soothfast-report 0.3.0

//! Changelog drafting: API-surface diff + perf deltas rendered as a draft
//! section, assembled from recorded facts instead of backfilled from memory.

use std::collections::BTreeMap;

use serde_json::Value;

use crate::llms::SurfaceEntry;

/// What the API section has to report.
///
/// The two cases are separate types rather than an empty-string convention:
/// "nothing changed" and "there was nothing to compare against" read the
/// same in prose but mean opposite things, and a changelog that confuses
/// them reports calm where it had no input at all.
pub enum ApiSection<'a> {
    /// Diff against an earlier release.
    Diff { against: &'a str, text: &'a str },
    /// No earlier release exists, so the surface itself is the news.
    Initial(&'a [SurfaceEntry]),
}

/// Per-metric movement a delta table is willing to report, as percentages.
///
/// These mirror the gate's own thresholds and are passed in rather than
/// defined here, so the changelog reports exactly what the gate would have
/// flagged instead of drifting from it.
///
/// Only deterministic metrics have thresholds, because a changelog is a
/// permanent record: walltime moves 15-20% between two runs of identical
/// code on a shared CI runner, so recording it means rewriting the section
/// on every merge to say nothing. Walltime regressions are `gate`'s job,
/// where a human reads the verdict against a live noise floor.
pub struct PerfThresholds {
    pub instructions_pct: f64,
    pub allocs_pct: f64,
}

/// One merged change, read off a conventional-commit subject.
pub struct Change {
    /// Commit type: `feat`, `fix`, `perf`, `docs`, and the rest.
    pub kind: String,
    /// Conventional-commit scope, the parenthesised part after the type.
    pub scope: Option<String>,
    /// The subject carried the `!` breaking-change marker.
    pub breaking: bool,
    /// Subject line with the type prefix and pull request number removed.
    pub subject: String,
    /// Pull request the subject ended with, when it named one.
    pub pr: Option<u32>,
}

/// Subjects the repo's own bots commit, matched whole. A prefix would be
/// tidier and would also swallow a real `regenerate ...` feature, which is
/// the worse failure: a stray bot line is visible, a missing feature is not.
const BOT_SUBJECTS: [&str; 3] = [
    "regenerate CHANGELOG.md",
    "regenerate API specs",
    "regenerate derived docs",
];

/// Reader-facing sections, in the order a release renders them. Anything
/// whose type is missing here lands under the last entry.
const SECTIONS: [(&str, &[&str]); 7] = [
    ("Breaking changes", &[]),
    ("Features", &["feat"]),
    ("Fixes", &["fix"]),
    ("Performance", &["perf"]),
    ("Documentation", &["docs"]),
    ("Dependencies", &["deps"]),
    ("Internal", &["refactor", "chore", "build", "test", "ci"]),
];

const BREAKING: &str = "Breaking changes";

/// Parse `type(scope)!: subject (#N)` subjects. Release commits and the bots
/// that regenerate derived artifacts are dropped, since a release listing
/// its own paperwork is noise.
pub fn changes_from_subjects(subjects: &[String]) -> Vec<Change> {
    subjects
        .iter()
        .filter_map(|line| parse_subject(line))
        .filter(|change| !is_bookkeeping(&change.subject))
        .collect()
}

/// Subjects that are not conventional commits of a known type: the ones a
/// release would otherwise drop in silence.
pub fn unparsed_subjects(subjects: &[String]) -> Vec<&str> {
    subjects
        .iter()
        .filter(|line| parse_subject(line).is_none())
        .map(String::as_str)
        .collect()
}

fn is_bookkeeping(subject: &str) -> bool {
    subject.starts_with("release v") || BOT_SUBJECTS.contains(&subject)
}

