use std::fmt::{Display, Formatter};
use std::{borrow::Cow, path::Path, sync::Arc};

use ruff_diagnostics::{Applicability, Fix};
use ruff_source_file::{LineColumn, SourceCode, SourceFile};

use annotate_snippets::Level as AnnotateLevel;
use ruff_text_size::{Ranged, TextRange, TextSize};
#[cfg(feature = "serde")]
use serde::Serialize;

pub use self::render::{
    DisplayDiagnostic, DisplayDiagnostics, DummyFileResolver, FileResolver, Input,
};
use crate::cancellation::CancellationToken;
use crate::{Db, files::File};

mod render;
mod stylesheet;

/// A collection of information that can be rendered into a diagnostic.
///
/// A diagnostic is a collection of information gathered by a tool intended
/// for presentation to an end user, and which describes a group of related
/// characteristics in the inputs given to the tool. Typically, but not always,
/// a characteristic is a deficiency. An example of a characteristic that is
/// _not_ a deficiency is the `reveal_type` diagnostic for our type checker.
#[derive(Debug, Clone, Eq, PartialEq, Hash, get_size2::GetSize)]
pub struct Diagnostic {
    /// The actual diagnostic.
    ///
    /// We box the diagnostic since it is somewhat big.
    inner: Arc<DiagnosticInner>,
}

impl Diagnostic {
    /// Create a new diagnostic with the given identifier, severity and
    /// message.
    ///
    /// The identifier should be something that uniquely identifies the _type_
    /// of diagnostic being reported. It should be usable as a reference point
    /// for humans communicating about diagnostic categories. It will also
    /// appear in the output when this diagnostic is rendered.
    ///
    /// The severity should describe the assumed level of importance to an end
    /// user.
    ///
    /// The message is meant to be read by end users. The primary message
    /// is meant to be a single terse description (usually a short phrase)
    /// describing the group of related characteristics that the diagnostic
    /// describes. Stated differently, if only one thing from a diagnostic can
    /// be shown to an end user in a particular context, it is the primary
    /// message.
    ///
    /// # Types implementing `IntoDiagnosticMessage`
    ///
    /// Callers can pass anything that implements `std::fmt::Display`
    /// directly. If callers want or need to avoid cloning the diagnostic
    /// message, then they can also pass a `DiagnosticMessage` directly.
    pub fn new<'a>(
        id: DiagnosticId,
        severity: Severity,
        message: impl IntoDiagnosticMessage + 'a,
    ) -> Diagnostic {
        let inner = Arc::new(DiagnosticInner {
            id,
            severity,
            message: message.into_diagnostic_message(),
            custom_concise_message: None,
            documentation_url: None,
            annotations: vec![],
            subs: vec![],
            fix: None,
            parent: None,
            noqa_offset: None,
            secondary_code: None,
            header_offset: 0,
        });
        Diagnostic { inner }
    }

    /// Creates a `Diagnostic` for a syntax error.
    ///
    /// Unlike the more general [`Diagnostic::new`], this requires a [`Span`] and a [`TextRange`]
    /// attached to it.
    ///
    /// This should _probably_ be a method on the syntax errors, but
    /// at time of writing, `ruff_db` depends on `ruff_python_parser` instead of
    /// the other way around. And since we want to do this conversion in a couple
    /// places, it makes sense to centralize it _somewhere_. So it's here for now.
    pub fn invalid_syntax(
        span: impl Into<Span>,
        message: impl IntoDiagnosticMessage,
        range: impl Ranged,
    ) -> Diagnostic {
        let mut diag = Diagnostic::new(DiagnosticId::InvalidSyntax, Severity::Error, message);
        let span = span.into().with_range(range.range());
        diag.annotate(Annotation::primary(span));
        diag
    }

    /// Adds sub diagnostics that tell the user that this is a bug in ty
    /// and asks them to open an issue on GitHub.
    pub fn add_bug_sub_diagnostics(&mut self, url_encoded_title: &str) {
        self.sub(SubDiagnostic::new(
            SubDiagnosticSeverity::Info,
            "This indicates a bug in ty.",
        ));

        self.sub(SubDiagnostic::new(
            SubDiagnosticSeverity::Info,
            format_args!(
                "If you could open an issue at https://github.com/astral-sh/ty/issues/new?title={url_encoded_title}, we'd be very appreciative!"
            ),
        ));
        self.sub(SubDiagnostic::new(
            SubDiagnosticSeverity::Info,
            format!(
                "Platform: {os} {arch}",
                os = std::env::consts::OS,
                arch = std::env::consts::ARCH
            ),
        ));
        if let Some(version) = crate::program_version() {
            self.sub(SubDiagnostic::new(
                SubDiagnosticSeverity::Info,
                format!("Version: {version}"),
            ));
        }

        self.sub(SubDiagnostic::new(
            SubDiagnosticSeverity::Info,
            format!(
                "Args: {args:?}",
                args = std::env::args().collect::<Vec<_>>()
            ),
        ));
    }

    /// Add an annotation to this diagnostic.
    ///
    /// Annotations for a diagnostic are optional, but if any are added,
    /// callers should strive to make at least one of them primary. That is, it
    /// should be constructed via [`Annotation::primary`]. A diagnostic with no
    /// primary annotations is allowed, but its rendering may be sub-optimal.
    pub fn annotate(&mut self, ann: Annotation) {
        Arc::make_mut(&mut self.inner).annotations.push(ann);
    }

    /// Adds an "info" sub-diagnostic with the given message.
    ///
    /// If callers want to add an "info" sub-diagnostic with annotations, then
    /// create a [`SubDiagnostic`] manually and use [`Diagnostic::sub`] to
    /// attach it to a parent diagnostic.
    ///
    /// An "info" diagnostic is useful when contextualizing or otherwise
    /// helpful information can be added to help end users understand the
    /// headline message better. For example, if the headline message is about
    /// a function call being invalid, a useful "info"
    /// sub-diagnostic could show the function definition (or only the relevant
    /// parts of it).
    ///
    /// # Types implementing `IntoDiagnosticMessage`
    ///
    /// Callers can pass anything that implements `std::fmt::Display`
    /// directly. If callers want or need to avoid cloning the diagnostic
    /// message, then they can also pass a `DiagnosticMessage` directly.
    pub fn info<'a>(&mut self, message: impl IntoDiagnosticMessage + 'a) {
        self.sub(SubDiagnostic::new(SubDiagnosticSeverity::Info, message));
    }

    /// Adds an "info" sub-diagnostic before any existing sub-diagnostics.
    pub fn prepend_info<'a>(&mut self, message: impl IntoDiagnosticMessage + 'a) {
        Arc::make_mut(&mut self.inner)
            .subs
            .insert(0, SubDiagnostic::new(SubDiagnosticSeverity::Info, message));
    }

    /// Adds a "help" sub-diagnostic with the given message.
    ///
    /// See the closely related [`Diagnostic::info`] method for more details.
    pub fn help<'a>(&mut self, message: impl IntoDiagnosticMessage + 'a) {
        self.sub(SubDiagnostic::new(SubDiagnosticSeverity::Help, message));
    }

    /// Adds a "sub" diagnostic to this diagnostic.
    ///
    /// This is useful when a sub diagnostic has its own annotations attached
    /// to it. For the simpler case of a sub-diagnostic with only a message,
    /// using a method like [`Diagnostic::info`] may be more convenient.
    pub fn sub(&mut self, sub: SubDiagnostic) {
        Arc::make_mut(&mut self.inner).subs.push(sub);
    }

    /// Return a `std::fmt::Display` implementation that renders this
    /// diagnostic into a human readable format.
    ///
    /// Note that this `Display` impl includes a trailing line terminator, so
    /// callers should prefer using this with `write!` instead of `writeln!`.
    pub fn display<'a>(
        &'a self,
        resolver: &'a dyn FileResolver,
        config: &'a DisplayDiagnosticConfig,
    ) -> DisplayDiagnostic<'a> {
        DisplayDiagnostic::new(resolver, config, self)
    }

