lints 0.2.0

use super::{
    ExitCode, HashSet, convert,
    io::{self, Write as _},
};
use core::{
    cmp::Ordering,
    hash::{Hash, Hasher},
};
// We skip all lines until: "name  default  meaning" trimming leading spaces.
// We verify the next line is "----  -------  -------" trimming leading spaces.
//
// Next we grab the lints.
// The regex for lints is verified to be `^ *[\-0-9A-Za-z]+ +(allow|warn|deny) +.*$`.
//
// We verify all three kinds of lints are non-empty and no lint exists more than once. We verify the
// `warn` lints contain a lint called "warnings" which does not count towards the emptiness of
// `warn` lints.
//
// Next we skip all lines until: "name  sub-lints" trimming leading spaces.
// We verify the next line is "----  ---------" trimming leading spaces.
//
// Next we grab the lint groups.
// The regex for lint groups is verified to be `^ +[\-0-9A-Za-z]+ +[ ,\-0-9A-Za-z]+$`.
//
// We verify lint group names are unique among themselves and the individual lints sans `"warnings"`
// which is allowed to exist.
// We verify the lint groups are non-empty except "warnings" if it is defined.
// We verify each lint in a lint group is unique.
// We verify each lint is the name of one of the lints unless `--allow-undefined-lints` was passed.
// We verify when there is multiple lints, each lint is separated with a single comma and space.
/// Error from parsing.
#[cfg_attr(test, derive(Debug, PartialEq))]
pub(crate) enum E<'a> {
    /// Output doesn't start as expected.
    Start,
    /// The contained line is not the format of a lint.
    UnexpectedLintLine(&'a [u8]),
    /// The contained lint appeared more than once.
    DuplicateLint(&'a [u8]),
    /// There wasn't a `warn`-by-default lint called `"warnings"`.
    MissingWarningLint,
    /// There were no `allow`-by-default lints.
    NoAllowLints,
    /// There were no `warn`-by-default lints except for `"warnings"`.
    NoWarnLints,
    /// There were no `deny`-by-default lints.
    NoDenyLints,
    /// Output doesn't contain what it should between the lints and lint groups.
    Middle,
    /// The contained line is not the format of a lint group.
    UnexpectedLintGroupLine(&'a [u8]),
    /// The contained lint group name appeared more than once.
    DuplicateLintGroup(&'a [u8]),
    /// The contained lint group name is the same as the name of a lint.
    LintSameNameAsLintGroup(&'a [u8]),
    /// The contained lint group name contained a lint more than once.
    LintGroupContainsDuplicateLint(&'a [u8], &'a [u8]),
    /// The contained lint group name contained an unknown lint.
    LintGroupContainsUnknownLint(&'a [u8], &'a [u8]),
    /// The contained lint group name has no lints.
    EmptyLintGroup(&'a [u8]),
    /// There were no lint groups.
    NoLintGroups,
    /// Output doesn't end as expected.
    End,
}
/// Lines before lints.
const START: &str = "name  default  meaning
----  -------  -------";
/// Lines between lints and lint groups.
const MIDDLE: &str = "name  sub-lints
----  ---------";
impl E<'_> {
    /// Writes `self` into `stderr`.
    pub(crate) fn into_exit_code(self) -> ExitCode {
        let mut stderr = io::stderr().lock();
        match self {
            Self::Start => writeln!(stderr, "rustc -Whelp doesn't contain '{START}' ignoring leading spaces"),
            Self::UnexpectedLintLine(line) => writeln!(
                stderr,
                "rustc -Whelp contained the following line that is not the expected format of a lint: {}.",
                String::from_utf8_lossy(line),
            ),
            Self::DuplicateLint(lint) => writeln!(
                stderr,
                "rustc -Whelp contained the lint '{}' more than once.",
                super::as_str(lint)
            ),
            Self::MissingWarningLint => writeln!(
                stderr,
                "rustc -Whelp didn't contain a warn-by-default lint called 'warnings'."