fn parse_subject(line: &str) -> Option<Change> {
    let (prefix, rest) = line.split_once(": ")?;
    let (prefix, breaking) = match prefix.strip_suffix('!') {
        Some(bare) => (bare, true),
        None => (prefix, false),
    };
    let (kind, scope) = match prefix.split_once('(') {
        Some((kind, scope)) => (kind, Some(scope.strip_suffix(')')?)),
        None => (prefix, None),
    };
    // A `deps` or `deps-dev` scope names the section itself, whatever type
    // carries it.
    let is_deps = scope.is_some_and(|s| s == "deps" || s.starts_with("deps-"));
    let kind = if is_deps { "deps" } else { kind };
    if !SECTIONS.iter().any(|(_, kinds)| kinds.contains(&kind)) {
        return None;
    }
    let rest = rest.trim();
    let (subject, pr) = match rest.rsplit_once(" (#") {
        Some((head, tail)) => (head, tail.strip_suffix(')').and_then(|n| n.parse().ok())),
        None => (rest, None),
    };
    Some(Change {
        kind: kind.to_string(),
        scope: scope.filter(|_| !is_deps).map(str::to_string),
        breaking,
        subject: subject.trim().to_string(),
        pr,
    })
}

/// Inputs already computed by the CLI (API section, two baselines).
pub struct DraftInputs<'a> {
    pub api: ApiSection<'a>,
    /// Merged changes since the reference, newest first.
    pub changes: &'a [Change],
    /// Section icons; `Icons::default()` for the shipped set.
    pub icons: &'a Icons,
    /// Reference baseline (older) — None renders current-only.
    pub old_baseline: Option<&'a Value>,
    pub new_baseline: &'a Value,
    /// Only consulted when `old_baseline` is Some.
    pub thresholds: PerfThresholds,
}

/// Render the "Unreleased" draft section: API surface + perf table.
pub fn draft(inputs: &DraftInputs) -> String {
    let heading = match &inputs.api {
        ApiSection::Diff { against, .. } => format!("Unreleased (draft vs {against})"),
        ApiSection::Initial(_) => "Unreleased (initial public surface)".to_string(),
    };
    let mut out = format!("## {heading}\n\n");
    out.push_str(&sections(inputs.changes, inputs.icons));

    let api = api_section(&inputs.api);
    let perf = perf_section(inputs);
    if api.is_empty() && perf.is_empty() {
        out.truncate(out.trim_end().len());
        out.push('\n');
        return out;
    }
    out.push_str("---\n\n");
    out.push_str(&api);
    out.push_str(&perf);
    out.truncate(out.trim_end().len());
    out.push('\n');
    out
}

/// One `### <emoji> <name>` block per type that has changes, omitting the
/// rest so an empty section never ships.
fn sections(changes: &[Change], icons: &Icons) -> String {
    let mut out = String::new();
    for (name, kinds) in SECTIONS {
        let mut entries = changes.iter().filter(|c| {
            if name == BREAKING {
                c.breaking
            } else {
                !c.breaking && kinds.contains(&c.kind.as_str())
            }
        });
        let Some(first) = entries.next() else {
            continue;
        };
        out.push_str(&format!("### {} {name}\n\n", icons.get(name)));
        for change in std::iter::once(first).chain(entries) {
            out.push_str(&format!("- {}\n", entry_line(change)));
        }
        out.push('\n');
    }
    out
}

fn entry_line(change: &Change) -> String {
    let subject = sentence_case(&change.subject);
    let scoped = match &change.scope {
        Some(scope) => format!("{scope}: {subject}"),
        None => subject,
    };
    match change.pr {
        Some(pr) => format!("{scoped} (#{pr})"),
        None => scoped,
    }
}

/// Commit subjects are imperative and lowercase; a release note reads as a
/// list of sentences. A subject opening on an identifier is left alone,
/// since `soothfast.lock` is not a word to capitalize. `-` is deliberately
/// not in that set: `cargo-soothfast` and `version-coupled` are the same
/// shape, and the ordinary word is the commoner case.
fn sentence_case(subject: &str) -> String {
    let first_token = subject.split_whitespace().next().unwrap_or_default();
    if first_token.contains(['.', '_', '(', ':']) {
        return subject.to_string();
    }
    let mut chars = subject.chars();
    match chars.next() {
        Some(first) => first.to_uppercase().collect::<String>() + chars.as_str(),
        None => String::new(),
    }
}

