fallow_output/

ci_output.rs

//! Shared CI comment output contracts for CLI and programmatic consumers.

use std::borrow::Cow;
use std::fmt::Write as _;

use crate::{
    CodeClimateIssue, CodeClimateSeverity, DiffIndex, GitHubReviewComment, GitHubReviewSide,
    GitLabReviewComment, GitLabReviewPosition, GitLabReviewPositionType, ReviewCheckConclusion,
    ReviewComment, ReviewEnvelopeEvent, ReviewEnvelopeMeta, ReviewEnvelopeOutput,
    ReviewEnvelopeSchema, ReviewEnvelopeSummary, ReviewId, ReviewProvider, default_marker_regex,
    default_marker_regex_flags, review_id_marker,
};
use serde_json::Value;

/// Supported CI review providers for generated comments.
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub enum CiProvider {
    /// GitHub pull requests and check runs.
    Github,
    /// GitLab merge requests and discussions.
    Gitlab,
}

impl CiProvider {
    /// Display name of the provider ("GitHub" / "GitLab").
    #[must_use]
    pub const fn name(self) -> &'static str {
        match self {
            Self::Github => "GitHub",
            Self::Gitlab => "GitLab",
        }
    }
}

/// Prefix prepended to a rendered path so CI platforms, which address files
/// from the repository root, can find it. Empty when the analysis root already
/// is the repository root.
///
/// This is presentation only. Nothing looks a path up in a diff after it has
/// been prefixed: matching happens on analysis-root-relative paths, which is
/// the namespace `DiffIndex::key_for_root_relative` translates from.
#[must_use]
pub fn apply_path_prefix(prefix: &str, path: &str) -> String {
    if prefix.is_empty() {
        return path.to_owned();
    }
    format!("{prefix}/{path}")
}

/// Normalized CodeClimate issue used by CI comment renderers.
#[derive(Clone, Debug, PartialEq, Eq)]
pub struct CiIssue {
    /// Fallow rule identifier, taken from the CodeClimate `check_name`.
    pub rule_id: String,
    /// Human-readable finding description.
    pub description: String,
    /// CodeClimate severity string, e.g. `minor` or `major`.
    pub severity: String,
    /// File path relative to the analysed root.
    pub path: String,
    /// 1-based line of the finding.
    pub line: u64,
    /// Inclusive 1-based end line for range findings.
    pub end_line: Option<u64>,
    /// Other source ranges that provide evidence for this finding.
    pub other_locations: Vec<CiLocation>,
    /// Stable finding fingerprint used for comment identity.
    pub fingerprint: String,
    /// The fingerprint an older Fallow release gave this finding, when it is
    /// different from `fingerprint`. Review comments carry it for one
    /// release, so a thread with the older marker still matches.
    pub legacy_fingerprint: Option<String>,
}

/// Source range attached to a normalized CI finding as supporting evidence.
#[derive(Clone, Debug, PartialEq, Eq, PartialOrd, Ord)]
pub struct CiLocation {
    /// File path relative to the analysed root.
    pub path: String,
    /// Inclusive 1-based start line.
    pub line: u64,
    /// Inclusive 1-based end line.
    pub end_line: u64,
}

/// Inputs for rendering a sticky PR/MR summary comment.
pub struct PrCommentRenderInput<'a> {
    /// Fallow command the comment reports on, e.g. `audit`.
    pub command: &'a str,
    /// CI provider whose comment conventions apply.
    pub provider: CiProvider,
    /// Findings to summarize, pre-sorted by severity and location.
    pub issues: &'a [CiIssue],
    /// Identity token embedded so reruns update the same sticky comment.
    pub marker_id: String,
    /// Maximum findings rendered in the comment body.
    pub max_comments: usize,
    /// Maps a rule id to its display category label.
    pub category_for_rule: &'a dyn Fn(&str) -> &'static str,
    /// A Markdown section after the findings and before the footer. The CLI
    /// uses it for the unmatched config patterns.
    pub trailing_section: Option<&'a str>,
}

/// GitLab diff refs for a review-envelope position.
#[derive(Clone, Debug, PartialEq, Eq)]
pub struct ReviewGitlabDiffRefs {
    /// Merge-base SHA of the MR diff.
    pub base_sha: String,
    /// First commit SHA of the MR diff.
    pub start_sha: String,
    /// Head commit SHA of the MR diff.
    pub head_sha: String,
}

/// Truncation signals produced while rendering a review envelope.
#[derive(Clone, Copy, Debug, Default, PartialEq, Eq)]
pub struct ReviewEnvelopeTruncation {
    /// A comment body hit [`MAX_COMMENT_BODY_BYTES`] and was truncated.
    pub body: bool,
    /// More findings existed than `max_comments` allowed.
    pub comment_limit: bool,
}

/// Rendered review envelope plus side-channel signals for CLI telemetry.
#[derive(Debug)]
pub struct ReviewEnvelopeRenderResult {
    /// Provider-ready review envelope.
    pub envelope: ReviewEnvelopeOutput,
    /// Truncation signals observed while rendering.
    pub truncation: ReviewEnvelopeTruncation,
}

/// Inputs for rendering a GitHub/GitLab review envelope.
pub struct ReviewEnvelopeRenderInput<'a> {
    /// Fallow command the review reports on.
    pub command: &'a str,
    /// CI provider whose review API shapes the envelope.
    pub provider: CiProvider,
    /// Findings to turn into review comments.
    pub issues: &'a [CiIssue],
    /// Diff index used to keep comments on lines the diff actually added.
    pub diff_index: Option<&'a DiffIndex>,
    /// Prepended to every emitted path after diff lookups have run.
    pub path_prefix: &'a str,
    /// Maximum inline comments to emit.
    pub max_comments: usize,
    /// Required for GitLab positioned discussions; ignored for GitHub.
    pub gitlab_diff_refs: Option<&'a ReviewGitlabDiffRefs>,
    /// Whether to append per-finding guidance blocks to comment bodies.
    pub include_guidance: bool,
    /// Produces a provider-specific suggestion block for a finding, when one
    /// applies.
    pub suggestion_block: &'a dyn Fn(CiProvider, &CiIssue) -> Option<String>,
    /// Produces a guidance block for a finding, when one applies.
    pub guidance_block: &'a dyn Fn(&CiIssue) -> Option<String>,
    /// A Markdown section in the summary body, after the inline-comment line
    /// and before the markers. The CLI uses it for the unmatched config
    /// patterns, as the sticky comment does.
    pub trailing_section: Option<&'a str>,
}

/// Marker prefix appended to every review-comment body.
///
/// Version 3 carries the line-stable fingerprint of dead-code findings.
pub const MARKER_PREFIX_V3: &str = "<!-- fallow-fingerprint:v3: ";

/// Closing of the v3 marker, after the fingerprint string.
pub const MARKER_SUFFIX_V3: &str = " -->";

/// Marker prefix of review comments that older Fallow releases wrote.
///
/// Fallow no longer writes it. Readers still match it against the legacy
/// fingerprint of a finding for one release.
pub const MARKER_PREFIX_V2: &str = "<!-- fallow-fingerprint:v2: ";

/// Closing of the v2 marker, after the fingerprint string.
pub const MARKER_SUFFIX_V2: &str = " -->";

