dioxus-docs-kit-build 0.6.0

use serde::Deserialize;
use std::collections::{HashMap, HashSet};
use std::env;
use std::fs;
use std::path::Path;

#[derive(Deserialize)]
struct NavConfig {
    groups: Vec<NavGroup>,
}

#[derive(Deserialize)]
struct NavGroup {
    pages: Vec<String>,
}

/// Builds the absolute path used inside the generated `include_str!()`.
///
/// Backslashes are normalized to forward slashes so the generated string
/// literal is valid on Windows (`C:\Users\...` would otherwise contain
/// invalid escape sequences).
fn include_path(manifest_dir: &str, relative: &str) -> String {
    format!("{manifest_dir}/{relative}").replace('\\', "/")
}

/// Emits a `map.insert(...)` line for `relative` if the file exists.
///
/// Missing files are skipped with a warning, but still registered via
/// `rerun-if-changed` so the build script re-runs once the file is created
/// (cargo re-runs when a watched path does not exist).
fn emit_entry(code: &mut String, manifest_dir: &str, key: &str, relative: &str) {
    let full_path = include_path(manifest_dir, relative);

    println!("cargo:rerun-if-changed={relative}");

    if !Path::new(&full_path).exists() {
        println!(
            "cargo:warning=\"{key}\" is listed in the nav/manifest but {full_path} does not exist — the page will 404. Create the file or remove the entry."
        );
        return;
    }

    // Use absolute path so include_str! works from OUT_DIR
    code.push_str(&format!(
        "    map.insert(\"{key}\", include_str!(\"{full_path}\"));\n"
    ));
}

/// Generates `doc_content_generated.rs` in `OUT_DIR` from a `_nav.json` file.
///
/// Call this from your `build.rs`:
///
/// ```rust,ignore
/// fn main() {
///     dioxus_docs_kit_build::generate_content_map("docs/_nav.json");
/// }
/// ```
///
/// The generated file is an expression that returns a `HashMap<&'static str, &'static str>`
/// and is intended to be used with `include!()`.
///
/// The docs directory is inferred from the parent of `nav_json_path`
/// (e.g. `"docs/_nav.json"` → `"docs"`).
pub fn generate_content_map(nav_json_path: &str) {
    let manifest_dir = env::var("CARGO_MANIFEST_DIR").unwrap();

    println!("cargo:rerun-if-changed={nav_json_path}");

    let json = fs::read_to_string(nav_json_path)
        .unwrap_or_else(|e| panic!("Failed to read {nav_json_path}: {e}"));
    let nav: NavConfig = serde_json::from_str(&json)
        .unwrap_or_else(|e| panic!("Failed to parse {nav_json_path}: {e}"));

    // Infer docs directory from nav path parent (e.g. "docs/_nav.json" → "docs")
    let docs_dir = Path::new(nav_json_path)
        .parent()
        .and_then(|p| p.to_str())
        .unwrap_or("docs");

    let mut code = String::from("// Auto-generated by dioxus-docs-kit-build — do not edit\n{\n");
    code.push_str("    let mut map = std::collections::HashMap::new();\n");

    for group in &nav.groups {
        for page in &group.pages {
            let mdx_path = format!("{docs_dir}/{page}.mdx");
            emit_entry(&mut code, &manifest_dir, page, &mdx_path);
        }
    }

    code.push_str("    map\n}\n");

    let out_dir = env::var("OUT_DIR").unwrap();
    let dest = Path::new(&out_dir).join("doc_content_generated.rs");
    fs::write(&dest, code).expect("Failed to write generated file");

    // Fail the build on malformed docs frontmatter, and warn about broken
    // internal links (warnings only — never fail the build for links).
    let pages: Vec<String> = nav
        .groups
        .iter()
        .flat_map(|g| g.pages.iter().cloned())
        .collect();
    validate_docs(&manifest_dir, docs_dir, &pages);
}

// ============================================================================
// Blog content map generation
// ============================================================================

#[derive(Deserialize)]
struct BlogManifest {
    posts: Vec<String>,
}

/// Generates `blog_content_generated.rs` in `OUT_DIR` from a `_blog.json` file.
///
/// Call this from your `build.rs`:
///
/// ```rust,ignore
/// fn main() {
///     dioxus_docs_kit_build::generate_blog_content_map("blog/_blog.json");
/// }
/// ```
///
/// The generated file is an expression that returns a `HashMap<&'static str, &'static str>`
/// and is intended to be used with `include!()`.
///
/// The blog directory is inferred from the parent of `manifest_path`
/// (e.g. `"blog/_blog.json"` → `"blog"`).
///
/// The manifest JSON itself is embedded under the key `"__manifest__"` so the
/// runtime library can parse author definitions and other metadata.
pub fn generate_blog_content_map(manifest_path: &str) {
    let manifest_dir = env::var("CARGO_MANIFEST_DIR").unwrap();

    println!("cargo:rerun-if-changed={manifest_path}");

    let json = fs::read_to_string(manifest_path)
        .unwrap_or_else(|e| panic!("Failed to read {manifest_path}: {e}"));
    let manifest: BlogManifest = serde_json::from_str(&json)
        .unwrap_or_else(|e| panic!("Failed to parse {manifest_path}: {e}"));

