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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 alloc::vec;
use alloc::vec::Vec;

use crate::{
    expression::{parse_expression, Expression},
    keywords::Keyword,
    lexer::Token,
    parser::{ParseError, Parser},
    Identifier, Span, Spanned,
};

/// Flags for deletion
#[derive(Clone, Debug)]
pub enum DeleteFlag {
    LowPriority(Span),
    Quick(Span),
    Ignore(Span),
}

impl Spanned for DeleteFlag {
    fn span(&self) -> Span {
        match &self {
            DeleteFlag::LowPriority(v) => v.span(),
            DeleteFlag::Quick(v) => v.span(),
            DeleteFlag::Ignore(v) => v.span(),
        }
    }
}

/// Represent a delete statement
/// ```
/// # use sql_parse::{SQLDialect, SQLArguments, ParseOptions, parse_statements, Delete, Statement};
/// # let options = ParseOptions::new().dialect(SQLDialect::MariaDB);
/// # let mut issues = Vec::new();
/// #
/// let sql = "DELETE FROM t1 WHERE c1 IN (SELECT b.c1 FROM t1 b WHERE b.c2=0);";
///
/// let mut stmts = parse_statements(sql, &mut issues, &options);
///
/// # assert!(issues.is_empty());
/// #
/// let delete: Delete = match stmts.pop() {
///     Some(Statement::Delete(d)) => d,
///     _ => panic!("We should get a delete statement")
/// };
///
/// assert!(delete.table.get(0).unwrap().as_str() == "t1");
/// println!("{:#?}", delete.where_)
/// ```
#[derive(Clone, Debug)]
pub struct Delete<'a> {
    /// Span of "DELETE"
    pub delete_span: Span,
    /// Flags following "DELETE"
    pub flags: Vec<DeleteFlag>,
    /// Span of "FROM"
    pub from_span: Span,
    /// Tables to do deletes on
    pub table: Vec<Identifier<'a>>,
    /// Where expression and Span of "WHERE" if specified
    pub where_: Option<(Expression<'a>, Span)>,
}

impl<'a> Spanned for Delete<'a> {
    fn span(&self) -> Span {
        self.delete_span
            .join_span(&self.flags)
            .join_span(&self.from_span)
            .join_span(&self.table)
            .join_span(&self.where_)
    }
}

pub(crate) fn parse_delete<'a, 'b>(parser: &mut Parser<'a, 'b>) -> Result<Delete<'a>, ParseError> {
    let delete_span = parser.consume_keyword(Keyword::DELETE)?;
    let mut flags = Vec::new();

    parser.recovered(
        "FROM",
        &|t| matches!(t, Token::Ident(_, Keyword::FROM)),
        |parser| {
            loop {
                match &parser.token {
                    Token::Ident(_, Keyword::LOW_PRIORITY) => flags.push(DeleteFlag::LowPriority(
                        parser.consume_keyword(Keyword::LOW_PRIORITY)?,
                    )),
                    Token::Ident(_, Keyword::QUICK) => {
                        flags.push(DeleteFlag::Quick(parser.consume_keyword(Keyword::QUICK)?))
                    }
                    Token::Ident(_, Keyword::IGNORE) => {
                        flags.push(DeleteFlag::Ignore(parser.consume_keyword(Keyword::IGNORE)?))
                    }
                    _ => break,
                }
            }
            Ok(())
        },
    )?;

    let from_span = parser.consume_keyword(Keyword::FROM)?;

    let mut table = vec![parser.consume_plain_identifier()?];
    loop {
        if parser.skip_token(Token::Period).is_none() {
            break;
        }
        table.push(parser.consume_plain_identifier()?);
    }

    //TODO [PARTITION (partition_list)]
    //TODO [FOR PORTION OF period FROM expr1 TO expr2]

    let where_ = if let Some(span) = parser.skip_keyword(Keyword::WHERE) {
        Some((parse_expression(parser, false)?, span))
    } else {
        None
    };
    //TODO [ORDER BY ...]
    //TODO LIMIT row_count]
    //TODO [RETURNING select_expr
    //TODO  [, select_expr ...]]

    Ok(Delete {
        flags,
        delete_span,
        table,
        from_span,
        where_,
    })
}