            ),
            Self::NoAllowLints => writeln!(
                stderr,
                "rustc -Whelp didn't contain any allow-by-default lints."
            ),
            Self::NoWarnLints => writeln!(
                stderr,
                "rustc -Whelp didn't contain any warn-by-default lints except for 'warnings'."
            ),
            Self::NoDenyLints => writeln!(
                stderr,
                "rustc -Whelp didn't contain any deny-by-default lints."
            ),
            Self::Middle => writeln!(
                stderr,
                "rustc -Whelp doesn't contain '{MIDDLE}' ignoring leading spaces after the lints."
            ),
            Self::UnexpectedLintGroupLine(line) => writeln!(
                stderr,
                "rustc -Whelp contained the following line that is not the expected format of a lint group: {}.",
                String::from_utf8_lossy(line),
            ),
            Self::DuplicateLintGroup(group) => {
                writeln!(
                    stderr,
                    "rustc -Whelp contained multiple lint groups called '{}'.",
                    super::as_str(group)
                )
            }
            Self::LintSameNameAsLintGroup(group) => {
                writeln!(
                    stderr,
                    "rustc -Whelp contained a lint and lint group both named '{}'.",
                    super::as_str(group)
                )
            }
            Self::LintGroupContainsDuplicateLint(group, lint) => writeln!(
                stderr,
                "rustc -Whelp contained the lint group '{}' which has the lint '{}' more than once.",
                super::as_str(group),
                super::as_str(lint),
            ),
            Self::LintGroupContainsUnknownLint(group, lint) => writeln!(
                stderr,
                "rustc -Whelp contained the lint group '{}' which has the unknown lint '{}'.",
                super::as_str(group),
                super::as_str(lint),
            ),
            Self::EmptyLintGroup(group) => {
                writeln!(
                    stderr,
                    "rustc -Whelp contained the empty lint group '{}'.",
                    super::as_str(group),
                )
            }
            Self::NoLintGroups => writeln!(
                stderr,
                "rustc -Whelp didn't contain any lint groups."
            ),
            Self::End => writeln!(stderr, "rustc -Whelp did not have at least one empty line after the lint groups."),
        }.map_or(ExitCode::FAILURE, |()| ExitCode::FAILURE)
    }
}
/// Moves `line` to start at the first non-space.
#[expect(
    clippy::arithmetic_side_effects,
    clippy::indexing_slicing,
    reason = "comments justifies correctness"
)]
fn skip_leading_space(line: &mut &[u8]) {
    // The `usize` contained in the `Result` is at most `line.len()`, we indexing is fine.
    *line = &line[line
        .iter()
        .try_fold(0, |idx, b| {
            if *b == b' ' {
                // `idx < line.len()`, so overflow is not possible.
                Ok(idx + 1)
            } else {
                Err(idx)
            }
        })
        .map_or_else(convert::identity, convert::identity)..];
}
/// [`Iterator`] of lines.
///
/// In the event a `b'\n'` doesn't exist, `None` will be returned. This means in the event the last
/// "line" does not end with `b'\n'`, it won't be returned.
struct Lines<'a>(&'a [u8]);
impl<'a> Iterator for Lines<'a> {
    type Item = &'a [u8];
    #[expect(
        clippy::arithmetic_side_effects,
        clippy::indexing_slicing,
        reason = "comments justify correctness"
    )]
    fn next(&mut self) -> Option<Self::Item> {
        self.0
            .iter()
            .try_fold(0, |idx, b| {
                if *b == b'\n' {
                    Err(idx)
                } else {
                    // `idx < self.0.len()`, so overflow is not possible.
                    Ok(idx + 1)
                }
            })
            .map_or_else(
                |idx| {
                    // `idx <= self.0.len()`, so this won't `panic`.
                    let (val, rem) = self.0.split_at(idx);
                    // `rem` starts with a newline, so this won't `panic`.
                    self.0 = &rem[1..];
                    Some(val)
                },
                |_| None,
            )
    }
}
/// Extracts the lint or lint group name from `line`.