    /// Returns the identifier for this diagnostic.
    pub fn id(&self) -> DiagnosticId {
        self.inner.id
    }

    /// Returns the headline message for this diagnostic.
    ///
    /// A diagnostic always has a message, but it may be empty.
    pub fn headline_message(&self) -> &str {
        self.inner.message.as_str()
    }

    /// Sets the headline message for this diagnostic.
    pub fn set_headline_message(&mut self, message: impl IntoDiagnosticMessage) {
        Arc::make_mut(&mut self.inner).message = message.into_diagnostic_message();
    }

    /// Introspects this diagnostic and returns its message for concise formatting.
    ///
    /// When we concisely format diagnostics, we likely want to not only
    /// include the headline message but also the message attached
    /// to the primary annotation. In particular, the primary annotation often
    /// contains *essential* information or context for understanding the
    /// diagnostic.
    ///
    /// The type returned implements the `std::fmt::Display` trait. In most
    /// cases, just converting it to a string (or printing it) will do what
    /// you want.
    pub fn concise_message(&self) -> ConciseMessage<'_> {
        if let Some(custom_message) = &self.inner.custom_concise_message {
            return ConciseMessage::Custom(custom_message.as_str());
        }

        let main = self.inner.message.as_str();
        let annotation = self
            .primary_annotation()
            .and_then(|ann| ann.get_message())
            .unwrap_or_default();
        if annotation.is_empty() {
            ConciseMessage::MainDiagnostic(main)
        } else {
            ConciseMessage::Both { main, annotation }
        }
    }

    /// Set a custom message for the concise formatting of this diagnostic.
    ///
    /// This overrides the default behavior of generating a concise message
    /// from the headline message and the primary annotation.
    pub fn set_concise_message(&mut self, message: impl IntoDiagnosticMessage) {
        Arc::make_mut(&mut self.inner).custom_concise_message =
            Some(message.into_diagnostic_message());
    }

    /// Remove the custom concise message, restoring the default behavior of generating a concise
    /// message from the headline message and the primary annotation.
    pub fn clear_concise_message(&mut self) {
        Arc::make_mut(&mut self.inner).custom_concise_message = None;
    }

    /// Returns the severity of this diagnostic.
    ///
    /// Note that this may be different than the severity of sub-diagnostics.
    pub fn severity(&self) -> Severity {
        self.inner.severity
    }

    /// Returns a shared borrow of the "primary" annotation of this diagnostic
    /// if one exists.
    ///
    /// When there are multiple primary annotations, then the first one that
    /// was added to this diagnostic is returned.
    pub fn primary_annotation(&self) -> Option<&Annotation> {
        self.inner.annotations.iter().find(|ann| ann.is_primary)
    }

    /// Returns a mutable borrow of the "primary" annotation of this diagnostic
    /// if one exists.
    ///
    /// When there are multiple primary annotations, then the first one that
    /// was added to this diagnostic is returned.
    pub fn primary_annotation_mut(&mut self) -> Option<&mut Annotation> {
        Arc::make_mut(&mut self.inner)
            .annotations
            .iter_mut()
            .find(|ann| ann.is_primary)
    }

    /// Returns all annotations in the order in which they were added.
    pub fn annotations(&self) -> &[Annotation] {
        &self.inner.annotations
    }

    /// Returns a mutable borrow of all annotations of this diagnostic.
    pub fn annotations_mut(&mut self) -> impl Iterator<Item = &mut Annotation> {
        Arc::make_mut(&mut self.inner).annotations.iter_mut()
    }

    /// Returns the "primary" span of this diagnostic if one exists.
    ///
    /// When there are multiple primary spans, then the first one that was
    /// added to this diagnostic is returned.
    pub fn primary_span(&self) -> Option<Span> {
        self.primary_annotation().map(|ann| ann.span.clone())
    }

    /// Returns a reference to the primary span of this diagnostic.
    fn primary_span_ref(&self) -> Option<&Span> {
        self.primary_annotation().map(|ann| &ann.span)
    }

    /// Returns the tags from the primary annotation of this diagnostic if it exists.
    pub fn primary_tags(&self) -> Option<&[DiagnosticTag]> {
        self.primary_annotation().map(|ann| ann.tags.as_slice())
    }

    /// Returns the "primary" span of this diagnostic, panicking if it does not exist.
    ///
    /// This should typically only be used when working with diagnostics in Ruff, where diagnostics
    /// are currently required to have a primary span.
    ///
    /// See [`Diagnostic::primary_span`] for more details.
    pub fn expect_primary_span(&self) -> Span {
        self.primary_span().expect("Expected a primary span")
    }

    /// Returns a key that can be used to sort two diagnostics into the canonical order
    /// in which they should appear when rendered.
    pub fn rendering_sort_key<'a>(&'a self, db: &'a dyn Db) -> impl Ord + 'a {
        RenderingSortKey {
            db,
            diagnostic: self,
        }
    }

    /// Returns all annotations, skipping the first primary annotation.
    pub fn secondary_annotations(&self) -> impl Iterator<Item = &Annotation> {
        secondary_annotations(self.inner.annotations.iter())
    }

    pub fn sub_diagnostics(&self) -> &[SubDiagnostic] {
        &self.inner.subs
    }

    /// Returns a mutable borrow of the sub-diagnostics of this diagnostic.
    pub fn sub_diagnostics_mut(&mut self) -> impl Iterator<Item = &mut SubDiagnostic> {
        Arc::make_mut(&mut self.inner).subs.iter_mut()
    }

    /// Returns the fix for this diagnostic if it exists.
    pub fn fix(&self) -> Option<&Fix> {
        self.inner.fix.as_ref()
    }

    #[cfg(test)]
    fn fix_mut(&mut self) -> Option<&mut Fix> {
        Arc::make_mut(&mut self.inner).fix.as_mut()
    }

    /// Set the fix for this diagnostic.
    pub fn set_fix(&mut self, fix: Fix) {
        debug_assert!(
            self.primary_span().is_some(),
            "Expected a source file for a diagnostic with a fix"
        );
        Arc::make_mut(&mut self.inner).fix = Some(fix);
    }

    /// If `fix` is `Some`, set the fix for this diagnostic.
    pub fn set_optional_fix(&mut self, fix: Option<Fix>) {
        if let Some(fix) = fix {
            self.set_fix(fix);
        }
    }

    /// Remove the fix for this diagnostic.
    pub fn remove_fix(&mut self) {
        Arc::make_mut(&mut self.inner).fix = None;
    }

    /// Returns `true` if the diagnostic has a fix that applies at the configured applicability
    /// level.
    pub fn has_applicable_fix(&self, fix_applicability: Applicability) -> bool {
        self.fix().is_some_and(|fix| fix.applies(fix_applicability))
    }

    pub fn documentation_url(&self) -> Option<&str> {
        self.inner.documentation_url.as_deref()
    }

    pub fn set_documentation_url(&mut self, url: Option<String>) {
        Arc::make_mut(&mut self.inner).documentation_url = url;
    }

    /// Returns the offset of the parent statement for this diagnostic if it exists.
    ///
    /// This is primarily used for checking noqa/secondary code suppressions.
    pub fn parent(&self) -> Option<TextSize> {
        self.inner.parent
    }

    /// Set the offset of the diagnostic's parent statement.
    pub fn set_parent(&mut self, parent: TextSize) {
        Arc::make_mut(&mut self.inner).parent = Some(parent);
    }

    /// Returns the remapped offset for a suppression comment if it exists.
    ///
    /// Like [`Diagnostic::parent`], this is used for noqa code suppression comments in Ruff.
    #[cfg(feature = "serde")]
    fn noqa_offset(&self) -> Option<TextSize> {
        self.inner.noqa_offset
    }

