MeiliSearch/filter-parser/src/lib.rs

//! BNF grammar:
//!
//! ```text
//! filter         = expression EOF
//! expression     = or
//! or             = and ("OR" WS+ and)*
//! and            = not ("AND" WS+ not)*
//! not            = ("NOT" WS+ not) | primary
//! primary        = (WS* "(" WS* expression WS* ")" WS*) | geoRadius | in | condition | exists | not_exists | to
//! in             = value "IN" WS* "[" value_list "]"
//! condition      = value ("=" | "!=" | ">" | ">=" | "<" | "<=") value
//! exists         = value "EXISTS"
//! not_exists     = value "NOT" WS+ "EXISTS"
//! to             = value value "TO" WS+ value
//! value          = WS* ( word | singleQuoted | doubleQuoted) WS+
//! value_list     = (value ("," value)* ","?)?
//! singleQuoted   = "'" .* all but quotes "'"
//! doubleQuoted   = "\"" .* all but double quotes "\""
//! word           = (alphanumeric | _ | - | .)+
//! geoRadius      = "_geoRadius(" WS* float WS* "," WS* float WS* "," float WS* ")"
//! ```
//!
//! Other BNF grammar used to handle some specific errors:
//! ```text
//! geoPoint       = WS* "_geoPoint(" (float ",")* ")"
//! ```
//!
//! Specific errors:
//! ================
//! - If a user try to use a geoPoint, as a primary OR as a value we must throw an error.
//! ```text
//! field = _geoPoint(12, 13, 14)
//! field < 12 AND _geoPoint(1, 2)
//! ```
//!
//! - If a user try to use a geoRadius as a value we must throw an error.
//! ```text
//! field = _geoRadius(12, 13, 14)
//! ```
//!

mod condition;
mod error;
mod value;

pub use condition::{parse_condition, parse_to, Condition};
use condition::{parse_exists, parse_not_exists};
use error::{cut_with_err, ExpectedValueKind, NomErrorExt};
pub use error::{Error, ErrorKind};
use nom::branch::alt;
use nom::bytes::complete::tag;
use nom::character::complete::{char, multispace0};
use nom::combinator::{cut, eof, map, opt};
use nom::multi::{many0, separated_list1};
use nom::number::complete::recognize_float;
use nom::sequence::{delimited, preceded, terminated, tuple};
use nom::Finish;
use nom_locate::LocatedSpan;
use std::fmt::Debug;
use std::str::FromStr;
pub(crate) use value::parse_value;
use value::word_exact;

pub type Span<'a> = LocatedSpan<&'a str, &'a str>;

type IResult<'a, Ret> = nom::IResult<Span<'a>, Ret, Error<'a>>;

#[derive(Debug, Clone, Eq)]
pub struct Token<'a> {
    /// The token in the original input, it should be used when possible.
    span: Span<'a>,
    /// If you need to modify the original input you can use the `value` field
    /// to store your modified input.
    value: Option<String>,
}

impl<'a> PartialEq for Token<'a> {
    fn eq(&self, other: &Self) -> bool {
        self.span.fragment() == other.span.fragment()
    }
}

impl<'a> Token<'a> {
    pub fn new(span: Span<'a>, value: Option<String>) -> Self {
        Self { span, value }
    }

    pub fn lexeme(&self) -> &str {
        &self.span
    }

    pub fn value(&self) -> &str {
        self.value.as_ref().map_or(&self.span, |value| value)
    }

    pub fn as_external_error(&self, error: impl std::error::Error) -> Error<'a> {
        Error::new_from_external(self.span, error)
    }

    pub fn parse<T>(&self) -> Result<T, Error>
    where
        T: FromStr,
        T::Err: std::error::Error,
    {
        self.span.parse().map_err(|e| self.as_external_error(e))
    }
}

impl<'a> From<Span<'a>> for Token<'a> {
    fn from(span: Span<'a>) -> Self {
        Self { span, value: None }
    }
}

