// Copyright Materialize, Inc. and contributors. All rights reserved.
//
// Use of this software is governed by the Business Source License
// included in the LICENSE file.
//
// As of the Change Date specified in that file, in accordance with
// the Business Source License, use of this software will be governed
// by the Apache License, Version 2.0.

//! Logging dataflows for events generated by differential dataflow.

use std::cell::RefCell;
use std::collections::BTreeMap;
use std::rc::Rc;
use std::time::Duration;

use differential_dataflow::consolidation::ConsolidatingContainerBuilder;
use differential_dataflow::logging::{
    BatchEvent, BatcherEvent, DifferentialEvent, DropEvent, MergeEvent, TraceShare,
};
use mz_ore::cast::CastFrom;
use mz_repr::{Datum, Diff, Timestamp};
use mz_timely_util::replay::MzReplay;
use timely::communication::Allocate;
use timely::container::CapacityContainerBuilder;
use timely::dataflow::channels::pact::Pipeline;
use timely::dataflow::channels::pushers::buffer::Session;
use timely::dataflow::channels::pushers::{Counter, Tee};
use timely::dataflow::operators::generic::builder_rc::OperatorBuilder;
use timely::dataflow::operators::Filter;
use timely::dataflow::Stream;
use timely::logging::WorkerIdentifier;

use crate::extensions::arrange::{MzArrange, MzArrangeCore};
use crate::logging::compute::ComputeEvent;
use crate::logging::{
    DifferentialLog, EventQueue, LogCollection, LogVariant, PermutedRowPacker, SharedLoggingState,
};
use crate::typedefs::{KeyValSpine, RowRowSpine};

/// Constructs the logging dataflow for differential logs.
///
/// Params
/// * `worker`: The Timely worker hosting the log analysis dataflow.
/// * `config`: Logging configuration
/// * `event_queue`: The source to read log events from.
pub(super) fn construct<A: Allocate>(
    worker: &mut timely::worker::Worker<A>,
    config: &mz_compute_client::logging::LoggingConfig,
    event_queue: EventQueue<Vec<(Duration, WorkerIdentifier, DifferentialEvent)>>,
    shared_state: Rc<RefCell<SharedLoggingState>>,
) -> BTreeMap<LogVariant, LogCollection> {
    let logging_interval_ms = std::cmp::max(1, config.interval.as_millis());
    let worker_id = worker.index();
    let dataflow_index = worker.next_dataflow_index();

    worker.dataflow_named("Dataflow: differential logging", move |scope| {
        let (mut logs, token) = Some(event_queue.link)
            .mz_replay::<_, CapacityContainerBuilder<_>, _>(
                scope,
                "differential logs",
                config.interval,
                event_queue.activator,
                |mut session, data| session.give_iterator(data.iter()),
            );

        // If logging is disabled, we still need to install the indexes, but we can leave them
        // empty. We do so by immediately filtering all logs events.
        if !config.enable_logging {
            logs = logs.filter(|_| false);
        }

        // Build a demux operator that splits the replayed event stream up into the separate
        // logging streams.
        let mut demux =
            OperatorBuilder::new("Differential Logging Demux".to_string(), scope.clone());
        let mut input = demux.new_input(&logs, Pipeline);
        let (mut batches_out, batches) = demux.new_output();
        let (mut records_out, records) = demux.new_output();
        let (mut sharing_out, sharing) = demux.new_output();
        let (mut batcher_records_out, batcher_records) = demux.new_output();
        let (mut batcher_size_out, batcher_size) = demux.new_output();
        let (mut batcher_capacity_out, batcher_capacity) = demux.new_output();
        let (mut batcher_allocations_out, batcher_allocations) = demux.new_output();

        let mut demux_state = Default::default();
        demux.build(move |_capability| {
            move |_frontiers| {
                let mut batches = batches_out.activate();
                let mut records = records_out.activate();
                let mut sharing = sharing_out.activate();
                let mut batcher_records = batcher_records_out.activate();
                let mut batcher_size = batcher_size_out.activate();
                let mut batcher_capacity = batcher_capacity_out.activate();
                let mut batcher_allocations = batcher_allocations_out.activate();

