// Copyright 2024 The NativeLink Authors. All rights reserved.

//

// Licensed under the Functional Source License, Version 1.1, Apache 2.0 Future License (the "License");

// you may not use this file except in compliance with the License.

// You may obtain a copy of the License at

//

//    See LICENSE file for details

//

// 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.

use core::fmt::Debug;

use core::mem;

use core::pin::Pin;

use core::task::{Context, Poll};

use std::borrow::Cow;

use std::sync::Arc;

use futures::{Stream, StreamExt};

use nativelink_error::{Error, ResultExt, error_if, make_input_err};

use nativelink_proto::google::bytestream::{ReadResponse, WriteRequest};

use parking_lot::Mutex;

use tonic::{Status, Streaming};

use crate::resource_info::ResourceInfo;

pub struct WriteRequestStreamWrapper<T> {

    pub resource_info: ResourceInfo<'static>,

    pub bytes_received: usize,

    stream: T,

    first_msg: Option<WriteRequest>,

    pub write_finished: bool,

}

impl<T> Debug for WriteRequestStreamWrapper<T> {

    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {

        f.debug_struct("WriteRequestStreamWrapper")

            .field("resource_info", &self.resource_info)

            .field("bytes_received", &self.bytes_received)

            .field("first_msg", &self.first_msg)

            .field("write_finished", &self.write_finished)

            .finish()

    }

}

impl<T, E> WriteRequestStreamWrapper<T>

where

    T: Stream<Item = Result<WriteRequest, E>> + Unpin,

    E: Into<Error>,

{

    pub async fn from(mut stream: T) -> Result<Self, Error> {

        let 
first_msg44
 = stream

            .next()

            .await

            .err_tip(|| "Error receiving first message in stream")
?0

            .err_tip(|| "Expected WriteRequest struct in stream (from)")
?1
;

        let resource_info = ResourceInfo::new(&first_msg.resource_name, true)

            .err_tip(|| 
{0

                format!(

                    "Could not extract resource info from first message of stream: {}",

                    first_msg.resource_name

                )

            })?

            .to_owned();

        Ok(Self {

            resource_info,

            bytes_received: 0,

            stream,

            first_msg: Some(first_msg),

            write_finished: false,

        })

    }

    pub async fn next(&mut self) -> Option<Result<WriteRequest, Error>> {

        
futures::future::poll_fn53
(|cx| Pin::new(&mut *self).poll_next(cx)).
await53

    }

    pub const fn is_first_msg(&self) -> bool {

        self.first_msg.is_some()

    }

    /// Returns whether the first message has `finish_write` set to true.

    /// This indicates a single-shot upload where all data is in one message.

    pub fn is_first_msg_complete(&self) -> bool {

        self.first_msg.as_ref().is_some_and(|msg| msg.finish_write)

    }

    fn enforce_wire_size_matches_digest_size(&self) -> bool {

        matches!(

            self.resource_info.compressor.as_deref(),

            None | Some("identity")

        )

    }

}

impl<T, E> Stream for WriteRequestStreamWrapper<T>

where

    E: Into<Error>,

    T: Stream<Item = Result<WriteRequest, E>> + Unpin,

{

    type Item = Result<WriteRequest, Error>;

    fn poll_next(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {

        // If the stream said that the previous message was the last one, then

        // return a stream EOF (i.e. None).

        if self.write_finished {

            if self.enforce_wire_size_matches_digest_size() {

                error_if!(

                    self.bytes_received != self.resource_info.expected_size,

                    "Did not send enough data. Expected {}, but so far received {}",

                    self.resource_info.expected_size,

                    self.bytes_received

                );

            }

            return Poll::Ready(None);

        }

        // Gets the next message, this is either the cached first or a

        // subsequent message from the wrapped Stream.

        let 
maybe_message84
 = if let Some(
first_msg42
) = self.first_msg.take() {

            Ok(first_msg)

        } else {

            match Pin::new(&mut self.stream).poll_next(cx) {

                Poll::Pending => return Poll::Pending,

                Poll::Ready(Some(maybe_message)) => maybe_message

                    .err_tip(|| 
format!0
("Stream error at byte {}", 
self.bytes_received0
)),

                Poll::Ready(None) => Err(make_input_err!(

                    "Expected WriteRequest struct in stream (got None)"

                )),

            }

        };

        // If we successfully got a message, update our internal state with the

        // message meta data.

        Poll::Ready(Some(maybe_message.and_then(|message| 
{80

            self.write_finished = message.finish_write;

            self.bytes_received += message.data.len();

            // Check that we haven't read past the expected end.

            if self.enforce_wire_size_matches_digest_size()

                && self.bytes_received > self.resource_info.expected_size

            {

                Err(make_input_err!(

                    "Sent too much data. Expected {}, but so far received {}",

                    self.resource_info.expected_size,

                    self.bytes_received

                ))

            } else {

                Ok(message)

            }

        })))

    }

}

/// Represents the state of the first response in a `FirstStream`.