/// Section icons, keyed by the lowercased section name a release renders
/// (`breaking changes`, `features`, `fixes`, `performance`, `documentation`,
/// `dependencies`, `internal`).
///
/// A repo overrides any subset through `[changelog.icons]` in its
/// `soothfast.toml`; whatever it leaves out keeps the shipped default, so a
/// consumer never has to restate the whole vocabulary to change one glyph.
#[derive(Debug, Default)]
pub struct Icons {
    overrides: BTreeMap<String, String>,
}

impl Icons {
    /// Build from configured pairs, rejecting a name that is not a section.
    /// A typo silently keeping the default is how config drifts from intent.
    pub fn new(overrides: BTreeMap<String, String>) -> Result<Icons, String> {
        for name in overrides.keys() {
            if !SECTIONS
                .iter()
                .any(|(section, _)| section.eq_ignore_ascii_case(name))
            {
                let known: Vec<&str> = SECTIONS.iter().map(|(s, _)| *s).collect();
                return Err(format!(
                    "`{name}` is not a changelog section; expected one of {}",
                    known.join(", ").to_lowercase()
                ));
            }
        }
        Ok(Icons {
            overrides: overrides
                .into_iter()
                .map(|(name, icon)| (name.to_ascii_lowercase(), icon))
                .collect(),
        })
    }

    fn get(&self, section: &str) -> &str {
        self.overrides
            .get(&section.to_ascii_lowercase())
            .map(String::as_str)
            .unwrap_or_else(|| default_icon(section))
    }
}

fn default_icon(name: &str) -> &'static str {
    match name {
        "Breaking changes" => "\u{1F4A5}",
        "Features" => "\u{2728}",
        "Fixes" => "\u{1F41B}",
        "Performance" => "\u{26A1}",
        "Documentation" => "\u{1F4DD}",
        "Dependencies" => "\u{1F4E6}",
        _ => "\u{1F527}",
    }
}

/// The API surface block, empty when there is nothing to report.
fn api_section(api: &ApiSection) -> String {
    let body = match api {
        ApiSection::Diff { text, .. } if is_empty_diff(text) => return String::new(),
        ApiSection::Diff { text, .. } => format!("```\n{}\n```\n", text.trim_end()),
        // An initial surface with nothing in it is a real finding, not an
        // empty section: the extraction produced nothing to describe.
        ApiSection::Initial([]) => {
            "No public items found: nothing was extracted to describe.\n".to_string()
        }
        ApiSection::Initial(entries) => inventory(entries),
    };
    format!("### \u{1F50D} API surface\n\n{body}\n")
}

/// The measured-movement table, empty when nothing moved past a threshold.
fn perf_section(inputs: &DraftInputs) -> String {
    let mut out = String::new();
    match inputs.old_baseline {
        None => {
            out.push_str(&crate::perf_table::markdown(inputs.new_baseline));
        }
        Some(old) => {
            let t = &inputs.thresholds;
            let metrics: [(&str, [&str; 2], f64); 2] = [
                (
                    "instructions",
                    ["perfcnt", "instructions"],
                    t.instructions_pct,
                ),
                ("allocs", ["alloc", "allocs"], t.allocs_pct),
            ];
            let mut rows = String::new();
            let empty = serde_json::Map::new();
            let new_items = inputs.new_baseline["items"].as_object().unwrap_or(&empty);
            for (id, m) in new_items {
                for (label, path, threshold) in &metrics {
                    let new_v = m[path[0]][path[1]].as_f64();
                    let old_v = old["items"][id][path[0]][path[1]].as_f64();
                    if let (Some(o), Some(n)) = (old_v, new_v)
                        && o > 0.0
                    {
                        let delta = (n - o) / o * 100.0;
                        if delta.abs() >= *threshold {
                            rows.push_str(&format!(
                                "| `{id}` | {label} | {o:.1} | {n:.1} | {delta:+.1}% |\n"
                            ));
                        }
                    }
                }
            }
            if rows.is_empty() {
                return String::new();
            }
            out.push_str("| item | metric | was | now | delta |\n|---|---|---:|---:|---:|\n");
            out.push_str(&rows);
        }
    }
    format!("### \u{1F4CA} Gate movement\n\n{out}")
}