/// Hard cap on a single review-comment body, matching GitHub's 65 536-char
/// comment limit; bodies at or over it are truncated with a marker suffix.
pub const MAX_COMMENT_BODY_BYTES: usize = 65_536;
const TRUNCATION_SUFFIX: &str = "\n\n<!-- fallow-truncated -->\n> Body truncated by fallow.";

/// Extract normalized CI issues from a raw CodeClimate JSON array, sorted by
/// severity then location.
#[must_use]
pub fn issues_from_codeclimate(value: &Value) -> Vec<CiIssue> {
    let mut issues = value
        .as_array()
        .into_iter()
        .flatten()
        .filter_map(issue_from_codeclimate)
        .collect::<Vec<_>>();
    sort_ci_issues(&mut issues);
    issues
}

/// Normalize typed CodeClimate issues into CI issues, sorted by severity then
/// location.
#[must_use]
pub fn issues_from_codeclimate_issues(issues: &[CodeClimateIssue]) -> Vec<CiIssue> {
    let mut issues = issues
        .iter()
        .map(issue_from_codeclimate_issue)
        .collect::<Vec<_>>();
    sort_ci_issues(&mut issues);
    issues
}

fn issue_from_codeclimate(value: &Value) -> Option<CiIssue> {
    let path = value.pointer("/location/path")?.as_str()?.to_string();
    let line = value
        .pointer("/location/lines/begin")
        .and_then(Value::as_u64)
        .unwrap_or(1);
    let end_line = value.pointer("/location/lines/end").and_then(Value::as_u64);
    let mut other_locations = value
        .get("other_locations")
        .and_then(Value::as_array)
        .into_iter()
        .flatten()
        .filter_map(|location| {
            let line = location.pointer("/lines/begin")?.as_u64()?;
            let end_line = location
                .pointer("/lines/end")
                .and_then(Value::as_u64)
                .filter(|end| *end >= line)
                .unwrap_or(line);
            Some(CiLocation {
                path: location.get("path")?.as_str()?.to_owned(),
                line,
                end_line,
            })
        })
        .collect::<Vec<_>>();
    other_locations.sort();
    Some(CiIssue {
        rule_id: value
            .get("check_name")
            .and_then(Value::as_str)
            .unwrap_or("fallow/finding")
            .to_string(),
        description: value
            .get("description")
            .and_then(Value::as_str)
            .unwrap_or("Fallow finding")
            .to_string(),
        severity: value
            .get("severity")
            .and_then(Value::as_str)
            .unwrap_or("minor")
            .to_string(),
        fingerprint: value
            .get("fingerprint")
            .and_then(Value::as_str)
            .unwrap_or("")
            .to_string(),
        legacy_fingerprint: None,
        path,
        line,
        end_line,
        other_locations,
    })
}

fn issue_from_codeclimate_issue(issue: &CodeClimateIssue) -> CiIssue {
    let mut other_locations = issue
        .other_locations
        .iter()
        .map(|location| CiLocation {
            path: location.path.clone(),
            line: u64::from(location.lines.begin),
            end_line: u64::from(
                location
                    .lines
                    .end
                    .filter(|end| *end >= location.lines.begin)
                    .unwrap_or(location.lines.begin),
            ),
        })
        .collect::<Vec<_>>();
    other_locations.sort();
    CiIssue {
        rule_id: issue.check_name.clone(),
        description: issue.description.clone(),
        severity: codeclimate_severity_label(issue.severity).to_owned(),
        path: issue.location.path.clone(),
        line: u64::from(issue.location.lines.begin),
        end_line: issue.location.lines.end.map(u64::from),
        other_locations,
        fingerprint: issue.fingerprint.clone(),
        legacy_fingerprint: issue.legacy_fingerprint.clone(),
    }
}

const fn codeclimate_severity_label(severity: CodeClimateSeverity) -> &'static str {
    match severity {
        CodeClimateSeverity::Info => "info",
        CodeClimateSeverity::Minor => "minor",
        CodeClimateSeverity::Major => "major",
        CodeClimateSeverity::Critical => "critical",
        CodeClimateSeverity::Blocker => "blocker",
    }
}

fn sort_ci_issues(issues: &mut [CiIssue]) {
    issues
        .sort_by(|a, b| (&a.path, a.line, &a.fingerprint).cmp(&(&b.path, b.line, &b.fingerprint)));
}

fn fingerprint_hash(parts: &[&str]) -> String {
    crate::codeclimate_fingerprint_hash(parts)
}

/// Render the sticky summary comment body: identity marker, run verdict,
/// headline count, and per-category findings tables.
///
/// The verdict is derived from the findings' severities. Use
/// [`render_pr_comment_with_verdict`] to fold in a gate conclusion the caller
/// already computed, such as a saved audit verdict.
#[must_use]
pub fn render_pr_comment(input: &PrCommentRenderInput<'_>) -> String {
    render_pr_comment_with_verdict(input, None)
}

/// Render the sticky summary comment body with an explicit gate conclusion.
///
/// The rendered verdict is the more severe of `gate` and the severity-derived
/// [`github_check_conclusion`], so a gate that only knows about thresholds
/// cannot mask an error-severity finding, and a failing gate cannot be masked
/// by findings that are all advisory.
///
/// This body is the surface a rerun edits in place. A provider review body is
/// a point-in-time record that no later run can rewrite, which is why the run
/// verdict lives here and not there.
#[must_use]
#[expect(clippy::expect_used, reason = "formatting into String is infallible")]
pub fn render_pr_comment_with_verdict(
    input: &PrCommentRenderInput<'_>,
    gate: Option<ReviewCheckConclusion>,
) -> String {
    let marker = format!("<!-- fallow-id: {} -->", input.marker_id);
    let title = command_title(input.command);
    let count = input.issues.len();
    let noun = if count == 1 { "finding" } else { "findings" };
    let verdict = most_severe_conclusion(github_check_conclusion(input.issues), gate);

    let mut out = String::new();
    out.push_str(&marker);
    out.push('\n');
    write!(&mut out, "### Fallow {title}\n\n").expect("write to string");
    write!(&mut out, "**{}**\n\n", pr_comment_verdict(verdict)).expect("write to string");
    if count == 0 {
        writeln!(
            &mut out,
            "No findings for this {}.",
            change_noun(input.provider)
        )
        .expect("write to string");
    } else {
        let groups = group_by_category(input.issues, input.category_for_rule);
        if groups.len() > 1 {
            write!(
                &mut out,
                "Found **{count}** {noun}: {}.\n\n",
                category_breakdown(&groups)
            )
            .expect("write to string");
        } else {
            write!(&mut out, "Found **{count}** {noun}.\n\n").expect("write to string");
        }
        for (category, group_issues) in &groups {
            let summary_label = summary_label(category, group_issues.len(), input.max_comments);
            render_findings_table(&mut out, group_issues, input.max_comments, &summary_label);
        }
    }
    if let Some(section) = input
        .trailing_section
        .map(str::trim)
        .filter(|section| !section.is_empty())
    {
        if !out.ends_with('\n') {
            out.push('\n');
        }
        out.push('\n');
        out.push_str(section);
        out.push('\n');
    }
    out.push_str("\nGenerated by fallow.");
    out
}

