address 0.23.0

use crate::{Domain, DomainRef};
use std::iter::FusedIterator;

impl Domain {
    //! Labels

    /// Gets the labels.
    pub const fn labels(&self) -> Labels<'_> {
        Labels::new(self.name())
    }
}

impl<'a> DomainRef<'a> {
    //! Labels

    /// Gets the labels.
    pub const fn labels(self) -> Labels<'a> {
        Labels::new(self.name())
    }
}

/// An iterator over the labels of a domain name.
#[must_use]
#[derive(Clone, Debug)]
pub struct Labels<'a> {
    name: Option<&'a str>,
}

impl<'a> Labels<'a> {
    //! Construction

    /// Creates a new label iterator for the domain `name`.
    const fn new(name: &'a str) -> Self {
        Self { name: Some(name) }
    }
}

impl<'a> Iterator for Labels<'a> {
    type Item = &'a str;

    fn next(&mut self) -> Option<&'a str> {
        let name: &str = self.name?;
        if let Some(dot) = name.find('.') {
            self.name = Some(&name[dot + 1..]);
            Some(&name[..dot])
        } else {
            self.name = None;
            Some(name)
        }
    }

    fn size_hint(&self) -> (usize, Option<usize>) {
        match self.name {
            Some(name) => (1, Some(name.len().div_ceil(2))),
            None => (0, Some(0)),
        }
    }
}

impl<'a> DoubleEndedIterator for Labels<'a> {
    fn next_back(&mut self) -> Option<&'a str> {
        let name: &str = self.name?;
        if let Some(dot) = name.rfind('.') {
            self.name = Some(&name[..dot]);
            Some(&name[dot + 1..])
        } else {
            self.name = None;
            Some(name)
        }
    }
}

impl<'a> FusedIterator for Labels<'a> {}

#[cfg(test)]
mod tests {
    use crate::{Domain, DomainRef, Labels};

    #[test]
    fn labels() {
        let test_cases: &[(&str, &[&str])] = &[
            ("localhost", &["localhost"]),
            ("example.com", &["example", "com"]),
            ("www.example.com", &["www", "example", "com"]),
        ];

        for (name, expected) in test_cases {
            let domain: Domain = name.parse().unwrap();
            let result: Vec<&str> = domain.labels().collect();
            assert_eq!(result, *expected, "name={}", name);

            let result: Vec<&str> = domain.to_ref().labels().collect();
            assert_eq!(result, *expected, "name={}", name);
        }
    }

    #[test]
    fn labels_size_hint() {
        let test_cases: &[&str] = &["x", "a.b", "a.b.c", "www.example.com", "a.bb.ccc.dddd"];

        for name in test_cases {
            let domain: Domain = name.parse().unwrap();
            let total: usize = domain.labels().count();
            let mut labels: Labels = domain.labels();

            for taken in 0..=total {
                let remaining: usize = total - taken;
                let (low, high): (usize, Option<usize>) = labels.size_hint();
                assert!(
                    low <= remaining,
                    "name={} taken={} low={}",
                    name,
                    taken,
                    low
                );
                assert!(
                    high.is_some_and(|high| remaining <= high),
                    "name={} taken={} high={:?}",
                    name,
                    taken,
                    high
                );
                labels.next();
            }
        }
    }

    #[test]
    fn labels_rev() {
        let test_cases: &[(&str, &[&str])] = &[
            ("localhost", &["localhost"]),
            ("example.com", &["com", "example"]),
            ("www.example.com", &["com", "example", "www"]),
        ];

        for (name, expected) in test_cases {
            let domain: Domain = name.parse().unwrap();
            let result: Vec<&str> = domain.labels().rev().collect();
            assert_eq!(result, *expected, "name={}", name);

            let result: Vec<&str> = domain.to_ref().labels().rev().collect();
            assert_eq!(result, *expected, "name={}", name);
        }
    }

    #[test]
    fn labels_mixed() {
        let domain: Domain = "a.b.c.d.e".parse().unwrap();
        let mut labels: Labels = domain.labels();

        assert_eq!(labels.next(), Some("a"));
        assert_eq!(labels.next_back(), Some("e"));
        assert_eq!(labels.next(), Some("b"));
        assert_eq!(labels.next_back(), Some("d"));
        assert_eq!(labels.next(), Some("c"));
        assert_eq!(labels.next(), None);
        assert_eq!(labels.next_back(), None);
    }

    #[test]
    fn labels_fused() {
        let mut labels: Labels = DomainRef::LOCALHOST.labels();
        assert_eq!(labels.next(), Some("localhost"));
        assert_eq!(labels.next(), None);
        assert_eq!(labels.next(), None);
        assert_eq!(labels.next_back(), None);
    }
}