// 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::builder::ArrayBuilder;

use crate::{ArrayRef, NullArray};

use arrow_data::ArrayData;

use arrow_schema::DataType;

use std::any::Any;

use std::sync::Arc;

/// Builder for [`NullArray`]

///

/// # Example

///

/// Create a `NullArray` from a `NullBuilder`

///

/// ```

///

/// # use arrow_array::{Array, NullArray, builder::NullBuilder};

///

/// let mut b = NullBuilder::new();

/// b.append_empty_value();

/// b.append_null();

/// b.append_nulls(3);

/// b.append_empty_values(3);

/// let arr = b.finish();

///

/// assert_eq!(8, arr.len());

/// assert_eq!(0, arr.null_count());

/// ```

#[derive(Debug)]

pub struct NullBuilder {

    len: usize,

}

impl Default for NullBuilder {

    fn default() -> Self {

        Self::new()

    }

}

impl NullBuilder {

    /// Creates a new null builder

    pub fn new() -> Self {

        Self { len: 0 }

    }

    /// Appends a null slot into the builder

    #[inline]

    pub fn append_null(&mut self) {

        self.len += 1;

    }

    /// Appends `n` `null`s into the builder.

    #[inline]

    pub fn append_nulls(&mut self, n: usize) {

        self.len += n;

    }

    /// Appends a null slot into the builder

    #[inline]

    pub fn append_empty_value(&mut self) {

        self.append_null();

    }

    /// Appends `n` `null`s into the builder.

    #[inline]

    pub fn append_empty_values(&mut self, n: usize) {

        self.append_nulls(n);

    }

    /// Builds the [NullArray] and reset this builder.

    pub fn finish(&mut self) -> NullArray {

        let len = self.len();

        let builder = ArrayData::new_null(&DataType::Null, len).into_builder();

        let array_data = unsafe { builder.build_unchecked() };

        NullArray::from(array_data)

    }

    /// Builds the [NullArray] without resetting the builder.

    pub fn finish_cloned(&self) -> NullArray {

        let len = self.len();

        let builder = ArrayData::new_null(&DataType::Null, len).into_builder();

        let array_data = unsafe { builder.build_unchecked() };

        NullArray::from(array_data)

    }

}

impl ArrayBuilder for NullBuilder {

    /// Returns the builder as a non-mutable `Any` reference.

    fn as_any(&self) -> &dyn Any {

        self

    }

    /// Returns the builder as a mutable `Any` reference.

    fn as_any_mut(&mut self) -> &mut dyn Any {

        self

    }

    /// Returns the boxed builder as a box of `Any`.

    fn into_box_any(self: Box<Self>) -> Box<dyn Any> {

        self

    }

    /// Returns the number of array slots in the builder

    fn len(&self) -> usize {

        self.len

    }

    /// Builds the array and reset this builder.

    fn finish(&mut self) -> ArrayRef {

        Arc::new(self.finish())

    }

    /// Builds the array without resetting the builder.

    fn finish_cloned(&self) -> ArrayRef {

        Arc::new(self.finish_cloned())

    }

}

#[cfg(test)]

mod tests {

    use super::*;

    use crate::Array;

    #[test]

    fn test_null_array_builder() {

        let mut builder = NullArray::builder(10);

        builder.append_null();

        builder.append_nulls(4);

        builder.append_empty_value();

        builder.append_empty_values(4);

        let arr = builder.finish();

        assert_eq!(10, arr.len());

        assert_eq!(0, arr.offset());

        assert_eq!(0, arr.null_count());

        assert!(arr.is_nullable());

    }

    #[test]

    fn test_null_array_builder_finish_cloned() {

        let mut builder = NullArray::builder(16);

        builder.append_null();

        builder.append_empty_value();

        builder.append_empty_values(3);

        let mut array = builder.finish_cloned();

        assert_eq!(5, array.len());

        builder.append_empty_values(5);

        array = builder.finish();

        assert_eq!(10, array.len());

    }

}