/// Verdict line rendered under the sticky comment heading.
const fn pr_comment_verdict(conclusion: ReviewCheckConclusion) -> &'static str {
    match conclusion {
        ReviewCheckConclusion::Failure => "Quality gate failed",
        ReviewCheckConclusion::Neutral => "Review needed",
        ReviewCheckConclusion::Success => "Quality gate passed",
    }
}

const fn conclusion_rank(conclusion: ReviewCheckConclusion) -> u8 {
    match conclusion {
        ReviewCheckConclusion::Success => 0,
        ReviewCheckConclusion::Neutral => 1,
        ReviewCheckConclusion::Failure => 2,
    }
}

const fn most_severe_conclusion(
    derived: ReviewCheckConclusion,
    gate: Option<ReviewCheckConclusion>,
) -> ReviewCheckConclusion {
    match gate {
        Some(gate) if conclusion_rank(gate) > conclusion_rank(derived) => gate,
        _ => derived,
    }
}

/// Rule ids whose findings describe project-wide config state rather than a
/// change touching a specific source line.
pub const PROJECT_LEVEL_RULE_IDS: &[&str] = &[
    "fallow/unused-catalog-entry",
    "fallow/empty-catalog-group",
    "fallow/unresolved-catalog-reference",
    "fallow/unused-dependency-override",
    "fallow/misconfigured-dependency-override",
    "fallow/unused-dependency",
    "fallow/unused-dev-dependency",
    "fallow/unused-optional-dependency",
    "fallow/type-only-dependency",
    "fallow/test-only-dependency",
    "fallow/dev-dependency-in-production",
];

/// Whether findings for `rule_id` describe the whole project (e.g. dependency
/// rules) rather than a specific file location.
#[must_use]
pub fn is_project_level_rule(rule_id: &str) -> bool {
    PROJECT_LEVEL_RULE_IDS.contains(&rule_id)
}

/// Section order for the sticky comment. Every category the rule registry
/// carries is listed, so a new bucket does not sort alphabetically into the
/// middle of the report. "Other" collects rules a downstream consumer added
/// without registering, and sorts last by construction.
const CATEGORY_ORDER: [&str; 10] = [
    "Dead code",
    "Dependencies",
    "Duplication",
    "Health",
    "Architecture",
    "Policy",
    "Security",
    "Flags",
    "Suppressions",
    "Other",
];

fn group_by_category<'a>(
    issues: &'a [CiIssue],
    category_for_rule: &dyn Fn(&str) -> &'static str,
) -> Vec<(&'static str, Vec<&'a CiIssue>)> {
    let mut buckets: std::collections::BTreeMap<&'static str, Vec<&CiIssue>> =
        std::collections::BTreeMap::new();
    for issue in issues {
        let category = category_for_rule(&issue.rule_id);
        buckets.entry(category).or_default().push(issue);
    }
    let mut ordered: Vec<(&'static str, Vec<&CiIssue>)> = Vec::with_capacity(buckets.len());
    for category in CATEGORY_ORDER {
        if let Some(items) = buckets.remove(category) {
            ordered.push((category, items));
        }
    }
    for (category, items) in buckets {
        ordered.push((category, items));
    }
    ordered
}

/// Table of contents for the collapsed sections below: "Dead code 13,
/// Dependencies 12". Section order, so the subtitle reads in the order a
/// reader scrolls.
fn category_breakdown(groups: &[(&'static str, Vec<&CiIssue>)]) -> String {
    groups
        .iter()
        .map(|(category, issues)| format!("{category} {}", issues.len()))
        .collect::<Vec<_>>()
        .join(", ")
}

/// Collapsible-section label for a findings category: appends "showing N"
/// when the table is capped below the category's total.
#[must_use]
pub fn summary_label(category: &str, total: usize, max: usize) -> String {
    if total > max {
        format!("{category} ({total}, showing {max})")
    } else {
        format!("{category} ({total})")
    }
}

#[expect(clippy::expect_used, reason = "formatting into String is infallible")]
fn render_findings_table(out: &mut String, issues: &[&CiIssue], max: usize, summary: &str) {
    writeln!(out, "<details>\n<summary>{summary}</summary>\n").expect("write to string");
    out.push_str("| Severity | Rule | Location | Description |\n");
    out.push_str("| --- | --- | --- | --- |\n");
    for issue in issues.iter().take(max) {
        writeln!(
            out,
            "| {} | `{}` | `{}`:{} | {} |",
            escape_md(&issue.severity),
            escape_md(&issue.rule_id),
            escape_md(&issue.path),
            issue.line,
            escape_md(&issue.description),
        )
        .expect("write to string");
    }
    if issues.len() > max {
        writeln!(
            out,
            "\nShowing {max} of {} findings. Run fallow locally or inspect the CI output for the full report.",
            issues.len(),
        )
        .expect("write to string");
    }
    out.push_str("\n</details>\n\n");
}

/// Human-readable report title for a fallow command name, e.g. `dupes` maps
/// to "duplication report".
#[must_use]
pub fn command_title(command: &str) -> &'static str {
    match command {
        "dead-code" | "check" => "codebase report",
        "dupes" => "duplication report",
        "health" => "health report",
        "audit" => "audit report",
        "security" => "security report",
        "fix" => "fix report",
        "" | "combined" => "combined report",
        _ => "report",
    }
}

/// How the provider names a change proposal ("pull request" / "merge request").
const fn change_noun(provider: CiProvider) -> &'static str {
    match provider {
        CiProvider::Github => "pull request",
        CiProvider::Gitlab => "merge request",
    }
}

/// The provider's diff tab, where inline review comments are read.
const fn changes_tab(provider: CiProvider) -> &'static str {
    match provider {
        CiProvider::Github => "Files changed",
        CiProvider::Gitlab => "Changes",
    }
}

/// Escape a string for inclusion in a Markdown table cell.
#[must_use]
pub fn escape_md(value: &str) -> String {
    let value = value.trim();
    // Collapse CRLF to one space; a bare CR is a CommonMark line ending and
    // would otherwise split the table row.
    let mut chars = value.chars().peekable();
    let mut out = String::with_capacity(value.len());
    while let Some(ch) = chars.next() {
        let ch = match ch {
            '\r' => {
                if chars.peek() == Some(&'\n') {
                    chars.next();
                }
                ' '
            }
            '\n' => ' ',
            _ => ch,
        };
        if matches!(
            ch,
            '\\' | '`'
                | '*'
                | '_'
                | '['
                | ']'
                | '('
                | ')'
                | '!'
                | '<'
                | '>'
                | '#'
                | '|'
                | '~'
                | '&'
        ) {
            out.push('\\');
        }
        out.push(ch);
    }
    out
}

/// Render a complete CommonMark code span around an untrusted value. The
/// fence grows past the longest backtick run inside the value, so the span
/// cannot be closed early from within.
#[must_use]
pub fn markdown_code_span(value: &str) -> String {
    let longest_run = value
        .split(|c| c != '`')
        .map(str::len)
        .max()
        .unwrap_or_default();
    let fence = "`".repeat(longest_run + 1);
    let needs_padding = value.starts_with('`')
        || value.ends_with('`')
        || (value.starts_with(' ') && value.ends_with(' ') && !value.chars().all(|c| c == ' '));
    if needs_padding {
        format!("{fence} {value} {fence}")
    } else {
        format!("{fence}{value}{fence}")
    }
}