    /// Set the remapped offset for a suppression comment.
    pub fn set_noqa_offset(&mut self, noqa_offset: TextSize) {
        Arc::make_mut(&mut self.inner).noqa_offset = Some(noqa_offset);
    }

    /// Returns the secondary code for the diagnostic if it exists.
    ///
    /// The "primary" code for the diagnostic is its lint name. Diagnostics in ty don't have
    /// secondary codes (yet), but in Ruff the noqa code is used.
    pub fn secondary_code(&self) -> Option<&SecondaryCode> {
        self.inner.secondary_code.as_ref()
    }

    /// Returns the secondary code for the diagnostic if it exists, or the lint name otherwise.
    ///
    /// This is a common pattern for Ruff diagnostics, which want to use the noqa code in general,
    /// but fall back on the `invalid-syntax` identifier for syntax errors, which don't have
    /// secondary codes.
    pub fn secondary_code_or_id(&self) -> &str {
        self.secondary_code()
            .map_or_else(|| self.inner.id.as_str(), SecondaryCode::as_str)
    }

    /// Set the secondary code for this diagnostic.
    pub fn set_secondary_code(&mut self, code: SecondaryCode) {
        Arc::make_mut(&mut self.inner).secondary_code = Some(code);
    }

    /// Returns the name used to represent the diagnostic.
    pub fn name(&self) -> &'static str {
        self.id().as_str()
    }

    /// Returns `true` if `self` is a syntax error message.
    pub fn is_invalid_syntax(&self) -> bool {
        self.id().is_invalid_syntax()
    }

    /// Returns the message of the first sub-diagnostic with a `Help` severity.
    ///
    /// Note that this is used as the fix title/suggestion for some of Ruff's output formats, but in
    /// general this is not the guaranteed meaning of such a message.
    pub fn first_help_text(&self) -> Option<&str> {
        self.sub_diagnostics()
            .iter()
            .find(|sub| matches!(sub.inner.severity, SubDiagnosticSeverity::Help))
            .map(|sub| sub.inner.message.as_str())
    }

    /// Returns the filename for the message.
    ///
    /// Panics if the diagnostic has no primary span, or if its file is not a `SourceFile`.
    pub fn expect_ruff_filename(&self) -> String {
        self.expect_primary_span()
            .expect_ruff_file()
            .name()
            .to_string()
    }

    /// Computes the start source location for the message.
    ///
    /// Returns None if the diagnostic has no primary span, if its file is not a `SourceFile`,
    /// or if the span has no range.
    pub fn ruff_start_location(&self) -> Option<LineColumn> {
        Some(
            self.ruff_source_file()?
                .to_source_code()
                .line_column(self.range()?.start()),
        )
    }

    /// Computes the end source location for the message.
    ///
    /// Returns None if the diagnostic has no primary span, if its file is not a `SourceFile`,
    /// or if the span has no range.
    pub fn ruff_end_location(&self) -> Option<LineColumn> {
        Some(
            self.ruff_source_file()?
                .to_source_code()
                .line_column(self.range()?.end()),
        )
    }

    /// Returns the [`SourceFile`] which the message belongs to.
    pub fn ruff_source_file(&self) -> Option<&SourceFile> {
        self.primary_span_ref()?.as_ruff_file()
    }

    /// Returns the [`SourceFile`] which the message belongs to.
    ///
    /// Panics if the diagnostic has no primary span, or if its file is not a `SourceFile`.
    fn expect_ruff_source_file(&self) -> &SourceFile {
        self.ruff_source_file()
            .expect("Expected a ruff source file")
    }

    /// Returns the [`TextRange`] for the diagnostic.
    pub fn range(&self) -> Option<TextRange> {
        self.primary_span()?.range()
    }

    /// Returns the ordering of diagnostics based on the start of their ranges, if they have any.
    ///
    /// Panics if either diagnostic has no primary span, or if its file is not a `SourceFile`.
    pub fn ruff_start_ordering(&self, other: &Self) -> std::cmp::Ordering {
        let a = (
            self.severity().is_fatal(),
            self.expect_ruff_source_file(),
            self.range().map(|r| r.start()),
        );
        let b = (
            other.severity().is_fatal(),
            other.expect_ruff_source_file(),
            other.range().map(|r| r.start()),
        );

        a.cmp(&b)
    }

    /// Add an offset for aligning the header sigil with the line number separators in a diff.
    pub fn set_header_offset(&mut self, offset: usize) {
        Arc::make_mut(&mut self.inner).header_offset = offset;
    }
}

#[derive(Debug, Clone, Eq, PartialEq, Hash, get_size2::GetSize)]
struct DiagnosticInner {
    id: DiagnosticId,
    documentation_url: Option<String>,
    severity: Severity,
    message: DiagnosticMessage,
    custom_concise_message: Option<DiagnosticMessage>,
    annotations: Vec<Annotation>,
    subs: Vec<SubDiagnostic>,
    fix: Option<Fix>,
    parent: Option<TextSize>,
    noqa_offset: Option<TextSize>,
    secondary_code: Option<SecondaryCode>,
    header_offset: usize,
}

struct RenderingSortKey<'a> {
    db: &'a dyn Db,
    diagnostic: &'a Diagnostic,
}

impl Ord for RenderingSortKey<'_> {
    // We sort diagnostics in a way that keeps them in source order
    // and grouped by file. After that, we fall back to severity
    // (with fatal messages sorting before info messages) and then
    // finally the diagnostic ID and concise message.
    fn cmp(&self, other: &Self) -> std::cmp::Ordering {
        if let (Some(span1), Some(span2)) = (
            self.diagnostic.primary_span(),
            other.diagnostic.primary_span(),
        ) {
            let file1 = span1.file();
            let file2 = span2.file();
            if file1 != file2 {
                let order = file1.path(&self.db).cmp(file2.path(&self.db));
                if order.is_ne() {
                    return order;
                }
            }

            if let (Some(range1), Some(range2)) = (span1.range(), span2.range()) {
                let order = range1.start().cmp(&range2.start());
                if order.is_ne() {
                    return order;
                }
            }
        }
        // Reverse so that, e.g., Fatal sorts before Info.
        let order = self
            .diagnostic
            .severity()
            .cmp(&other.diagnostic.severity())
            .reverse();
        if order.is_ne() {
            return order;
        }
        let order = self.diagnostic.id().cmp(&other.diagnostic.id());
        if order.is_ne() {
            return order;
        }

        self.diagnostic
            .concise_message()
            .to_str()
            .cmp(&other.diagnostic.concise_message().to_str())
    }
}

impl PartialOrd for RenderingSortKey<'_> {
    fn partial_cmp(&self, other: &Self) -> Option<std::cmp::Ordering> {
        Some(self.cmp(other))
    }
}

impl PartialEq for RenderingSortKey<'_> {
    fn eq(&self, other: &Self) -> bool {
        self.cmp(other).is_eq()
    }
}

impl Eq for RenderingSortKey<'_> {}

/// A collection of information subservient to a diagnostic.
///
/// A sub-diagnostic is always rendered after the parent diagnostic it is
/// attached to. A parent diagnostic may have many sub-diagnostics, and it is
/// guaranteed that they will not interleave with one another in rendering.
///
/// Currently, the order in which sub-diagnostics are rendered relative to one
/// another (for a single parent diagnostic) is the order in which they were
/// attached to the diagnostic.
#[derive(Debug, Clone, Eq, PartialEq, Hash, get_size2::GetSize)]
pub struct SubDiagnostic {
    /// Like with `Diagnostic`, we box the `SubDiagnostic` to make it
    /// pointer-sized.
    inner: Box<SubDiagnosticInner>,
}

impl SubDiagnostic {
    /// Create a new sub-diagnostic with the given severity and message.
    ///
    /// The severity should describe the assumed level of importance to an end
    /// user.
    ///
    /// The message is meant to be read by end users. The primary message
    /// is meant to be a single terse description (usually a short phrase)
    /// describing the group of related characteristics that the sub-diagnostic
    /// describes. Stated differently, if only one thing from a diagnostic can
    /// be shown to an end user in a particular context, it is the primary
    /// message.
    ///
    /// # Types implementing `IntoDiagnosticMessage`
    ///
    /// Callers can pass anything that implements `std::fmt::Display`
    /// directly. If callers want or need to avoid cloning the diagnostic
    /// message, then they can also pass a `DiagnosticMessage` directly.
    pub fn new<'a>(
        severity: SubDiagnosticSeverity,
        message: impl IntoDiagnosticMessage + 'a,
    ) -> SubDiagnostic {
        let inner = Box::new(SubDiagnosticInner {
            severity,
            message: message.into_diagnostic_message(),
            annotations: vec![],
        });
        SubDiagnostic { inner }
    }

