// 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.

use super::prelude::{PlanRef, *};
use crate::optimizer::PlanVisitor;
use crate::optimizer::plan_node::generic::GenericPlanRef;
use crate::optimizer::plan_node::{LogicalValues, PlanTreeNodeUnary};
use crate::optimizer::plan_visitor::{LogicalCardinalityExt, SideEffectVisitor};

pub struct TrivialProjectToValuesRule {}
impl Rule<Logical> for TrivialProjectToValuesRule {
    fn apply(&self, plan: PlanRef) -> Option<PlanRef> {
        let project = plan.as_logical_project()?;

        if !project.exprs().iter().all(|e| e.is_const()) {
            return None;
        }
        if SideEffectVisitor.visit(project.input()) {
            return None;
        }

        let row_count = project.input().row_count()?;
        let values = LogicalValues::new(
            vec![project.exprs().clone(); row_count],
            project.schema().clone(),
            project.ctx(),
        );
        Some(values.into())
    }
}

impl TrivialProjectToValuesRule {
    pub fn create() -> BoxedRule {
        Box::new(TrivialProjectToValuesRule {})
    }
}
