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// 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 crate::dialect::Dialect;
use core::iter::Peekable;
use core::str::Chars;

use super::PostgreSqlDialect;

/// A [`Dialect`] for [RedShift](https://aws.amazon.com/redshift/)
#[derive(Debug)]
pub struct RedshiftSqlDialect {}

// In most cases the redshift dialect is identical to [`PostgresSqlDialect`].
//
// Notable differences:
// 1. Redshift treats brackets `[` and `]` differently. For example, `SQL SELECT a[1][2] FROM b`
// in the Postgres dialect, the query will be parsed as an array, while in the Redshift dialect it will
// be a json path
impl Dialect for RedshiftSqlDialect {
    fn is_delimited_identifier_start(&self, ch: char) -> bool {
        ch == '"' || ch == '['
    }

    /// Determine if quoted characters are proper for identifier
    /// It's needed to distinguish treating square brackets as quotes from
    /// treating them as json path. If there is identifier then we assume
    /// there is no json path.
    fn is_proper_identifier_inside_quotes(&self, mut chars: Peekable<Chars<'_>>) -> bool {
        chars.next();
        let mut not_white_chars = chars.skip_while(|ch| ch.is_whitespace()).peekable();
        if let Some(&ch) = not_white_chars.peek() {
            return self.is_identifier_start(ch);
        }
        false
    }

    fn is_identifier_start(&self, ch: char) -> bool {
        // Extends Postgres dialect with sharp
        PostgreSqlDialect {}.is_identifier_start(ch) || ch == '#'
    }

    fn is_identifier_part(&self, ch: char) -> bool {
        // Extends Postgres dialect with sharp
        PostgreSqlDialect {}.is_identifier_part(ch) || ch == '#'
    }

    /// redshift has `CONVERT(type, value)` instead of `CONVERT(value, type)`
    /// <https://docs.aws.amazon.com/redshift/latest/dg/r_CONVERT_function.html>
    fn convert_type_before_value(&self) -> bool {
        true
    }

    fn supports_connect_by(&self) -> bool {
        true
    }
}