///
/// Returns `Some` iff a valid lint or lint group name is found ignoring leading spaces and
/// if there is non-spaces after. The first `slice` is the name and the second slice is
/// the remaining portion of `line` with leading spaces removed.
#[expect(
    clippy::arithmetic_side_effects,
    reason = "comment justifies correctness"
)]
fn get_lint_name(mut line: &[u8]) -> Option<(&[u8], &[u8])> {
    skip_leading_space(&mut line);
    line.iter()
        .try_fold(0, |idx, b| {
            if *b == b' ' {
                Err(Some(idx))
            } else if *b == b'-' || b.is_ascii_alphanumeric() {
                // `idx < line.len()`, so overflow is not possible.
                Ok(idx + 1)
            } else {
                Err(None)
            }
        })
        .map_or_else(
            |opt| {
                opt.and_then(|idx| {
                    let (name, mut rem) = line.split_at(idx);
                    let len = rem.len();
                    skip_leading_space(&mut rem);
                    if len == rem.len() {
                        None
                    } else {
                        Some((name, rem))
                    }
                })
            },
            |_| None,
        )
}
/// The lints.
///
/// All `HashSet`s are non-empty with no overlap. `warn` doesn't contain `"warnings"`.
struct Lints<'a> {
    /// `allow`-by-default lints.
    allow: HashSet<&'a [u8]>,
    /// `warn`-by-default lints.
    warn: HashSet<&'a [u8]>,
    /// `deny`-by-default lints.
    deny: HashSet<&'a [u8]>,
}
/// `"warnings"`.
pub(crate) const WARNINGS: &str = "warnings";
impl<'a> Lints<'a> {
    /// Gets the lints from `lines` erring when there are duplicates, there is no `warn`-by-default
    /// lint called `"warnings"`, or the lints are empty (ignoring the `"warnings"` lint).
    #[expect(
        clippy::arithmetic_side_effects,
        clippy::indexing_slicing,
        reason = "comments justify correctness"
    )]
    fn new(lines: &mut Lines<'a>) -> Result<Self, E<'a>> {
        /// Get the lint from `line`.
        ///
        /// Returns `Some` iff a valid lint name is found after removing leading spaces.
        /// The first `slice` is the name, and the second `slice` is the next "word".
        fn get_lint(line: &[u8]) -> Option<(&[u8], &[u8])> {
            get_lint_name(line).and_then(|(lint, rem)| {
                rem.iter()
                    // `idx < rem.len()`, so overflow is not possible.
                    .try_fold(0, |idx, b| if *b == b' ' { Err(idx) } else { Ok(idx + 1) })
                    // `idx <= rem.len()`, so this won't `panic`.
                    .map_or_else(|idx| Some((lint, &rem[..idx])), |_| None)
            })
        }
        let mut allow = HashSet::with_capacity(128);
        let mut warn = HashSet::with_capacity(128);
        let mut deny = HashSet::with_capacity(128);
        lines
            .try_fold((), |(), line| {
                if line.is_empty() {
                    Err(None)
                } else {
                    get_lint(line)
                        .ok_or(Some(E::UnexpectedLintLine(line)))
                        .and_then(|(lint, status)| match status {
                            b"allow" => {
                                if !allow.insert(lint) || warn.contains(lint) || deny.contains(lint)
                                {
                                    Err(Some(E::DuplicateLint(lint)))
                                } else {
                                    Ok(())
                                }
                            }
                            b"warn" => {
                                if !warn.insert(lint) || allow.contains(lint) || deny.contains(lint)
                                {
                                    Err(Some(E::DuplicateLint(lint)))
                                } else {
                                    Ok(())
                                }
                            }
                            b"deny" => {
                                if !deny.insert(lint) || allow.contains(lint) || warn.contains(lint)
                                {
                                    Err(Some(E::DuplicateLint(lint)))
                                } else {
                                    Ok(())
                                }
                            }
                            _ => Err(Some(E::UnexpectedLintLine(line))),
                        })
                }
            })
            .map_or_else(
                |opt| {
                    opt.map_or_else(
                        || {
                            if warn.remove(WARNINGS.as_bytes()) {
                                if allow.is_empty() {
                                    Err(E::NoAllowLints)
                                } else if warn.is_empty() {
                                    Err(E::NoWarnLints)
                                } else if deny.is_empty() {
                                    Err(E::NoDenyLints)
                                } else {
                                    Ok(Self { allow, warn, deny })
                                }
                            } else {
                                Err(E::MissingWarningLint)
                            }
                        },
                        Err,
                    )
                },
                |()| Err(E::Middle),
            )
    }
}
/// [`Iterator`] of values separated by commas and spaces.
