// Copyright 2024 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.

//! This module contains wrappers over `Aggregator` trait that implement `order by`, `filter`,
//! `distinct` and project.

mod distinct;
mod filter;
mod orderby;
mod projection;

use risingwave_expr::Result;
use risingwave_expr::aggregate::{AggCall, BoxedAggregateFunction, build_append_only};

use self::distinct::Distinct;
use self::filter::*;
use self::orderby::ProjectionOrderBy;
use self::projection::Projection;

/// Build an `BoxedAggregateFunction` from `AggCall`.
pub fn build(agg: &AggCall) -> Result<BoxedAggregateFunction> {
    let mut aggregator = build_append_only(agg)?;

    if agg.distinct {
        aggregator = Box::new(Distinct::new(aggregator));
    }
    if agg.column_orders.is_empty() {
        aggregator = Box::new(Projection::new(agg.args.val_indices().to_vec(), aggregator));
    } else {
        aggregator = Box::new(ProjectionOrderBy::new(
            agg.args.arg_types().to_vec(),
            agg.args.val_indices().to_vec(),
            agg.column_orders.clone(),
            aggregator,
        ));
    }
    if let Some(expr) = &agg.filter {
        aggregator = Box::new(Filter::new(expr.clone(), aggregator));
    }

    Ok(aggregator)
}
