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// Licensed to the Apache Software Foundation (ASF) under one
// or more contributor license agreements.  See the NOTICE file
// distributed with this work for additional information
// regarding copyright ownership.  The ASF licenses this file
// to you 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.

//! Defines physical expression for `ntile` that can evaluated
//! at runtime during query execution

use crate::expressions::Column;
use crate::window::BuiltInWindowFunctionExpr;
use crate::{PhysicalExpr, PhysicalSortExpr};

use arrow::array::{ArrayRef, UInt64Array};
use arrow::datatypes::Field;
use arrow_schema::{DataType, SchemaRef, SortOptions};
use datafusion_common::Result;
use datafusion_expr::PartitionEvaluator;

use std::any::Any;
use std::sync::Arc;

#[derive(Debug)]
pub struct Ntile {
    name: String,
    n: u64,
    /// Output data type
    data_type: DataType,
}

impl Ntile {
    pub fn new(name: String, n: u64, data_type: &DataType) -> Self {
        Self {
            name,
            n,
            data_type: data_type.clone(),
        }
    }

    pub fn get_n(&self) -> u64 {
        self.n
    }
}

impl BuiltInWindowFunctionExpr for Ntile {
    fn as_any(&self) -> &dyn Any {
        self
    }

    fn field(&self) -> Result<Field> {
        let nullable = false;
        Ok(Field::new(self.name(), self.data_type.clone(), nullable))
    }

    fn expressions(&self) -> Vec<Arc<dyn PhysicalExpr>> {
        vec![]
    }

    fn name(&self) -> &str {
        &self.name
    }

    fn create_evaluator(&self) -> Result<Box<dyn PartitionEvaluator>> {
        Ok(Box::new(NtileEvaluator { n: self.n }))
    }

    fn get_result_ordering(&self, schema: &SchemaRef) -> Option<PhysicalSortExpr> {
        // The built-in NTILE window function introduces a new ordering:
        schema.column_with_name(self.name()).map(|(idx, field)| {
            let expr = Arc::new(Column::new(field.name(), idx));
            let options = SortOptions {
                descending: false,
                nulls_first: false,
            }; // ASC, NULLS LAST
            PhysicalSortExpr { expr, options }
        })
    }
}

#[derive(Debug)]
pub(crate) struct NtileEvaluator {
    n: u64,
}

impl PartitionEvaluator for NtileEvaluator {
    fn evaluate_all(
        &mut self,
        _values: &[ArrayRef],
        num_rows: usize,
    ) -> Result<ArrayRef> {
        let num_rows = num_rows as u64;
        let mut vec: Vec<u64> = Vec::new();
        let n = u64::min(self.n, num_rows);
        for i in 0..num_rows {
            let res = i * n / num_rows;
            vec.push(res + 1)
        }
        Ok(Arc::new(UInt64Array::from(vec)))
    }
}