lwb_parser/sources/

character_class.rs

use itertools::Itertools;
use serde::{Deserialize, Serialize};
use std::fmt::{Display, Formatter};
use std::ops::{Range, RangeInclusive};

/// Represent a class of characters like in a regex
/// such as [a-z] or [^0-9]
#[derive(Clone, Debug, Serialize, Deserialize, Hash, Eq, PartialEq)]
pub enum CharacterClass {
    /// Inclusive range. Both `from` and `to` are inclusive
    RangeInclusive {
        from: char,
        // inclusive!
        to: char, // inclusive!
    },
    /// Exclusive range. `from` is inclusive but `to` is exclusive
    Range {
        from: char,
        // inclusive!
        to: char, // exclusive!
    },
    /// all characters in the vec are in the character class.
    Contained(Vec<char>),
    /// True when one of the character class parts is true
    Choice(Vec<CharacterClass>),
    /// inverts the outcome of the embedded character class
    Not(Box<CharacterClass>),
    /// Always false. Use Not(Nothing) for always true.
    Nothing,
}

/// This display trait is very heavily improvised, should be improved in the future!
impl Display for CharacterClass {
    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
        match self {
            CharacterClass::RangeInclusive { from, to } if from == to => {
                write!(f, "{}", from)
            }
            CharacterClass::RangeInclusive { from, to } => {
                write!(f, "[{}-{}]", from, to)
            }
            CharacterClass::Range { from, to } => {
                write!(f, "[{}-{}] (exclusive)", from, to)
            }
            CharacterClass::Contained(list) => {
                write!(f, "{}", list.iter().join(""))
            }
            CharacterClass::Choice(ccs) => {
                write!(f, "{}", ccs.iter().map(|cc| cc.to_string()).join(" or "))
            }
            CharacterClass::Not(not) => {
                write!(f, "not {}", not)
            }
            CharacterClass::Nothing => {
                write!(f, "")
            }
        }
    }
}

impl CharacterClass {
    /// Contains returns true when a character is
    /// included in this character class.
    ///
    /// ```
    /// # use lwb_parser::sources::character_class::CharacterClass;
    ///
    /// let c = CharacterClass::from('a'..='z');
    /// assert!(c.contains('a'));
    /// assert!(c.contains('z'));
    /// assert!(!c.contains('0'));
    /// ```
    ///
    /// ```
    /// # use lwb_parser::sources::character_class::CharacterClass;
    ///
    /// // exclusive range so does not contain 'z'
    /// let c = CharacterClass::from('a'..'z');
    /// assert!(c.contains('a'));
    /// assert!(c.contains('y'));
    /// assert!(!c.contains('z'));
    /// assert!(!c.contains('0'));
    /// ```
    ///
    /// ```
    /// # use lwb_parser::sources::character_class::CharacterClass;
    ///
    /// // always return false
    /// let c = CharacterClass::Nothing;
    /// assert!(!c.contains('a'));
    /// assert!(!c.contains('0'));
    /// ```
    ///
    /// ```
    /// # use lwb_parser::sources::character_class::CharacterClass;
    ///
    /// // always return true
    /// let c = CharacterClass::Nothing.invert();
    /// assert!(c.contains('a'));
    /// assert!(c.contains('0'));
    /// ```
    pub fn contains(&self, c: char) -> bool {
        match self {
            CharacterClass::RangeInclusive { from, to } => {
                c as u32 >= *from as u32 && c as u32 <= *to as u32
            }
            CharacterClass::Range { from, to } => {
                (c as u32) >= *from as u32 && (c as u32) < *to as u32
            }
            CharacterClass::Choice(parts) => parts.iter().map(|i| i.contains(c)).any(|i| i),
            CharacterClass::Not(cls) => !cls.contains(c),
            CharacterClass::Nothing => false,
            CharacterClass::Contained(chars) => chars.contains(&c),
        }
    }

    /// returns a character class that contains all elements
    /// of the slice.
    pub const fn all_in_vec(chars: Vec<char>) -> Self {
        Self::Contained(chars)
    }

    /// Invert this character class. The new class accepts any character
    /// not in the original character class
    pub fn invert(self) -> Self {
        Self::Not(Box::new(self))
    }

    /// Combine two character classes such that the result
    /// contains all characters from either of the two character
    /// class sets.
    ///
    /// ```
    /// use lwb_parser::sources::character_class::CharacterClass;
    ///
    /// let a = CharacterClass::from('a'..'z');
    /// let b = CharacterClass::from('0'..'9');
    /// assert!(a.contains('a'));
    /// assert!(!a.contains('0'));
    /// assert!(!b.contains('a'));
    /// assert!(b.contains('0'));
    ///
    /// let c = a.combine(b);
    /// assert!(c.contains('a'));
    /// assert!(c.contains('0'));
    /// ```
    pub fn combine(self, other: CharacterClass) -> CharacterClass {
        CharacterClass::Choice(vec![self, other])
    }
}

impl From<RangeInclusive<char>> for CharacterClass {
    fn from(r: RangeInclusive<char>) -> Self {
        Self::RangeInclusive {
            from: *r.start(),
            to: *r.end(),
        }
    }
}

impl From<Range<char>> for CharacterClass {
    fn from(r: Range<char>) -> Self {
        Self::Range {
            from: r.start,
            to: r.end,
        }
    }
}

impl From<char> for CharacterClass {
    fn from(c: char) -> Self {
        Self::RangeInclusive { from: c, to: c }
    }
}

impl From<&[char]> for CharacterClass {
    fn from(s: &[char]) -> Self {
        Self::Contained(s.to_vec())
    }
}

impl From<Vec<char>> for CharacterClass {
    fn from(s: Vec<char>) -> Self {
        Self::Contained(s)
    }
}

impl From<String> for CharacterClass {
    fn from(s: String) -> Self {
        Self::Contained(s.chars().collect())
    }
}

impl<'a> From<&'a str> for CharacterClass {
    fn from(s: &'a str) -> Self {
        Self::Contained(s.chars().collect())
    }
}