    // Infer blog directory from manifest path parent
    let blog_dir = Path::new(manifest_path)
        .parent()
        .and_then(|p| p.to_str())
        .unwrap_or("blog");

    let mut code = String::from("// Auto-generated by dioxus-docs-kit-build — do not edit\n{\n");
    code.push_str("    let mut map = std::collections::HashMap::new();\n");

    // Embed the manifest JSON itself
    let manifest_full_path = include_path(&manifest_dir, manifest_path);
    code.push_str(&format!(
        "    map.insert(\"__manifest__\", include_str!(\"{manifest_full_path}\"));\n"
    ));

    for slug in &manifest.posts {
        let mdx_path = format!("{blog_dir}/{slug}.mdx");
        emit_entry(&mut code, &manifest_dir, slug, &mdx_path);

        // Fail the build on malformed frontmatter instead of letting the post
        // silently vanish from the site at runtime.
        let full_path = include_path(&manifest_dir, &mdx_path);
        if let Ok(content) = fs::read_to_string(&full_path) {
            validate_blog_frontmatter(&mdx_path, &content);
        }
    }

    code.push_str("    map\n}\n");

    let out_dir = env::var("OUT_DIR").unwrap();
    let dest = Path::new(&out_dir).join("blog_content_generated.rs");
    fs::write(&dest, code).expect("Failed to write generated file");
}

// ============================================================================
// Build-time validation: internal links + frontmatter
// ============================================================================

/// Convert a heading title to a URL anchor slug.
///
/// Mirrors `dioxus_mdx`'s `slugify` (in `components/toc.rs`) exactly, so
/// build-time anchor checks resolve to the same ids the renderer injects. The
/// build crate cannot depend on `dioxus-mdx` (that would pull `dioxus` into
/// every consumer's build-dependencies), so this small function is duplicated.
fn slugify(text: &str) -> String {
    let text = text
        .replace("&lt;", "<")
        .replace("&gt;", ">")
        .replace("&quot;", "\"")
        .replace("&#39;", "'")
        .replace("&amp;", "&");
    let text = strip_markdown_links(&text);
    text.to_lowercase()
        .chars()
        .filter_map(|c| {
            if c.is_alphanumeric() {
                Some(c)
            } else if c.is_whitespace() || c == '-' || c == '_' || c == '.' {
                Some('-')
            } else {
                None
            }
        })
        .collect::<String>()
        .split('-')
        .filter(|s| !s.is_empty())
        .collect::<Vec<_>>()
        .join("-")
}

/// Reduce markdown links/images `[text](url)` to their text (mirrors
/// `dioxus_mdx`'s `strip_markdown_links`, for the same slug-agreement reason).
fn strip_markdown_links(text: &str) -> String {
    let mut out = String::new();
    let mut rest = text;
    while let Some(open) = rest.find('[') {
        if let Some(mid) = rest[open..].find("](") {
            let mid = open + mid;
            if let Some(close) = rest[mid..].find(')') {
                out.push_str(&rest[..open]);
                out.push_str(&rest[open + 1..mid]);
                rest = &rest[mid + close + 1..];
                continue;
            }
        }
        out.push_str(&rest[..=open]);
        rest = &rest[open + 1..];
    }
    out.push_str(rest);
    out
}

/// Remove fenced code blocks (``` or ~~~) so markdown-looking text inside code
/// samples is not mistaken for links or headings.
fn strip_code_fences(content: &str) -> String {
    let mut out = String::new();
    let mut fence: Option<char> = None;
    for line in content.lines() {
        let trimmed = line.trim_start();
        let marker = if trimmed.starts_with("```") {
            Some('`')
        } else if trimmed.starts_with("~~~") {
            Some('~')
        } else {
            None
        };
        match (fence, marker) {
            (None, Some(m)) => fence = Some(m), // opening fence
            (Some(open), Some(m)) if open == m => fence = None, // closing fence
            (None, None) => {
                out.push_str(line);
                out.push('\n');
            }
            _ => {} // inside a fence (or a mismatched fence marker within one)
        }
    }
    out
}

