// Copyright 2023 PingCAP, Inc.
//
// 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.

#include <Common/Exception.h>
#include <Operators/SharedQueue.h>

#include <magic_enum.hpp>

namespace DB
{
SharedQueuePtr SharedQueue::buildInternal(
    size_t producer,
    size_t consumer,
    Int64 max_buffered_bytes,
    Int64 max_queue_size)
{
    RUNTIME_CHECK(producer > 0 && consumer > 0);
    // The default queue size is same as UnionBlockInputStream = concurrency * 5.
    if (max_queue_size <= 0)
        max_queue_size = std::max(producer, consumer) * 5;
    CapacityLimits queue_limits(max_queue_size, max_buffered_bytes);
    return std::make_shared<SharedQueue>(queue_limits, producer);
}

std::pair<SharedQueueSinkHolderPtr, SharedQueueSourceHolderPtr> SharedQueue::build(
    PipelineExecutorContext & exec_context,
    size_t producer,
    size_t consumer,
    Int64 max_buffered_bytes,
    Int64 max_queue_size)
{
    auto shared_queue = buildInternal(producer, consumer, max_buffered_bytes, max_queue_size);
    exec_context.addSharedQueue(shared_queue);
    return {
        std::make_shared<SharedQueueSinkHolder>(shared_queue),
        std::make_shared<SharedQueueSourceHolder>(shared_queue)};
}

SharedQueue::SharedQueue(CapacityLimits queue_limits, size_t init_producer)
    : queue(queue_limits, [](const Block & block) { return block.allocatedBytes(); })
    , active_producer(init_producer)
{}

MPMCQueueResult SharedQueue::tryPush(Block && block)
{
    return queue.tryPush(std::move(block));
}

MPMCQueueResult SharedQueue::tryPop(Block & block)
{
    return queue.tryPop(block);
}

void SharedQueue::producerFinish()
{
    auto cur_value = active_producer.fetch_sub(1);
    RUNTIME_CHECK(cur_value >= 1);
    if (1 == cur_value)
        queue.finish();
}

void SharedQueue::cancel()
{
    queue.cancel();
}

OperatorStatus SharedQueueSinkOp::writeImpl(Block && block)
{
    if unlikely (!block)
        return OperatorStatus::FINISHED;

    assert(!buffer);
    buffer.emplace(std::move(block));
    return tryFlush();
}

OperatorStatus SharedQueueSinkOp::prepareImpl()
{
    return buffer ? tryFlush() : OperatorStatus::NEED_INPUT;
}

OperatorStatus SharedQueueSinkOp::tryFlush()
{
    auto queue_result = shared_queue->tryPush(std::move(*buffer));
    switch (queue_result)
    {
    case MPMCQueueResult::FULL:
        setNotifyFuture(shared_queue.get());
        return OperatorStatus::WAIT_FOR_NOTIFY;
    case MPMCQueueResult::OK:
        buffer.reset();
        return OperatorStatus::NEED_INPUT;
    case MPMCQueueResult::CANCELLED:
        return OperatorStatus::CANCELLED;
    default:
        // queue result can not be finish/empty here.
        RUNTIME_CHECK_MSG(
            false,
            "Unexpected queue result for SharedQueueSinkOp: {}",
            magic_enum::enum_name(queue_result));
    }
}

OperatorStatus SharedQueueSourceOp::readImpl(Block & block)
{
    auto queue_result = shared_queue->tryPop(block);
    switch (queue_result)
    {
    case MPMCQueueResult::EMPTY:
        setNotifyFuture(shared_queue.get());
        return OperatorStatus::WAIT_FOR_NOTIFY;
    case MPMCQueueResult::OK:
        return OperatorStatus::HAS_OUTPUT;
    case MPMCQueueResult::FINISHED:
        // Even after queue has finished, source op still needs to return HAS_OUTPUT.
        return OperatorStatus::HAS_OUTPUT;
    case MPMCQueueResult::CANCELLED:
        return OperatorStatus::CANCELLED;
    default:
        // queue result can not be full here.
        RUNTIME_CHECK_MSG(
            false,
            "Unexpected queue result for SharedQueueSourceOp: {}",
            magic_enum::enum_name(queue_result));
    }
}
} // namespace DB