/// [`markdown_code_span`] for a Markdown table cell: pipes are additionally
/// escaped so the value cannot terminate the cell, and line endings collapse
/// to spaces because any CommonMark line ending would split the table row.
#[must_use]
pub fn markdown_table_code_span(value: &str) -> String {
    let collapsed = value.replace("\r\n", " ").replace(['\n', '\r'], " ");
    markdown_code_span(&collapsed.replace('|', "\\|"))
}

/// Escape prose for a Markdown table cell while leaving intentional inline
/// markup alone: pipes are escaped and line endings collapse to spaces.
#[must_use]
pub fn markdown_table_text(value: &str) -> String {
    value
        .replace("\r\n", " ")
        .replace(['\n', '\r'], " ")
        .replace('|', "\\|")
}

/// Render a provider-specific review envelope from typed CI issues.
#[must_use]
pub fn render_review_envelope(
    input: &ReviewEnvelopeRenderInput<'_>,
    status_message: Option<&str>,
) -> ReviewEnvelopeRenderResult {
    render_review_envelope_with_id(input, None, None, status_message)
}

/// Render a review envelope with an explicit gate conclusion and status.
#[must_use]
pub fn render_review_envelope_with_conclusion(
    input: &ReviewEnvelopeRenderInput<'_>,
    conclusion: ReviewCheckConclusion,
    status_message: Option<&str>,
) -> ReviewEnvelopeRenderResult {
    render_review_envelope_with_id(input, None, Some(conclusion), status_message)
}

/// Render a review envelope whose bodies carry the supplied review scope.
#[must_use]
pub fn render_scoped_review_envelope(
    input: &ReviewEnvelopeRenderInput<'_>,
    review_id: &ReviewId,
    status_message: Option<&str>,
) -> ReviewEnvelopeRenderResult {
    render_review_envelope_with_id(input, Some(review_id), None, status_message)
}

/// Render a scoped review envelope with an explicit gate conclusion and status.
#[must_use]
pub fn render_scoped_review_envelope_with_conclusion(
    input: &ReviewEnvelopeRenderInput<'_>,
    review_id: &ReviewId,
    conclusion: ReviewCheckConclusion,
    status_message: Option<&str>,
) -> ReviewEnvelopeRenderResult {
    render_review_envelope_with_id(input, Some(review_id), Some(conclusion), status_message)
}

fn render_review_envelope_with_id(
    input: &ReviewEnvelopeRenderInput<'_>,
    review_id: Option<&ReviewId>,
    conclusion: Option<ReviewCheckConclusion>,
    status_message: Option<&str>,
) -> ReviewEnvelopeRenderResult {
    let grouped = group_review_issues_by_path_line(input.issues, input.max_comments);

    let comments: Vec<ReviewComment> = grouped
        .groups
        .iter()
        .map(|group| {
            render_review_comment_for_group_with_id(
                &ReviewCommentRenderInput {
                    provider: input.provider,
                    group,
                    gitlab_diff_refs: input.gitlab_diff_refs,
                    diff_index: input.diff_index,
                    path_prefix: input.path_prefix,
                    include_guidance: input.include_guidance,
                    suggestion_block: input.suggestion_block,
                    guidance_block: input.guidance_block,
                },
                review_id,
            )
        })
        .collect();

    let conclusion = conclusion.unwrap_or_else(|| github_check_conclusion(input.issues));
    let summary_text = review_summary_text(
        input.command,
        input.provider,
        comments.len(),
        status_message,
        input.trailing_section,
    );
    let summary_fp = summary_fingerprint(&summary_text);
    let summary_marker = review_markers(&summary_fp, review_id);
    let body = format!("{summary_text}{summary_marker}");
    let summary = ReviewEnvelopeSummary {
        body: body.clone(),
        fingerprint: summary_fp,
    };

    let truncation = ReviewEnvelopeTruncation {
        body: comments.iter().any(review_comment_truncated),
        comment_limit: grouped.truncated,
    };

    ReviewEnvelopeRenderResult {
        envelope: build_review_envelope_output(input.provider, body, summary, comments, conclusion),
        truncation,
    }
}

/// Review body: what this review carries and where to read it.
///
/// No run verdict. A provider review is a point-in-time record that a later
/// run cannot rewrite, so a verdict rendered here keeps asserting a state the
/// editable sticky comment has already moved on from. The machine-readable
/// gate result still travels on `meta.check_conclusion`.
fn review_summary_text(
    command: &str,
    provider: CiProvider,
    comment_count: usize,
    status_message: Option<&str>,
    trailing_section: Option<&str>,
) -> String {
    let status = status_message.map_or_else(String::new, |message| format!("\n\n> {message}"));
    let section = trailing_section
        .map(str::trim)
        .filter(|section| !section.is_empty())
        .map_or_else(String::new, |section| format!("\n\n{section}"));
    format!(
        "### Fallow {}{}\n\n{}{}\n\n<!-- fallow-review -->",
        command_title(command),
        status,
        inline_comment_line(provider, comment_count),
        section,
    )
}

fn inline_comment_line(provider: CiProvider, count: usize) -> String {
    if count == 0 {
        return format!(
            "No findings anchored to the changed lines in this {}.",
            change_noun(provider)
        );
    }
    format!(
        "{count} inline comment{} on the changed lines. Open the {} tab to review.",
        if count == 1 { "" } else { "s" },
        changes_tab(provider),
    )
}

/// Review issues grouped per `(path, line)` for one-comment-per-location
/// rendering.
#[derive(Debug, PartialEq, Eq)]
pub struct GroupedReviewIssues<'a> {
    /// One group per distinct location, in input order.
    pub groups: Vec<Vec<&'a CiIssue>>,
    /// True when the group cap cut off remaining issues.
    pub truncated: bool,
}

/// Group consecutive same-(path, line) issues. Input is already sorted by
/// `(path, line, fingerprint)` so a single linear pass collects runs.
#[must_use]
pub fn group_review_issues_by_path_line(
    issues: &[CiIssue],
    max_groups: usize,
) -> GroupedReviewIssues<'_> {
    if max_groups == 0 {
        return GroupedReviewIssues {
            groups: Vec::new(),
            truncated: !issues.is_empty(),
        };
    }
    let mut groups: Vec<Vec<&CiIssue>> = Vec::with_capacity(max_groups.min(issues.len()));
    let mut current: Vec<&CiIssue> = Vec::new();
    let mut current_key: Option<(&str, u64)> = None;
    for issue in issues {
        let key = (issue.path.as_str(), issue.line);
        if Some(key) != current_key {
            if !current.is_empty() {
                groups.push(std::mem::take(&mut current));
                if groups.len() == max_groups {
                    return GroupedReviewIssues {
                        groups,
                        truncated: true,
                    };
                }
            }
            current_key = Some(key);
        }
        current.push(issue);
    }
    if !current.is_empty() && groups.len() < max_groups {
        groups.push(current);
    }
    GroupedReviewIssues {
        groups,
        truncated: false,
    }
}

fn review_comment_truncated(comment: &ReviewComment) -> bool {
    match comment {
        ReviewComment::GitHub(comment) => comment.truncated,
        ReviewComment::GitLab(comment) => comment.truncated,
    }
}