#[derive(Debug, Clone, PartialEq, Eq)]
pub enum FilterCondition<'a> {
    Not(Box<Self>),
    Condition { fid: Token<'a>, op: Condition<'a> },
    In { fid: Token<'a>, els: Vec<Token<'a>> },
    Or(Vec<Self>),
    And(Vec<Self>),
    GeoLowerThan { point: [Token<'a>; 2], radius: Token<'a> },
}

impl<'a> FilterCondition<'a> {
    /// Returns the first token found at the specified depth, `None` if no token at this depth.
    pub fn token_at_depth(&self, depth: usize) -> Option<&Token> {
        match self {
            FilterCondition::Condition { fid, .. } if depth == 0 => Some(fid),
            FilterCondition::Or(subfilters) => {
                let depth = depth.saturating_sub(1);
                for f in subfilters.iter() {
                    if let Some(t) = f.token_at_depth(depth) {
                        return Some(t);
                    }
                }
                None
            }
            FilterCondition::And(subfilters) => {
                let depth = depth.saturating_sub(1);
                for f in subfilters.iter() {
                    if let Some(t) = f.token_at_depth(depth) {
                        return Some(t);
                    }
                }
                None
            }
            FilterCondition::GeoLowerThan { point: [point, _], .. } if depth == 0 => Some(point),
            _ => None,
        }
    }

    pub fn parse(input: &'a str) -> Result<Option<Self>, Error> {
        if input.trim().is_empty() {
            return Ok(None);
        }
        let span = Span::new_extra(input, input);
        parse_filter(span).finish().map(|(_rem, output)| Some(output))
    }
}

/// remove OPTIONAL whitespaces before AND after the provided parser.
fn ws<'a, O>(inner: impl FnMut(Span<'a>) -> IResult<O>) -> impl FnMut(Span<'a>) -> IResult<O> {
    delimited(multispace0, inner, multispace0)
}

/// value_list = (value ("," value)* ","?)?
fn parse_value_list<'a>(input: Span<'a>) -> IResult<Vec<Token<'a>>> {
    let (input, first_value) = opt(parse_value)(input)?;
    if let Some(first_value) = first_value {
        let value_list_el_parser = preceded(ws(tag(",")), parse_value);

        let (input, mut values) = many0(value_list_el_parser)(input)?;
        let (input, _) = opt(ws(tag(",")))(input)?;
        values.insert(0, first_value);

        Ok((input, values))
    } else {
        Ok((input, vec![]))
    }
}

/// in = value "IN" "[" value_list "]"
fn parse_in(input: Span) -> IResult<FilterCondition> {
    let (input, value) = parse_value(input)?;
    let (input, _) = ws(word_exact("IN"))(input)?;

    // everything after `IN` can be a failure
    let (input, _) =
        cut_with_err(tag("["), |_| Error::new_from_kind(input, ErrorKind::InOpeningBracket))(
            input,
        )?;

    let (input, content) = cut(parse_value_list)(input)?;

    // everything after `IN` can be a failure
    let (input, _) = cut_with_err(tag("]"), |_| {
        if eof::<_, ()>(input).is_ok() {
            Error::new_from_kind(input, ErrorKind::InClosingBracket)
        } else {
            let expected_value_kind = match parse_value(input) {
                Err(nom::Err::Error(e)) => match e.kind() {
                    ErrorKind::ReservedKeyword(_) => ExpectedValueKind::ReservedKeyword,
                    _ => ExpectedValueKind::Other,
                },
                _ => ExpectedValueKind::Other,
            };
            Error::new_from_kind(input, ErrorKind::InExpectedValue(expected_value_kind))
        }
    })(input)?;

    let filter = FilterCondition::In { fid: value, els: content };
    Ok((input, filter))
}
/// in = value "NOT" WS* "IN" "[" value_list "]"
fn parse_not_in(input: Span) -> IResult<FilterCondition> {
    let (input, value) = parse_value(input)?;
    let (input, _) = word_exact("NOT")(input)?;
    let (input, _) = ws(word_exact("IN"))(input)?;

    // everything after `IN` can be a failure
    let (input, _) =
        cut_with_err(tag("["), |_| Error::new_from_kind(input, ErrorKind::InOpeningBracket))(
            input,
        )?;

    let (input, content) = cut(parse_value_list)(input)?;

    // everything after `IN` can be a failure
    let (input, _) =
        cut_with_err(tag("]"), |_| Error::new_from_kind(input, ErrorKind::InClosingBracket))(
            input,
        )?;

    let filter = FilterCondition::Not(Box::new(FilterCondition::In { fid: value, els: content }));
    Ok((input, filter))
}

