directiva 0.1.0

//! Minimal glob matching: `*` (any run), `?` (single byte), `{a,b,c}` (one level of alternation),
//! `[a-z]` / `[!neg]` (shell-style char-classes), and `\x` (one universal backslash escape).
//!
//! Design choices that distinguish this from a general-purpose glob crate:
//!
//! 1. **Linear matching.** The matcher is the classic two-pointer wildcard algorithm with a single
//!    backtrack anchor — `O(n·m)` worst case, never the exponential blow-up of naive recursive
//!    globs (`a*a*a*a*b` against a long run of `a`s). Directives may carry untrusted patterns.
//! 2. **Not path-aware.** `*` matches `/` like any other byte. A NAME glob runs against bare
//!    identifiers; a PATH glob runs against whole paths where one `*` is expected to span `/`
//!    (`*/tests/*`). Path-segment semantics would be wrong here.
//! 3. **Byte-oriented.** `?` and char-classes match a single **byte**, not a Unicode scalar.
//!
//! Compilation order, both stages escape-aware: brace alternation is expanded first into a small
//! set of sub-patterns (`{,s}` allows an empty branch; an unmatched/`\{`-escaped brace is a
//! literal; only one level expands), then each sub-pattern is tokenized into [`Tok`]s.

/// A compiled glob pattern: brace alternation pre-expanded into one or more tokenized
/// sub-patterns. [`Pattern::matches`] succeeds if *any* sub-pattern matches the whole input.
#[derive(Clone, Debug)]
pub struct Pattern {
    /// Original source text, retained for `Display` / round-tripping.
    src: String,
    /// One tokenized program per brace-expanded alternative.
    alts: Vec<Vec<Tok>>,
}

/// One compiled glob token.
#[derive(Clone, Debug)]
enum Tok {
    /// `*` — match any run of bytes (including `/`).
    Star,
    /// `?` — match exactly one byte.
    AnyOne,
    /// A literal byte (possibly the un-escaped form of `\x`).
    Lit(u8),
    /// `[...]` char-class.
    Class {
        negated: bool,
        items: Vec<ClassItem>,
    },
}

#[derive(Clone, Debug)]
enum ClassItem {
    Byte(u8),
    Range(u8, u8),
}

/// A raw char-class element before range resolution: a literal byte or an unescaped `-`.
enum E {
    Ch(u8),
    Dash,
}

impl Pattern {
    /// Compile a glob pattern. Never fails: malformed brace/class syntax degrades to literals
    /// (shell-glob leniency), so any string is a valid pattern.
    #[must_use]
    pub fn compile(pat: &str) -> Self {
        let alts = expand_braces(pat).iter().map(|s| compile_alt(s)).collect();
        Self {
            src: pat.to_owned(),
            alts,
        }
    }

    /// Returns `true` if any expanded alternative matches `s` in full.
    #[must_use]
    pub fn matches(&self, s: &str) -> bool {
        let bytes = s.as_bytes();
        self.alts.iter().any(|toks| match_one(toks, bytes))
    }

    /// The original pattern text this was compiled from.
    #[must_use]
    pub fn as_str(&self) -> &str {
        &self.src
    }

    /// Number of brace-expanded alternatives (1 when the pattern has no alternation).
    #[must_use]
    pub fn alt_count(&self) -> usize {
        self.alts.len()
    }
}

impl std::fmt::Display for Pattern {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.write_str(&self.src)
    }
}

/// `Pattern`s compare by their source text (the compiled form is a pure function of it).
impl PartialEq for Pattern {
    fn eq(&self, other: &Self) -> bool {
        self.src == other.src
    }
}
impl Eq for Pattern {}

// ── matcher ──────────────────────────────────────────────────────────────────

/// Linear wildcard match of one tokenized sub-pattern against `s`.
///
/// Two-pointer with a single `*` backtrack anchor: when the bytes after a `*` later fail to match,
/// the `*` swallows one more byte and we retry, instead of re-exploring every split recursively.
fn match_one(toks: &[Tok], s: &[u8]) -> bool {
    let (mut ti, mut si) = (0usize, 0usize);
    // `star` = index in `toks` of the `*`; `star_s` = where in `s` it currently stops consuming.
    let mut star: Option<usize> = None;
    let mut star_s = 0usize;

    while si < s.len() {
        match toks.get(ti) {
            Some(Tok::Star) => {
                star = Some(ti);
                star_s = si;
                ti += 1;
            }
            Some(t) if tok_matches(t, s[si]) => {
                ti += 1;
                si += 1;
            }
            _ => {
                if let Some(sp) = star {
                    ti = sp + 1;
                    star_s += 1;
                    si = star_s;
                } else {
                    return false;
                }
            }
        }
    }
    // Trailing `*`s match the empty remainder.
    while matches!(toks.get(ti), Some(Tok::Star)) {
        ti += 1;
    }
    ti == toks.len()
}

fn tok_matches(t: &Tok, b: u8) -> bool {
    match t {
        Tok::Star => false, // handled by the caller; never a single-byte match
        Tok::AnyOne => true,
        Tok::Lit(c) => *c == b,
        Tok::Class { negated, items } => {
            let inside = items.iter().any(|it| match it {
                ClassItem::Byte(x) => *x == b,
                ClassItem::Range(lo, hi) => *lo <= b && b <= *hi,
            });
            inside ^ negated
        }
    }
}