/// Inputs for rendering one inline review comment from a location group.
pub struct ReviewCommentRenderInput<'a, 'group> {
    /// CI provider whose comment shape to produce.
    pub provider: CiProvider,
    /// Issues sharing the same `(path, line)`; the first is the representative.
    pub group: &'a [&'group CiIssue],
    /// Required for GitLab positioned discussions; ignored for GitHub.
    pub gitlab_diff_refs: Option<&'a ReviewGitlabDiffRefs>,
    /// Diff index used to resolve renamed paths for GitLab positions.
    pub diff_index: Option<&'a DiffIndex>,
    /// Prepended to every emitted path after diff lookups have run.
    pub path_prefix: &'a str,
    /// Whether to append per-finding guidance blocks to the body.
    pub include_guidance: bool,
    /// Produces a provider-specific suggestion block for a finding, when one
    /// applies.
    pub suggestion_block: &'a dyn Fn(CiProvider, &CiIssue) -> Option<String>,
    /// Produces a guidance block for a finding, when one applies.
    pub guidance_block: &'a dyn Fn(&CiIssue) -> Option<String>,
}

/// Render one comment from a group of issues sharing the same `(path, line)`.
#[must_use]
pub fn render_review_comment_for_group(input: &ReviewCommentRenderInput<'_, '_>) -> ReviewComment {
    render_review_comment_for_group_with_id(input, None)
}

fn render_review_comment_for_group_with_id(
    input: &ReviewCommentRenderInput<'_, '_>,
    review_id: Option<&ReviewId>,
) -> ReviewComment {
    assert!(
        !input.group.is_empty(),
        "group_review_issues_by_path_line never yields empty"
    );
    let representative = input.group[0];
    let fingerprint = if input.group.len() == 1 {
        representative.fingerprint.clone()
    } else {
        let constituents: Vec<&str> = input.group.iter().map(|i| i.fingerprint.as_str()).collect();
        composite_fingerprint(&constituents)
    };
    let legacy_fingerprint = group_legacy_fingerprint(input.group);

    let content = build_merged_comment_content(input);
    let marker_line = review_markers(&fingerprint, review_id);
    let (body, truncated) = cap_body_with_marker(&content, &marker_line);

    build_review_comment(ReviewCommentInput {
        provider: input.provider,
        representative,
        gitlab_diff_refs: input.gitlab_diff_refs,
        diff_index: input.diff_index,
        path_prefix: input.path_prefix,
        body,
        fingerprint,
        legacy_fingerprint,
        truncated,
    })
}

/// The fingerprint an older Fallow release gave a comment for `group`, or
/// `None` when no issue in the group has a legacy fingerprint.
///
/// A merged comment hashes the legacy fingerprint of each constituent, or its
/// fingerprint when the constituent has no legacy value. This is the value
/// that the older release wrote into the merged marker.
fn group_legacy_fingerprint(group: &[&CiIssue]) -> Option<String> {
    if group.iter().all(|issue| issue.legacy_fingerprint.is_none()) {
        return None;
    }
    if let [issue] = group {
        return issue.legacy_fingerprint.clone();
    }
    let constituents: Vec<&str> = group
        .iter()
        .map(|issue| {
            issue
                .legacy_fingerprint
                .as_deref()
                .unwrap_or(issue.fingerprint.as_str())
        })
        .collect();
    Some(composite_fingerprint(&constituents))
}

#[expect(clippy::expect_used, reason = "formatting into String is infallible")]
fn build_merged_comment_content(input: &ReviewCommentRenderInput<'_, '_>) -> String {
    let mut content = String::new();
    for (index, issue) in input.group.iter().enumerate() {
        let label = review_label_from_codeclimate(&issue.severity);
        if index > 0 {
            content.push_str("\n\n");
        }
        write!(
            content,
            "**{}** `{}`: {}",
            label,
            escape_md(&issue.rule_id),
            escape_md(&issue.description)
        )
        .expect("write to String is infallible");
        if !issue.other_locations.is_empty() {
            content.push_str("\n\nOther locations: ");
            let locations = issue
                .other_locations
                .iter()
                .map(|location| {
                    markdown_code_span(&format!(
                        "{}:{}-{}",
                        apply_path_prefix(input.path_prefix, &location.path),
                        location.line,
                        location.end_line
                    ))
                })
                .collect::<Vec<_>>()
                .join(", ");
            content.push_str(&locations);
        }
        if let Some(suggestion) = (input.suggestion_block)(input.provider, issue) {
            content.push_str(&suggestion);
        }
        if input.include_guidance
            && let Some(guidance) = (input.guidance_block)(issue)
        {
            content.push_str(&guidance);
        }
    }
    content
}

struct ReviewCommentInput<'a> {
    provider: CiProvider,
    representative: &'a CiIssue,
    gitlab_diff_refs: Option<&'a ReviewGitlabDiffRefs>,
    diff_index: Option<&'a DiffIndex>,
    path_prefix: &'a str,
    body: String,
    fingerprint: String,
    legacy_fingerprint: Option<String>,
    truncated: bool,
}

fn build_review_comment(input: ReviewCommentInput<'_>) -> ReviewComment {
    let ReviewCommentInput {
        provider,
        representative,
        gitlab_diff_refs,
        diff_index,
        path_prefix,
        body,
        fingerprint,
        legacy_fingerprint,
        truncated,
    } = input;
    match provider {
        CiProvider::Github => ReviewComment::GitHub(GitHubReviewComment {
            path: apply_path_prefix(path_prefix, &representative.path),
            line: u32::try_from(representative.line).unwrap_or(u32::MAX),
            side: GitHubReviewSide::Right,
            body,
            fingerprint,
            legacy_fingerprint,
            truncated,
        }),
        CiProvider::Gitlab => {
            // Renames resolve on the analysis-root-relative path, before the
            // presentation prefix goes on: the diff's keys never carry it.
            let old_rel = diff_index
                .and_then(|di| di.old_path_for_root_relative(&representative.path))
                .map_or_else(|| representative.path.clone(), Cow::into_owned);
            let new_path = apply_path_prefix(path_prefix, &representative.path);
            let old_path = apply_path_prefix(path_prefix, &old_rel);
            let position = GitLabReviewPosition {
                base_sha: gitlab_diff_refs.map(|r| r.base_sha.clone()),
                start_sha: gitlab_diff_refs.map(|r| r.start_sha.clone()),
                head_sha: gitlab_diff_refs.map(|r| r.head_sha.clone()),
                position_type: GitLabReviewPositionType::Text,
                old_path,
                new_path,
                new_line: u32::try_from(representative.line).unwrap_or(u32::MAX),
            };
            ReviewComment::GitLab(GitLabReviewComment {
                body,
                position,
                fingerprint,
                legacy_fingerprint,
                truncated,
            })
        }
    }
}