/// or             = and ("OR" and)
fn parse_or(input: Span) -> IResult<FilterCondition> {
    let (input, first_filter) = parse_and(input)?;
    // if we found a `OR` then we MUST find something next
    let (input, mut ors) = many0(preceded(ws(word_exact("OR")), cut(parse_and)))(input)?;

    let filter = if ors.is_empty() {
        first_filter
    } else {
        ors.insert(0, first_filter);
        FilterCondition::Or(ors)
    };

    Ok((input, filter))
}

/// and            = not ("AND" not)*
fn parse_and(input: Span) -> IResult<FilterCondition> {
    let (input, first_filter) = parse_not(input)?;
    // if we found a `AND` then we MUST find something next
    let (input, mut ands) = many0(preceded(ws(word_exact("AND")), cut(parse_not)))(input)?;

    let filter = if ands.is_empty() {
        first_filter
    } else {
        ands.insert(0, first_filter);
        FilterCondition::And(ands)
    };

    Ok((input, filter))
}

/// not            = ("NOT" WS+ not) | primary
/// We can have multiple consecutive not, eg: `NOT NOT channel = mv`.
/// If we parse a `NOT` we MUST parse something behind.
fn parse_not(input: Span) -> IResult<FilterCondition> {
    alt((
        map(preceded(ws(word_exact("NOT")), cut(parse_not)), |e| FilterCondition::Not(Box::new(e))),
        parse_primary,
    ))(input)
}

/// geoRadius      = WS* "_geoRadius(float WS* "," WS* float WS* "," WS* float)
/// If we parse `_geoRadius` we MUST parse the rest of the expression.
fn parse_geo_radius(input: Span) -> IResult<FilterCondition> {
    // we want to allow space BEFORE the _geoRadius but not after
    let parsed = preceded(
        tuple((multispace0, word_exact("_geoRadius"))),
        // if we were able to parse `_geoRadius` and can't parse the rest of the input we return a failure
        cut(delimited(char('('), separated_list1(tag(","), ws(recognize_float)), char(')'))),
    )(input)
    .map_err(|e| e.map(|_| Error::new_from_kind(input, ErrorKind::Geo)));

    let (input, args) = parsed?;

    if args.len() != 3 {
        return Err(nom::Err::Failure(Error::new_from_kind(input, ErrorKind::Geo)));
    }

    let res = FilterCondition::GeoLowerThan {
        point: [args[0].into(), args[1].into()],
        radius: args[2].into(),
    };
    Ok((input, res))
}

/// geoPoint      = WS* "_geoPoint(float WS* "," WS* float WS* "," WS* float)
fn parse_geo_point(input: Span) -> IResult<FilterCondition> {
    // we want to forbid space BEFORE the _geoPoint but not after
    tuple((
        multispace0,
        tag("_geoPoint"),
        // if we were able to parse `_geoPoint` we are going to return a Failure whatever happens next.
        cut(delimited(char('('), separated_list1(tag(","), ws(recognize_float)), char(')'))),
    ))(input)
    .map_err(|e| e.map(|_| Error::new_from_kind(input, ErrorKind::ReservedGeo("_geoPoint"))))?;
    // if we succeeded we still return a `Failure` because geoPoints are not allowed
    Err(nom::Err::Failure(Error::new_from_kind(input, ErrorKind::ReservedGeo("_geoPoint"))))
}

fn parse_error_reserved_keyword(input: Span) -> IResult<FilterCondition> {
    match parse_condition(input) {
        Ok(result) => Ok(result),
        Err(nom::Err::Error(inner) | nom::Err::Failure(inner)) => match inner.kind() {
            ErrorKind::ExpectedValue(ExpectedValueKind::ReservedKeyword) => {
                return Err(nom::Err::Failure(inner));
            }
            _ => return Err(nom::Err::Error(inner)),
        },
        Err(e) => {
            return Err(e);
        }
    }
}

/// primary        = (WS* "(" WS* expression WS* ")" WS*) | geoRadius | condition | exists | not_exists | to
fn parse_primary(input: Span) -> IResult<FilterCondition> {
    alt((
        // if we find a first parenthesis, then we must parse an expression and find the closing parenthesis
        delimited(
            ws(char('(')),
            cut(parse_expression),
            cut_with_err(ws(char(')')), |c| {
                Error::new_from_kind(input, ErrorKind::MissingClosingDelimiter(c.char()))
            }),
        ),
        parse_geo_radius,
        parse_in,
        parse_not_in,
        parse_condition,
        parse_exists,
        parse_not_exists,
        parse_to,
        // the next lines are only for error handling and are written at the end to have the less possible performance impact
        parse_geo_point,
        parse_error_reserved_keyword,
    ))(input)
    // if the inner parsers did not match enough information to return an accurate error
    .map_err(|e| e.map_err(|_| Error::new_from_kind(input, ErrorKind::InvalidPrimary)))

