// 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.

use crate::coalesce::InProgressArray;

use arrow_array::cast::AsArray;

use arrow_array::{Array, ArrayRef, ArrowPrimitiveType, PrimitiveArray};

use arrow_buffer::{NullBufferBuilder, ScalarBuffer};

use arrow_schema::{ArrowError, DataType};

use std::fmt::Debug;

use std::sync::Arc;

/// InProgressArray for [`PrimitiveArray`]

#[derive(Debug)]

pub(crate) struct InProgressPrimitiveArray<T: ArrowPrimitiveType> {

    /// Data type of the array

    data_type: DataType,

    /// The current source, if any

    source: Option<ArrayRef>,

    /// the target batch size (and thus size for views allocation)

    batch_size: usize,

    /// In progress nulls

    nulls: NullBufferBuilder,

    /// The currently in progress array

    current: Vec<T::Native>,

}

impl<T: ArrowPrimitiveType> InProgressPrimitiveArray<T> {

    /// Create a new `InProgressPrimitiveArray`

    pub(crate) fn new(batch_size: usize, data_type: DataType) -> Self {

        Self {

            data_type,

            batch_size,

            source: None,

            nulls: NullBufferBuilder::new(batch_size),

            current: vec![],

        }

    }

    /// Allocate space for output values if necessary.

    ///

    /// This is done on write (when we know it is necessary) rather than

    /// eagerly to avoid allocations that are not used.

    fn ensure_capacity(&mut self) {

        self.current.reserve(self.batch_size);

    }

}

impl<T: ArrowPrimitiveType + Debug> InProgressArray for InProgressPrimitiveArray<T> {

    fn set_source(&mut self, source: Option<ArrayRef>) {

        self.source = source;

    }

    fn copy_rows(&mut self, offset: usize, len: usize) -> Result<(), ArrowError> {

        self.ensure_capacity();

        let s = self

            .source

            .as_ref()

            .ok_or_else(|| {

                ArrowError::InvalidArgumentError(

                    "Internal Error: InProgressPrimitiveArray: source not set".to_string(),

                )

            })?

            .as_primitive::<T>();

        // add nulls if necessary

        if let Some(nulls) = s.nulls().as_ref() {

            let nulls = nulls.slice(offset, len);

            self.nulls.append_buffer(&nulls);

        } else {

            self.nulls.append_n_non_nulls(len);

        };

        // Copy the values

        self.current

            .extend_from_slice(&s.values()[offset..offset + len]);

        Ok(())

    }

    fn finish(&mut self) -> Result<ArrayRef, ArrowError> {

        // take and reset the current values and nulls

        let values = std::mem::take(&mut self.current);

        let nulls = self.nulls.finish();

        self.nulls = NullBufferBuilder::new(self.batch_size);

        let array = PrimitiveArray::<T>::try_new(ScalarBuffer::from(values), nulls)?

            // preserve timezone / precision+scale if applicable

            .with_data_type(self.data_type.clone());

        Ok(Arc::new(array))

    }

}