/// Append `marker_line` to `content`, truncating `content` on a char boundary
/// so the whole body stays within [`MAX_COMMENT_BODY_BYTES`]. The marker is
/// never sacrificed. Returns the body and whether truncation happened.
#[must_use]
pub fn cap_body_with_marker(content: &str, marker_line: &str) -> (String, bool) {
    let intact_len = content.len() + marker_line.len();
    if intact_len <= MAX_COMMENT_BODY_BYTES {
        let mut out = String::with_capacity(intact_len);
        out.push_str(content);
        out.push_str(marker_line);
        return (out, false);
    }
    let reserved = marker_line.len() + TRUNCATION_SUFFIX.len();
    let budget = MAX_COMMENT_BODY_BYTES.saturating_sub(reserved);
    let mut cut = budget.min(content.len());
    while cut > 0 && !content.is_char_boundary(cut) {
        cut -= 1;
    }
    let mut out = String::with_capacity(MAX_COMMENT_BODY_BYTES);
    out.push_str(&content[..cut]);
    out.push_str(TRUNCATION_SUFFIX);
    out.push_str(marker_line);
    (out, true)
}

/// Map a CodeClimate severity name to the review badge label: `error` for
/// major and above, `warn` otherwise.
#[must_use]
pub const fn review_label_from_codeclimate(severity_name: &str) -> &'static str {
    match severity_name.as_bytes() {
        b"major" | b"critical" | b"blocker" => "error",
        _ => "warn",
    }
}

/// GitHub check conclusion for a set of findings: `Failure` when any is major
/// or above, `Success` when empty, `Neutral` otherwise.
#[must_use]
pub fn github_check_conclusion(issues: &[CiIssue]) -> ReviewCheckConclusion {
    if issues
        .iter()
        .any(|issue| matches!(issue.severity.as_str(), "major" | "critical" | "blocker"))
    {
        ReviewCheckConclusion::Failure
    } else if issues.is_empty() {
        ReviewCheckConclusion::Success
    } else {
        ReviewCheckConclusion::Neutral
    }
}

fn build_review_envelope_output(
    provider: CiProvider,
    body: String,
    summary: ReviewEnvelopeSummary,
    comments: Vec<ReviewComment>,
    conclusion: ReviewCheckConclusion,
) -> ReviewEnvelopeOutput {
    match provider {
        CiProvider::Github => ReviewEnvelopeOutput {
            event: Some(ReviewEnvelopeEvent::Comment),
            body,
            summary,
            comments,
            marker_regex: default_marker_regex(),
            marker_regex_flags: default_marker_regex_flags(),
            meta: ReviewEnvelopeMeta {
                schema: ReviewEnvelopeSchema::V3,
                provider: ReviewProvider::Github,
                check_conclusion: Some(conclusion),
            },
        },
        CiProvider::Gitlab => ReviewEnvelopeOutput {
            event: None,
            body,
            summary,
            comments,
            marker_regex: default_marker_regex(),
            marker_regex_flags: default_marker_regex_flags(),
            meta: ReviewEnvelopeMeta {
                schema: ReviewEnvelopeSchema::V3,
                provider: ReviewProvider::Gitlab,
                check_conclusion: None,
            },
        },
    }
}

fn review_markers(fingerprint: &str, review_id: Option<&ReviewId>) -> String {
    let fingerprint = format!("\n\n{MARKER_PREFIX_V3}{fingerprint}{MARKER_SUFFIX_V3}");
    match review_id {
        Some(review_id) => format!("{fingerprint}\n{}", review_id_marker(review_id)),
        None => fingerprint,
    }
}

/// Stable fingerprint for a summary comment body.
#[must_use]
pub fn summary_fingerprint(body: &str) -> String {
    fingerprint_hash(&[body])
}

/// Order-independent fingerprint for a comment merged from several findings:
/// constituents are sorted before hashing and the result carries a `merged:`
/// prefix.
#[must_use]
pub fn composite_fingerprint(constituents: &[&str]) -> String {
    let mut sorted: Vec<&str> = constituents.to_vec();
    sorted.sort_unstable();
    let joined = sorted.join(":");
    format!("merged:{}", fingerprint_hash(&[joined.as_str()]))
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::{CodeClimateIssueKind, CodeClimateLines, CodeClimateLocation};

    fn category_for_rule(rule_id: &str) -> &'static str {
        match rule_id {
            "fallow/code-duplication" => "Duplication",
            "fallow/high-complexity" => "Health",
            "fallow/unused-dependency" => "Dependencies",
            _ => "Dead code",
        }
    }

    #[test]
    fn extracts_issues_from_codeclimate() {
        let value = serde_json::json!([{
            "check_name": "fallow/unused-export",
            "description": "Export x is never imported",
            "severity": "minor",
            "fingerprint": "abc",
            "location": { "path": "src/a.ts", "lines": { "begin": 7 } }
        }]);
        let issues = issues_from_codeclimate(&value);
        assert_eq!(issues.len(), 1);
        assert_eq!(issues[0].path, "src/a.ts");
        assert_eq!(issues[0].line, 7);
    }

    #[test]
    fn typed_codeclimate_issues_extract_like_json_codeclimate() {
        let severities = [
            (CodeClimateSeverity::Info, "info"),
            (CodeClimateSeverity::Minor, "minor"),
            (CodeClimateSeverity::Major, "major"),
            (CodeClimateSeverity::Critical, "critical"),
            (CodeClimateSeverity::Blocker, "blocker"),
        ];
        let typed = severities
            .iter()
            .enumerate()
            .map(|(index, (severity, _))| CodeClimateIssue {
                kind: CodeClimateIssueKind::Issue,
                check_name: format!("fallow/rule-{index}"),
                description: format!("Finding {index}"),
                categories: vec!["Complexity".to_owned()],
                severity: *severity,
                fingerprint: format!("fp-{index}"),
                location: CodeClimateLocation {
                    path: format!("src/{index}.ts"),
                    lines: CodeClimateLines {
                        begin: u32::try_from(index + 1).expect("small fixture index"),
                        end: Some(u32::try_from(index + 3).expect("small fixture index")),
                    },
                },
                other_locations: vec![CodeClimateLocation {
                    path: format!("src/peer-{index}.ts"),
                    lines: CodeClimateLines {
                        begin: 20,
                        end: Some(24),
                    },
                }],
                owner: None,
                group: None,
                legacy_fingerprint: None,
            })
            .collect::<Vec<_>>();
        let value = serde_json::to_value(&typed).expect("typed fixture serializes");

        assert_eq!(
            issues_from_codeclimate_issues(&typed),
            issues_from_codeclimate(&value)
        );
        let normalized = issues_from_codeclimate_issues(&typed);
        assert_eq!(normalized[0].end_line, Some(3));
        assert_eq!(normalized[0].other_locations[0].path, "src/peer-0.ts");
        assert_eq!(normalized[0].other_locations[0].line, 20);
        assert_eq!(normalized[0].other_locations[0].end_line, 24);
        let typed_labels = issues_from_codeclimate_issues(&typed)
            .into_iter()
            .map(|issue| issue.severity)
            .collect::<Vec<_>>();
        let expected_labels = severities
            .iter()
            .map(|(_, label)| (*label).to_owned())
            .collect::<Vec<_>>();
        assert_eq!(typed_labels, expected_labels);
    }

