// 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 std::collections::BTreeMap;
use std::vec;

use itertools::Itertools;
use risingwave_common::types::DataType;
use risingwave_common::util::sort_util::{ColumnOrder, OrderType};
use risingwave_expr::aggregate::{AggType, PbAggKind};

use super::prelude::{PlanRef, *};
use crate::expr::{ExprImpl, ExprType, FunctionCall, InputRef};
use crate::optimizer::plan_node::generic::{Agg, GenericPlanRef};
use crate::optimizer::plan_node::{
    LogicalAgg, LogicalFilter, LogicalScan, LogicalTopN, PlanAggCall, PlanTreeNodeUnary,
};
use crate::optimizer::property::Order;
use crate::utils::{Condition, IndexSet};

pub struct MinMaxOnIndexRule {}

impl Rule<Logical> for MinMaxOnIndexRule {
    fn apply(&self, plan: PlanRef) -> Option<PlanRef> {
        let logical_agg: &LogicalAgg = plan.as_logical_agg()?;
        if !logical_agg.group_key().is_empty() {
            return None;
        }
        let calls = logical_agg.agg_calls();
        if calls.is_empty() {
            return None;
        }
        let first_call = Itertools::exactly_one(calls.iter()).ok()?;

        if matches!(
            first_call.agg_type,
            AggType::Builtin(PbAggKind::Min | PbAggKind::Max)
        ) && !first_call.distinct
            && first_call.filter.always_true()
            && first_call.order_by.is_empty()
        {
            let logical_scan: LogicalScan = logical_agg.input().as_logical_scan()?.to_owned();
            let kind = &calls.first()?.agg_type;
            if !logical_scan.predicate().always_true() {
                return None;
            }
            let order = Order {
                column_orders: vec![ColumnOrder::new(
                    calls.first()?.inputs.first()?.index(),
                    if matches!(kind, AggType::Builtin(PbAggKind::Min)) {
                        OrderType::ascending()
                    } else {
                        OrderType::descending()
                    },
                )],
            };
            if let Some(p) = self.try_on_index(logical_agg, logical_scan.clone(), &order) {
                Some(p)
            } else {
                self.try_on_pk(logical_agg, logical_scan, &order)
            }
        } else {
            None
        }
    }
}

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

    fn try_on_index(
        &self,
        logical_agg: &LogicalAgg,
        logical_scan: LogicalScan,
        required_order: &Order,
    ) -> Option<PlanRef> {
        let order_satisfied_index = logical_scan.indexes_satisfy_order(required_order);
        for index in order_satisfied_index {
            if let Some(index_scan) = logical_scan.to_index_scan_if_index_covered(index) {
                let non_null_filter = LogicalFilter::create_with_expr(
                    index_scan.into(),
                    FunctionCall::new_unchecked(
                        ExprType::IsNotNull,
                        vec![ExprImpl::InputRef(Box::new(InputRef::new(
                            0,
                            logical_agg.schema().fields[0].data_type.clone(),
                        )))],
                        DataType::Boolean,
                    )
                    .into(),
                );

                let topn =
                    LogicalTopN::new(non_null_filter, 1, 0, false, required_order.clone(), vec![]);

                let formatting_agg = Agg::new(
                    vec![PlanAggCall {
                        agg_type: logical_agg.agg_calls().first()?.agg_type.clone(),
                        return_type: logical_agg.schema().fields[0].data_type.clone(),
                        inputs: vec![InputRef::new(
                            0,
                            logical_agg.schema().fields[0].data_type.clone(),
                        )],
                        order_by: vec![],
                        distinct: false,
                        filter: Condition {
                            conjunctions: vec![],
                        },
                        direct_args: vec![],
                    }],
                    IndexSet::empty(),
                    topn.into(),
                );

                return Some(formatting_agg.into());
            }
        }

        None
    }

    fn try_on_pk(
        &self,
        logical_agg: &LogicalAgg,
        logical_scan: LogicalScan,
        order: &Order,
    ) -> Option<PlanRef> {
        let output_col_map = logical_scan
            .output_col_idx()
            .iter()
            .cloned()
            .enumerate()
            .map(|(id, col)| (col, id))
            .collect::<BTreeMap<_, _>>();
        let unmatched_idx = output_col_map.len();
        let primary_key = logical_scan.primary_key();
        let primary_key_order = Order {
            column_orders: primary_key
                .iter()
                .map(|o| {
                    ColumnOrder::new(
                        *output_col_map
                            .get(&o.column_index)
                            .unwrap_or(&unmatched_idx),
                        o.order_type,
                    )
                })
                .collect::<Vec<_>>(),
        };
        if primary_key_order.satisfies(order) {
            let non_null_filter = LogicalFilter::create_with_expr(
                logical_scan.into(),
                FunctionCall::new_unchecked(
                    ExprType::IsNotNull,
                    vec![ExprImpl::InputRef(Box::new(InputRef::new(
                        0,
                        logical_agg.schema().fields[0].data_type.clone(),
                    )))],
                    DataType::Boolean,
                )
                .into(),
            );

            let topn = LogicalTopN::new(non_null_filter, 1, 0, false, order.clone(), vec![]);

            let formatting_agg = Agg::new(
                vec![PlanAggCall {
                    agg_type: logical_agg.agg_calls().first()?.agg_type.clone(),
                    return_type: logical_agg.schema().fields[0].data_type.clone(),
                    inputs: vec![InputRef::new(
                        0,
                        logical_agg.schema().fields[0].data_type.clone(),
                    )],
                    order_by: vec![],
                    distinct: false,
                    filter: Condition {
                        conjunctions: vec![],
                    },
                    direct_args: vec![],
                }],
                IndexSet::empty(),
                topn.into(),
            );

            Some(formatting_agg.into())
        } else {
            None
        }
    }
}
