Result<(RpRead, Box<dyn oio::ReadStreamDyn>)> {
            let backend = &self.backend;
            let rp = RpRead::new(Metadata::new(EntryMode::FILE).with_content_length(0));
            let stream = MockReadStream {
                buf: Bytes::from("Hello, World!").into(),
                range,
                attempt: backend.attempt.clone(),
            };

            Ok((rp, Box::new(stream) as Box<dyn oio::ReadStreamDyn>))
        }
    }

    impl Service for MockService {
        type Reader = oio::StreamReader<MockReader>;
        type Writer = MockWriter;
        type Lister = MockLister;
        type Deleter = MockDeleter;
        type Copier = MockCopier;

        fn info(&self) -> ServiceInfo {
            ServiceInfo::with_scheme("mock")
        }

        fn capability(&self) -> Capability {
            Capability {
                read: true,
                write: true,
                write_can_multi: true,
                delete: true,
                delete_max_size: Some(10),
                stat: true,
                list: true,
                list_with_recursive: true,
                copy: true,
                ..Default::default()
            }
        }

        async fn create_dir(
            &self,
            _: &OperationContext,
            _: &str,
            _: OpCreateDir,
        ) -> Result<RpCreateDir> {
            Err(Error::new(
                ErrorKind::Unsupported,
                "operation is not supported",
            ))
        }

        async fn stat(&self, _: &OperationContext, _: &str, _: OpStat) -> Result<RpStat> {
            Ok(RpStat::new(
                Metadata::new(EntryMode::FILE).with_content_length(13),
            ))
        }

        fn read(&self, _: &OperationContext, path: &str, args: OpRead) -> Result<Self::Reader> {
            Ok(oio::StreamReader::new(MockReader::new(
                self.clone(),
                path,
                args,
            )))
        }

        fn delete(&self, _ctx: &OperationContext) -> Result<Self::Deleter> {
            Ok(MockDeleter {
                size: 0,
                attempt: self.attempt.clone(),
            })
        }

        fn write(&self, _ctx: &OperationContext, _: &str, _: OpWrite) -> Result<Self::Writer> {
            Ok(MockWriter {})
        }

        fn list(&self, _ctx: &OperationContext, _: &str, _: OpList) -> Result<Self::Lister> {
            let lister = MockLister::default();
            Ok(lister)
        }

        fn copy(
            &self,
            _: &OperationContext,
            _: &str,
            _: &str,
            _: OpCopy,
            _: OpCopier,
        ) -> Result<Self::Copier> {
            Ok(MockCopier {
                attempt: self.attempt.clone(),
            })
        }

        async fn rename(
            &self,
            _: &OperationContext,
            _: &str,
            _: &str,
            _: OpRename,
        ) -> Result<RpRename> {
            Err(Error::new(
                ErrorKind::Unsupported,
                "operation is not supported",
            ))
        }

        async fn presign(&self, _: &OperationContext, _: &str, _: OpPresign) -> Result<RpPresign> {
            Err(Error::new(
                ErrorKind::Unsupported,
                "operation is not supported",
            ))
        }
    }

    #[derive(Debug, Clone, Default)]
    struct MockReadStream {
        buf: Buffer,
        range: BytesRange,
        attempt: Arc<Mutex<usize>>,
    }

    impl oio::ReadStream for MockReadStream {
        async fn read(&mut self) -> Result<Buffer> {
            let mut attempt = self.attempt.lock().unwrap();
            *attempt += 1;

            match *attempt {
                1 => Err(
                    Error::new(ErrorKind::Unexpected, "retryable_error from reader")
                        .set_temporary(),
                ),
                2 => Err(
                    Error::new(ErrorKind::Unexpected, "retryable_error from reader")
                        .set_temporary(),
                ),
                // Should read out all data.
                3 => Ok(self.buf.slice(self.range.to_range_as_usize())),
                4 => Err(
                    Error::new(ErrorKind::Unexpected, "retryable_error from reader")
                        .set_temporary(),
                ),
                // Should be empty.
                5 => Ok(self.buf.slice(self.range.to_range_as_usize())),
                _ => unreachable!(),
            }
        }
    }

    #[derive(Debug, Clone, Default)]
    struct MockWriter {}

    impl oio::Write for MockWriter {
        async fn write(&mut self, _: Buffer) -> Result<()> {
            Ok(())
        }

        async fn close(&mut self) -> Result<Metadata> {
            Err(Error::new(ErrorKind::Unexpected, "always close failed").set_temporary())
        }

        async fn abort(&mut self) -> Result<()> {
            Ok(())
        }
    }

    #[derive(Debug, Clone, Default)]
    struct MockLister {
        attempt: usize,
    }