/// A diff the surface engine produced no findings for.
fn is_empty_diff(text: &str) -> bool {
    text.trim().is_empty() || text.trim() == "surface: no public API changes"
}

/// Every public item, grouped by crate. Nothing is capped: a first release
/// listing "the 12 most interesting items" would be a claim about taste,
/// not a record of what shipped.
fn inventory(entries: &[SurfaceEntry]) -> String {
    let mut by_pkg: BTreeMap<&str, Vec<&SurfaceEntry>> = BTreeMap::new();
    for e in entries {
        by_pkg.entry(&e.pkg).or_default().push(e);
    }

    let mut out = format!(
        "Initial release: {} public items across {} crates.\n",
        entries.len(),
        by_pkg.len()
    );
    for (pkg, mut items) in by_pkg {
        items.sort_by(|a, b| a.path.cmp(&b.path));
        out.push_str(&format!("\n#### `{pkg}` ({})\n\n", items.len()));
        for e in items {
            out.push_str(&format!("- `{}` ({})", e.path, e.kind));
            if !e.summary.trim().is_empty() {
                out.push_str(&format!(": {}", e.summary.trim()));
            }
            out.push('\n');
        }
    }
    out
}

#[cfg(test)]
mod tests {
    use std::collections::BTreeMap;

    use serde_json::json;

    use super::{
        ApiSection, Change, DraftInputs, Icons, PerfThresholds, changes_from_subjects, draft,
        sections, unparsed_subjects,
    };
    use crate::llms::SurfaceEntry;

    /// The values `cargo-soothfast` passes from its gate constants.
    fn gate_thresholds() -> PerfThresholds {
        PerfThresholds {
            instructions_pct: 5.0,
            allocs_pct: 5.0,
        }
    }

    fn entry(pkg: &str, path: &str, kind: &str, summary: &str) -> SurfaceEntry {
        SurfaceEntry {
            path: path.into(),
            kind: kind.into(),
            signature: String::new(),
            pkg: pkg.into(),
            summary: summary.into(),
            docs: String::new(),
        }
    }

    fn subjects(lines: &[&str]) -> Vec<String> {
        lines.iter().map(|l| l.to_string()).collect()
    }

    #[test]
    fn drafts_diff_and_deltas() {
        let old = json!({ "items": { "demo::f": { "perfcnt": { "instructions": 100 } } } });
        let new = json!({ "items": { "demo::f": { "perfcnt": { "instructions": 90 } } } });
        let text = draft(&DraftInputs {
            changes: &[],
            icons: &Icons::default(),
            api: ApiSection::Diff {
                against: "v1.0.0",
                text: "ADDED    demo::g\n",
            },
            old_baseline: Some(&old),
            new_baseline: &new,
            thresholds: gate_thresholds(),
        });
        assert!(text.contains("draft vs v1.0.0"));
        assert!(text.contains("ADDED    demo::g"));
        assert!(text.contains("-10.0%"));
    }

    #[test]
    fn an_unchanged_crates_sentinel_must_not_hide_findings() {
        let new = json!({ "items": {} });
        let text = draft(&DraftInputs {
            changes: &[],
            icons: &Icons::default(),
            api: ApiSection::Diff {
                against: "v1.0.0",
                text: "# a\nsurface: no public API changes\n\n# b\nADDED    b::x\n",
            },
            old_baseline: None,
            new_baseline: &new,
            thresholds: gate_thresholds(),
        });
        assert!(text.contains("ADDED    b::x"), "{text}");
        assert!(!text.contains("No public API changes"), "{text}");
    }

