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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.

use crate::utils::make_scalar_function;
use arrow::array::Int32Array;
use arrow::array::{ArrayRef, OffsetSizeTrait};
use arrow::datatypes::DataType;
use datafusion_common::{cast::as_generic_string_array, internal_err, Result};
use datafusion_expr::ColumnarValue;
use datafusion_expr::{ScalarUDFImpl, Signature, Volatility};
use std::any::Any;
use std::sync::Arc;

/// Returns the numeric code of the first character of the argument.
/// ascii('x') = 120
pub fn ascii<T: OffsetSizeTrait>(args: &[ArrayRef]) -> Result<ArrayRef> {
    let string_array = as_generic_string_array::<T>(&args[0])?;

    let result = string_array
        .iter()
        .map(|string| {
            string.map(|string: &str| {
                let mut chars = string.chars();
                chars.next().map_or(0, |v| v as i32)
            })
        })
        .collect::<Int32Array>();

    Ok(Arc::new(result) as ArrayRef)
}

#[derive(Debug)]
pub struct AsciiFunc {
    signature: Signature,
}

impl Default for AsciiFunc {
    fn default() -> Self {
        Self::new()
    }
}

impl AsciiFunc {
    pub fn new() -> Self {
        use DataType::*;
        Self {
            signature: Signature::uniform(
                1,
                vec![Utf8, LargeUtf8],
                Volatility::Immutable,
            ),
        }
    }
}

impl ScalarUDFImpl for AsciiFunc {
    fn as_any(&self) -> &dyn Any {
        self
    }

    fn name(&self) -> &str {
        "ascii"
    }

    fn signature(&self) -> &Signature {
        &self.signature
    }

    fn return_type(&self, _arg_types: &[DataType]) -> Result<DataType> {
        use DataType::*;

        Ok(Int32)
    }

    fn invoke(&self, args: &[ColumnarValue]) -> Result<ColumnarValue> {
        match args[0].data_type() {
            DataType::Utf8 => make_scalar_function(ascii::<i32>, vec![])(args),
            DataType::LargeUtf8 => {
                return make_scalar_function(ascii::<i64>, vec![])(args);
            }
            _ => internal_err!("Unsupported data type"),
        }
    }
}