// Copyright 2022 RisingWave Labs
//
// 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::ops::Bound;

use futures::TryStreamExt;
use itertools::Itertools;
use risingwave_common::catalog::ColumnDesc;
use risingwave_common::row::RowExt;
use risingwave_common::util::iter_util::ZipEqDebug;
use risingwave_common::util::sort_util::ColumnOrder;
use risingwave_common_estimate_size::collections::EstimatedVec;
use risingwave_storage::row_serde::value_serde::ValueRowSerde;
use risingwave_storage::store::PrefetchOptions;

use super::sides::{stream_lookup_arrange_prev_epoch, stream_lookup_arrange_this_epoch};
use crate::common::metrics::MetricsInfo;
use crate::common::table::state_table::ReplicatedStateTable;
use crate::executor::join::builder::JoinStreamChunkBuilder;
use crate::executor::lookup::LookupExecutor;
use crate::executor::lookup::cache::LookupCache;
use crate::executor::lookup::sides::{ArrangeJoinSide, ArrangeMessage, StreamJoinSide};
use crate::executor::monitor::LookupExecutorMetrics;
use crate::executor::prelude::*;

/// Parameters for [`LookupExecutor`].
pub struct LookupExecutorParams<S: StateStore, SD: ValueRowSerde> {
    pub ctx: ActorContextRef,
    pub info: ExecutorInfo,

    /// The side for arrangement. Currently, it should be a
    /// `MaterializeExecutor`.
    pub arrangement: Executor,

    /// The side for stream. It can be any stream, but it will generally be a
    /// `MaterializeExecutor`.
    pub stream: Executor,

    /// Should be the same as [`ColumnDesc`] in the arrangement.
    ///
    /// From the perspective of arrangements, `arrangement_col_descs` include all columns of the
    /// `MaterializeExecutor`. For example, if we already have a table with 3 columns: `a, b,
    /// _row_id`, and we create an arrangement with join key `a` on it. `arrangement_col_descs`
    /// should contain all 3 columns.
    pub arrangement_col_descs: Vec<ColumnDesc>,

    /// Should only contain [`ColumnOrder`] for arrange in the arrangement.
    ///
    /// Still using the above `a, b, _row_id` example. If we create an arrangement with join key
    /// `a`, there will be 3 elements in `arrangement_col_descs`, and only 1 element in
    /// `arrangement_order_rules`.
    ///
    /// * The only element is the order rule for `a`, which is the join key. Join keys should
    ///   always come first.
    ///
    /// For the MV pk, they will only be contained in `arrangement_col_descs`, without being part
    /// of this `arrangement_order_rules`.
    pub arrangement_order_rules: Vec<ColumnOrder>,

    /// By default, the output of [`LookupExecutor`] is `stream columns + arrangement columns`.
    /// The executor will do a reorder of columns before producing output, so that data can be
    /// consistent among A lookup B and B lookup A.
    pub column_mapping: Vec<usize>,

    /// Whether to use the current epoch of the arrangement to lookup.
    ///
    /// [`LookupExecutor`] will act differently on whether `use_current_epoch` is set to true. In a
    /// nutshell, lookup in the previous epoch (this option set to false) will be more efficient.
    /// Therefore, the optimizer should choose an optimal order for lookup executors.
    ///
    /// See [`stream_lookup_arrange_this_epoch`] and [`stream_lookup_arrange_prev_epoch`] for more
    /// information.
    pub use_current_epoch: bool,

    /// The join keys on the stream side.
    pub stream_join_key_indices: Vec<usize>,

    /// The join keys on the arrangement side.
    pub arrange_join_key_indices: Vec<usize>,

    pub state_table: ReplicatedStateTable<S, SD>,

    pub watermark_epoch: AtomicU64Ref,

    pub chunk_size: usize,
}

impl<S: StateStore, SD: ValueRowSerde> LookupExecutor<S, SD> {
    pub fn new(params: LookupExecutorParams<S, SD>) -> Self {
        let LookupExecutorParams {
            ctx,
            info,
            arrangement,
            stream,
            arrangement_col_descs,
            arrangement_order_rules,
            use_current_epoch,
            stream_join_key_indices,
            arrange_join_key_indices,
            column_mapping,
            state_table: storage_table,
            watermark_epoch,
            chunk_size,
        } = params;

        let output_column_length = stream.schema().len() + arrangement.schema().len();

        // internal output schema: | stream | arrange |
        // will be rewritten using `column_mapping`.

