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// Copyright 2023 Greptime Team
//
// 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 datafusion_expr::ColumnarValue as DfColumnarValue;
use datatypes::prelude::ConcreteDataType;
use datatypes::vectors::{Helper, VectorRef};
use snafu::ResultExt;

use crate::error::{self, GeneralDataFusionSnafu, IntoVectorSnafu, Result};
use crate::prelude::ScalarValue;

/// Represents the result from an expression
#[derive(Clone)]
pub enum ColumnarValue {
    Vector(VectorRef),
    /// A single value
    Scalar(ScalarValue),
}

impl ColumnarValue {
    pub fn data_type(&self) -> ConcreteDataType {
        match self {
            ColumnarValue::Vector(vector) => vector.data_type(),
            ColumnarValue::Scalar(scalar_value) => {
                ConcreteDataType::from_arrow_type(&scalar_value.data_type())
            }
        }
    }

    /// Convert a columnar value into an VectorRef
    pub fn try_into_vector(self, num_rows: usize) -> Result<VectorRef> {
        Ok(match self {
            ColumnarValue::Vector(v) => v,
            ColumnarValue::Scalar(s) => {
                let v = s
                    .to_array_of_size(num_rows)
                    .context(GeneralDataFusionSnafu)?;
                let data_type = v.data_type().clone();
                Helper::try_into_vector(v).context(IntoVectorSnafu { data_type })?
            }
        })
    }
}

impl TryFrom<&DfColumnarValue> for ColumnarValue {
    type Error = error::Error;
    fn try_from(value: &DfColumnarValue) -> Result<Self> {
        Ok(match value {
            DfColumnarValue::Scalar(v) => ColumnarValue::Scalar(v.clone()),
            DfColumnarValue::Array(v) => {
                ColumnarValue::Vector(Helper::try_into_vector(v.clone()).with_context(|_| {
                    IntoVectorSnafu {
                        data_type: v.data_type().clone(),
                    }
                })?)
            }
        })
    }
}

impl From<ColumnarValue> for DfColumnarValue {
    fn from(columnar_value: ColumnarValue) -> Self {
        match columnar_value {
            ColumnarValue::Scalar(v) => DfColumnarValue::Scalar(v),
            ColumnarValue::Vector(v) => DfColumnarValue::Array(v.to_arrow_array()),
        }
    }
}

#[cfg(test)]
mod tests {
    use std::sync::Arc;

    use datatypes::arrow::datatypes::DataType as ArrowDataType;
    use datatypes::vectors::BooleanVector;

    use super::*;

    #[test]
    fn test_scalar_columnar_value() {
        let value = ColumnarValue::Scalar(ScalarValue::Boolean(Some(true)));

        assert_eq!(ConcreteDataType::boolean_datatype(), value.data_type());
        let v = value.clone().try_into_vector(1).unwrap();
        assert_eq!(1, v.len());

        let df_value = DfColumnarValue::from(value);
        assert_eq!(ArrowDataType::Boolean, df_value.data_type());
    }

    #[test]
    fn test_vector_columnar_value() {
        let value = ColumnarValue::Vector(Arc::new(BooleanVector::from(vec![true, false, true])));

        assert_eq!(ConcreteDataType::boolean_datatype(), value.data_type());
        let v = value.clone().try_into_vector(1).unwrap();
        assert_eq!(3, v.len());

        let df_value = DfColumnarValue::from(value);
        assert_eq!(ArrowDataType::Boolean, df_value.data_type());
    }
}