///
/// In the event a value comes after a comma, a single leading space is assumed to exist and will be removed.
struct Csv<'a>(&'a [u8]);
impl<'a> Iterator for Csv<'a> {
    type Item = Result<&'a [u8], ()>;
    #[expect(
        clippy::arithmetic_side_effects,
        reason = "comments justify correctness"
    )]
    fn next(&mut self) -> Option<Self::Item> {
        /// `b", "`.
        const COMMA_SPACE: &[u8; 2] = b", ";
        (!self.0.is_empty()).then(|| {
            match self.0.iter().try_fold(0, |idx, b| {
                if *b == b',' {
                    Err(idx)
                } else {
                    // `idx < self.0.len()`, so overflow is not possible.
                    Ok(idx + 1)
                }
            }) {
                Ok(_) => {
                    let val = self.0;
                    self.0 = &[];
                    Ok(val)
                }
                Err(idx) => {
                    // `idx <= self.0.len()`, so this won't `panic`.
                    let (val, rem) = self.0.split_at(idx);
                    rem.split_at_checked(COMMA_SPACE.len())
                        .ok_or(())
                        .and_then(|(fst, fst_rem)| {
                            if fst == COMMA_SPACE {
                                self.0 = fst_rem;
                                Ok(val)
                            } else {
                                Err(())
                            }
                        })
                }
            }
        })
    }
}
/// Group of lints.
pub(crate) struct LintGroup<'a> {
    /// Name of the group.
    pub name: &'a [u8],
    /// Lints that make up the group.
    pub lints: HashSet<&'a [u8]>,
}
impl Eq for LintGroup<'_> {}
impl PartialEq for LintGroup<'_> {
    fn eq(&self, other: &Self) -> bool {
        self.name == other.name
    }
}
impl Hash for LintGroup<'_> {
    fn hash<H: Hasher>(&self, state: &mut H) {
        self.name.hash(state);
    }
}
impl PartialOrd for LintGroup<'_> {
    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
        Some(self.cmp(other))
    }
}
impl Ord for LintGroup<'_> {
    fn cmp(&self, other: &Self) -> Ordering {
        self.name.cmp(other.name)
    }
}
/// Data from `rustc -Whelp`.
pub(crate) struct Data<'a> {
    /// `allow`-by-default lints.
    pub allow: Vec<&'a [u8]>,
    /// `warn`-by-default lints.
    pub warn: Vec<&'a [u8]>,
    /// `deny`-by-default lints.
    pub deny: Vec<&'a [u8]>,
    /// Lint groups.
    pub groups: Vec<LintGroup<'a>>,
}
impl<'a> Data<'a> {
    /// Moves until the lints.
    ///
    /// Returns `true` iff the header was found.
    fn move_to_lints(lines: &mut Lines<'_>) -> bool {
        lines
            .try_fold((), |(), mut line| {
                skip_leading_space(&mut line);
                if line == b"name  default  meaning" {
                    Err(())
                } else {
                    Ok(())
                }
            })
            .map_or_else(
                |()| {
                    lines.next().is_some_and(|mut line| {
                        skip_leading_space(&mut line);
                        line == b"----  -------  -------"
                    })
                },
                |()| false,
            )
    }
    /// Moves until the lint groups.