    #[test]
    fn review_comment_renders_repository_prefixed_peer_ranges() {
        let issue = CiIssue {
            rule_id: "fallow/code-duplication".to_owned(),
            description: "Code clone dup:abcd1234 (11 lines, 2 instances)".to_owned(),
            severity: "minor".to_owned(),
            path: "src/a.ts".to_owned(),
            line: 5,
            end_line: Some(15),
            other_locations: vec![CiLocation {
                path: "src/b.ts".to_owned(),
                line: 30,
                end_line: 40,
            }],
            fingerprint: "instance-fingerprint".to_owned(),
            legacy_fingerprint: None,
        };
        let comment = render_review_comment_for_group(&ReviewCommentRenderInput {
            provider: CiProvider::Gitlab,
            group: &[&issue],
            gitlab_diff_refs: None,
            diff_index: None,
            path_prefix: "packages/app",
            include_guidance: false,
            suggestion_block: &|_, _| None,
            guidance_block: &|_| None,
        });
        let ReviewComment::GitLab(comment) = comment else {
            panic!("expected GitLab comment");
        };

        assert_eq!(comment.position.new_path, "packages/app/src/a.ts");
        assert!(
            comment
                .body
                .contains("Other locations: `packages/app/src/b.ts:30-40`")
        );
    }

    #[test]
    fn renders_default_empty_comment() {
        let body = render_pr_comment(&PrCommentRenderInput {
            command: "check",
            provider: CiProvider::Github,
            issues: &[],
            marker_id: "fallow-results".to_owned(),
            max_comments: 50,
            category_for_rule: &category_for_rule,
            trailing_section: None,
        });
        assert!(body.contains("<!-- fallow-id: fallow-results"));
        assert!(body.contains("No findings for this pull request."));
    }

    fn pr_comment_issue(rule_id: &str, description: &str, severity: &str, path: &str) -> CiIssue {
        CiIssue {
            rule_id: rule_id.to_owned(),
            description: description.to_owned(),
            severity: severity.to_owned(),
            path: path.to_owned(),
            line: 3,
            end_line: None,
            other_locations: Vec::new(),
            fingerprint: path.to_owned(),
            legacy_fingerprint: None,
        }
    }

    fn dead_code_issue(line: u64, fingerprint: &str, legacy: Option<&str>) -> CiIssue {
        CiIssue {
            rule_id: "fallow/unused-export".to_owned(),
            description: "Export 'helper' is never imported by other modules".to_owned(),
            severity: "major".to_owned(),
            path: "src/lib.ts".to_owned(),
            line,
            end_line: None,
            other_locations: Vec::new(),
            fingerprint: fingerprint.to_owned(),
            legacy_fingerprint: legacy.map(str::to_owned),
        }
    }

    fn github_comment(group: &[&CiIssue]) -> GitHubReviewComment {
        let comment = render_review_comment_for_group(&ReviewCommentRenderInput {
            provider: CiProvider::Github,
            group,
            gitlab_diff_refs: None,
            diff_index: None,
            path_prefix: "",
            include_guidance: false,
            suggestion_block: &|_, _| None,
            guidance_block: &|_| None,
        });
        let ReviewComment::GitHub(comment) = comment else {
            panic!("expected GitHub comment");
        };
        comment
    }

    /// A comment carries the stable fingerprint in a v3 marker, and the
    /// legacy fingerprint on the side, so a thread with the v2 marker of an
    /// older release still matches.
    #[test]
    fn review_comment_writes_a_v3_marker_and_keeps_the_legacy_fingerprint() {
        let issue = dead_code_issue(3, "0123456789abcdef", Some("fedcba9876543210"));

        let comment = github_comment(&[&issue]);

        assert!(
            comment
                .body
                .ends_with("<!-- fallow-fingerprint:v3: 0123456789abcdef -->"),
            "{}",
            comment.body
        );
        assert!(!comment.body.contains("fallow-fingerprint:v2:"));
        assert_eq!(comment.fingerprint, "0123456789abcdef");
        assert_eq!(
            comment.legacy_fingerprint.as_deref(),
            Some("fedcba9876543210")
        );
        let value = serde_json::to_value(&comment).expect("comment serializes");
        assert_eq!(value["legacy_fingerprint"], "fedcba9876543210");
    }

    /// A finding whose fingerprint did not change carries no legacy value,
    /// and the wire shape has no `legacy_fingerprint` key.
    #[test]
    fn review_comment_omits_an_unchanged_legacy_fingerprint() {
        let issue = dead_code_issue(3, "0123456789abcdef", None);

        let comment = github_comment(&[&issue]);

        assert_eq!(comment.legacy_fingerprint, None);
        let value = serde_json::to_value(&comment).expect("comment serializes");
        assert!(value.get("legacy_fingerprint").is_none());
    }

    /// A merged comment gets the composite that the older release computed:
    /// the legacy value of each constituent, or its fingerprint when it has
    /// no legacy value.
    #[test]
    fn merged_review_comment_rebuilds_the_legacy_composite() {
        let moved = dead_code_issue(3, "0123456789abcdef", Some("fedcba9876543210"));
        let kept = dead_code_issue(3, "1111111111111111", None);

        let comment = github_comment(&[&moved, &kept]);

        assert_eq!(
            comment.fingerprint,
            composite_fingerprint(&["0123456789abcdef", "1111111111111111"])
        );
        assert_eq!(
            comment.legacy_fingerprint,
            Some(composite_fingerprint(&[
                "fedcba9876543210",
                "1111111111111111"
            ]))
        );
    }

    #[test]
    fn pr_comment_titles_by_content_and_names_its_only_category() {
        let issues = vec![
            pr_comment_issue(
                "fallow/unresolved-import",
                "Import './x' could not be resolved",
                "major",
                "src/a.ts",
            ),
            pr_comment_issue(
                "fallow/unresolved-import",
                "Import './y' could not be resolved",
                "major",
                "src/b.ts",
            ),
        ];
        let body = render_pr_comment(&PrCommentRenderInput {
            command: "dead-code",
            provider: CiProvider::Github,
            issues: &issues,
            marker_id: "fallow-results".to_owned(),
            max_comments: 50,
            category_for_rule: &category_for_rule,
            trailing_section: None,
        });
        assert!(body.contains("### Fallow codebase report"), "{body}");
        assert!(body.contains("**Quality gate failed**"), "{body}");
        assert!(body.contains("Found **2** findings."), "{body}");
        assert!(body.contains("<summary>Dead code (2)</summary>"), "{body}");
    }

    #[test]
    fn pr_comment_breakdown_indexes_several_categories() {
        let issues = vec![
            pr_comment_issue(
                "fallow/unresolved-import",
                "Import './x' could not be resolved",
                "major",
                "src/a.ts",
            ),
            pr_comment_issue(
                "fallow/unused-dependency",
                "Package 'lodash' is never imported",
                "minor",
                "package.json",
            ),
        ];
        let body = render_pr_comment(&PrCommentRenderInput {
            command: "check",
            provider: CiProvider::Github,
            issues: &issues,
            marker_id: "fallow-results".to_owned(),
            max_comments: 50,
            category_for_rule: &category_for_rule,
            trailing_section: None,
        });
        assert!(
            body.contains("Found **2** findings: Dead code 1, Dependencies 1."),
            "{body}"
        );
    }

