f00-core 0.8.0

use crate::entry::{Entry, EntryKind};
use crate::options::{ListOptions, SortBy};

/// Case-insensitive name comparison.
///
/// In GNU mode, compare raw byte/string order without stripping leading dots.
pub fn cmp_name(a: &str, b: &str) -> std::cmp::Ordering {
    cmp_name_with_mode(a, b, false)
}

pub fn cmp_name_with_mode(a: &str, b: &str, gnu: bool) -> std::cmp::Ordering {
    if gnu {
        // Approximate LC_COLLATE=C: byte-wise, case-sensitive.
        return a.cmp(b);
    }
    // Friendly default: case-insensitive, interleave hidden files.
    let a_key = a.trim_start_matches('.').to_ascii_lowercase();
    let b_key = b.trim_start_matches('.').to_ascii_lowercase();
    match a_key.cmp(&b_key) {
        std::cmp::Ordering::Equal => a.cmp(b),
        other => other,
    }
}

/// strverscmp-like natural / version comparison (`ls -v`).
///
/// Digit runs compare numerically (with leading-zero special-case similar to glibc);
/// non-digit runs compare byte-wise.
pub fn cmp_version(a: &str, b: &str) -> std::cmp::Ordering {
    use std::cmp::Ordering;
    let ab = a.as_bytes();
    let bb = b.as_bytes();
    let mut i = 0usize;
    let mut j = 0usize;

    while i < ab.len() || j < bb.len() {
        if i >= ab.len() {
            return Ordering::Less;
        }
        if j >= bb.len() {
            return Ordering::Greater;
        }

        let a_digit = ab[i].is_ascii_digit();
        let b_digit = bb[j].is_ascii_digit();

        if a_digit && b_digit {
            // Leading zeros: all-zero prefix is "fractional" in glibc strverscmp.
            let a_zeros = count_leading(ab, i, b'0');
            let b_zeros = count_leading(bb, j, b'0');
            let i0 = i + a_zeros;
            let j0 = j + b_zeros;
            let a_digits = count_digits(ab, i0);
            let b_digits = count_digits(bb, j0);

            // If one side has more leading zeros, it compares as smaller when
            // the remaining numeric parts are equal length / equal value (glibc).
            match (a_zeros > 0, b_zeros > 0) {
                (true, false) => {
                    // a has leading zeros → treat as fractional / smaller if equal digits after.
                    // Fall through to numeric compare of remaining digits first.
                }
                (false, true) => {}
                _ => {}
            }

            // Compare digit values first by length then lexicographically.
            match a_digits.cmp(&b_digits) {
                Ordering::Equal => {
                    let acmp = ab[i0..i0 + a_digits].cmp(&bb[j0..j0 + b_digits]);
                    if acmp != Ordering::Equal {
                        return acmp;
                    }
                    // Equal numbers: more leading zeros → less (glibc).
                    if a_zeros != b_zeros {
                        return b_zeros.cmp(&a_zeros);
                    }
                }
                ord => return ord,
            }
            i = i0 + a_digits;
            j = j0 + b_digits;
            continue;
        }

        if a_digit != b_digit {
            // Non-digit vs digit: compare bytes.
            return ab[i].cmp(&bb[j]);
        }

        // Both non-digit: compare until digit or end.
        while i < ab.len() && j < bb.len() && !ab[i].is_ascii_digit() && !bb[j].is_ascii_digit() {
            match ab[i].cmp(&bb[j]) {
                Ordering::Equal => {
                    i += 1;
                    j += 1;
                }
                ord => return ord,
            }
        }
        if i < ab.len() && j < bb.len() {
            // One hit a digit boundary.
            if ab[i].is_ascii_digit() != bb[j].is_ascii_digit() {
                return ab[i].cmp(&bb[j]);
            }
        }
    }
    Ordering::Equal
}

fn count_leading(bytes: &[u8], start: usize, ch: u8) -> usize {
    let mut n = 0;
    while start + n < bytes.len() && bytes[start + n] == ch {
        n += 1;
    }
    n
}

fn count_digits(bytes: &[u8], start: usize) -> usize {
    let mut n = 0;
    while start + n < bytes.len() && bytes[start + n].is_ascii_digit() {
        n += 1;
    }
    n
}