    // TODO: if the filter starts with a reserved keyword that is not NOT, then we should return the reserved keyword error
    // TODO: if the filter is x = reserved, idem
}

/// expression     = or
pub fn parse_expression(input: Span) -> IResult<FilterCondition> {
    parse_or(input)
}

/// filter     = expression EOF
pub fn parse_filter(input: Span) -> IResult<FilterCondition> {
    terminated(parse_expression, eof)(input)
}

#[cfg(test)]
pub mod tests {
    use super::*;

    /// Create a raw [Token]. You must specify the string that appear BEFORE your element followed by your element
    pub fn rtok<'a>(before: &'a str, value: &'a str) -> Token<'a> {
        // if the string is empty we still need to return 1 for the line number
        let lines = before.is_empty().then(|| 1).unwrap_or_else(|| before.lines().count());
        let offset = before.chars().count();
        // the extra field is not checked in the tests so we can set it to nothing
        unsafe { Span::new_from_raw_offset(offset, lines as u32, value, "") }.into()
    }

    #[test]
    fn parse() {
        use FilterCondition as Fc;

        macro_rules! p {
            ($s:literal) => {
                Fc::parse($s).unwrap().unwrap()
            };
        }

        // Test equal
        insta::assert_display_snapshot!(p!("channel = Ponce"), @"{channel} = {Ponce}");
        insta::assert_display_snapshot!(p!("subscribers = 12"), @"{subscribers} = {12}");
        insta::assert_display_snapshot!(p!("channel = 'Mister Mv'"), @"{channel} = {Mister Mv}");
        insta::assert_display_snapshot!(p!("channel = \"Mister Mv\""), @"{channel} = {Mister Mv}");
        insta::assert_display_snapshot!(p!("'dog race' = Borzoi"), @"{dog race} = {Borzoi}");
        insta::assert_display_snapshot!(p!("\"dog race\" = Chusky"), @"{dog race} = {Chusky}");
        insta::assert_display_snapshot!(p!("\"dog race\" = \"Bernese Mountain\""), @"{dog race} = {Bernese Mountain}");
        insta::assert_display_snapshot!(p!("'dog race' = 'Bernese Mountain'"), @"{dog race} = {Bernese Mountain}");
        insta::assert_display_snapshot!(p!("\"dog race\" = 'Bernese Mountain'"), @"{dog race} = {Bernese Mountain}");

        // Test IN
        insta::assert_display_snapshot!(p!("colour IN[]"), @"{colour} IN[]");
        insta::assert_display_snapshot!(p!("colour IN[green]"), @"{colour} IN[{green}, ]");
        insta::assert_display_snapshot!(p!("colour IN[green,]"), @"{colour} IN[{green}, ]");
        insta::assert_display_snapshot!(p!("colour NOT IN[green,blue]"), @"NOT ({colour} IN[{green}, {blue}, ])");
        insta::assert_display_snapshot!(p!(" colour IN [  green , blue , ]"), @"{colour} IN[{green}, {blue}, ]");

        // Test conditions
        insta::assert_display_snapshot!(p!("channel != ponce"), @"{channel} != {ponce}");
        insta::assert_display_snapshot!(p!("NOT channel = ponce"), @"NOT ({channel} = {ponce})");
        insta::assert_display_snapshot!(p!("subscribers < 1000"), @"{subscribers} < {1000}");
        insta::assert_display_snapshot!(p!("subscribers > 1000"), @"{subscribers} > {1000}");
        insta::assert_display_snapshot!(p!("subscribers <= 1000"), @"{subscribers} <= {1000}");
        insta::assert_display_snapshot!(p!("subscribers >= 1000"), @"{subscribers} >= {1000}");
        insta::assert_display_snapshot!(p!("subscribers <= 1000"), @"{subscribers} <= {1000}");
        insta::assert_display_snapshot!(p!("subscribers 100 TO 1000"), @"{subscribers} {100} TO {1000}");

