// 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.

//! Hotpath layer implementation for Apache OpenDAL.

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

use std::pin::Pin;
use std::task::Context;
use std::task::Poll;

use futures::Stream;
use futures::StreamExt;
use opendal_core::raw::*;
use opendal_core::*;

const LABEL_CREATE_DIR: &str = "opendal.create_dir";
const LABEL_READ: &str = "opendal.read";
const LABEL_WRITE: &str = "opendal.write";
const LABEL_COPY: &str = "opendal.copy";
const LABEL_RENAME: &str = "opendal.rename";
const LABEL_STAT: &str = "opendal.stat";
const LABEL_DELETE: &str = "opendal.delete";
const LABEL_LIST: &str = "opendal.list";
const LABEL_PRESIGN: &str = "opendal.presign";

const LABEL_READER_READ: &str = "opendal.reader.read";
const LABEL_WRITER_WRITE: &str = "opendal.writer.write";
const LABEL_WRITER_CLOSE: &str = "opendal.writer.close";
const LABEL_WRITER_ABORT: &str = "opendal.writer.abort";
const LABEL_LISTER_NEXT: &str = "opendal.lister.next";
const LABEL_DELETER_DELETE: &str = "opendal.deleter.delete";
const LABEL_DELETER_CLOSE: &str = "opendal.deleter.close";
const LABEL_COPIER_NEXT: &str = "opendal.copier.next";
const LABEL_COPIER_CLOSE: &str = "opendal.copier.close";
const LABEL_COPIER_ABORT: &str = "opendal.copier.abort";
const LABEL_HTTP_FETCH: &str = "opendal.http.fetch";
const LABEL_HTTP_BODY_POLL: &str = "opendal.http.body.poll";

/// Add [hotpath](https://docs.rs/hotpath/) profiling for every operation.
///
/// # Notes
///
/// When `hotpath` profiling is enabled, initialize a guard via
/// [`hotpath::HotpathGuardBuilder`] or `#[hotpath::main]` before running
/// operations. Otherwise, hotpath will panic on the first measurement.
///
/// # Examples
///
/// ```no_run
/// # use opendal_core::services;
/// # use opendal_core::Operator;
/// # use opendal_core::Result;
/// # use opendal_layer_hotpath::HotpathLayer;
/// #
/// # #[tokio::main]
/// # async fn main() -> Result<()> {
/// let _guard = hotpath::HotpathGuardBuilder::new("opendal").build();
/// let op = Operator::new(services::Memory::default())?
///     .layer(HotpathLayer::new())
///     .finish();
/// op.write("test", "hello").await?;
/// # Ok(())
/// # }
/// ```
#[derive(Clone, Default)]
#[non_exhaustive]
pub struct HotpathLayer {}

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

impl<A: Access> Layer<A> for HotpathLayer {
    type LayeredAccess = HotpathAccessor<A>;

    fn layer(&self, inner: A) -> Self::LayeredAccess {
        let info = inner.info();
        info.update_http_client(|client| {
            HttpClient::with(HotpathHttpFetcher {
                inner: client.into_inner(),
            })
        });

        HotpathAccessor { inner }
    }
}

#[doc(hidden)]
#[derive(Debug)]
pub struct HotpathAccessor<A> {
    inner: A,
}

impl<A: Access> LayeredAccess for HotpathAccessor<A> {
    type Inner = A;
    type Reader = HotpathWrapper<A::Reader>;
    type Writer = HotpathWrapper<A::Writer>;
    type Lister = HotpathWrapper<A::Lister>;
    type Deleter = HotpathWrapper<A::Deleter>;
    type Copier = HotpathWrapper<A::Copier>;

    fn inner(&self) -> &Self::Inner {
        &self.inner
    }

    async fn create_dir(&self, path: &str, args: OpCreateDir) -> Result<RpCreateDir> {
        hotpath::measure_async(LABEL_CREATE_DIR, self.inner.create_dir(path, args)).await
    }

    async fn read(&self, path: &str, args: OpRead) -> Result<(RpRead, Self::Reader)> {
        let (rp, reader) = hotpath::measure_async(LABEL_READ, self.inner.read(path, args)).await?;
        Ok((rp, HotpathWrapper::new(reader)))
    }

    async fn write(&self, path: &str, args: OpWrite) -> Result<(RpWrite, Self::Writer)> {
        let (rp, writer) =
            hotpath::measure_async(LABEL_WRITE, self.inner.write(path, args)).await?;
        Ok((rp, HotpathWrapper::new(writer)))
    }