    #[test]
    fn pr_comment_empty_state_speaks_the_provider_language() {
        let github = render_pr_comment(&PrCommentRenderInput {
            command: "dead-code",
            provider: CiProvider::Github,
            issues: &[],
            marker_id: "fallow-results".to_owned(),
            max_comments: 50,
            category_for_rule: &category_for_rule,
            trailing_section: None,
        });
        let gitlab = render_pr_comment(&PrCommentRenderInput {
            command: "dead-code",
            provider: CiProvider::Gitlab,
            issues: &[],
            marker_id: "fallow-results".to_owned(),
            max_comments: 50,
            category_for_rule: &category_for_rule,
            trailing_section: None,
        });
        assert!(
            github.contains("No findings for this pull request."),
            "{github}"
        );
        assert!(
            gitlab.contains("No findings for this merge request."),
            "{gitlab}"
        );
        assert!(
            github.starts_with("<!-- fallow-id: fallow-results -->\n"),
            "{github}"
        );
        assert!(github.contains("Generated by fallow."), "{github}");
    }

    #[test]
    fn escape_md_escapes_inline_commonmark_specials() {
        let raw = "foo*bar_baz [a](u) `c` <h> #x !i ~s | p";
        let escaped = escape_md(raw);
        for ch in [
            '*', '_', '[', ']', '(', ')', '`', '<', '>', '#', '!', '~', '|',
        ] {
            let raw_count = raw.chars().filter(|c| c == &ch).count();
            let escaped_count = escaped.matches(&format!("\\{ch}")).count();
            assert_eq!(
                raw_count, escaped_count,
                "char {ch:?}: raw {raw_count} occurrences, escaped {escaped_count} in {escaped:?}"
            );
        }
    }

    #[test]
    fn escape_md_escapes_ampersand_to_block_numeric_entity_bypass() {
        let raw = "value &#42;suspicious&#42; here";
        let escaped = escape_md(raw);
        assert!(escaped.contains(r"\&"), "got: {escaped}");
        assert!(escaped.contains(r"\#"), "got: {escaped}");
        assert!(!escaped.contains(" *suspicious"), "got: {escaped}");
    }

    #[test]
    fn summary_label_foreshadows_truncation() {
        assert_eq!(
            summary_label("Duplication", 160, 50),
            "Duplication (160, showing 50)"
        );
        assert_eq!(summary_label("Health", 12, 50), "Health (12)");
        assert_eq!(summary_label("Dependencies", 50, 50), "Dependencies (50)");
    }

    #[test]
    fn escape_md_does_not_escape_block_only_markers() {
        let raw = "fallow/test-only-dependency package.json:12";
        let escaped = escape_md(raw);
        assert!(!escaped.contains("\\-"), "should not escape `-`");
        assert!(!escaped.contains("\\."), "should not escape `.`");
        assert_eq!(escaped, raw);
    }

    #[test]
    fn escape_md_collapses_newlines_to_spaces() {
        let raw = "first\nsecond\nthird";
        assert_eq!(escape_md(raw), "first second third");
    }

    #[test]
    fn escape_md_collapses_carriage_returns_to_spaces() {
        assert_eq!(escape_md("first\r\nsecond\rthird"), "first second third");
    }

    #[test]
    fn escape_md_trims_surrounding_whitespace() {
        assert_eq!(escape_md("  a\u{2003}\r\n"), "a");
        assert_eq!(escape_md(" \t\r\n\u{2003} "), "");
    }

    #[test]
    fn escape_md_collapses_crlf_to_one_space() {
        let collapsed = escape_md("a\r\nb\rc\nd");
        assert_eq!(collapsed, "a b c d");
        assert_eq!(collapsed.len(), 7, "CRLF must not expand to two spaces");
    }

    #[test]
    fn escape_md_preserves_interior_tabs_and_wide_spaces() {
        assert_eq!(escape_md("a\tb"), "a\tb");
        assert_eq!(escape_md("a\u{2003}b"), "a\u{2003}b");
    }

    #[test]
    fn escape_md_passes_non_ascii_through_unchanged() {
        assert_eq!(escape_md("é🦀"), "é🦀");
    }

    #[test]
    fn markdown_code_span_grows_fence_past_inner_backticks() {
        assert_eq!(markdown_code_span("plain"), "`plain`");
        assert_eq!(markdown_code_span("has`tick"), "``has`tick``");
        assert_eq!(markdown_code_span("`leading"), "`` `leading ``");
    }

    #[test]
    fn markdown_table_code_span_escapes_pipes() {
        assert_eq!(markdown_table_code_span("a|b"), "`a\\|b`");
        assert_eq!(markdown_table_code_span("x`|y"), "``x`\\|y``");
    }

    #[test]
    fn markdown_table_code_span_collapses_line_endings() {
        assert_eq!(markdown_table_code_span("a\r\nb\rc\nd"), "`a b c d`");
    }

    #[test]
    fn markdown_table_text_neutralizes_pipes_and_line_endings() {
        assert_eq!(markdown_table_text("a|b"), "a\\|b");
        assert_eq!(markdown_table_text("a\r\nb\rc\nd"), "a b c d");
    }

    #[test]
    fn escape_md_leaves_safe_chars_unchanged() {
        let raw = "Export 'helperFn' is never imported by other modules";
        assert_eq!(
            escape_md(raw),
            r"Export 'helperFn' is never imported by other modules"
        );
    }

    #[test]
    fn is_project_level_rule_covers_config_anchored_dependency_findings() {
        for rule_id in PROJECT_LEVEL_RULE_IDS {
            assert!(
                is_project_level_rule(rule_id),
                "{rule_id} must be project-level"
            );
        }
        for rule_id in [
            "fallow/unused-file",
            "fallow/unused-export",
            "fallow/unused-type",
            "fallow/unused-enum-member",
            "fallow/unused-class-member",
            "fallow/unused-store-member",
            "fallow/unresolved-import",
            "fallow/unlisted-dependency",
            "fallow/duplicate-export",
            "fallow/circular-dependency",
            "fallow/re-export-cycle",
            "fallow/package-cycle",
            "fallow/boundary-violation",
            "fallow/stale-suppression",
            "fallow/private-type-leak",
            "fallow/high-complexity",
            "fallow/high-crap-score",
        ] {
            assert!(
                !is_project_level_rule(rule_id),
                "{rule_id} must NOT be project-level"
            );
        }
    }

    #[test]
    fn escape_md_double_apply_is_safe() {
        let raw = "code with `backticks` and *stars*";
        let once = escape_md(raw);
        let twice = escape_md(&once);
        assert_eq!(once, r"code with \`backticks\` and \*stars\*");
        assert_eq!(twice, r"code with \\\`backticks\\\` and \\\*stars\\\*");
    }

    #[test]
    fn pr_comment_trailing_section_renders_before_the_footer() {
        let body = render_pr_comment(&PrCommentRenderInput {
            command: "check",
            provider: CiProvider::Github,
            issues: &[],
            marker_id: "fallow-results".to_owned(),
            max_comments: 50,
            category_for_rule: &category_for_rule,
            trailing_section: Some("\n## Unmatched config patterns\n\n- `@typo/*`"),
        });
        assert!(
            body.ends_with(
                "\n\n## Unmatched config patterns\n\n- `@typo/*`\n\nGenerated by fallow."
            ),
            "{body}"
        );
    }
}