/*
 * Copyright (c) Meta Platforms, Inc. and affiliates.
 *
 * Licensed 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.
 */

use std::marker::PhantomData;

use anyhow::Error;

use crate::bufext::BufExt;
use crate::framing::Framing;
use crate::framing::FramingDecoded;
use crate::framing::FramingEncodedFinal;
use crate::thrift_protocol::ProtocolID;

pub struct SerializedMessage<'a, Name: ?Sized, Buffer> {
    pub protocol: ProtocolID,
    pub buffer: Buffer,
    pub method_name: &'a Name,
}

pub trait ContextStack {
    /// Type for method names
    type Name: ?Sized;
    /// Type for serialized read and write buffers
    type Frame: Framing;

    /// Called before the request is read.
    fn pre_read(&mut self) -> Result<(), Error>;

    /// Called before post_read after reading arguments (server) / after reading
    /// reply (client), with the actual (unparsed, serialized) data.
    fn on_read_data(
        &mut self,
        msg: SerializedMessage<Self::Name, FramingDecoded<Self::Frame>>,
    ) -> Result<(), Error>;

    /// Called after the request is read.
    fn post_read(&mut self, bytes: u32) -> Result<(), Error>;

    /// Called before a response is written.
    fn pre_write(&mut self) -> Result<(), Error>;

    /// Called before post_write, after serializing response (server) / after
    /// serializing request (client), with the actual (serialized) data.
    fn on_write_data(
        &mut self,
        msg: SerializedMessage<Self::Name, FramingEncodedFinal<Self::Frame>>,
    ) -> Result<(), Error>;

    /// Called after a response a written.
    fn post_write(&mut self, bytes: u32) -> Result<(), Error>;
}

pub struct DummyContextStack<Name: ?Sized, Frame> {
    _phantom: PhantomData<(Frame, Name)>,
}

impl<Name: ?Sized, Frame> DummyContextStack<Name, Frame> {
    pub fn new() -> Self {
        Self {
            _phantom: PhantomData,
        }
    }
}

impl<Name: ?Sized, Frame: Framing> ContextStack for DummyContextStack<Name, Frame>
where
    FramingEncodedFinal<Frame>: BufExt,
{
    type Name = Name;
    type Frame = Frame;

    fn pre_read(&mut self) -> Result<(), Error> {
        Ok(())
    }

    fn on_read_data(
        &mut self,
        _msg: SerializedMessage<Self::Name, FramingDecoded<Self::Frame>>,
    ) -> Result<(), Error> {
        Ok(())
    }

    fn post_read(&mut self, _bytes: u32) -> Result<(), Error> {
        Ok(())
    }

    fn pre_write(&mut self) -> Result<(), Error> {
        Ok(())
    }

    fn on_write_data(
        &mut self,
        _msg: SerializedMessage<Self::Name, FramingEncodedFinal<Self::Frame>>,
    ) -> Result<(), Error> {
        Ok(())
    }

    fn post_write(&mut self, _bytes: u32) -> Result<(), Error> {
        Ok(())
    }
}

#[cfg(test)]
mod test {
    use bytes::Bytes;

    use super::*;

    fn assert_context_stack(_: &impl ContextStack) {}

    #[test]
    fn check_unsized() {
        assert_context_stack(&DummyContextStack::<std::ffi::CStr, Bytes>::new());
    }
}