    /// A changelog is permanent, so it records only metrics that reproduce.
    /// Two CI runs of identical code moved walltime -15.2% and +18.2% on
    /// separate items, which rewrote this section on every merge.
    #[test]
    fn walltime_never_reaches_the_table_however_far_it_moved() {
        let old = json!({ "items": { "demo::f": {
            "walltime": { "median_ns": 275028.3 }, "alloc": { "allocs": 6 } } } });
        let new = json!({ "items": { "demo::f": {
            "walltime": { "median_ns": 324972.0 }, "alloc": { "allocs": 6 } } } });
        let text = draft(&DraftInputs {
            changes: &[],
            icons: &Icons::default(),
            api: ApiSection::Diff {
                against: "v1.0.0",
                text: "",
            },
            old_baseline: Some(&old),
            new_baseline: &new,
            thresholds: gate_thresholds(),
        });
        assert_eq!(text.trim(), "## Unreleased (draft vs v1.0.0)");
    }

    /// The deterministic metrics are the point: they must still land.
    #[test]
    fn an_allocation_regression_is_still_reported() {
        let old = json!({ "items": { "demo::f": {
            "walltime": { "median_ns": 100.0 }, "alloc": { "allocs": 100 } } } });
        let new = json!({ "items": { "demo::f": {
            "walltime": { "median_ns": 200.0 }, "alloc": { "allocs": 120 } } } });
        let text = draft(&DraftInputs {
            changes: &[],
            icons: &Icons::default(),
            api: ApiSection::Diff {
                against: "v1.0.0",
                text: "",
            },
            old_baseline: Some(&old),
            new_baseline: &new,
            thresholds: gate_thresholds(),
        });
        assert!(!text.contains("median_ns"), "{text}");
        assert!(text.contains("allocs"), "{text}");
        assert!(text.contains("+20.0%"), "{text}");
    }

    /// The bug this section's types exist to prevent: an empty diff and a
    /// missing reference are different facts and must not read alike.
    #[test]
    fn nothing_to_compare_against_does_not_claim_nothing_changed() {
        let new = json!({ "items": {} });
        let unchanged = draft(&DraftInputs {
            changes: &[],
            icons: &Icons::default(),
            api: ApiSection::Diff {
                against: "v1.0.0",
                text: "",
            },
            old_baseline: None,
            new_baseline: &new,
            thresholds: gate_thresholds(),
        });
        assert!(!unchanged.contains("API surface"), "{unchanged}");
        assert!(unchanged.contains("draft vs v1.0.0"), "{unchanged}");

        let items = [entry("demo", "demo::f", "fn", "Does a thing.")];
        let initial = draft(&DraftInputs {
            changes: &[],
            icons: &Icons::default(),
            api: ApiSection::Initial(&items),
            old_baseline: None,
            new_baseline: &new,
            thresholds: gate_thresholds(),
        });
        assert!(initial.contains("API surface"), "{initial}");
        assert!(initial.contains("initial public surface"), "{initial}");
        assert!(
            initial.contains("1 public items across 1 crates"),
            "{initial}"
        );
        assert!(
            initial.contains("`demo::f` (fn): Does a thing."),
            "{initial}"
        );
    }

    #[test]
    fn an_empty_initial_surface_says_so_rather_than_looking_calm() {
        let new = json!({ "items": {} });
        let text = draft(&DraftInputs {
            changes: &[],
            icons: &Icons::default(),
            api: ApiSection::Initial(&[]),
            old_baseline: None,
            new_baseline: &new,
            thresholds: gate_thresholds(),
        });
        assert!(text.contains("No public items found"), "{text}");
    }

    #[test]
    fn a_release_with_nothing_to_report_renders_only_its_heading() {
        let new = json!({ "items": {} });
        let old = json!({ "items": {} });
        let text = draft(&DraftInputs {
            changes: &[],
            icons: &Icons::default(),
            api: ApiSection::Diff {
                against: "v1.0.0",
                text: "",
            },
            old_baseline: Some(&old),
            new_baseline: &new,
            thresholds: gate_thresholds(),
        });
        assert_eq!(text.trim(), "## Unreleased (draft vs v1.0.0)");
    }