        // Test NOT + EXISTS
        insta::assert_display_snapshot!(p!("subscribers EXISTS"), @"{subscribers} EXISTS");
        insta::assert_display_snapshot!(p!("NOT subscribers < 1000"), @"NOT ({subscribers} < {1000})");
        insta::assert_display_snapshot!(p!("NOT subscribers EXISTS"), @"NOT ({subscribers} EXISTS)");
        insta::assert_display_snapshot!(p!("subscribers NOT EXISTS"), @"NOT ({subscribers} EXISTS)");
        insta::assert_display_snapshot!(p!("NOT subscribers NOT EXISTS"), @"NOT (NOT ({subscribers} EXISTS))");
        insta::assert_display_snapshot!(p!("subscribers NOT   EXISTS"), @"NOT ({subscribers} EXISTS)");
        insta::assert_display_snapshot!(p!("NOT subscribers 100 TO 1000"), @"NOT ({subscribers} {100} TO {1000})");

        // Test geo radius
        insta::assert_display_snapshot!(p!("_geoRadius(12, 13, 14)"), @"_geoRadius({12}, {13}, {14})");
        insta::assert_display_snapshot!(p!("NOT _geoRadius(12, 13, 14)"), @"NOT (_geoRadius({12}, {13}, {14}))");

        // Test OR + AND
        insta::assert_display_snapshot!(p!("channel = ponce AND 'dog race' != 'bernese mountain'"), @"AND[{channel} = {ponce}, {dog race} != {bernese mountain}, ]");
        insta::assert_display_snapshot!(p!("channel = ponce OR 'dog race' != 'bernese mountain'"), @"OR[{channel} = {ponce}, {dog race} != {bernese mountain}, ]");
        insta::assert_display_snapshot!(p!("channel = ponce AND 'dog race' != 'bernese mountain' OR subscribers > 1000"), @"OR[AND[{channel} = {ponce}, {dog race} != {bernese mountain}, ], {subscribers} > {1000}, ]");
        insta::assert_display_snapshot!(
        p!("channel = ponce AND 'dog race' != 'bernese mountain' OR subscribers > 1000 OR colour = red OR colour = blue AND size = 7"),
        @"OR[AND[{channel} = {ponce}, {dog race} != {bernese mountain}, ], {subscribers} > {1000}, {colour} = {red}, AND[{colour} = {blue}, {size} = {7}, ], ]"
        );

        // test parentheses
        insta::assert_display_snapshot!(p!("channel = ponce AND ( 'dog race' != 'bernese mountain' OR subscribers > 1000 )"), @"AND[{channel} = {ponce}, OR[{dog race} != {bernese mountain}, {subscribers} > {1000}, ], ]");
        insta::assert_display_snapshot!(p!("(channel = ponce AND 'dog race' != 'bernese mountain' OR subscribers > 1000) AND _geoRadius(12, 13, 14)"), @"AND[OR[AND[{channel} = {ponce}, {dog race} != {bernese mountain}, ], {subscribers} > {1000}, ], _geoRadius({12}, {13}, {14}), ]");
    }

    #[test]
    fn error() {
        use FilterCondition as Fc;

        macro_rules! p {
            ($s:literal) => {
                Fc::parse($s).unwrap_err().to_string()
            };
        }

        insta::assert_display_snapshot!(p!("channel = Ponce = 12"), @r###"
        Found unexpected characters at the end of the filter: `= 12`. You probably forgot an `OR` or an `AND` rule.
        17:21 channel = Ponce = 12
        "###);

        insta::assert_display_snapshot!(p!("channel =    "), @r###"
        Was expecting a value but instead got nothing.
        14:14 channel =    
        "###);

        insta::assert_display_snapshot!(p!("channel = 🐻"), @r###"
        Was expecting a value but instead got `🐻`.
        11:12 channel = 🐻
        "###);

        insta::assert_display_snapshot!(p!("channel = 🐻 AND followers < 100"), @r###"
        Was expecting a value but instead got `🐻`.
        11:12 channel = 🐻 AND followers < 100
        "###);

        insta::assert_display_snapshot!(p!("'OR'"), @r###"
        Was expecting an operation `=`, `!=`, `>=`, `>`, `<=`, `<`, `TO`, `EXISTS`, `NOT EXISTS`, or `_geoRadius` at `\'OR\'`.
        1:5 'OR'
        "###);

