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// License: see LICENSE file at root directory of `master` branch

//! # Glob

use std::{
    fmt,
    hash::{Hash, Hasher},
};

/// # Parts of a `&str`
#[derive(Debug, Eq, PartialEq)]
enum Part<'a> {

    /// # A string
    Str(&'a str),

    /// # Any (`*`)
    Any,

    /// # One character (`?`)
    OneChar,
}

impl<'a> Part<'a> {

    /// # Parses
    fn parse(mut s: &'a str) -> Vec<Self> {
        let mut result = vec![];
        loop {
            match s.find(|c| match c { '*' | '?' => true, _ => false }) {
                Some(i) => {
                    if i > 0 {
                        result.push(Part::Str(&s[..i]));
                    }
                    match s.as_bytes()[i] {
                        b'*' => if result.last() != Some(&Part::Any) {
                            result.push(Part::Any);
                        },
                        b'?' => result.push(Part::OneChar),
                        _ => {},
                    };
                    if i + 1 == s.len() {
                        break;
                    }
                    s = &s[i + 1..];
                },
                None => {
                    result.push(Part::Str(s));
                    break;
                },
            };
        }

        result
    }

}

/// # Glob
///
/// This struct is used to find matches from a pattern string against some string.
///
/// The pattern string supports 2 special characters: `*` and `?`:
///
/// - `*`: matches any characters or nothing at all.
/// - `?`: matches one single character.
///
/// ## Notes
///
/// - The idea is inspired by <https://en.wikipedia.org/wiki/Glob_%28programming%29>, but this is _not_ an implementation of that specification.
/// - Matches are _case sensitive_. If you want to ignore case, consider using [`to_lowercase()`][r://String/to_lowercase()] (or
///   [`to_uppercase()`][r://String/to_uppercase()]) on _both_ pattern and target string.
///
/// [r://String/to_lowercase()]: https://doc.rust-lang.org/std/string/struct.String.html#method.to_lowercase
/// [r://String/to_uppercase()]: https://doc.rust-lang.org/std/string/struct.String.html#method.to_uppercase
#[derive(Debug, Eq)]
pub struct Glob<'a> {

    /// # Source string
    src: &'a str,

    /// # Parts
    parts: Vec<Part<'a>>,

}

impl<'a> Glob<'a> {

    /// # Makes new instance
    pub fn new(src: &'a str) -> Self {
        Self {
            src,
            parts: Part::parse(src),
        }
    }

    /// # Checks if this glob matches a string
    pub fn matches<S>(&self, s: S) -> bool where S: AsRef<str> {
        let mut s = s.as_ref();
        let mut parts = self.parts.iter().peekable();
        let mut must_start_with = true;
        loop {
            match parts.next() {
                Some(Part::Any) => {
                    let mut min_target_chars: usize = 0;
                    loop {
                        match parts.peek() {
                            Some(Part::Any) => drop(parts.next()),
                            Some(Part::OneChar) => {
                                parts.next();
                                min_target_chars += 1;
                            },
                            Some(Part::Str(_)) => {
                                let mut i = 0;

                                let mut chars = s.chars();
                                for _ in 0..min_target_chars {
                                    match chars.next() {
                                        Some(c) => i += c.len_utf8(),
                                        None => return false,
                                    };
                                }

                                s = &s[i..];
                                break;
                            },
                            None => return s.chars().count() >= min_target_chars,
                        };
                    }
                    must_start_with = false;
                },
                Some(Part::OneChar) => match s.chars().next() {
                    Some(c) => {
                        s = &s[c.len_utf8()..];
                        must_start_with = true;
                    },
                    None => return false,
                },
                Some(Part::Str(sub)) => match s.find(sub) {
                    Some(i) if i == 0 || must_start_with == false => {
                        s = &s[i + sub.len()..];
                        must_start_with = true;
                    },
                    _ => return false,
                },
                None => return s.is_empty(),
            };
        }
    }

}

impl PartialEq for Glob<'_> {

    fn eq(&self, other: &Self) -> bool {
        self.src == other.src
    }

}

impl Hash for Glob<'_> {

    fn hash<H>(&self, h: &mut H) where H: Hasher {
        self.src.hash(h);
    }

}

/// # Converts from a `&str` to [`Glob`][::Glob]
///
/// [::Glob]: struct.Glob.html
impl<'a> From<&'a str> for Glob<'a> {

    fn from(src: &'a str) -> Self {
        Self::new(src)
    }

}

impl fmt::Display for Glob<'_> {

    fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error> {
        f.write_str(self.src)
    }

}