    #[test]
    fn subjects_group_by_type_and_carry_their_pull_request() {
        let changes = changes_from_subjects(&subjects(&[
            "feat: add gate accept for reviewed regressions (#110)",
            "fix: sync untracked config into gate worktrees (#113)",
            "chore: release v0.1.19 (#112)",
            "docs: regenerate CHANGELOG.md (#115)",
            "docs: regenerate derived docs (#126)",
            "not a conventional subject",
        ]));
        assert_eq!(changes.len(), 2);
        assert_eq!(changes[0].kind, "feat");
        assert_eq!(
            changes[0].subject,
            "add gate accept for reviewed regressions"
        );
        assert_eq!(changes[0].pr, Some(110));
        assert_eq!(changes[1].pr, Some(113));
    }

    #[test]
    fn scoped_subjects_keep_their_section_and_show_the_scope() {
        let changes = changes_from_subjects(&subjects(&[
            "feat(api): add grouped daily bars (#1)",
            "fix(server): drop a stale cache (#2)",
            "chore(deps): bump serde (#3)",
            "build(deps): bump tokio (#4)",
            "build: switch to lld (#5)",
            "chore(deps-dev): bump typescript (#6)",
        ]));
        let kinds: Vec<&str> = changes.iter().map(|c| c.kind.as_str()).collect();
        assert_eq!(kinds, ["feat", "fix", "deps", "deps", "build", "deps"]);
        assert_eq!(changes[0].scope.as_deref(), Some("api"));
        assert_eq!(changes[2].scope, None);
        assert_eq!(changes[5].scope, None);
        let text = sections(&changes, &Icons::default());
        assert!(text.contains("- api: Add grouped daily bars (#1)"));
        assert!(text.contains("- server: Drop a stale cache (#2)"));
        assert!(
            text.contains("### \u{1F4E6} Dependencies\n\n- Bump serde (#3)\n- Bump tokio (#4)\n- Bump typescript (#6)")
        );
        assert!(text.contains("### \u{1F527} Internal\n\n- Switch to lld (#5)"));
    }

    #[test]
    fn a_breaking_marker_moves_the_entry_to_its_own_section() {
        let changes = changes_from_subjects(&subjects(&[
            "feat!: drop the v1 endpoints (#7)",
            "fix(api)!: rename the cursor field (#8)",
            "feat: add a thing (#9)",
        ]));
        assert!(changes[0].breaking && changes[1].breaking && !changes[2].breaking);
        let text = sections(&changes, &Icons::default());
        let breaking = text.find("Breaking changes").unwrap();
        let features = text.find("Features").unwrap();
        assert!(breaking < features);
        assert!(
            text.contains("- Drop the v1 endpoints (#7)\n- api: Rename the cursor field (#8)\n")
        );
        assert!(!text[features..].contains("v1 endpoints"));
    }

    #[test]
    fn unparsed_subjects_are_reported_but_paperwork_is_not() {
        let lines = subjects(&[
            "feat: add a thing (#1)",
            "wip: something",
            "Merge branch 'x'",
            "chore: release v0.2.0 (#3)",
            "docs: regenerate CHANGELOG.md (#4)",
        ]);
        assert_eq!(
            unparsed_subjects(&lines),
            ["wip: something", "Merge branch 'x'"]
        );
    }

    #[test]
    fn a_configured_icon_replaces_only_the_section_it_names() {
        let changes = changes_from_subjects(&subjects(&["feat: add a thing", "fix: mend a thing"]));
        let icons =
            Icons::new(BTreeMap::from([("features".to_string(), "A".to_string())])).unwrap();
        let rendered = super::sections(&changes, &icons);
        assert!(rendered.contains("### A Features"), "{rendered}");
        assert!(rendered.contains("### \u{1F41B} Fixes"), "{rendered}");
    }