    ///
    /// Returns `true` iff the header was found.
    fn move_to_lint_groups(lines: &mut Lines<'_>) -> bool {
        lines
            .try_fold((), |(), mut line| {
                skip_leading_space(&mut line);
                if line == b"name  sub-lints" {
                    Err(())
                } else {
                    Ok(())
                }
            })
            .map_or_else(
                |()| {
                    lines.next().is_some_and(|mut line| {
                        skip_leading_space(&mut line);
                        line == b"----  ---------"
                    })
                },
                |()| false,
            )
    }
    /// Gets the lint groups from `lines` erring when there are duplicate lint group names or if a lint group
    /// name is the name of a lint (with the exception of `"warnings"`), or if a group contains duplicate lints.
    /// In the event `allow_undefined_lints` is `false`, every lint in a lint group must exist in `single_lints`.
    fn get_lint_groups(
        output: &mut Lines<'a>,
        single_lints: &Lints<'_>,
        allow_undefined_lints: bool,
    ) -> Result<HashSet<LintGroup<'a>>, E<'a>> {
        let mut groups = HashSet::with_capacity(16);
        output
            .try_fold((), |(), line| {
                if line.is_empty() {
                    Err(None)
                } else {
                    get_lint_name(line)
                        .ok_or(Some(E::UnexpectedLintGroupLine(line)))
                        .and_then(|(name, group_lints)| {
                            if name == WARNINGS.as_bytes() {
                                Ok(())
                            } else if single_lints.allow.contains(name)
                                || single_lints.warn.contains(name)
                                || single_lints.deny.contains(name)
                            {
                                Err(Some(E::LintSameNameAsLintGroup(name)))
                            } else {
                                let mut lints = HashSet::with_capacity(32);
                                Csv(group_lints)
                                    .try_fold((), |(), res| {
                                        res.map_err(|()| Some(E::UnexpectedLintGroupLine(line)))
                                            .and_then(|lint| {
                                                if allow_undefined_lints
                                                    || single_lints.allow.contains(lint)
                                                    || single_lints.warn.contains(lint)
                                                    || single_lints.deny.contains(lint)
                                                {
                                                    if lints.insert(lint) {
                                                        Ok(())
                                                    } else {
                                                        Err(Some(
                                                            E::LintGroupContainsDuplicateLint(
                                                                name, lint,
                                                            ),
                                                        ))
                                                    }
                                                } else {
                                                    Err(Some(E::LintGroupContainsUnknownLint(
                                                        name, lint,
                                                    )))
                                                }
                                            })
                                    })
                                    .and_then(|()| {
                                        if lints.is_empty() {
                                            Err(Some(E::EmptyLintGroup(name)))
                                        } else if groups.insert(LintGroup { name, lints }) {
                                            Ok(())
                                        } else {
                                            Err(Some(E::DuplicateLintGroup(name)))
                                        }
                                    })
                            }
                        })
                }
            })
            .map_or_else(
                |opt| {
                    opt.map_or_else(
                        || {
                            if groups.is_empty() {
                                Err(E::NoLintGroups)
                            } else {
                                Ok(groups)
                            }
                        },
                        Err,
                    )
                },
                |()| Err(E::End),
            )
    }
    /// Parses output and returns lints and lint groups.