    /// Add an annotation to this sub-diagnostic.
    ///
    /// Annotations for a sub-diagnostic, like for a diagnostic, are optional.
    /// If any are added, callers should strive to make at least one of them
    /// primary. That is, it should be constructed via [`Annotation::primary`].
    /// A diagnostic with no primary annotations is allowed, but its rendering
    /// may be sub-optimal.
    ///
    /// Note that it is expected to be somewhat more common for sub-diagnostics
    /// to have no annotations (e.g., a simple note) than for a diagnostic to
    /// have no annotations.
    pub fn annotate(&mut self, ann: Annotation) {
        self.inner.annotations.push(ann);
    }

    pub fn annotations(&self) -> &[Annotation] {
        &self.inner.annotations
    }

    /// Returns all annotations, skipping the first primary annotation.
    pub fn secondary_annotations(&self) -> impl Iterator<Item = &Annotation> {
        secondary_annotations(self.inner.annotations.iter())
    }

    /// Returns a mutable borrow of the annotations of this sub-diagnostic.
    pub fn annotations_mut(&mut self) -> impl Iterator<Item = &mut Annotation> {
        self.inner.annotations.iter_mut()
    }

    /// Returns a shared borrow of the "primary" annotation of this diagnostic
    /// if one exists.
    ///
    /// When there are multiple primary annotations, then the first one that
    /// was added to this diagnostic is returned.
    pub fn primary_annotation(&self) -> Option<&Annotation> {
        self.inner.annotations.iter().find(|ann| ann.is_primary)
    }

    /// Returns a reference to the primary span of this sub-diagnostic.
    pub fn primary_span_ref(&self) -> Option<&Span> {
        self.primary_annotation().map(Annotation::get_span)
    }

    /// Returns the headline message for this sub-diagnostic.
    ///
    /// A sub-diagnostic always has a message, but it may be empty.
    pub fn headline_message(&self) -> &str {
        self.inner.message.as_str()
    }

    /// Introspects this sub-diagnostic and returns its message for concise formatting.
    ///
    /// When we concisely format diagnostics, we likely want to not only
    /// include the headline message but also the message attached
    /// to the primary annotation. In particular, the primary annotation often
    /// contains *essential* information or context for understanding the
    /// diagnostic.
    ///
    /// The type returned implements the `std::fmt::Display` trait. In most
    /// cases, just converting it to a string (or printing it) will do what
    /// you want.
    pub fn concise_message(&self) -> ConciseMessage<'_> {
        let main = self.headline_message();
        let annotation = self
            .primary_annotation()
            .and_then(|ann| ann.get_message())
            .unwrap_or_default();
        if annotation.is_empty() {
            ConciseMessage::MainDiagnostic(main)
        } else {
            ConciseMessage::Both { main, annotation }
        }
    }

    pub fn severity(&self) -> SubDiagnosticSeverity {
        self.inner.severity
    }
}

#[derive(Debug, Clone, Eq, PartialEq, Hash, get_size2::GetSize)]
struct SubDiagnosticInner {
    severity: SubDiagnosticSeverity,
    message: DiagnosticMessage,
    annotations: Vec<Annotation>,
}

/// Returns all annotations, skipping the first primary annotation.
fn secondary_annotations<'a>(
    annotations: impl Iterator<Item = &'a Annotation>,
) -> impl Iterator<Item = &'a Annotation> {
    let mut seen_primary = false;
    annotations.filter(move |ann| {
        if seen_primary {
            true
        } else if ann.is_primary {
            seen_primary = true;
            false
        } else {
            true
        }
    })
}

/// A pointer to a subsequence in the end user's input.
///
/// Also known as an annotation, the pointer can optionally contain a short
/// message, typically describing in general terms what is being pointed to.
///
/// An annotation is either primary or secondary, depending on whether it was
/// constructed via [`Annotation::primary`] or [`Annotation::secondary`].
/// Semantically, a primary annotation is meant to point to the "locus" of a
/// diagnostic. Visually, the difference between a primary and a secondary
/// annotation is usually just a different form of highlighting on the
/// corresponding span.
///
/// # Advice
///
/// The span on an annotation should be as _specific_ as possible. For example,
/// if there is a problem with a function call because one of its arguments has
/// an invalid type, then the span should point to the specific argument and
/// not to the entire function call.
///
/// Messages attached to annotations should also be as brief and specific as
/// possible. Long messages could negative impact the quality of rendering.
#[derive(Debug, Clone, Eq, PartialEq, Hash, get_size2::GetSize)]
pub struct Annotation {
    /// The span of this annotation, corresponding to some subsequence of the
    /// user's input that we want to highlight.
    span: Span,
    /// An optional message associated with this annotation's span.
    ///
    /// When present, rendering will include this message in the output and
    /// draw a line between the highlighted span and the message.
    message: Option<DiagnosticMessage>,
    /// Whether this annotation is "primary" or not. When it isn't primary, an
    /// annotation is said to be "secondary."
    is_primary: bool,
    /// The diagnostic tags associated with this annotation.
    tags: Vec<DiagnosticTag>,
    /// Whether the snippet for this annotation should be hidden.
    ///
    /// When set, rendering will only include the file's name and (optional) range. Everything else
    /// is omitted, including any file snippet or message.
    hide_snippet: bool,
}

impl Annotation {
    /// Create a "primary" annotation.
    ///
    /// A primary annotation is meant to highlight the "locus" of a diagnostic.
    /// That is, it should point to something in the end user's input that is
    /// the subject or "point" of a diagnostic.
    ///
    /// A diagnostic may have many primary annotations. A diagnostic may not
    /// have any annotations, but if it does, at least one _ought_ to be
    /// primary.
    pub fn primary(span: Span) -> Annotation {
        Annotation {
            span,
            message: None,
            is_primary: true,
            tags: Vec::new(),
            hide_snippet: false,
        }
    }

    /// Create a "secondary" annotation.
    ///
    /// A secondary annotation is meant to highlight relevant context for a
    /// diagnostic, but not to point to the "locus" of the diagnostic.
    ///
    /// A diagnostic with only secondary annotations is usually not sensible,
    /// but it is allowed and will produce a reasonable rendering.
    pub fn secondary(span: Span) -> Annotation {
        Annotation {
            span,
            message: None,
            is_primary: false,
            tags: Vec::new(),
            hide_snippet: false,
        }
    }

    /// Attach a message to this annotation.
    ///
    /// An annotation without a message will still have a presence in
    /// rendering. In particular, it will highlight the span association with
    /// this annotation in some way.
    ///
    /// When a message is attached to an annotation, then it will be associated
    /// with the highlighted span in some way during rendering.
    ///
    /// # Types implementing `IntoDiagnosticMessage`
    ///
    /// Callers can pass anything that implements `std::fmt::Display`
    /// directly. If callers want or need to avoid cloning the diagnostic
    /// message, then they can also pass a `DiagnosticMessage` directly.
    pub fn message<'a>(self, message: impl IntoDiagnosticMessage + 'a) -> Annotation {
        let message = Some(message.into_diagnostic_message());
        Annotation { message, ..self }
    }

