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// to you under the Apache License, Version 2.0 (the
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//
//   http://www.apache.org/licenses/LICENSE-2.0
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//! Projection operator builder

use std::sync::Arc;

use datafusion::physical_plan::projection::ProjectionExec;
use datafusion_comet_proto::spark_operator::Operator;
use jni::objects::{Global, JObject};

use crate::{
    execution::{
        planner::{operator_registry::OperatorBuilder, PhysicalPlanner, PlanCreationResult},
        spark_plan::SparkPlan,
    },
    extract_op,
};

/// Builder for Projection operators
pub struct ProjectionBuilder;

impl OperatorBuilder for ProjectionBuilder {
    fn build(
        &self,
        spark_plan: &Operator,
        inputs: &mut Vec<Arc<Global<JObject<'static>>>>,
        partition_count: usize,
        planner: &PhysicalPlanner,
    ) -> PlanCreationResult {
        let project = extract_op!(spark_plan, Projection);
        let children = &spark_plan.children;

        assert_eq!(children.len(), 1);
        let (scans, shuffle_scans, child) =
            planner.create_plan(&children[0], inputs, partition_count)?;

        // Create projection expressions
        let exprs: Result<Vec<_>, _> = project
            .project_list
            .iter()
            .enumerate()
            .map(|(idx, expr)| {
                planner
                    .create_expr(expr, child.schema())
                    .map(|r| (r, format!("col_{idx}")))
            })
            .collect();

        let projection = Arc::new(ProjectionExec::try_new(
            exprs?,
            Arc::clone(&child.native_plan),
        )?);

        Ok((
            scans,
            shuffle_scans,
            Arc::new(SparkPlan::new(spark_plan.plan_id, projection, vec![child])),
        ))
    }
}
