// Copyright 2023 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.

// Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
// This source code is licensed under both the GPLv2 (found in the
// COPYING file in the root directory) and Apache 2.0 License
// (found in the LICENSE.Apache file in the root directory).

use std::collections::HashMap;

use risingwave_hummock_sdk::{CompactionGroupId, HummockCompactionTaskId};
use risingwave_pb::hummock::compact_task;

use super::{CompactionSelector, DynamicLevelSelectorCore};
use crate::hummock::compaction::picker::{SpaceReclaimCompactionPicker, SpaceReclaimPickerState};
use crate::hummock::compaction::selector::CompactionSelectorContext;
use crate::hummock::compaction::{CompactionTask, create_compaction_task};

#[derive(Default)]
pub struct SpaceReclaimCompactionSelector {
    state: HashMap<CompactionGroupId, SpaceReclaimPickerState>,
}

impl CompactionSelector for SpaceReclaimCompactionSelector {
    fn pick_compaction(
        &mut self,
        task_id: HummockCompactionTaskId,
        context: CompactionSelectorContext<'_>,
    ) -> Option<CompactionTask> {
        let CompactionSelectorContext {
            group,
            levels,
            member_table_ids,
            level_handlers,
            developer_config,
            ..
        } = context;
        let dynamic_level_core =
            DynamicLevelSelectorCore::new(group.compaction_config.clone(), developer_config);
        let mut picker = SpaceReclaimCompactionPicker::new(
            group.compaction_config.max_space_reclaim_bytes,
            member_table_ids.iter().copied().collect(),
        );
        let ctx = dynamic_level_core.calculate_level_base_size(levels);
        let state = self.state.entry(group.group_id).or_default();

        let compaction_input = picker.pick_compaction(levels, level_handlers, state)?;
        compaction_input.add_pending_task(task_id, level_handlers);

        Some(create_compaction_task(
            dynamic_level_core.get_config(),
            compaction_input,
            ctx.base_level,
            self.task_type(),
        ))
    }

    fn name(&self) -> &'static str {
        "SpaceReclaimCompaction"
    }

    fn task_type(&self) -> compact_task::TaskType {
        compact_task::TaskType::SpaceReclaim
    }
}