    /// Sets the message on this annotation.
    ///
    /// If one was already set, then this overwrites it.
    ///
    /// This is useful if one needs to set the message on an annotation,
    /// and all one has is a `&mut Annotation`. For example, via
    /// `Diagnostic::primary_annotation_mut`.
    pub fn set_message<'a>(&mut self, message: impl IntoDiagnosticMessage + 'a) {
        self.message = Some(message.into_diagnostic_message());
    }

    /// Returns the message attached to this annotation, if one exists.
    pub fn get_message(&self) -> Option<&str> {
        self.message.as_ref().map(|m| m.as_str())
    }

    /// Returns the `Span` associated with this annotation.
    pub fn get_span(&self) -> &Span {
        &self.span
    }

    /// Sets the span on this annotation.
    pub fn set_span(&mut self, span: Span) {
        self.span = span;
    }

    /// Attaches an additional tag to this annotation.
    pub fn push_tag(&mut self, tag: DiagnosticTag) {
        self.tags.push(tag);
    }

    /// Set whether or not the snippet on this annotation should be suppressed when rendering.
    ///
    /// Such annotations are only rendered with their file name and range, if available. This is
    /// intended for backwards compatibility with Ruff diagnostics, which historically used
    /// `TextRange::default` to indicate a file-level diagnostic. In the new diagnostic model, a
    /// [`Span`] with a range of `None` should be used instead, as mentioned in the `Span`
    /// documentation.
    ///
    /// TODO(brent) update this usage in Ruff and remove `is_file_level` entirely. See
    /// <https://github.com/astral-sh/ruff/issues/19688>, especially my first comment, for more
    /// details. As of 2025-09-26 we also use this to suppress snippet rendering for formatter
    /// diagnostics, which also need to have a range, so we probably can't eliminate this entirely.
    pub fn hide_snippet(&mut self, yes: bool) {
        self.hide_snippet = yes;
    }

    pub fn is_primary(&self) -> bool {
        self.is_primary
    }
}

/// Tags that can be associated with an annotation.
///
/// These tags are used to provide additional information about the annotation.
/// and are passed through to the language server protocol.
#[derive(Debug, Clone, Eq, PartialEq, Hash, get_size2::GetSize)]
pub enum DiagnosticTag {
    /// Unused or unnecessary code. Used for unused parameters, unreachable code, etc.
    Unnecessary,
    /// Deprecated or obsolete code.
    Deprecated,
}

/// A string identifier for a lint rule.
///
/// This string is used in command line and configuration interfaces. The name should always
/// be in kebab case, e.g. `no-foo` (all lower case).
///
/// Rules use kebab case, e.g. `no-foo`.
#[derive(Debug, Copy, Clone, PartialOrd, Ord, PartialEq, Eq, Hash, get_size2::GetSize)]
pub struct LintName(&'static str);

impl LintName {
    pub const fn of(name: &'static str) -> Self {
        Self(name)
    }

    pub const fn as_str(&self) -> &'static str {
        self.0
    }
}

impl std::ops::Deref for LintName {
    type Target = str;

    fn deref(&self) -> &Self::Target {
        self.0
    }
}

impl std::fmt::Display for LintName {
    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
        f.write_str(self.0)
    }
}

impl PartialEq<str> for LintName {
    fn eq(&self, other: &str) -> bool {
        self.0 == other
    }
}

impl PartialEq<&str> for LintName {
    fn eq(&self, other: &&str) -> bool {
        self.0 == *other
    }
}

/// Uniquely identifies the kind of a diagnostic.
#[derive(Debug, Copy, Clone, Eq, PartialEq, PartialOrd, Ord, Hash, get_size2::GetSize)]
pub enum DiagnosticId {
    Panic,

    /// Some I/O operation failed
    Io,

    /// Some code contains a syntax error
    InvalidSyntax,

    /// A lint violation.
    ///
    /// Lints can be suppressed and some lints can be enabled or disabled in the configuration.
    Lint(LintName),

    /// A revealed type: Created by `reveal_type(expression)`.
    RevealedType,

    /// No rule with the given name exists.
    UnknownRule,

    /// A glob pattern doesn't follow the expected syntax.
    InvalidGlob,

    /// An `include` glob without any patterns.
    ///
    /// ## Why is this bad?
    /// An `include` glob without any patterns won't match any files. This is probably a mistake and
    /// either the `include` should be removed or a pattern should be added.
    ///
    /// ## Example
    /// ```toml
    /// [src]
    /// include = []
    /// ```
    ///
    /// Use instead:
    ///
    /// ```toml
    /// [src]
    /// include = ["src"]
    /// ```
    ///
    /// or remove the `include` option.
    EmptyInclude,

    /// An override configuration is unnecessary because it applies to all files.
    ///
    /// ## Why is this bad?
    /// An overrides section that applies to all files is probably a mistake and can be rolled-up into the root configuration.
    ///
    /// ## Example
    /// ```toml
    /// [[overrides]]
    /// [overrides.rules]
    /// unused-reference = "ignore"
    /// ```
    ///
    /// Use instead:
    ///
    /// ```toml
    /// [rules]
    /// unused-reference = "ignore"
    /// ```
    ///
    /// or
    ///
    /// ```toml
    /// [[overrides]]
    /// include = ["test"]
    ///
    /// [overrides.rules]
    /// unused-reference = "ignore"
    /// ```
    UnnecessaryOverridesSection,

    /// An `overrides` section in the configuration that doesn't contain any overrides.
    ///
    /// ## Why is this bad?
    /// An `overrides` section without any configuration overrides is probably a mistake.
    /// It is either a leftover after removing overrides, or a user forgot to add any overrides,
    /// or used an incorrect syntax to do so (e.g. used `rules` instead of `overrides.rules`).
    ///
    /// ## Example
    /// ```toml
    /// [[overrides]]
    /// include = ["test"]
    /// # no `[overrides.rules]`
    /// ```
    UselessOverridesSection,

    /// Use of a deprecated setting.
    DeprecatedSetting,

    /// Use of a Python version that ty doesn't support.
    UnsupportedPythonVersion,

    /// The code needs to be formatted.
    Unformatted,

    /// Use of an invalid command-line option.
    InvalidCliOption,

    /// Experimental feature requires preview mode.
    PreviewFeature,

    /// An internal assumption was violated.
    ///
    /// This indicates a bug in the program rather than a user error.
    InternalError,
}

impl DiagnosticId {
    /// Creates a new `DiagnosticId` for a lint with the given name.
    pub const fn lint(name: &'static str) -> Self {
        Self::Lint(LintName::of(name))
    }

    /// Returns `true` if this `DiagnosticId` represents a lint.
    pub fn is_lint(&self) -> bool {
        matches!(self, DiagnosticId::Lint(_))
    }

    pub const fn as_lint(&self) -> Option<LintName> {
        match self {
            DiagnosticId::Lint(name) => Some(*name),
            _ => None,
        }
    }

    /// Returns `true` if this `DiagnosticId` represents a lint with the given name.
    pub fn is_lint_named(&self, name: &str) -> bool {
        matches!(self, DiagnosticId::Lint(self_name) if self_name == name)
    }

    pub fn strip_category(code: &str) -> Option<&str> {
        code.split_once(':').map(|(_, rest)| rest)
    }