pub(crate) fn cmp_entry(a: &Entry, b: &Entry, opts: &ListOptions) -> std::cmp::Ordering {
    use std::cmp::Ordering;

    if opts.dirs_first {
        let a_dir = a.kind == EntryKind::Directory;
        let b_dir = b.kind == EntryKind::Directory;
        match (a_dir, b_dir) {
            (true, false) => return Ordering::Less,
            (false, true) => return Ordering::Greater,
            _ => {}
        }
    }

    let name_cmp = || cmp_name_with_mode(&a.name, &b.name, opts.gnu_mode);

    let primary = match opts.sort_by {
        SortBy::None => Ordering::Equal,
        SortBy::Name => name_cmp(),
        // GNU `-S`: largest first.
        SortBy::Size => b.size.cmp(&a.size).then_with(name_cmp),
        SortBy::Time => {
            let ta = a.time_for(opts.time_field);
            let tb = b.time_for(opts.time_field);
            // Newest first.
            tb.cmp(&ta).then_with(name_cmp)
        }
        SortBy::Extension => {
            let ea = a.extension().unwrap_or("");
            let eb = b.extension().unwrap_or("");
            if opts.gnu_mode {
                ea.cmp(eb).then_with(name_cmp)
            } else {
                ea.to_ascii_lowercase()
                    .cmp(&eb.to_ascii_lowercase())
                    .then_with(name_cmp)
            }
        }
        SortBy::Version => cmp_version(&a.name, &b.name).then_with(name_cmp),
    };

    if opts.reverse {
        primary.reverse()
    } else {
        primary
    }
}

/// Sort entries according to options. Directory headers keep relative order.
pub fn sort_entries(entries: &mut [Entry], opts: &ListOptions) {
    if opts.sort_by == SortBy::None {
        if opts.reverse {
            entries.reverse();
        }
        return;
    }

    entries.sort_by(|a, b| match (a.is_dir_header, b.is_dir_header) {
        (true, false) => std::cmp::Ordering::Less,
        (false, true) => std::cmp::Ordering::Greater,
        _ => cmp_entry(a, b, opts),
    });
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::entry::{Entry, EntryKind, GitStatus, TimeField};
    use std::path::PathBuf;
    use std::time::{Duration, SystemTime};

    fn entry(name: &str, kind: EntryKind, size: u64, secs: Option<u64>) -> Entry {
        Entry {
            path: PathBuf::from(name),
            name: name.to_string(),
            kind,
            size,
            modified: secs.map(|s| SystemTime::UNIX_EPOCH + Duration::from_secs(s)),
            created: None,
            accessed: None,
            changed: secs.map(|s| SystemTime::UNIX_EPOCH + Duration::from_secs(s)),
            mode: 0,
            readonly: false,
            symlink_target: None,
            depth: 0,
            git_status: GitStatus::Clean,
            is_dir_header: false,
            nlink: 1,
            uid: 0,
            gid: 0,
            inode: 0,
            blocks: 0,
            owner: "u".into(),
            group: "g".into(),
            author: "u".into(),
            context: String::new(),
        }
    }

    #[test]
    fn sort_by_name_case_insensitive() {
        let mut entries = vec![
            entry("Banana", EntryKind::File, 0, None),
            entry("apple", EntryKind::File, 0, None),
            entry("Cherry", EntryKind::File, 0, None),
        ];
        sort_entries(&mut entries, &ListOptions::default());
        let names: Vec<_> = entries.iter().map(|e| e.name.as_str()).collect();
        assert_eq!(names, vec!["apple", "Banana", "Cherry"]);
    }

    #[test]
    fn sort_by_size_largest_first() {
        let mut entries = vec![
            entry("big", EntryKind::File, 100, None),
            entry("small", EntryKind::File, 1, None),
            entry("mid", EntryKind::File, 50, None),
        ];
        let opts = ListOptions {
            sort_by: SortBy::Size,
            ..Default::default()
        };
        sort_entries(&mut entries, &opts);
        let names: Vec<_> = entries.iter().map(|e| e.name.as_str()).collect();
        assert_eq!(names, vec!["big", "mid", "small"]);
    }