        let schema_fields = stream
            .schema()
            .fields
            .iter()
            .chain(arrangement.schema().fields.iter())
            .cloned()
            .collect_vec();

        assert_eq!(schema_fields.len(), output_column_length);

        let schema = Schema::new(schema_fields);

        let chunk_data_types = schema.data_types();
        let arrangement_data_types = arrangement.schema().data_types();
        let stream_data_types = stream.schema().data_types();

        let arrangement_pk_indices = arrangement.stream_key().to_vec();
        let stream_pk_indices = stream.stream_key().to_vec();

        // check if arrange join key is exactly the same as order rules
        {
            let mut arrange_join_key_indices = arrange_join_key_indices.clone();
            arrange_join_key_indices.sort_unstable();
            let mut arrangement_order_types_indices = arrangement_order_rules
                .iter()
                .map(|x| x.column_index)
                .collect_vec();
            arrangement_order_types_indices.sort_unstable();
            assert_eq!(
                arrange_join_key_indices,
                &arrangement_order_types_indices[0..arrange_join_key_indices.len()],
                "invalid join key: arrange_join_key_indices = {:?}, order_rules: {:?}",
                arrange_join_key_indices,
                arrangement_order_rules
            );
        }

        // check whether join keys are of the same length.
        assert_eq!(
            stream_join_key_indices.len(),
            arrange_join_key_indices.len()
        );

        // resolve mapping from join keys in stream row -> joins keys for arrangement.
        let key_indices_mapping = arrangement_order_rules
            .iter()
            .map(|x| x.column_index) // the required column idx in this position
            .filter_map(|x| arrange_join_key_indices.iter().position(|y| *y == x)) // the position of the item in join keys
            .map(|x| stream_join_key_indices[x]) // the actual column idx in stream
            .collect_vec();

        // check the inferred schema is really the same as the output schema of the lookup executor.
        assert_eq!(
            info.schema
                .fields
                .iter()
                .map(|x| x.data_type())
                .collect_vec(),
            column_mapping
                .iter()
                .map(|x| schema.fields[*x].data_type())
                .collect_vec(),
            "mismatched output schema"
        );

        let metrics_info = MetricsInfo::new(
            ctx.streaming_metrics.clone(),
            storage_table.table_id(),
            ctx.id,
            "Lookup",
        );

        Self {
            ctx,
            chunk_data_types,
            stream_executor: Some(stream),
            arrangement_executor: Some(arrangement),
            stream: StreamJoinSide {
                key_indices: stream_join_key_indices,
                pk_indices: stream_pk_indices,
                col_types: stream_data_types,
            },
            arrangement: ArrangeJoinSide {
                pk_indices: arrangement_pk_indices,
                col_types: arrangement_data_types,
                col_descs: arrangement_col_descs,
                order_rules: arrangement_order_rules,
                key_indices: arrange_join_key_indices,
                use_current_epoch,
                state_table: storage_table,
            },
            column_mapping,
            key_indices_mapping,
            lookup_cache: LookupCache::new(watermark_epoch, metrics_info),
            chunk_size,
        }
    }

    /// Try produce one stream message from [`LookupExecutor`]. If there's no message to produce, it
    /// will return `None`, and the `next` function of [`LookupExecutor`] will continuously polling
    /// messages until there's one.
    ///
    /// If we can use `async_stream` to write this part, things could be easier.
    #[try_stream(ok = Message, error = StreamExecutorError)]
    pub async fn execute_inner(mut self: Box<Self>) {
        let mut stream_input = self.stream_executor.take().unwrap().execute();
        let mut arrangement_input = self.arrangement_executor.take().unwrap().execute();

        let first_barrier = expect_first_barrier(&mut stream_input).await?;
        let arrangement_first_barrier = expect_first_barrier(&mut arrangement_input).await?;
        if first_barrier.epoch != arrangement_first_barrier.epoch {
            return Err(StreamExecutorError::align_barrier(
                first_barrier.clone(),
                arrangement_first_barrier,
            ));
        }

        let input = if self.arrangement.use_current_epoch {
            stream_lookup_arrange_this_epoch(stream_input, arrangement_input).boxed()
        } else {
            stream_lookup_arrange_prev_epoch(stream_input, arrangement_input).boxed()
        };

        let metrics = self.ctx.streaming_metrics.new_lookup_executor_metrics(
            self.arrangement.state_table.table_id(),
            self.ctx.id,
            self.ctx.fragment_id,
        );

        let (stream_to_output, arrange_to_output) = JoinStreamChunkBuilder::get_i2o_mapping(
            &self.column_mapping,
            self.stream.col_types.len(),
            self.arrangement.col_types.len(),
        );

        let reorder_chunk_data_types = self
            .column_mapping
            .iter()
            .map(|x| self.chunk_data_types[*x].clone())
            .collect_vec();