    pub(crate) fn new(output: &'a [u8], allow_undefined_lints: bool) -> Result<Self, E<'a>> {
        let mut lines = Lines(output);
        if Self::move_to_lints(&mut lines) {
            Lints::new(&mut lines).and_then(|lints| {
                if Self::move_to_lint_groups(&mut lines) {
                    Self::get_lint_groups(&mut lines, &lints, allow_undefined_lints).map(
                        |group_set| {
                            let mut allow = Vec::with_capacity(lints.allow.len());
                            lints.allow.into_iter().fold((), |(), lint| {
                                allow.push(lint);
                            });
                            allow.sort_unstable();
                            let mut warn = Vec::with_capacity(lints.warn.len());
                            lints.warn.into_iter().fold((), |(), lint| {
                                warn.push(lint);
                            });
                            warn.sort_unstable();
                            let mut deny = Vec::with_capacity(lints.deny.len());
                            lints.deny.into_iter().fold((), |(), lint| {
                                deny.push(lint);
                            });
                            deny.sort_unstable();
                            let mut groups = Vec::with_capacity(group_set.len());
                            group_set.into_iter().fold((), |(), group| {
                                groups.push(group);
                            });
                            groups.sort_unstable();
                            Self {
                                allow,
                                warn,
                                deny,
                                groups,
                            }
                        },
                    )
                } else {
                    Err(E::Middle)
                }
            })
        } else {
            Err(E::Start)
        }
    }
}
#[cfg(all(test, not(target_pointer_width = "16")))]
mod tests {
    use super::{Data, E, io::Read as _};
    use std::fs::{self, File};
    #[expect(
        clippy::assertions_on_constants,
        reason = "want to pretty-print problematic file"
    )]
    #[expect(clippy::verbose_file_reads, reason = "want to lock file")]
    #[expect(clippy::tests_outside_test_module, reason = "false positive")]
    #[test]
    fn outputs() {
        let mut output = Vec::with_capacity(u16::MAX.into());
        assert!(
            fs::read_dir("./outputs/").is_ok_and(|mut dir| {
                dir.try_fold((), |(), ent_res| {
                    if ent_res.is_ok_and(|ent| {
                        File::options()
                            .read(true)
                            .open(ent.path())
                            .is_ok_and(|mut file| {
                                file.lock_shared().is_ok_and(|()| {
                                    output.clear();
                                    file.read_to_end(&mut output).is_ok_and(|_| {
                                        // Release lock.
                                        drop(file);
                                        let file_name = ent.file_name();
                                        let file_name_bytes = file_name.as_encoded_bytes();
                                        Data::new(&output, false).map_or_else(
                                            |e| match file_name_bytes {
                                                b"1.34.0.txt" | b"1.34.1.txt" | b"1.34.2.txt" => {
                                                    assert_eq!(
                                                        e,
                                                        E::LintGroupContainsUnknownLint(
                                                            b"future-incompatible",
                                                            b"duplicate-matcher-binding-name"
                                                        ),
                                                        "1.34.0.txt, 1.34.1.txt, and 1.34.2.txt can't be parsed for a reason other than the expected reason"
                                                    );
                                                    Data::new(&output, true).is_ok()
                                                }
                                                b"1.48.0.txt" => {
                                                    assert_eq!(
                                                        e,
                                                        E::LintGroupContainsUnknownLint(
                                                            b"rustdoc",
                                                            b"private-intra-doc-links"
                                                        ),
                                                        "1.48.0.txt can't be parsed for a reason other than the expected reason"
                                                    );
                                                    Data::new(&output, true).is_ok()
                                                }
                                                _ => {
                                                    assert!(
                                                        false,
                                                        "{} cannot be parsed due to {e:?}.",
                                                        String::from_utf8_lossy(file_name_bytes),
                                                    );
                                                    false
                                                }
                                            },
                                            |_| {
                                                if matches!(file_name_bytes, b"1.34.0.txt" | b"1.34.1.txt" | b"1.34.2.txt" | b"1.48.0.txt") {
                                                    assert!(false, "{} shouldn't be parsable", String::from_utf8_lossy(file_name_bytes));
                                                    false
                                                } else {
                                                    true
                                                }
                                            },
                                        )
                                    })
                                })
                            })
                    }) {
                        Ok(())
                    } else {
                        Err(())
                    }
                })
                .is_ok()
            })
        );
    }
}