    #[test]
    fn a_capitalized_section_name_is_honored_rather_than_quietly_ignored() {
        let icons =
            Icons::new(BTreeMap::from([("Features".to_string(), "A".to_string())])).unwrap();
        let changes = changes_from_subjects(&subjects(&["feat: add a thing"]));
        let rendered = super::sections(&changes, &icons);
        assert!(rendered.contains("### A Features"), "{rendered}");
    }

    #[test]
    fn dependency_bumps_get_their_own_section_rather_than_vanishing() {
        let changes = changes_from_subjects(&subjects(&[
            "deps: bump linkme from 0.3.36 to 0.3.37 (#85)",
            "deps: bump actions/download-artifact from 4.3.0 to 8.0.1 (#90)",
            "ci: harden the gate workflow (#91)",
        ]));
        let rendered = super::sections(&changes, &Icons::default());
        assert!(rendered.contains("\u{1F4E6} Dependencies"), "{rendered}");
        assert!(
            rendered.contains("- Bump linkme from 0.3.36 to 0.3.37 (#85)"),
            "{rendered}"
        );
        assert!(
            rendered.contains("- Bump actions/download-artifact from 4.3.0 to 8.0.1 (#90)"),
            "{rendered}"
        );
        let deps = rendered.find("Dependencies").unwrap();
        let internal = rendered.find("Internal").unwrap();
        assert!(deps < internal, "dependencies should precede internal");
        assert!(
            rendered.contains("- Harden the gate workflow (#91)"),
            "{rendered}"
        );
    }

    #[test]
    fn a_real_feature_that_regenerates_something_is_not_mistaken_for_a_bot() {
        let changes = changes_from_subjects(&subjects(&[
            "feat: regenerate SDK clients on a spec change",
            "docs: regenerate derived docs (#126)",
            "chore: regenerate API specs (#99)",
        ]));
        assert_eq!(changes.len(), 1);
        assert_eq!(
            changes[0].subject,
            "regenerate SDK clients on a spec change"
        );
    }

    #[test]
    fn an_icon_for_something_that_is_not_a_section_is_rejected() {
        let bad = Icons::new(BTreeMap::from([("feature".to_string(), "A".to_string())]));
        assert!(bad.unwrap_err().contains("not a changelog section"));
    }

    #[test]
    fn a_subject_opening_on_an_identifier_keeps_its_case() {
        let changes = changes_from_subjects(&subjects(&[
            "fix: soothfast.lock moves to v2",
            "fix: keep_alive is honored",
            "fix: resume changelog regen",
        ]));
        let rendered = super::sections(&changes, &Icons::default());
        assert!(
            rendered.contains("- soothfast.lock moves to v2"),
            "{rendered}"
        );
        assert!(rendered.contains("- keep_alive is honored"), "{rendered}");
        assert!(rendered.contains("- Resume changelog regen"), "{rendered}");
    }

    #[test]
    fn a_subject_without_a_pull_request_still_lists() {
        let changes = changes_from_subjects(&subjects(&["fix: land a direct commit"]));
        assert_eq!(changes.len(), 1);
        assert_eq!(changes[0].pr, None);
    }

    #[test]
    fn only_the_types_with_changes_get_a_section() {
        let new = json!({ "items": {} });
        let changes = vec![Change {
            kind: "fix".into(),
            scope: None,
            breaking: false,
            subject: "stop hashing comments".into(),
            pr: Some(124),
        }];
        let text = draft(&DraftInputs {
            changes: &changes,
            icons: &Icons::default(),
            api: ApiSection::Diff {
                against: "v1.0.0",
                text: "",
            },
            old_baseline: None,
            new_baseline: &new,
            thresholds: gate_thresholds(),
        });
        assert!(text.contains("Fixes"), "{text}");
        assert!(text.contains("- Stop hashing comments (#124)"), "{text}");
        assert!(!text.contains("Features"), "{text}");
        assert!(!text.contains("Internal"), "{text}");
    }
}