        // Yield the barrier before init_epoch: init_epoch calls wait_for_epoch(epoch.prev)
        // which blocks until the previous epoch is committed, and that requires all actors
        // to have already forwarded this barrier downstream.
        yield Message::Barrier(first_barrier.clone());
        self.arrangement
            .state_table
            .init_epoch(first_barrier.epoch)
            .await?;

        #[for_await]
        for msg in input {
            let msg = msg?;
            self.lookup_cache.evict();
            match msg {
                ArrangeMessage::Barrier(barrier) => {
                    barrier.assume_no_update_vnode_bitmap(self.ctx.id)?;
                    self.arrangement
                        .state_table
                        .commit_assert_no_update_vnode_bitmap(barrier.epoch)
                        .await?;

                    if self.arrangement.use_current_epoch {
                        // When lookup this epoch, stream side barrier always come after arrangement
                        // ready, so we can forward barrier now.
                        yield Message::Barrier(barrier.clone());
                    }
                }
                ArrangeMessage::ArrangeReady(arrangement_chunks, barrier) => {
                    // The arrangement is ready, and we will receive a bunch of stream messages for
                    // the next poll.
                    // TODO: apply chunk as soon as we receive them, instead of batching.
                    for chunk in &arrangement_chunks {
                        self.arrangement.state_table.write_chunk(chunk.clone());
                    }

                    for chunk in arrangement_chunks {
                        self.lookup_cache
                            .apply_batch(chunk, &self.arrangement.key_indices)
                    }

                    if !self.arrangement.use_current_epoch {
                        // When look prev epoch, arrange ready will always come after stream
                        // barrier. So we yield barrier now.
                        yield Message::Barrier(barrier);
                    }
                }
                ArrangeMessage::Stream(chunk) => {
                    let chunk = chunk.compact_vis();
                    let (chunk, ops) = chunk.into_parts();

                    let mut builder = JoinStreamChunkBuilder::new(
                        self.chunk_size,
                        reorder_chunk_data_types.clone(),
                        stream_to_output.clone(),
                        arrange_to_output.clone(),
                    );

                    for (op, row) in ops.iter().zip_eq_debug(chunk.rows()) {
                        for matched_row in self.lookup_one_row(&row, &metrics).await? {
                            tracing::debug!(target: "events::stream::lookup::put", "{:?} {:?}", row, matched_row);

                            if let Some(chunk) = builder.append_row(*op, row, &matched_row) {
                                yield Message::Chunk(chunk);
                            }
                        }
                        // TODO: support outer join (return null if no rows are matched)
                    }

                    if let Some(chunk) = builder.take() {
                        yield Message::Chunk(chunk);
                    }
                }
            }
        }
    }

    /// Lookup all rows corresponding to a join key in the replicated state table.
    async fn lookup_one_row(
        &mut self,
        stream_row: &RowRef<'_>,
        metrics: &LookupExecutorMetrics,
    ) -> StreamExecutorResult<Vec<OwnedRow>> {
        // stream_row is the row from stream side, we need to transform into the correct order of
        // the arrangement side.
        let lookup_row = stream_row
            .project(&self.key_indices_mapping)
            .into_owned_row();

        metrics.lookup_total_query_cache_count.inc();
        if let Some(result) = self.lookup_cache.lookup(&lookup_row) {
            return Ok(result.iter().cloned().collect_vec());
        }

        // cache miss
        metrics.lookup_cache_miss_count.inc();

        tracing::debug!(target: "events::stream::lookup::lookup_row", "{:?}", lookup_row);

        let mut all_rows = EstimatedVec::new();
        {
            let all_data_iter = self
                .arrangement
                .state_table
                .iter_with_prefix(
                    &lookup_row,
                    &(Bound::<OwnedRow>::Unbounded, Bound::<OwnedRow>::Unbounded),
                    PrefetchOptions::default(),
                )
                .await?;

            pin_mut!(all_data_iter);
            while let Some(row) = all_data_iter.try_next().await? {
                all_rows.push(row);
            }
        }

        tracing::debug!(target: "events::stream::lookup::result", "{:?} => {:?}", lookup_row, all_rows.inner());

        self.lookup_cache.batch_update(lookup_row, all_rows.clone());

        metrics
            .lookup_cached_entry_count
            .set(self.lookup_cache.len() as i64);

        Ok(all_rows.into_inner())
    }
}