                input.for_each(|cap, data| {
                    let mut output_buffers = DemuxOutput {
                        batches: batches.session_with_builder(&cap),
                        records: records.session_with_builder(&cap),
                        sharing: sharing.session_with_builder(&cap),
                        batcher_records: batcher_records.session_with_builder(&cap),
                        batcher_size: batcher_size.session_with_builder(&cap),
                        batcher_capacity: batcher_capacity.session_with_builder(&cap),
                        batcher_allocations: batcher_allocations.session_with_builder(&cap),
                    };

                    for (time, logger_id, event) in data.drain(..) {
                        // We expect the logging infrastructure to not shuffle events between
                        // workers and this code relies on the assumption that each worker handles
                        // its own events.
                        assert_eq!(logger_id, worker_id);

                        DemuxHandler {
                            state: &mut demux_state,
                            output: &mut output_buffers,
                            logging_interval_ms,
                            time,
                            shared_state: &mut shared_state.borrow_mut(),
                        }
                        .handle(event);
                    }
                });
            }
        });

        let stream_to_collection = |input: Stream<_, ((usize, ()), Timestamp, Diff)>, log, name| {
            let packer = PermutedRowPacker::new(log);
            input
                .mz_arrange_core::<_, KeyValSpine<_, _, _, _>>(
                    Pipeline,
                    &format!("PreArrange Differential {name}"),
                )
                .as_collection(move |op, ()| {
                    packer.pack_slice(&[
                        Datum::UInt64(u64::cast_from(*op)),
                        Datum::UInt64(u64::cast_from(worker_id)),
                    ])
                })
        };

        // Encode the contents of each logging stream into its expected `Row` format.
        let arrangement_batches = stream_to_collection(batches, ArrangementBatches, "batches");
        let arrangement_records = stream_to_collection(records, ArrangementRecords, "records");
        let sharing = stream_to_collection(sharing, Sharing, "sharing");
        let batcher_records =
            stream_to_collection(batcher_records, BatcherRecords, "batcher records");
        let batcher_size = stream_to_collection(batcher_size, BatcherSize, "batcher size");
        let batcher_capacity =
            stream_to_collection(batcher_capacity, BatcherCapacity, "batcher capacity");
        let batcher_allocations = stream_to_collection(
            batcher_allocations,
            BatcherAllocations,
            "batcher allocations",
        );

        use DifferentialLog::*;
        let logs = [
            (ArrangementBatches, arrangement_batches),
            (ArrangementRecords, arrangement_records),
            (Sharing, sharing),
            (BatcherRecords, batcher_records),
            (BatcherSize, batcher_size),
            (BatcherCapacity, batcher_capacity),
            (BatcherAllocations, batcher_allocations),
        ];

        // Build the output arrangements.
        let mut result = BTreeMap::new();
        for (variant, collection) in logs {
            let variant = LogVariant::Differential(variant);
            if config.index_logs.contains_key(&variant) {
                let trace = collection
                    .mz_arrange::<RowRowSpine<_, _>>(&format!("Arrange {variant:?}"))
                    .trace;
                let collection = LogCollection {
                    trace,
                    token: Rc::clone(&token),
                    dataflow_index,
                };
                result.insert(variant, collection);
            }
        }

        result
    })
}

type Pusher<D> =
    Counter<Timestamp, Vec<(D, Timestamp, Diff)>, Tee<Timestamp, Vec<(D, Timestamp, Diff)>>>;
type OutputSession<'a, D> =
    Session<'a, Timestamp, ConsolidatingContainerBuilder<Vec<(D, Timestamp, Diff)>>, Pusher<D>>;

/// Bundled output buffers used by the demux operator.
struct DemuxOutput<'a> {
    batches: OutputSession<'a, (usize, ())>,
    records: OutputSession<'a, (usize, ())>,
    sharing: OutputSession<'a, (usize, ())>,
    batcher_records: OutputSession<'a, (usize, ())>,
    batcher_size: OutputSession<'a, (usize, ())>,
    batcher_capacity: OutputSession<'a, (usize, ())>,
    batcher_allocations: OutputSession<'a, (usize, ())>,
}

/// State maintained by the demux operator.
#[derive(Default)]
struct DemuxState {
    /// Arrangement trace sharing
    sharing: BTreeMap<usize, usize>,
}