#[derive(Debug)]

pub enum FirstResponseState {

    /// Contains an optional first response that hasn't been consumed yet.

    /// A `None` value indicates the first response was EOF.

    Unused(Option<ReadResponse>),

    /// Indicates the first response has been consumed and future reads should

    /// come from the underlying stream.

    Used,

}

/// This provides a buffer for the first response from GrpcStore.read in order

/// to allow the first read to occur within the retry loop.  That means that if

/// the connection establishes fine, but reading the first byte of the file

/// fails we have the ability to retry before returning to the caller.

#[derive(Debug)]

pub struct FirstStream {

    /// The current state of the first response. When in the `Unused` state,

    /// contains an optional response which could be `None` or an EOF.

    /// Once consumed, transitions to the `Used` state.

    state: FirstResponseState,

    /// The stream to get responses from after the first response is consumed.

    stream: Streaming<ReadResponse>,

}

impl FirstStream {

    /// Creates a new `FirstStream` with the given first response and underlying

    /// stream.

    pub const fn new(

        first_response: Option<ReadResponse>,

        stream: Streaming<ReadResponse>,

    ) -> Self {

        Self {

            state: FirstResponseState::Unused(first_response),

            stream,

        }

    }

}

impl Stream for FirstStream {

    type Item = Result<ReadResponse, Status>;

    fn poll_next(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {

        match mem::replace(&mut self.state, FirstResponseState::Used) {

            FirstResponseState::Unused(first_response) => Poll::Ready(first_response.map(Ok)),

            FirstResponseState::Used => Pin::new(&mut self.stream).poll_next(cx),

        }

    }

}

/// Largest `data` payload in a single `ByteStream` `WriteRequest`, kept under

/// tonic's 4MiB default `max_decoding_message_size` with room to spare.

pub const MAX_WRITE_REQUEST_DATA_BYTES: usize = 2 * 1024 * 1024;

/// This structure wraps all of the information required to perform a write

/// request on the `GrpcStore`.  It stores the last message retrieved which allows

/// the write to resume since the UUID allows upload resume at the server.

#[derive(Debug)]

pub struct WriteState<T, E>

where

    T: Stream<Item = Result<WriteRequest, E>> + Unpin + Send + 'static,

    E: Into<Error> + 'static,

{

    instance_name: String,

    read_stream_error: Option<Error>,

    read_stream: WriteRequestStreamWrapper<T>,

    // Tonic doesn't appear to report an error until it has taken two messages,

    // therefore we are required to buffer the last two messages.

    cached_messages: [Option<WriteRequest>; 2],

    // When resuming after an error, the previous messages are cloned into this

    // queue upfront to allow them to be served back.

    resume_queue: [Option<WriteRequest>; 2],

    // An optimisation to avoid having to manage resume_queue when it's empty.

    is_resumed: bool,

    // Remainder of an incoming frame too large to forward in one message.

    // Drained before the next frame is read so ordering is preserved.

    pending: Option<WriteRequest>,

    // When false, a partially-consumed stream never reports `can_resume()`:

    // uploads whose server-side protocol cannot accept a replay from a

    // nonzero offset (REAPI compressed-blobs writes) must fail fast instead

    // of burning retries on guaranteed-rejected resumes. A stream that has

    // not yet been consumed can always be retried from the start.

    resumable: bool,

}

impl<T, E> WriteState<T, E>

where

    T: Stream<Item = Result<WriteRequest, E>> + Unpin + Send + 'static,

    E: Into<Error> + 'static,

{

    pub const fn new(instance_name: String, read_stream: WriteRequestStreamWrapper<T>) -> Self {

        Self {

            instance_name,

            read_stream_error: None,

            read_stream,

            cached_messages: [None, None],

            resume_queue: [None, None],

            is_resumed: false,

            pending: None,

            resumable: true,

        }

    }

    /// Caps the payload of an outgoing message, stashing anything over the

    /// limit to be sent as the following message.

    ///

    /// A caller can hand us a whole blob in one frame, and forwarding that

    /// verbatim produces a message the receiver rejects at its 4MiB default.