        insta::assert_display_snapshot!(p!("OR"), @r###"
        Was expecting a value but instead got `OR`, which is a reserved keyword. To use `OR` as a field name or a value, surround it by quotes.
        1:3 OR
        "###);

        insta::assert_display_snapshot!(p!("channel Ponce"), @r###"
        Was expecting an operation `=`, `!=`, `>=`, `>`, `<=`, `<`, `TO`, `EXISTS`, `NOT EXISTS`, or `_geoRadius` at `channel Ponce`.
        1:14 channel Ponce
        "###);

        insta::assert_display_snapshot!(p!("channel = Ponce OR"), @r###"
        Was expecting an operation `=`, `!=`, `>=`, `>`, `<=`, `<`, `TO`, `EXISTS`, `NOT EXISTS`, or `_geoRadius` but instead got nothing.
        19:19 channel = Ponce OR
        "###);

        insta::assert_display_snapshot!(p!("_geoRadius"), @r###"
        The `_geoRadius` filter expects three arguments: `_geoRadius(latitude, longitude, radius)`.
        1:11 _geoRadius
        "###);

        insta::assert_display_snapshot!(p!("_geoRadius = 12"), @r###"
        The `_geoRadius` filter expects three arguments: `_geoRadius(latitude, longitude, radius)`.
        1:16 _geoRadius = 12
        "###);

        insta::assert_display_snapshot!(p!("_geoPoint(12, 13, 14)"), @r###"
        `_geoPoint` is a reserved keyword and thus can't be used as a filter expression. Use the `_geoRadius(latitude, longitude, distance) built-in rule to filter on `_geo` coordinates.
        1:22 _geoPoint(12, 13, 14)
        "###);

        insta::assert_display_snapshot!(p!("position <= _geoPoint(12, 13, 14)"), @r###"
        `_geoPoint` is a reserved keyword and thus can't be used as a filter expression. Use the `_geoRadius(latitude, longitude, distance) built-in rule to filter on `_geo` coordinates.
        13:34 position <= _geoPoint(12, 13, 14)
        "###);

        insta::assert_display_snapshot!(p!("position <= _geoRadius(12, 13, 14)"), @r###"
        The `_geoRadius` filter is an operation and can't be used as a value.
        13:35 position <= _geoRadius(12, 13, 14)
        "###);

        insta::assert_display_snapshot!(p!("channel = 'ponce"), @r###"
        Expression `\'ponce` is missing the following closing delimiter: `'`.
        11:17 channel = 'ponce
        "###);

        insta::assert_display_snapshot!(p!("channel = \"ponce"), @r###"
        Expression `\"ponce` is missing the following closing delimiter: `"`.
        11:17 channel = "ponce
        "###);

        insta::assert_display_snapshot!(p!("channel = mv OR (followers >= 1000"), @r###"
        Expression `(followers >= 1000` is missing the following closing delimiter: `)`.
        17:35 channel = mv OR (followers >= 1000
        "###);

        insta::assert_display_snapshot!(p!("channel = mv OR followers >= 1000)"), @r###"
        Found unexpected characters at the end of the filter: `)`. You probably forgot an `OR` or an `AND` rule.
        34:35 channel = mv OR followers >= 1000)
        "###);

        insta::assert_display_snapshot!(p!("colour NOT EXIST"), @r###"
        Was expecting an operation `=`, `!=`, `>=`, `>`, `<=`, `<`, `TO`, `EXISTS`, `NOT EXISTS`, or `_geoRadius` at `colour NOT EXIST`.
        1:17 colour NOT EXIST
        "###);

        insta::assert_display_snapshot!(p!("subscribers 100 TO1000"), @r###"
        Was expecting an operation `=`, `!=`, `>=`, `>`, `<=`, `<`, `TO`, `EXISTS`, `NOT EXISTS`, or `_geoRadius` at `subscribers 100 TO1000`.
        1:23 subscribers 100 TO1000
        "###);

        insta::assert_display_snapshot!(p!("channel = ponce ORdog != 'bernese mountain'"), @r###"
        Found unexpected characters at the end of the filter: `ORdog != \'bernese mountain\'`. You probably forgot an `OR` or an `AND` rule.
        17:44 channel = ponce ORdog != 'bernese mountain'
        "###);