// ── compilation ──────────────────────────────────────────────────────────────

/// Tokenize one brace-free sub-pattern. Escape-aware (`\x` → literal `x`); a `[` that opens no
/// valid class is demoted to a literal byte.
fn compile_alt(s: &str) -> Vec<Tok> {
    let b = s.as_bytes();
    let mut toks = Vec::new();
    let mut i = 0;
    while i < b.len() {
        match b[i] {
            b'\\' => {
                if i + 1 < b.len() {
                    toks.push(Tok::Lit(b[i + 1]));
                    i += 2;
                } else {
                    toks.push(Tok::Lit(b'\\')); // trailing backslash is a literal
                    i += 1;
                }
            }
            b'*' => {
                toks.push(Tok::Star);
                i += 1;
            }
            b'?' => {
                toks.push(Tok::AnyOne);
                i += 1;
            }
            b'[' => {
                if let Some((class, next)) = parse_class(b, i) {
                    toks.push(class);
                    i = next;
                } else {
                    toks.push(Tok::Lit(b'[')); // lenient: unmatched '['
                    i += 1;
                }
            }
            c => {
                toks.push(Tok::Lit(c));
                i += 1;
            }
        }
    }
    toks
}

/// Parse `[...]` starting at `b[start] == '['`. Returns `(Tok::Class, index_after_])` or `None` if
/// there's no closing `]` (caller treats the `[` as a literal). Shell-style:
/// leading `!` negates; `]` is literal when first; `-` is literal when first or last.
fn parse_class(b: &[u8], start: usize) -> Option<(Tok, usize)> {
    let mut i = start + 1;
    let mut negated = false;
    if b.get(i) == Some(&b'!') {
        negated = true;
        i += 1;
    }

    // Collect the class body as bytes-or-dashes, resolving escapes; `]` as the first element is a
    // literal, otherwise it closes the class.
    let mut elems: Vec<E> = Vec::new();
    let mut first = true;
    loop {
        let c = *b.get(i)?; // EOF before ']' ⇒ None
        match c {
            b'\\' => {
                if let Some(&n) = b.get(i + 1) {
                    elems.push(E::Ch(n));
                    i += 2;
                } else {
                    elems.push(E::Ch(b'\\'));
                    i += 1;
                }
            }
            b']' if first => {
                elems.push(E::Ch(b']'));
                i += 1;
            }
            b']' => {
                i += 1;
                break;
            }
            b'-' => {
                elems.push(E::Dash);
                i += 1;
            }
            other => {
                elems.push(E::Ch(other));
                i += 1;
            }
        }
        first = false;
    }

    // Resolve ranges: `Ch lo, Dash, Ch hi` ⇒ Range(lo,hi); a stray Dash (first/last) is literal.
    let mut items: Vec<ClassItem> = Vec::new();
    let mut k = 0;
    while k < elems.len() {
        match elems[k] {
            E::Ch(lo) => {
                if matches!(elems.get(k + 1), Some(E::Dash)) {
                    if let Some(E::Ch(hi)) = elems.get(k + 2) {
                        items.push(ClassItem::Range(lo, *hi));
                        k += 3;
                        continue;
                    }
                }
                items.push(ClassItem::Byte(lo));
                k += 1;
            }
            E::Dash => {
                items.push(ClassItem::Byte(b'-'));
                k += 1;
            }
        }
    }

    Some((Tok::Class { negated, items }, i))
}

/// Expand one level of `{a,b,c}` brace alternation, recursively re-expanding the tail. Escape-aware
/// — `\{`, `\}`, `\,` are skipped (left for the tokenizer to turn into literals). An unmatched
/// brace falls through as a single literal pattern.
fn expand_braces(pat: &str) -> Vec<String> {
    let b = pat.as_bytes();
    let Some(open) = find_unescaped(b, 0, b'{') else {
        return vec![pat.to_owned()];
    };
    let Some(close) = find_unescaped(b, open + 1, b'}') else {
        return vec![pat.to_owned()];
    };
    let prefix = &pat[..open];
    let alts = &pat[open + 1..close];
    let suffix = &pat[close + 1..];

    let mut out = Vec::new();
    for alt in split_unescaped(alts, b',') {
        for tail in expand_braces(suffix) {
            out.push(format!("{prefix}{alt}{tail}"));
        }
    }
    out
}

/// Index of the first unescaped `needle` byte at or after `from`, honoring `\`-escapes.
fn find_unescaped(b: &[u8], from: usize, needle: u8) -> Option<usize> {
    let mut i = from;
    while i < b.len() {
        match b[i] {
            b'\\' => i += 2, // skip the escaped byte
            c if c == needle => return Some(i),
            _ => i += 1,
        }
    }
    None
}