    /// Only the final piece carries `finish_write`, and each piece advances

    /// `write_offset` by what came before it.

    fn split_oversized(&mut self, mut message: WriteRequest) -> WriteRequest {

        if message.data.len() <= MAX_WRITE_REQUEST_DATA_BYTES {

            return message;

        }

        let rest = message.data.split_off(MAX_WRITE_REQUEST_DATA_BYTES);

        let sent_len = i64::try_from(message.data.len()).unwrap_or(i64::MAX);

        self.pending = Some(WriteRequest {

            resource_name: message.resource_name.clone(),

            write_offset: message.write_offset.saturating_add(sent_len),

            finish_write: message.finish_write,

            data: rest,

        });

        message.finish_write = false;

        message

    }

    /// Marks this write as non-resumable: once the stream has been partially

    /// consumed, `can_resume()` reports false so the caller fails fast with

    /// the original error instead of replaying messages the server-side

    /// protocol is guaranteed to reject. Retrying an unconsumed stream from

    /// the start remains allowed.

    pub const fn set_non_resumable(&mut self) {

        self.resumable = false;

    }

    pub(crate) const fn is_resumable(&self) -> bool {

        self.resumable

    }

    fn push_message(&mut self, message: WriteRequest) {

        self.cached_messages.swap(0, 1);

        self.cached_messages[0] = Some(message);

    }

    const fn resumed_message(&mut self) -> Option<WriteRequest> {

        if self.is_resumed {

            // The resume_queue is a circular buffer, that we have to shift,

            // since its only got two elements its a trivial swap.

            self.resume_queue.swap(0, 1);

            let message = self.resume_queue[0].take();

            if message.is_none() {

                self.is_resumed = false;

            }

            message

        } else {

            None

        }

    }

    pub const fn can_resume(&self) -> bool {

        self.read_stream_error.is_none()

            && ((self.resumable && 
self.cached_messages[0]0
.
is_some0
())

                || self.read_stream.is_first_msg())

    }

    pub fn resume(&mut self) {

        self.resume_queue.clone_from(&self.cached_messages);

        self.is_resumed = true;

    }

    pub const fn take_read_stream_error(&mut self) -> Option<Error> {

        self.read_stream_error.take()

    }

}

/// A wrapper around `WriteState` to allow it to be reclaimed from the underlying

/// write call in the case of failure.

#[derive(Debug)]

pub struct WriteStateWrapper<T, E>

where

    T: Stream<Item = Result<WriteRequest, E>> + Unpin + Send + 'static,

    E: Into<Error> + 'static,

{

    shared_state: Arc<Mutex<WriteState<T, E>>>,

}

impl<T, E> WriteStateWrapper<T, E>

where

    T: Stream<Item = Result<WriteRequest, E>> + Unpin + Send + 'static,

    E: Into<Error> + 'static,

{

    pub const fn new(shared_state: Arc<Mutex<WriteState<T, E>>>) -> Self {

        Self { shared_state }

    }

}

impl<T, E> Stream for WriteStateWrapper<T, E>

where

    T: Stream<Item = Result<WriteRequest, E>> + Unpin + Send + 'static,

    E: Into<Error> + 'static,

{

    type Item = WriteRequest;

    fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {

        const IS_UPLOAD_TRUE: bool = true;

        // This should be an uncontended lock since write was called.

        let mut local_state = self.shared_state.lock();

        // If this is the first or second call after a failure and we have

        // cached messages, then use the cached write requests.

        let cached_message = local_state.resumed_message();

        if cached_message.is_some() {

            return Poll::Ready(cached_message);

        }

        // Finish draining an oversized frame before reading the next one.

        if let Some(
pending2
) = local_state.pending.take() {

            let message = local_state.split_oversized(pending);

            if local_state.is_resumable() {

                local_state.push_message(message.clone());

            
}0

            return Poll::Ready(Some(message));

        }

        // Read a new write request from the downstream.

        let Poll::Ready(
maybe_message42
) = Pin::new(&mut local_state.read_stream).poll_next(cx)

        else {

            return Poll::Pending;

        };

        // Update the instance name in the write request and forward it on.

        let result = match 
maybe_message32
 {

            Some(Ok(mut message)) => {

                if !message.resource_name.is_empty() {

                    // Replace the instance name in the resource name if it is

                    // different from the instance name in the write state.

                    match ResourceInfo::new(&message.resource_name, IS_UPLOAD_TRUE) {

                        Ok(mut resource_name) => {

                            if resource_name.instance_name != local_state.instance_name {

                                resource_name.instance_name =

                                    Cow::Borrowed(&local_state.instance_name);

                                message.resource_name = resource_name.to_string(IS_UPLOAD_TRUE);

                            }

                        }

                        Err(err) => {

                            local_state.read_stream_error = Some(err);

                            return Poll::Ready(None);

                        }

                    }

                }

                let message = local_state.split_oversized(message);

                // Cache the last request in case there is an error to allow

                // the upload to be resumed. Non-resumable writes skip the

                // clone: cached messages would never be replayed.

                if local_state.is_resumable() {

                    local_state.push_message(message.clone());

                
}14

                Some(message)

            }

            Some(Err(err)) => {

                local_state.read_stream_error = Some(err);

                None

            }

            None => None,

        };

        Poll::Ready(result)

    }

}