        insta::assert_display_snapshot!(p!("colour IN blue, green]"), @r###"
        Expected `[` after `IN` keyword.
        11:23 colour IN blue, green]
        "###);

        insta::assert_display_snapshot!(p!("colour IN [blue, green, 'blue' > 2]"), @r###"
        Expected only comma-separated field names inside `IN[..]` but instead found `> 2]`.
        32:36 colour IN [blue, green, 'blue' > 2]
        "###);

        insta::assert_display_snapshot!(p!("colour IN [blue, green, AND]"), @r###"
        Expected only comma-separated field names inside `IN[..]` but instead found `AND]`.
        25:29 colour IN [blue, green, AND]
        "###);

        insta::assert_display_snapshot!(p!("colour IN [blue, green"), @r###"
        Expected matching `]` after the list of field names given to `IN[`
        23:23 colour IN [blue, green
        "###);

        insta::assert_display_snapshot!(p!("colour IN ['blue, green"), @r###"
        Expression `\'blue, green` is missing the following closing delimiter: `'`.
        12:24 colour IN ['blue, green
        "###);

        insta::assert_display_snapshot!(p!("x = EXISTS"), @r###"
        Was expecting a value but instead got `EXISTS`, which is a reserved keyword. To use `EXISTS` as a field name or a value, surround it by quotes.
        5:11 x = EXISTS
        "###);

        insta::assert_display_snapshot!(p!("AND = 8"), @r###"
        Was expecting a value but instead got `AND`, which is a reserved keyword. To use `AND` as a field name or a value, surround it by quotes.
        1:4 AND = 8
        "###);
    }

    #[test]
    fn depth() {
        let filter = FilterCondition::parse("account_ids=1 OR account_ids=2 OR account_ids=3 OR account_ids=4 OR account_ids=5 OR account_ids=6").unwrap().unwrap();
        assert!(filter.token_at_depth(1).is_some());
        assert!(filter.token_at_depth(2).is_none());

        let filter = FilterCondition::parse("(account_ids=1 OR (account_ids=2 AND account_ids=3) OR (account_ids=4 AND account_ids=5) OR account_ids=6)").unwrap().unwrap();
        assert!(filter.token_at_depth(2).is_some());
        assert!(filter.token_at_depth(3).is_none());

        let filter = FilterCondition::parse("account_ids=1 OR account_ids=2 AND account_ids=3 OR account_ids=4 AND account_ids=5 OR account_ids=6").unwrap().unwrap();
        assert!(filter.token_at_depth(2).is_some());
        assert!(filter.token_at_depth(3).is_none());
    }
}

impl<'a> std::fmt::Display for FilterCondition<'a> {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        match self {
            FilterCondition::Not(filter) => {
                write!(f, "NOT ({filter})")
            }
            FilterCondition::Condition { fid, op } => {
                write!(f, "{fid} {op}")
            }
            FilterCondition::In { fid, els } => {
                write!(f, "{fid} IN[")?;
                for el in els {
                    write!(f, "{el}, ")?;
                }
                write!(f, "]")
            }
            FilterCondition::Or(els) => {
                write!(f, "OR[")?;
                for el in els {
                    write!(f, "{el}, ")?;
                }
                write!(f, "]")
            }
            FilterCondition::And(els) => {
                write!(f, "AND[")?;
                for el in els {
                    write!(f, "{el}, ")?;
                }
                write!(f, "]")
            }
            FilterCondition::GeoLowerThan { point, radius } => {
                write!(f, "_geoRadius({}, {}, {})", point[0], point[1], radius)
            }
        }
    }
}
impl<'a> std::fmt::Display for Condition<'a> {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        match self {
            Condition::GreaterThan(token) => write!(f, "> {token}"),
            Condition::GreaterThanOrEqual(token) => write!(f, ">= {token}"),
            Condition::Equal(token) => write!(f, "= {token}"),
            Condition::NotEqual(token) => write!(f, "!= {token}"),
            Condition::Exists => write!(f, "EXISTS"),
            Condition::LowerThan(token) => write!(f, "< {token}"),
            Condition::LowerThanOrEqual(token) => write!(f, "<= {token}"),
            Condition::Between { from, to } => write!(f, "{from} TO {to}"),
        }
    }
}
impl<'a> std::fmt::Display for Token<'a> {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(f, "{{{}}}", self.value())
    }
}