    impl oio::List for MockLister {
        async fn next(&mut self) -> Result<Option<oio::Entry>> {
            self.attempt += 1;
            match self.attempt {
                1 => Err(Error::new(
                    ErrorKind::RateLimited,
                    "retryable rate limited error from lister",
                )
                .set_temporary()),
                2 => Ok(Some(oio::Entry::new(
                    "hello",
                    Metadata::new(EntryMode::FILE),
                ))),
                3 => Ok(Some(oio::Entry::new(
                    "world",
                    Metadata::new(EntryMode::FILE),
                ))),
                4 => Err(
                    Error::new(ErrorKind::Unexpected, "retryable internal server error")
                        .set_temporary(),
                ),
                5 => Ok(Some(oio::Entry::new(
                    "2023/",
                    Metadata::new(EntryMode::DIR),
                ))),
                6 => Ok(Some(oio::Entry::new(
                    "0208/",
                    Metadata::new(EntryMode::DIR),
                ))),
                7 => Ok(None),
                _ => {
                    unreachable!()
                }
            }
        }
    }

    #[derive(Debug, Clone, Default)]
    struct MockDeleter {
        size: usize,
        attempt: Arc<Mutex<usize>>,
    }

    impl oio::Delete for MockDeleter {
        async fn delete(&mut self, _: &str, _: OpDelete) -> Result<()> {
            self.size += 1;
            Ok(())
        }

        async fn close(&mut self) -> Result<()> {
            let mut attempt = self.attempt.lock().unwrap();
            *attempt += 1;

            match *attempt {
                1 => Err(
                    Error::new(ErrorKind::Unexpected, "retryable_error from deleter")
                        .set_temporary(),
                ),
                2..=4 => {
                    self.size = self.size.saturating_sub(1);
                    Err(
                        Error::new(ErrorKind::Unexpected, "retryable_error from deleter")
                            .set_temporary(),
                    )
                }
                5 => {
                    self.size = self.size.saturating_sub(1);
                    if self.size == 0 {
                        Ok(())
                    } else {
                        Err(
                            Error::new(ErrorKind::Unexpected, "retryable_error from deleter")
                                .set_temporary(),
                        )
                    }
                }
                _ => unreachable!(),
            }
        }
    }

    #[derive(Debug, Clone, Default)]
    struct MockCopier {
        attempt: Arc<Mutex<usize>>,
    }

    impl oio::Copy for MockCopier {
        async fn next(&mut self) -> Result<Option<usize>> {
            let mut attempt = self.attempt.lock().unwrap();
            *attempt += 1;

            match *attempt {
                1 => Err(
                    Error::new(ErrorKind::Unexpected, "retryable_error from copier")
                        .set_temporary(),
                ),
                2 => Err(
                    Error::new(ErrorKind::Unexpected, "retryable_error from copier")
                        .set_temporary(),
                ),
                3 => Ok(Some(8)),
                4 => Err(
                    Error::new(ErrorKind::Unexpected, "retryable_error from copier")
                        .set_temporary(),
                ),
                5 => Ok(Some(5)),
                6 => Ok(None),
                _ => unreachable!(),
            }
        }

        async fn close(&mut self) -> Result<Metadata> {
            Ok(Metadata::default())
        }

        async fn abort(&mut self) -> Result<()> {
            Ok(())
        }
    }

    fn setup() {
        let _ = logforth::starter_log::builder()
            .dispatch(|d| {
                d.filter(RustLogFilterBuilder::from_default_env().build())
                    .append(Testing::default().with_layout(TextLayout::default()))
            })
            .try_apply();
    }

    #[tokio::test]
    async fn test_retry_read() -> Result<()> {
        setup();

        let builder = MockBuilder::default();
        let op = Operator::new(builder.clone())?
            .layer(LoggingLayer::default())
            .layer(RetryLayer::default());

        let r = op.reader("retryable_error").await?;
        let mut content = Vec::new();
        let size = r
            .read_into(&mut content, ..)
            .await
            .expect("read must succeed");
        assert_eq!(size, 13);
        assert_eq!(content, "Hello, World!".as_bytes());
        // The error is retryable, we should request it 3 times.
        assert_eq!(*builder.attempt.lock().unwrap(), 5);
        Ok(())
    }

    /// This test is used to reproduce the panic issue while composing retry layer with timeout layer.
    #[tokio::test]
    async fn test_retry_write_fail_on_close() -> Result<()> {
        setup();

        let builder = MockBuilder::default();
        let op = Operator::new(builder.clone())?
            .layer(
                RetryLayer::default()
                    .with_min_delay(Duration::from_millis(1))
                    .with_max_delay(Duration::from_millis(1))
                    .with_jitter(),
            )
            // Uncomment this to reproduce timeout layer panic.
            // .layer(TimeoutLayer::default().with_io_timeout(Duration::from_nanos(1)))
            .layer(LoggingLayer::default());

        let mut w = op.writer("test_write").await?;
        w.write("aaa").await?;
        w.write("bbb").await?;
        match w.close().await {
            Ok(_) => (),
            Err(_) => {
                w.abort().await?;
            }
        };
        Ok(())
    }