/// Event handler of the demux operator.
struct DemuxHandler<'a, 'b> {
    /// State kept by the demux operator
    state: &'a mut DemuxState,
    /// Demux output buffers.
    output: &'a mut DemuxOutput<'b>,
    /// The logging interval specifying the time granularity for the updates.
    logging_interval_ms: u128,
    /// The current event time.
    time: Duration,
    /// State shared across log receivers.
    shared_state: &'a mut SharedLoggingState,
}

impl DemuxHandler<'_, '_> {
    /// Return the timestamp associated with the current event, based on the event time and the
    /// logging interval.
    fn ts(&self) -> Timestamp {
        let time_ms = self.time.as_millis();
        let interval = self.logging_interval_ms;
        let rounded = (time_ms / interval + 1) * interval;
        rounded.try_into().expect("must fit")
    }

    /// Handle the given differential event.
    fn handle(&mut self, event: DifferentialEvent) {
        use DifferentialEvent::*;

        match event {
            Batch(e) => self.handle_batch(e),
            Merge(e) => self.handle_merge(e),
            Drop(e) => self.handle_drop(e),
            TraceShare(e) => self.handle_trace_share(e),
            Batcher(e) => self.handle_batcher_event(e),
            _ => (),
        }
    }

    fn handle_batch(&mut self, event: BatchEvent) {
        let ts = self.ts();
        let op = event.operator;
        self.output.batches.give(((op, ()), ts, 1));

        let diff = Diff::try_from(event.length).expect("must fit");
        self.output.records.give(((op, ()), ts, diff));
        self.notify_arrangement_size(op);
    }

    fn handle_merge(&mut self, event: MergeEvent) {
        let Some(done) = event.complete else { return };

        let ts = self.ts();
        let op = event.operator;
        self.output.batches.give(((op, ()), ts, -1));

        let diff = Diff::try_from(done).expect("must fit")
            - Diff::try_from(event.length1 + event.length2).expect("must fit");
        if diff != 0 {
            self.output.records.give(((op, ()), ts, diff));
        }
        self.notify_arrangement_size(op);
    }

    fn handle_drop(&mut self, event: DropEvent) {
        let ts = self.ts();
        let op = event.operator;
        self.output.batches.give(((op, ()), ts, -1));

        let diff = -Diff::try_from(event.length).expect("must fit");
        if diff != 0 {
            self.output.records.give(((op, ()), ts, diff));
        }
        self.notify_arrangement_size(op);
    }

    fn handle_trace_share(&mut self, event: TraceShare) {
        let ts = self.ts();
        let op = event.operator;
        let diff = Diff::cast_from(event.diff);
        debug_assert_ne!(diff, 0);
        self.output.sharing.give(((op, ()), ts, diff));

        if let Some(logger) = &mut self.shared_state.compute_logger {
            let sharing = self.state.sharing.entry(op).or_default();
            *sharing = (i64::try_from(*sharing).expect("must fit") + diff)
                .try_into()
                .expect("under/overflow");
            if *sharing == 0 {
                self.state.sharing.remove(&op);
                logger.log(ComputeEvent::ArrangementHeapSizeOperatorDrop { operator: op });
            }
        }
    }

    fn handle_batcher_event(&mut self, event: BatcherEvent) {
        let ts = self.ts();
        let op = event.operator;
        let records_diff = Diff::cast_from(event.records_diff);
        let size_diff = Diff::cast_from(event.size_diff);
        let capacity_diff = Diff::cast_from(event.capacity_diff);
        let allocations_diff = Diff::cast_from(event.allocations_diff);
        self.output
            .batcher_records
            .give(((op, ()), ts, records_diff));
        self.output.batcher_size.give(((op, ()), ts, size_diff));
        self.output
            .batcher_capacity
            .give(((op, ()), ts, capacity_diff));
        self.output
            .batcher_allocations
            .give(((op, ()), ts, allocations_diff));
    }

    fn notify_arrangement_size(&self, operator: usize) {
        // While every arrangement should have a corresponding arrangement size operator,
        // we have no guarantee that it already/still exists. Otherwise we could print a warning
        // here, but it's difficult to implement without maintaining state for a longer period than
        // while the arrangement actually exists.
        if let Some(activator) = self.shared_state.arrangement_size_activators.get(&operator) {
            activator.activate();
        }
    }
}