// 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.

//! OpenTelemetry trace layer implementation for Apache OpenDAL.

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

use std::future::Future;
use std::sync::Arc;

use opendal_core::raw::*;
use opendal_core::*;
use opentelemetry::Context as TraceContext;
use opentelemetry::KeyValue;
use opentelemetry::global;
use opentelemetry::global::BoxedSpan;
use opentelemetry::trace::FutureExt as TraceFutureExt;
use opentelemetry::trace::Span;
use opentelemetry::trace::TraceContextExt;
use opentelemetry::trace::Tracer;

/// Add [opentelemetry::trace](https://docs.rs/opentelemetry/latest/opentelemetry/trace/index.html) for every operation.
///
/// # Examples
///
/// ## Basic Setup
///
/// ```no_run
/// # use opendal_core::services;
/// # use opendal_core::Operator;
/// # use opendal_core::Result;
/// # use opendal_layer_oteltrace::OtelTraceLayer;
/// #
/// # fn main() -> Result<()> {
/// let _ = Operator::new(services::Memory::default())?
///     .layer(OtelTraceLayer::new())
///     .finish();
/// # Ok(())
/// # }
/// ```
#[derive(Clone, Default)]
#[non_exhaustive]
pub struct OtelTraceLayer {}

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

impl<A: Access> Layer<A> for OtelTraceLayer {
    type LayeredAccess = OtelTraceAccessor<A>;

    fn layer(&self, inner: A) -> Self::LayeredAccess {
        OtelTraceAccessor { inner }
    }
}

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

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

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

    fn info(&self) -> Arc<AccessorInfo> {
        let tracer = global::tracer("opendal");
        tracer.in_span("info", |_cx| self.inner.info())
    }

    async fn create_dir(&self, path: &str, args: OpCreateDir) -> Result<RpCreateDir> {
        let tracer = global::tracer("opendal");
        let mut span = tracer.start("create");
        span.set_attribute(KeyValue::new("path", path.to_string()));
        span.set_attribute(KeyValue::new("args", format!("{args:?}")));
        let cx = TraceContext::current_with_span(span);
        self.inner.create_dir(path, args).with_context(cx).await
    }

    async fn read(&self, path: &str, args: OpRead) -> Result<(RpRead, Self::Reader)> {
        let tracer = global::tracer("opendal");
        let mut span = tracer.start("read");
        span.set_attribute(KeyValue::new("path", path.to_string()));
        span.set_attribute(KeyValue::new("args", format!("{args:?}")));
        self.inner
            .read(path, args)
            .await
            .map(|(rp, r)| (rp, OtelTraceWrapper::new(span, r)))
    }

    async fn write(&self, path: &str, args: OpWrite) -> Result<(RpWrite, Self::Writer)> {
        let tracer = global::tracer("opendal");
        let mut span = tracer.start("write");
        span.set_attribute(KeyValue::new("path", path.to_string()));
        span.set_attribute(KeyValue::new("args", format!("{args:?}")));
        self.inner
            .write(path, args)
            .await
            .map(|(rp, r)| (rp, OtelTraceWrapper::new(span, r)))
    }

    async fn copy(
        &self,
        from: &str,
        to: &str,
        args: OpCopy,
        opts: OpCopier,
    ) -> Result<(RpCopy, Self::Copier)> {
        let tracer = global::tracer("opendal");
        let mut span = tracer.start("copy");
        span.set_attribute(KeyValue::new("from", from.to_string()));
        span.set_attribute(KeyValue::new("to", to.to_string()));
        span.set_attribute(KeyValue::new("args", format!("{args:?}")));
        let cx = TraceContext::current_with_span(span);
        self.inner()
            .copy(from, to, args, opts.clone())
            .with_context(cx)
            .await
    }

    async fn rename(&self, from: &str, to: &str, args: OpRename) -> Result<RpRename> {
        let tracer = global::tracer("opendal");
        let mut span = tracer.start("rename");
        span.set_attribute(KeyValue::new("from", from.to_string()));
        span.set_attribute(KeyValue::new("to", to.to_string()));
        span.set_attribute(KeyValue::new("args", format!("{args:?}")));
        let cx = TraceContext::current_with_span(span);
        self.inner().rename(from, to, args).with_context(cx).await
    }

    async fn stat(&self, path: &str, args: OpStat) -> Result<RpStat> {
        let tracer = global::tracer("opendal");
        let mut span = tracer.start("stat");
        span.set_attribute(KeyValue::new("path", path.to_string()));
        span.set_attribute(KeyValue::new("args", format!("{args:?}")));
        let cx = TraceContext::current_with_span(span);
        self.inner().stat(path, args).with_context(cx).await
    }

    async fn delete(&self) -> Result<(RpDelete, Self::Deleter)> {
        self.inner().delete().await
    }

    async fn list(&self, path: &str, args: OpList) -> Result<(RpList, Self::Lister)> {
        let tracer = global::tracer("opendal");
        let mut span = tracer.start("list");
        span.set_attribute(KeyValue::new("path", path.to_string()));
        span.set_attribute(KeyValue::new("args", format!("{args:?}")));
        self.inner
            .list(path, args)
            .await
            .map(|(rp, s)| (rp, OtelTraceWrapper::new(span, s)))
    }

    async fn presign(&self, path: &str, args: OpPresign) -> Result<RpPresign> {
        let tracer = global::tracer("opendal");
        let mut span = tracer.start("presign");
        span.set_attribute(KeyValue::new("path", path.to_string()));
        span.set_attribute(KeyValue::new("args", format!("{args:?}")));
        let cx = TraceContext::current_with_span(span);
        self.inner().presign(path, args).with_context(cx).await
    }
}

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

impl<R> OtelTraceWrapper<R> {
    fn new(_span: BoxedSpan, inner: R) -> Self {
        Self { _span, inner }
    }
}

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

impl<R: oio::Write> oio::Write for OtelTraceWrapper<R> {
    fn write(&mut self, bs: Buffer) -> impl Future<Output = Result<()>> + MaybeSend {
        self.inner.write(bs)
    }

    fn abort(&mut self) -> impl Future<Output = Result<()>> + MaybeSend {
        self.inner.abort()
    }

    fn close(&mut self) -> impl Future<Output = Result<Metadata>> + MaybeSend {
        self.inner.close()
    }
}

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