    /// Returns a concise description of this diagnostic ID.
    ///
    /// Note that this doesn't include the lint's category. It
    /// only includes the lint's name.
    pub fn as_str(&self) -> &'static str {
        match self {
            DiagnosticId::Panic => "panic",
            DiagnosticId::Io => "io",
            DiagnosticId::InvalidSyntax => "invalid-syntax",
            DiagnosticId::Lint(name) => name.as_str(),
            DiagnosticId::RevealedType => "revealed-type",
            DiagnosticId::UnknownRule => "unknown-rule",
            DiagnosticId::InvalidGlob => "invalid-glob",
            DiagnosticId::EmptyInclude => "empty-include",
            DiagnosticId::UnnecessaryOverridesSection => "unnecessary-overrides-section",
            DiagnosticId::UselessOverridesSection => "useless-overrides-section",
            DiagnosticId::DeprecatedSetting => "deprecated-setting",
            DiagnosticId::UnsupportedPythonVersion => "unsupported-python-version",
            DiagnosticId::Unformatted => "unformatted",
            DiagnosticId::InvalidCliOption => "invalid-cli-option",
            DiagnosticId::PreviewFeature => "preview-feature",
            DiagnosticId::InternalError => "internal-error",
        }
    }

    fn is_invalid_syntax(&self) -> bool {
        matches!(self, Self::InvalidSyntax)
    }
}

impl std::fmt::Display for DiagnosticId {
    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
        write!(f, "{}", self.as_str())
    }
}

/// A unified file representation for both ruff and ty.
///
/// Such a representation is needed for rendering [`Diagnostic`]s that can optionally contain
/// [`Annotation`]s with [`Span`]s that need to refer to the text of a file. However, ty and ruff
/// use very different file types: a `Copy`-able salsa-interned [`File`], and a heavier-weight
/// [`SourceFile`], respectively.
///
/// This enum presents a unified interface to these two types for the sake of creating [`Span`]s and
/// emitting diagnostics from both ty and ruff.
#[derive(Debug, Clone, PartialEq, Eq, Hash, get_size2::GetSize)]
pub enum UnifiedFile {
    Ty(File),
    Ruff(SourceFile),
}

impl UnifiedFile {
    fn path<'a>(&'a self, resolver: &'a dyn FileResolver) -> &'a str {
        match self {
            UnifiedFile::Ty(file) => resolver.path(*file),
            UnifiedFile::Ruff(file) => file.name(),
        }
    }

    /// Return the file's path relative to the current working directory.
    fn relative_path<'a>(&'a self, resolver: &'a dyn FileResolver) -> &'a Path {
        let cwd = resolver.current_directory();
        let path = Path::new(self.path(resolver));

        if let Ok(path) = path.strip_prefix(cwd) {
            return path;
        }

        path
    }

    fn diagnostic_source(&self, resolver: &dyn FileResolver) -> DiagnosticSource {
        match self {
            UnifiedFile::Ty(file) => DiagnosticSource::Ty(resolver.input(*file)),
            UnifiedFile::Ruff(file) => DiagnosticSource::Ruff(file.clone()),
        }
    }
}

/// A unified wrapper for types that can be converted to a [`SourceCode`].
///
/// As with [`UnifiedFile`], ruff and ty use slightly different representations for source code.
/// [`DiagnosticSource`] wraps both of these and provides the single
/// [`DiagnosticSource::as_source_code`] method to produce a [`SourceCode`] with the appropriate
/// lifetimes.
///
/// See [`UnifiedFile::diagnostic_source`] for a way to obtain a [`DiagnosticSource`] from a file
/// and [`FileResolver`].
#[derive(Clone, Debug)]
enum DiagnosticSource {
    Ty(Input),
    Ruff(SourceFile),
}

impl DiagnosticSource {
    /// Returns this input as a `SourceCode` for convenient querying.
    fn as_source_code(&self) -> SourceCode<'_, '_> {
        match self {
            DiagnosticSource::Ty(input) => SourceCode::new(input.text.as_str(), &input.line_index),
            DiagnosticSource::Ruff(source) => SourceCode::new(source.source_text(), source.index()),
        }
    }
}

/// A span represents the source of a diagnostic.
///
/// It consists of a `File` and an optional range into that file. When the
/// range isn't present, it semantically implies that the diagnostic refers to
/// the entire file. For example, when the file should be executable but isn't.
#[derive(Debug, Clone, PartialEq, Eq, Hash, get_size2::GetSize)]
pub struct Span {
    file: UnifiedFile,
    range: Option<TextRange>,
}

impl Span {
    /// Returns the `UnifiedFile` attached to this `Span`.
    pub fn file(&self) -> &UnifiedFile {
        &self.file
    }

    /// Returns the range, if available, attached to this `Span`.
    ///
    /// When there is no range, it is convention to assume that this `Span`
    /// refers to the corresponding `File` as a whole. In some cases, consumers
    /// of this API may use the range `0..0` to represent this case.
    pub fn range(&self) -> Option<TextRange> {
        self.range
    }

    /// Returns a new `Span` with the given `range` attached to it.
    pub fn with_range(self, range: TextRange) -> Span {
        self.with_optional_range(Some(range))
    }

    /// Returns a new `Span` with the given optional `range` attached to it.
    pub fn with_optional_range(self, range: Option<TextRange>) -> Span {
        Span { range, ..self }
    }

    /// Returns the [`File`] attached to this [`Span`].
    ///
    /// Panics if the file is a [`UnifiedFile::Ruff`] instead of a [`UnifiedFile::Ty`].
    pub fn expect_ty_file(&self) -> File {
        match self.file {
            UnifiedFile::Ty(file) => file,
            UnifiedFile::Ruff(_) => panic!("Expected a ty `File`, found a ruff `SourceFile`"),
        }
    }

    /// Returns the [`SourceFile`] attached to this [`Span`].
    ///
    /// Panics if the file is a [`UnifiedFile::Ty`] instead of a [`UnifiedFile::Ruff`].
    fn expect_ruff_file(&self) -> &SourceFile {
        self.as_ruff_file()
            .expect("Expected a ruff `SourceFile`, found a ty `File`")
    }

    /// Returns the [`SourceFile`] attached to this [`Span`].
    pub fn as_ruff_file(&self) -> Option<&SourceFile> {
        match &self.file {
            UnifiedFile::Ty(_) => None,
            UnifiedFile::Ruff(file) => Some(file),
        }
    }
}

impl From<File> for Span {
    fn from(file: File) -> Span {
        let file = UnifiedFile::Ty(file);
        Span { file, range: None }
    }
}

impl From<SourceFile> for Span {
    fn from(file: SourceFile) -> Self {
        let file = UnifiedFile::Ruff(file);
        Span { file, range: None }
    }
}

impl From<crate::files::FileRange> for Span {
    fn from(file_range: crate::files::FileRange) -> Span {
        Span::from(file_range.file()).with_range(file_range.range())
    }
}

#[derive(Debug, Clone, Copy, PartialEq, Eq, Ord, PartialOrd, Hash, get_size2::GetSize)]
#[cfg_attr(feature = "serde", derive(Serialize))]
#[cfg_attr(feature = "serde", serde(rename_all = "lowercase"))]
pub enum Severity {
    Info,
    Warning,
    Error,
    Fatal,
}

impl Severity {
    fn to_annotate(self) -> AnnotateLevel<'static> {
        match self {
            Severity::Info => AnnotateLevel::INFO,
            Severity::Warning => AnnotateLevel::WARNING,
            Severity::Error => AnnotateLevel::ERROR,
            // NOTE: Should we really collapse this to "error"?
            //
            // After collapsing this, the snapshot tests seem to reveal that we
            // don't currently have any *tests* with a `fatal` severity level.
            // And maybe *rendering* this as just an `error` is fine. If we
            // really do need different rendering, then I think we can add a
            // `Level::Fatal`. ---AG
            Severity::Fatal => AnnotateLevel::ERROR,
        }
    }

    pub const fn is_fatal(self) -> bool {
        matches!(self, Severity::Fatal)
    }
}