    #[tokio::test]
    async fn test_retry_list() -> Result<()> {
        setup();

        let builder = MockBuilder::default();
        let op = Operator::new(builder.clone())?.layer(RetryLayer::default());

        let expected = vec!["hello", "world", "2023/", "0208/"];

        let mut lister = op
            .lister("retryable_error/")
            .await
            .expect("service must support list");
        let mut actual = Vec::new();
        while let Some(obj) = lister.try_next().await.expect("must success") {
            actual.push(obj.name().to_owned());
        }

        assert_eq!(actual, expected);
        Ok(())
    }

    #[tokio::test]
    async fn test_retry_event_attempt_and_op() -> Result<()> {
        setup();

        #[derive(Default, Clone)]
        struct Recorder {
            events: Arc<Mutex<Vec<(Operation, u32)>>>,
        }

        impl RetryInterceptor for Recorder {
            fn intercept(&self, event: RetryEvent<'_>) {
                self.events.lock().unwrap().push((event.op, event.attempt));
            }
        }

        let recorder = Recorder::default();
        let builder = MockBuilder::default();
        let op = Operator::new(builder.clone())?.layer(
            RetryLayer::default()
                .with_min_delay(Duration::from_millis(1))
                .with_max_delay(Duration::from_millis(1))
                .with_notify(recorder.clone()),
        );

        let r = op.reader("retryable_error").await?;
        let mut content = Vec::new();
        let _ = r.read_into(&mut content, ..).await?;

        let events = recorder.events.lock().unwrap().clone();
        assert_eq!(
            events,
            vec![
                (Operation::Read, 1),
                (Operation::Read, 2),
                (Operation::Read, 1),
            ],
        );
        Ok(())
    }

    #[tokio::test]
    async fn test_retry_read_stream_error_enters_retry_budget() -> Result<()> {
        setup();

        #[derive(Default, Clone)]
        struct Recorder {
            events: Arc<Mutex<Vec<(Operation, u32)>>>,
        }

        impl RetryInterceptor for Recorder {
            fn intercept(&self, event: RetryEvent<'_>) {
                self.events.lock().unwrap().push((event.op, event.attempt));
            }
        }

        let recorder = Recorder::default();
        let backend = MockService::default();
        let reader = RetryReader::new(
            oio::StreamReader::new(MockReader::new(
                backend.clone(),
                "retryable_error",
                OpRead::default(),
            )),
            Arc::new(recorder.clone()),
            ExponentialBuilder::default()
                .with_min_delay(Duration::from_millis(1))
                .with_max_delay(Duration::from_millis(1)),
        );

        let (_, mut stream) = oio::Read::open(&reader, BytesRange::default()).await?;
        let buf = oio::ReadStream::read_all(&mut stream).await?;

        assert_eq!(buf.to_bytes(), Bytes::from_static(b"Hello, World!"));
        assert_eq!(*backend.attempt.lock().unwrap(), 5);

        let events = recorder.events.lock().unwrap().clone();
        assert_eq!(
            events,
            vec![
                (Operation::Read, 1),
                (Operation::Read, 2),
                (Operation::Read, 1),
            ],
        );
        Ok(())
    }

    #[tokio::test]
    async fn test_retry_batch() -> Result<()> {
        setup();

        let builder = MockBuilder::default();
        // set to a lower delay to make it run faster
        let op = Operator::new(builder.clone())?.layer(
            RetryLayer::default()
                .with_min_delay(Duration::from_secs_f32(0.1))
                .with_max_times(5),
        );

        let paths = vec!["hello", "world", "test", "batch"];
        op.delete_stream(stream::iter(paths)).await?;
        assert_eq!(*builder.attempt.lock().unwrap(), 5);
        Ok(())
    }

    #[tokio::test]
    async fn test_retry_copy() -> Result<()> {
        setup();

        #[derive(Default, Clone)]
        struct Recorder {
            events: Arc<Mutex<Vec<(Operation, u32)>>>,
        }

        impl RetryInterceptor for Recorder {
            fn intercept(&self, event: RetryEvent<'_>) {
                self.events.lock().unwrap().push((event.op, event.attempt));
            }
        }

        let recorder = Recorder::default();
        let builder = MockBuilder::default();
        let op = Operator::new(builder.clone())?.layer(
            RetryLayer::default()
                .with_min_delay(Duration::from_millis(1))
                .with_max_delay(Duration::from_millis(1))
                .with_notify(recorder.clone()),
        );

        op.copy("from", "to").await.expect("copy must succeed");

        // The MockCopier returns errors on attempts 1, 2, 4 and progress
        // on attempts 3, 5; finishing on attempt 6. The retry layer must
        // retry `Copier::next` to drive the operation to completion.
        assert_eq!(*builder.attempt.lock().unwrap(), 6);

        let events = recorder.events.lock().unwrap().clone();
        assert_eq!(
            events,
            vec![
                (Operation::Copy, 1),
                (Operation::Copy, 2),
                (Operation::Copy, 1),
            ],
        );
        Ok(())
    }
}