    async fn copy(
        &self,
        from: &str,
        to: &str,
        args: OpCopy,
        opts: OpCopier,
    ) -> Result<(RpCopy, Self::Copier)> {
        let (rp, copier) =
            hotpath::measure_async(LABEL_COPY, self.inner.copy(from, to, args, opts.clone()))
                .await?;
        Ok((rp, HotpathWrapper::new(copier)))
    }

    async fn rename(&self, from: &str, to: &str, args: OpRename) -> Result<RpRename> {
        hotpath::measure_async(LABEL_RENAME, self.inner.rename(from, to, args)).await
    }

    async fn stat(&self, path: &str, args: OpStat) -> Result<RpStat> {
        hotpath::measure_async(LABEL_STAT, self.inner.stat(path, args)).await
    }

    async fn delete(&self) -> Result<(RpDelete, Self::Deleter)> {
        let (rp, deleter) = hotpath::measure_async(LABEL_DELETE, self.inner.delete()).await?;
        Ok((rp, HotpathWrapper::new(deleter)))
    }

    async fn list(&self, path: &str, args: OpList) -> Result<(RpList, Self::Lister)> {
        let (rp, lister) = hotpath::measure_async(LABEL_LIST, self.inner.list(path, args)).await?;
        Ok((rp, HotpathWrapper::new(lister)))
    }

    async fn presign(&self, path: &str, args: OpPresign) -> Result<RpPresign> {
        hotpath::measure_async(LABEL_PRESIGN, self.inner.presign(path, args)).await
    }
}

#[doc(hidden)]
pub struct HotpathWrapper<R> {
    inner: R,
}

impl<R> HotpathWrapper<R> {
    fn new(inner: R) -> Self {
        Self { inner }
    }
}

impl<R: oio::Read> oio::Read for HotpathWrapper<R> {
    async fn read(&mut self) -> Result<Buffer> {
        hotpath::measure_async(LABEL_READER_READ, self.inner.read()).await
    }
}

impl<R: oio::Write> oio::Write for HotpathWrapper<R> {
    async fn write(&mut self, bs: Buffer) -> Result<()> {
        hotpath::measure_async(LABEL_WRITER_WRITE, self.inner.write(bs)).await
    }

    async fn close(&mut self) -> Result<Metadata> {
        hotpath::measure_async(LABEL_WRITER_CLOSE, self.inner.close()).await
    }

    async fn abort(&mut self) -> Result<()> {
        hotpath::measure_async(LABEL_WRITER_ABORT, self.inner.abort()).await
    }
}

impl<R: oio::List> oio::List for HotpathWrapper<R> {
    async fn next(&mut self) -> Result<Option<oio::Entry>> {
        hotpath::measure_async(LABEL_LISTER_NEXT, self.inner.next()).await
    }
}

impl<R: oio::Delete> oio::Delete for HotpathWrapper<R> {
    async fn delete(&mut self, path: &str, args: OpDelete) -> Result<()> {
        hotpath::measure_async(LABEL_DELETER_DELETE, self.inner.delete(path, args)).await
    }

    async fn close(&mut self) -> Result<()> {
        hotpath::measure_async(LABEL_DELETER_CLOSE, self.inner.close()).await
    }
}

impl<C: oio::Copy> oio::Copy for HotpathWrapper<C> {
    async fn next(&mut self) -> Result<Option<usize>> {
        hotpath::measure_async(LABEL_COPIER_NEXT, self.inner.next()).await
    }

    async fn close(&mut self) -> Result<Metadata> {
        hotpath::measure_async(LABEL_COPIER_CLOSE, self.inner.close()).await
    }

    async fn abort(&mut self) -> Result<()> {
        hotpath::measure_async(LABEL_COPIER_ABORT, self.inner.abort()).await
    }
}

struct HotpathHttpFetcher {
    inner: HttpFetcher,
}

impl HttpFetch for HotpathHttpFetcher {
    async fn fetch(&self, req: http::Request<Buffer>) -> Result<http::Response<HttpBody>> {
        let resp = hotpath::measure_async(LABEL_HTTP_FETCH, self.inner.fetch(req)).await?;
        let (parts, body) = resp.into_parts();
        let body = body.map_inner(|stream| Box::new(HotpathStream { inner: stream }));
        Ok(http::Response::from_parts(parts, body))
    }
}

struct HotpathStream<S> {
    inner: S,
}

impl<S> Stream for HotpathStream<S>
where
    S: Stream<Item = Result<Buffer>> + Unpin + 'static,
{
    type Item = Result<Buffer>;

    fn poll_next(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
        let _label = LABEL_HTTP_BODY_POLL;
        hotpath::measure_block!(_label, self.inner.poll_next_unpin(cx))
    }
}