/// Like [`Severity`] but exclusively for sub-diagnostics.
///
/// This type only exists to add an additional `Help` severity that isn't present in `Severity` or
/// used for main diagnostics. If we want to add `Severity::Help` in the future, this type could be
/// deleted and the two combined again.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Ord, PartialOrd, Hash, get_size2::GetSize)]
pub enum SubDiagnosticSeverity {
    Help,
    Info,
    Warning,
    Error,
    Fatal,
}

impl SubDiagnosticSeverity {
    fn to_annotate(self) -> AnnotateLevel<'static> {
        match self {
            SubDiagnosticSeverity::Help => AnnotateLevel::HELP,
            SubDiagnosticSeverity::Info => AnnotateLevel::INFO,
            SubDiagnosticSeverity::Warning => AnnotateLevel::WARNING,
            SubDiagnosticSeverity::Error => AnnotateLevel::ERROR,
            SubDiagnosticSeverity::Fatal => AnnotateLevel::ERROR,
        }
    }
}

impl Display for SubDiagnosticSeverity {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        let s = match self {
            SubDiagnosticSeverity::Help => "help",
            SubDiagnosticSeverity::Info => "info",
            SubDiagnosticSeverity::Warning => "warning",
            SubDiagnosticSeverity::Error => "error",
            SubDiagnosticSeverity::Fatal => "fatal",
        };
        f.write_str(s)
    }
}

/// Controls whether colored diagnostic output includes hyperlinks.
#[derive(Clone, Copy, Debug, Default, PartialEq, Eq)]
pub enum HyperlinkMode {
    /// Detect hyperlink support from the environment.
    #[default]
    Auto,
    /// Always emit hyperlinks.
    Always,
    /// Never emit hyperlinks.
    Never,
}

/// Configuration for rendering diagnostics.
#[derive(Clone, Debug)]
pub struct DisplayDiagnosticConfig {
    /// The program name used in structured output formats (e.g., JUnit, GitHub).
    program: &'static str,
    /// The format to use for diagnostic rendering.
    ///
    /// This uses the "full" format by default.
    format: DiagnosticFormat,
    /// Whether to enable colors or not.
    ///
    /// Disabled by default.
    color: bool,
    /// Whether to emit hyperlinks in colored diagnostic output.
    ///
    /// By default, hyperlink support is detected from the environment.
    hyperlinks: HyperlinkMode,
    /// Whether to anonymize line numbers in full diagnostic output.
    ///
    /// Disabled by default.
    anonymized_line_numbers: bool,
    /// The number of non-empty lines to show around each snippet.
    ///
    /// NOTE: It seems like making this a property of rendering *could*
    /// be wrong. In particular, I have a suspicion that we may want
    /// more granular control over this, perhaps based on the kind of
    /// diagnostic or even the snippet itself. But I chose to put this
    /// here for now as the most "sensible" place for it to live until
    /// we had more concrete use cases. ---AG
    context: usize,
    /// The "merge window" for annotations and fix diff hunks.
    ///
    /// Nearby annotations or fix edits are rendered in a single source frame even when their
    /// configured context windows would not otherwise overlap.
    merge_window: usize,
    /// Whether to use preview formatting for Ruff diagnostics.
    preview: bool,
    /// Whether to prefer rule codes over human-readable rule names in Ruff diagnostic output.
    prefer_rule_codes: bool,
    /// Whether to hide the real `Severity` of diagnostics.
    ///
    /// This is intended for temporary use by Ruff, which only has a single `error` severity at the
    /// moment. We should be able to remove this option when Ruff gets more severities.
    hide_severity: bool,
    /// Whether to show the availability of a fix in a diagnostic.
    show_fix_status: bool,
    /// The lowest applicability that should be shown when reporting diagnostics.
    fix_applicability: Applicability,

    cancellation_token: Option<CancellationToken>,
}

impl DisplayDiagnosticConfig {
    pub fn new(program: &'static str) -> DisplayDiagnosticConfig {
        DisplayDiagnosticConfig {
            program,
            format: DiagnosticFormat::default(),
            color: false,
            hyperlinks: HyperlinkMode::Auto,
            anonymized_line_numbers: false,
            context: 2,
            merge_window: 2,
            preview: false,
            prefer_rule_codes: false,
            hide_severity: false,
            show_fix_status: false,
            fix_applicability: Applicability::Safe,
            cancellation_token: None,
        }
    }

    /// Whether to enable concise diagnostic output or not.
    pub fn format(self, format: DiagnosticFormat) -> DisplayDiagnosticConfig {
        DisplayDiagnosticConfig { format, ..self }
    }

    /// Whether to enable colors or not.
    pub fn color(self, yes: bool) -> DisplayDiagnosticConfig {
        DisplayDiagnosticConfig { color: yes, ..self }
    }

    /// Configures hyperlink rendering for colored diagnostic output.
    pub fn hyperlinks(self, mode: HyperlinkMode) -> DisplayDiagnosticConfig {
        DisplayDiagnosticConfig {
            hyperlinks: mode,
            ..self
        }
    }

    /// Whether to anonymize line numbers in full diagnostic output.
    pub fn anonymized_line_numbers(self, yes: bool) -> DisplayDiagnosticConfig {
        DisplayDiagnosticConfig {
            anonymized_line_numbers: yes,
            ..self
        }
    }

    /// Set the number of contextual lines to show around each snippet.
    pub fn context(self, lines: usize) -> DisplayDiagnosticConfig {
        DisplayDiagnosticConfig {
            context: lines,
            ..self
        }
    }

    /// Set the "merge window" for annotations and fix diff hunks.
    ///
    /// Nearby annotations or fix edits are rendered in a single source frame even when their
    /// configured context windows would not otherwise overlap.
    #[cfg(test)]
    fn merge_window(self, lines: usize) -> DisplayDiagnosticConfig {
        DisplayDiagnosticConfig {
            merge_window: lines,
            ..self
        }
    }

    /// Whether to enable preview behavior or not.
    pub fn preview(self, yes: bool) -> DisplayDiagnosticConfig {
        DisplayDiagnosticConfig {
            preview: yes,
            ..self
        }
    }

    pub fn preview_enabled(&self) -> bool {
        self.preview
    }

    /// Whether to prefer rule codes over human-readable rule names, even in preview mode.
    pub fn prefer_rule_codes(self, yes: bool) -> DisplayDiagnosticConfig {
        DisplayDiagnosticConfig {
            prefer_rule_codes: yes,
            ..self
        }
    }

    /// Whether rule codes are explicitly preferred over human-readable rule names.
    pub fn is_prefer_rule_codes_enabled(&self) -> bool {
        self.prefer_rule_codes
    }

    /// Whether to hide a diagnostic's severity or not.
    pub fn hide_severity(self, yes: bool) -> DisplayDiagnosticConfig {
        DisplayDiagnosticConfig {
            hide_severity: yes,
            ..self
        }
    }

    /// Whether to show a fix's availability or not.
    pub fn with_show_fix_status(self, yes: bool) -> DisplayDiagnosticConfig {
        DisplayDiagnosticConfig {
            show_fix_status: yes,
            ..self
        }
    }

    /// Set the lowest fix applicability that should be shown.
    ///
    /// In other words, an applicability of `Safe` (the default) would suppress showing fixes or fix
    /// availability for unsafe or display-only fixes.
    ///
    /// Note that this option is currently ignored when `hide_severity` is false.
    pub fn with_fix_applicability(self, applicability: Applicability) -> DisplayDiagnosticConfig {
        DisplayDiagnosticConfig {
            fix_applicability: applicability,
            ..self
        }
    }

    pub fn show_fix_status(&self) -> bool {
        self.show_fix_status
    }

    pub fn fix_applicability(&self) -> Applicability {
        self.fix_applicability
    }

    pub fn with_cancellation_token(
        mut self,
        token: Option<CancellationToken>,
    ) -> DisplayDiagnosticConfig {
        self.cancellation_token = token;
        self
    }

    fn is_canceled(&self) -> bool {
        self.cancellation_token
            .as_ref()
            .is_some_and(|token| token.is_cancelled())
    }
}