    #[test]
    fn sort_by_time_newest_first() {
        let mut entries = vec![
            entry("old", EntryKind::File, 0, Some(10)),
            entry("new", EntryKind::File, 0, Some(100)),
            entry("mid", EntryKind::File, 0, Some(50)),
        ];
        let opts = ListOptions {
            sort_by: SortBy::Time,
            ..Default::default()
        };
        sort_entries(&mut entries, &opts);
        let names: Vec<_> = entries.iter().map(|e| e.name.as_str()).collect();
        assert_eq!(names, vec!["new", "mid", "old"]);
    }

    #[test]
    fn reverse_name_sort() {
        let mut entries = vec![
            entry("a", EntryKind::File, 0, None),
            entry("b", EntryKind::File, 0, None),
            entry("c", EntryKind::File, 0, None),
        ];
        let opts = ListOptions {
            reverse: true,
            ..Default::default()
        };
        sort_entries(&mut entries, &opts);
        let names: Vec<_> = entries.iter().map(|e| e.name.as_str()).collect();
        assert_eq!(names, vec!["c", "b", "a"]);
    }

    #[test]
    fn dirs_first() {
        let mut entries = vec![
            entry("zfile", EntryKind::File, 0, None),
            entry("adir", EntryKind::Directory, 0, None),
            entry("bfile", EntryKind::File, 0, None),
        ];
        let opts = ListOptions {
            dirs_first: true,
            ..Default::default()
        };
        sort_entries(&mut entries, &opts);
        assert_eq!(entries[0].name, "adir");
    }

    #[test]
    fn sort_by_extension() {
        let mut entries = vec![
            entry("a.txt", EntryKind::File, 0, None),
            entry("b.rs", EntryKind::File, 0, None),
            entry("c.md", EntryKind::File, 0, None),
            entry("noext", EntryKind::File, 0, None),
        ];
        let opts = ListOptions {
            sort_by: SortBy::Extension,
            ..Default::default()
        };
        sort_entries(&mut entries, &opts);
        let names: Vec<_> = entries.iter().map(|e| e.name.as_str()).collect();
        assert_eq!(names, vec!["noext", "c.md", "b.rs", "a.txt"]);
    }

    #[test]
    fn sort_by_version() {
        let mut entries = vec![
            entry("file10.txt", EntryKind::File, 0, None),
            entry("file2.txt", EntryKind::File, 0, None),
            entry("file1.txt", EntryKind::File, 0, None),
        ];
        let opts = ListOptions {
            sort_by: SortBy::Version,
            ..Default::default()
        };
        sort_entries(&mut entries, &opts);
        let names: Vec<_> = entries.iter().map(|e| e.name.as_str()).collect();
        assert_eq!(names, vec!["file1.txt", "file2.txt", "file10.txt"]);
    }

    #[test]
    fn cmp_version_basic() {
        use std::cmp::Ordering;
        assert_eq!(cmp_version("a2", "a10"), Ordering::Less);
        assert_eq!(cmp_version("a10", "a2"), Ordering::Greater);
        assert_eq!(cmp_version("abc", "abc"), Ordering::Equal);
        assert_eq!(cmp_version("file1", "file01"), Ordering::Greater); // fewer leading zeros wins? glibc: more leading zeros is less
                                                                       // file01 has leading zero → smaller than file1 when numbers equal
        assert_eq!(cmp_version("file01", "file1"), Ordering::Less);
    }

    #[test]
    fn cmp_name_strips_dot_for_key() {
        assert!(cmp_name(".foo", "foo").is_le());
        assert!(cmp_name("apple", "banana").is_lt());
    }

    #[test]
    fn gnu_name_sort_is_bytewise() {
        assert_eq!(cmp_name_with_mode("B", "a", true), std::cmp::Ordering::Less);
        // 'B' < 'a' in ASCII
    }

    #[test]
    fn time_field_access() {
        let mut e = entry("x", EntryKind::File, 0, Some(50));
        e.accessed = Some(SystemTime::UNIX_EPOCH + Duration::from_secs(10));
        assert_eq!(
            e.time_for(TimeField::Accessed),
            Some(SystemTime::UNIX_EPOCH + Duration::from_secs(10))
        );
    }

    #[test]
    fn time_field_changed_uses_ctime() {
        let mut e = entry("x", EntryKind::File, 0, Some(50));
        e.changed = Some(SystemTime::UNIX_EPOCH + Duration::from_secs(7));
        assert_eq!(
            e.time_for(TimeField::Changed),
            Some(SystemTime::UNIX_EPOCH + Duration::from_secs(7))
        );
    }
}