/// Split `s` on unescaped `sep` bytes (escaped separators stay in the piece).
fn split_unescaped(s: &str, sep: u8) -> Vec<&str> {
    let b = s.as_bytes();
    let mut out = Vec::new();
    let (mut start, mut i) = (0usize, 0usize);
    while i < b.len() {
        match b[i] {
            b'\\' => i += 2,
            c if c == sep => {
                out.push(&s[start..i]);
                i += 1;
                start = i;
            }
            _ => i += 1,
        }
    }
    out.push(&s[start..]);
    out
}

#[cfg(test)]
mod tests {
    use super::{expand_braces, Pattern};

    fn m(pat: &str, s: &str) -> bool {
        Pattern::compile(pat).matches(s)
    }

    #[test]
    fn literal_and_anchors() {
        assert!(m("abc", "abc"));
        assert!(!m("abc", "abd"));
        assert!(!m("abc", "abcd"));
        assert!(!m("abc", "ab"));
    }

    #[test]
    fn star_spans_anything_including_slash() {
        assert!(m("*", ""));
        assert!(m("*", "anything/at/all"));
        assert!(m("a*c", "ac"));
        assert!(m("a*c", "abbbc"));
        assert!(m("*/tests/*", "src/pkg/tests/foo.rs"));
        assert!(!m("*/tests/*", "src/pkg/test/foo.rs"));
    }

    // byte-oriented `?`
    #[test]
    fn question_matches_single_byte() {
        assert!(m("a?c", "abc"));
        assert!(!m("a?c", "ac"));
        assert!(!m("a?c", "abbc"));
        // a 2-byte UTF-8 scalar ('é' = 0xC3 0xA9) needs two `?`
        assert!(m("??", "é"));
        assert!(!m("?", "é"));
    }

    // no exponential blow-up
    #[test]
    fn collapsed_stars_do_not_blow_up() {
        let pat = "a*a*a*a*a*a*a*a*b";
        let s = "a".repeat(64);
        assert!(!m(pat, &s));
        assert!(m("***", "anything"));
    }

    // shell-style char-classes
    #[test]
    fn char_classes() {
        assert!(m("[a-z]bc", "xbc"));
        assert!(!m("[a-z]bc", "Xbc"));
        assert!(m("test_[0-9]*", "test_42x"));
        // negation
        assert!(m("[!0-9]", "a"));
        assert!(!m("[!0-9]", "7"));
        // ']' literal when first; '-' literal when first or last
        assert!(m("[]a]", "]"));
        assert!(m("[]a]", "a"));
        assert!(m("[a-]", "a"));
        assert!(m("[a-]", "-"));
        assert!(m("[-a]", "-"));
    }

    // escaping reaches the glob layer
    #[test]
    fn escaping_literals() {
        assert!(m(r"\*", "*"));
        assert!(!m(r"\*", "anything"));
        assert!(m(r"\[lit\]", "[lit]"));
        assert!(m(r"a\?b", "a?b"));
        assert!(!m(r"a\?b", "axb"));
        // escaped brace is NOT alternation
        assert_eq!(Pattern::compile(r"\{a,b\}").alt_count(), 1);
        assert!(m(r"\{a,b\}", "{a,b}"));
    }

    #[test]
    fn brace_expansion_covers_all_conventions() {
        let e = expand_braces("*/{test,tests,__tests__}/*");
        assert_eq!(e.len(), 3);
        assert!(e.contains(&"*/test/*".to_owned()));
        assert!(e.contains(&"*/tests/*".to_owned()));
        assert!(e.contains(&"*/__tests__/*".to_owned()));
    }

    #[test]
    fn brace_alternation_matches() {
        let p = Pattern::compile("*/{test,tests,__tests__}/*");
        assert!(p.matches("packages/compiler-cli/test/compliance/foo.ts"));
        assert!(p.matches("packages/svelte/tests/css/test.ts"));
        assert!(p.matches("packages/next/src/__tests__/foo.test.ts"));
        assert!(!p.matches("src/components/Button.ts"));
    }

    #[test]
    fn file_extension_alternation() {
        let p = Pattern::compile("*.{test,spec}.*");
        assert!(p.matches("src/foo.test.ts"));
        assert!(p.matches("src/foo.spec.ts"));
        assert!(!p.matches("src/foo.ts"));
    }

    #[test]
    fn empty_alternation_branch_is_legal() {
        let e = expand_braces("*/{,s}post*");
        assert!(e.contains(&"*/post*".to_owned()));
        assert!(e.contains(&"*/spost*".to_owned()));
    }

    #[test]
    fn two_groups_compose() {
        let e = expand_braces("{a,b}{c,d}");
        assert_eq!(e.len(), 4);
        for want in ["ac", "ad", "bc", "bd"] {
            assert!(e.contains(&want.to_owned()), "missing {want}");
        }
    }

    #[test]
    fn no_braces_is_one_alternative() {
        assert_eq!(Pattern::compile("*tests/*").alt_count(), 1);
        assert_eq!(expand_braces("*tests/*"), vec!["*tests/*".to_owned()]);
    }

    #[test]
    fn unmatched_brace_is_literal() {
        assert!(m("a{b", "a{b"));
        assert_eq!(Pattern::compile("a{b").alt_count(), 1);
    }
}