/// The diagnostic output format.
#[derive(Copy, Clone, Debug, Default, Eq, Hash, PartialEq, PartialOrd, Ord)]
#[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
#[cfg_attr(feature = "serde", serde(rename_all = "kebab-case"))]
#[cfg_attr(feature = "schemars", derive(schemars::JsonSchema))]
pub enum DiagnosticFormat {
    /// The default full mode will print "pretty" diagnostics.
    ///
    /// That is, color will be used when printing to a `tty`.
    /// Moreover, diagnostic messages may include additional
    /// context and annotations on the input to help understand
    /// the message.
    #[default]
    Full,
    /// Print diagnostics in a concise mode.
    ///
    /// This will guarantee that each diagnostic is printed on
    /// a single line. Only the most important or primary aspects
    /// of the diagnostic are included. Contextual information is
    /// dropped.
    ///
    /// This may use color when printing to a `tty`.
    Concise,
    /// Print diagnostics in the [Azure Pipelines] format.
    ///
    /// [Azure Pipelines]: https://learn.microsoft.com/en-us/azure/devops/pipelines/scripts/logging-commands?view=azure-devops&tabs=bash#logissue-log-an-error-or-warning
    Azure,
    /// Print diagnostics in JSON format.
    ///
    /// Unlike `json-lines`, this prints all of the diagnostics as a JSON array.
    #[cfg(feature = "serde")]
    Json,
    /// Print diagnostics in JSON format, one per line.
    ///
    /// This will print each diagnostic as a separate JSON object on its own line. See the `json`
    /// format for an array of all diagnostics. See <https://jsonlines.org/> for more details.
    #[cfg(feature = "serde")]
    JsonLines,
    /// Print diagnostics in the JSON format expected by [reviewdog].
    ///
    /// [reviewdog]: https://github.com/reviewdog/reviewdog
    #[cfg(feature = "serde")]
    Rdjson,
    /// Print diagnostics in the format emitted by Pylint.
    Pylint,
    /// Print diagnostics in the format expected by JUnit.
    #[cfg(feature = "junit")]
    Junit,
    /// Print diagnostics in the JSON format used by GitLab [Code Quality] reports.
    ///
    /// [Code Quality]: https://docs.gitlab.com/ci/testing/code_quality/#code-quality-report-format
    #[cfg(feature = "serde")]
    Gitlab,

    /// Print diagnostics in the format used by [GitHub Actions] workflow error annotations.
    ///
    /// [GitHub Actions]: https://docs.github.com/en/actions/reference/workflows-and-actions/workflow-commands#setting-an-error-message
    Github,
}

/// A representation of the kinds of messages inside a diagnostic.
pub enum ConciseMessage<'a> {
    /// A diagnostic contains a non-empty headline message and an empty
    /// primary annotation message.
    MainDiagnostic(&'a str),
    /// A diagnostic contains a non-empty headline message and a non-empty
    /// primary annotation message.
    Both { main: &'a str, annotation: &'a str },
    /// A custom concise message has been provided.
    Custom(&'a str),
}

impl<'a> ConciseMessage<'a> {
    pub fn to_str(&self) -> Cow<'a, str> {
        match self {
            ConciseMessage::MainDiagnostic(s) | ConciseMessage::Custom(s) => Cow::Borrowed(s),
            ConciseMessage::Both { .. } => Cow::Owned(self.to_string()),
        }
    }
}

impl std::fmt::Display for ConciseMessage<'_> {
    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
        match *self {
            ConciseMessage::MainDiagnostic(main) => {
                write!(f, "{main}")
            }
            ConciseMessage::Both { main, annotation } => {
                write!(f, "{main}: {annotation}")
            }
            ConciseMessage::Custom(message) => {
                write!(f, "{message}")
            }
        }
    }
}

#[cfg(feature = "serde")]
impl serde::Serialize for ConciseMessage<'_> {
    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
    where
        S: serde::Serializer,
    {
        serializer.collect_str(self)
    }
}

/// A diagnostic message string.
///
/// This is, for all intents and purposes, equivalent to a `Box<str>`.
/// But it does not implement `std::fmt::Display`. Indeed, that it its
/// entire reason for existence. It provides a way to pass a string
/// directly into diagnostic methods that accept messages without copying
/// that string. This works via the `IntoDiagnosticMessage` trait.
///
/// In most cases, callers shouldn't need to use this. Instead, there is
/// a blanket trait implementation for `IntoDiagnosticMessage` for
/// anything that implements `std::fmt::Display`.
#[derive(Clone, Debug, Eq, PartialEq, Hash, get_size2::GetSize)]
pub struct DiagnosticMessage(Box<str>);

impl DiagnosticMessage {
    /// Returns this message as a borrowed string.
    pub fn as_str(&self) -> &str {
        &self.0
    }
}

impl From<&str> for DiagnosticMessage {
    fn from(s: &str) -> DiagnosticMessage {
        DiagnosticMessage(s.into())
    }
}

impl From<String> for DiagnosticMessage {
    fn from(s: String) -> DiagnosticMessage {
        DiagnosticMessage(s.into())
    }
}

impl From<Box<str>> for DiagnosticMessage {
    fn from(s: Box<str>) -> DiagnosticMessage {
        DiagnosticMessage(s)
    }
}

impl IntoDiagnosticMessage for DiagnosticMessage {
    fn into_diagnostic_message(self) -> DiagnosticMessage {
        self
    }
}

/// A trait for values that can be converted into a diagnostic message.
///
/// Users of the diagnostic API can largely think of this trait as effectively
/// equivalent to `std::fmt::Display`. Indeed, everything that implements
/// `Display` also implements this trait. That means wherever this trait is
/// accepted, you can use things like `format_args!`.
///
/// The purpose of this trait is to provide a means to give arguments _other_
/// than `std::fmt::Display` trait implementations. Or rather, to permit
/// the diagnostic API to treat them differently. For example, this lets
/// callers wrap a string in a `DiagnosticMessage` and provide it directly
/// to any of the diagnostic APIs that accept a message. This will move the
/// string and avoid any unnecessary copies. (If we instead required only
/// `std::fmt::Display`, then this would potentially result in a copy via the
/// `ToString` trait implementation.)
pub trait IntoDiagnosticMessage {
    fn into_diagnostic_message(self) -> DiagnosticMessage;
}

/// Every `IntoDiagnosticMessage` is accepted, so to is `std::fmt::Display`.
impl<T: std::fmt::Display> IntoDiagnosticMessage for T {
    fn into_diagnostic_message(self) -> DiagnosticMessage {
        DiagnosticMessage::from(self.to_string())
    }
}

/// A secondary identifier for a lint diagnostic.
///
/// For Ruff rules this means the noqa code.
#[derive(Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Default, Hash, get_size2::GetSize)]
#[cfg_attr(feature = "serde", derive(serde::Serialize), serde(transparent))]
pub struct SecondaryCode(String);

impl SecondaryCode {
    pub fn new(code: String) -> Self {
        Self(code)
    }

    pub fn as_str(&self) -> &str {
        &self.0
    }
}

impl std::fmt::Display for SecondaryCode {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.write_str(&self.0)
    }
}

impl std::ops::Deref for SecondaryCode {
    type Target = str;

    fn deref(&self) -> &Self::Target {
        &self.0
    }
}

impl PartialEq<&str> for SecondaryCode {
    fn eq(&self, other: &&str) -> bool {
        self.0 == *other
    }
}

impl PartialEq<SecondaryCode> for &str {
    fn eq(&self, other: &SecondaryCode) -> bool {
        other.eq(self)
    }
}

// for `hashbrown::EntryRef`
impl From<&SecondaryCode> for SecondaryCode {
    fn from(value: &SecondaryCode) -> Self {
        value.clone()
    }
}
