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//! BNF grammar:
//!
//! ```text
//! condition = value ("==" | ">" ...) value
//! to = value value TO value
//! ```
use nom::branch::alt;
use nom::bytes::complete::tag;
use nom::character::complete::multispace1;
use nom::combinator::cut;
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use nom::sequence::{terminated, tuple};
use Condition::*;
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use crate::{parse_value, FilterCondition, IResult, Span, Token};
#[derive(Debug, Clone, PartialEq, Eq)]
pub enum Condition<'a> {
GreaterThan(Token<'a>),
GreaterThanOrEqual(Token<'a>),
Equal(Token<'a>),
NotEqual(Token<'a>),
Exists,
NotExists,
LowerThan(Token<'a>),
LowerThanOrEqual(Token<'a>),
Between { from: Token<'a>, to: Token<'a> },
}
impl<'a> Condition<'a> {
/// This method can return two operations in case it must express
/// an OR operation for the between case (i.e. `TO`).
pub fn negate(self) -> (Self, Option<Self>) {
match self {
GreaterThan(n) => (LowerThanOrEqual(n), None),
GreaterThanOrEqual(n) => (LowerThan(n), None),
Equal(s) => (NotEqual(s), None),
NotEqual(s) => (Equal(s), None),
Exists => (NotExists, None),
NotExists => (Exists, None),
LowerThan(n) => (GreaterThanOrEqual(n), None),
LowerThanOrEqual(n) => (GreaterThan(n), None),
Between { from, to } => (LowerThan(from), Some(GreaterThan(to))),
}
}
}
/// condition = value ("=" | "!=" | ">" | ">=" | "<" | "<=") value
pub fn parse_condition(input: Span) -> IResult<FilterCondition> {
let operator = alt((tag("<="), tag(">="), tag("!="), tag("<"), tag(">"), tag("=")));
let (input, (fid, op, value)) = tuple((parse_value, operator, cut(parse_value)))(input)?;
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let condition = match *op.fragment() {
"<=" => FilterCondition::Condition { fid, op: LowerThanOrEqual(value) },
">=" => FilterCondition::Condition { fid, op: GreaterThanOrEqual(value) },
"!=" => FilterCondition::Condition { fid, op: NotEqual(value) },
"<" => FilterCondition::Condition { fid, op: LowerThan(value) },
">" => FilterCondition::Condition { fid, op: GreaterThan(value) },
"=" => FilterCondition::Condition { fid, op: Equal(value) },
_ => unreachable!(),
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};
Ok((input, condition))
}
/// exist = value "EXISTS"
pub fn parse_exists(input: Span) -> IResult<FilterCondition> {
let (input, key) = terminated(parse_value, tag("EXISTS"))(input)?;
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Ok((input, FilterCondition::Condition { fid: key.into(), op: Exists }))
}
/// exist = value "NOT" WS+ "EXISTS"
pub fn parse_not_exists(input: Span) -> IResult<FilterCondition> {
let (input, key) = parse_value(input)?;
let (input, _) = tuple((tag("NOT"), multispace1, tag("EXISTS")))(input)?;
Ok((input, FilterCondition::Condition { fid: key.into(), op: NotExists }))
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}
/// to = value value "TO" WS+ value
pub fn parse_to(input: Span) -> IResult<FilterCondition> {
let (input, (key, from, _, _, to)) =
tuple((parse_value, parse_value, tag("TO"), multispace1, cut(parse_value)))(input)?;
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Ok((input, FilterCondition::Condition { fid: key, op: Between { from, to } }))
}