/// Extract anchor slugs for level 2-4 ATX headings, matching the ids the
/// renderer injects (`dioxus_mdx`'s `extract_headers` + `slugify`). H1 is
/// excluded (it is not linkable and is stripped as the duplicate page title).
fn extract_heading_slugs(content: &str) -> Vec<String> {
    let mut slugs = Vec::new();
    for line in content.lines() {
        let hashes = line.bytes().take_while(|&b| b == b'#').count();
        if (2..=4).contains(&hashes) && matches!(line.as_bytes().get(hashes), Some(b' ' | b'\t')) {
            let title = line[hashes..].trim();
            if !title.is_empty() {
                slugs.push(slugify(title));
            }
        }
    }
    slugs
}

/// Extract non-image markdown link targets (`[text](target)`), stripping any
/// `"title"` suffix and `<>` wrappers. Image links (`![...](...)`) are skipped.
fn extract_links(content: &str) -> Vec<String> {
    let bytes = content.as_bytes();
    let mut links = Vec::new();
    let mut i = 0;
    while i < bytes.len() {
        if bytes[i] == b'[' {
            let is_image = i > 0 && bytes[i - 1] == b'!';
            if let Some(close) = (i + 1..bytes.len()).find(|&j| bytes[j] == b']') {
                if bytes.get(close + 1) == Some(&b'(')
                    && let Some(pclose) = (close + 2..bytes.len()).find(|&j| bytes[j] == b')')
                {
                    if !is_image
                        && let Some(tok) = content[close + 2..pclose].split_whitespace().next()
                    {
                        let tok = tok.trim_start_matches('<').trim_end_matches('>');
                        if !tok.is_empty() {
                            links.push(tok.to_string());
                        }
                    }
                    i = pclose + 1;
                    continue;
                }
                i = close + 1;
                continue;
            }
        }
        i += 1;
    }
    links
}

/// Returns true if `target` begins with a URL scheme (`https:`, `mailto:`, …).
fn has_scheme(target: &str) -> bool {
    let mut chars = target.chars();
    match chars.next() {
        Some(c) if c.is_ascii_alphabetic() => {}
        _ => return false,
    }
    for c in chars {
        if c == ':' {
            return true;
        }
        if !(c.is_ascii_alphanumeric() || c == '+' || c == '-' || c == '.') {
            return false;
        }
    }
    false
}

/// Strip a trailing slash and any `.mdx`/`.md` extension so a link target lines
/// up with the extension-less nav page keys.
fn normalize_page_key(s: &str) -> String {
    let s = s.trim_end_matches('/');
    let s = s
        .strip_suffix(".mdx")
        .or_else(|| s.strip_suffix(".md"))
        .unwrap_or(s);
    s.to_string()
}

/// Resolve a relative link target against the directory of `current_page`.
/// Returns `None` if the path escapes the docs root.
fn resolve_relative(current_page: &str, path: &str) -> Option<String> {
    let mut base: Vec<&str> = current_page.split('/').collect();
    base.pop(); // drop the current file component, keeping its directory
    for seg in path.split('/') {
        match seg {
            "" | "." => {}
            ".." => {
                base.pop()?;
            }
            s => base.push(s),
        }
    }
    Some(base.join("/"))
}

/// Outcome of resolving an internal link target to a docs page.
enum LinkResolution {
    /// Resolved to a known page (carries its key for anchor validation).
    Valid(String),
    /// Clearly targets a docs page, but no page matches.
    Broken,
    /// Not validatable (external route, runtime-generated section, …).
    Skip,
}

/// A group directory is "validatable" only if it holds at least two static nav
/// pages. Single-page groups (e.g. an `api-reference` group whose remaining
/// pages are generated at runtime from an OpenAPI spec) are skipped, since the
/// build crate cannot know those slugs and would false-positive on them.
fn group_is_validatable(page: &str, group_counts: &HashMap<&str, usize>) -> bool {
    page.split_once('/')
        .map(|(g, _)| group_counts.get(g).copied().unwrap_or(0) >= 2)
        .unwrap_or(false)
}

/// Classify a root-absolute link (e.g. `/docs/guides/foo`). The consumer's base
/// path (e.g. `/docs`) is unknown, so both the full path and the path with its
/// first segment stripped are tried against the known pages.
fn classify_root_absolute(
    rest: &str,
    page_set: &HashSet<&str>,
    group_counts: &HashMap<&str, usize>,
) -> LinkResolution {
    let full = normalize_page_key(rest);
    let stripped = rest.split_once('/').map(|(_, s)| normalize_page_key(s));

    if page_set.contains(full.as_str()) {
        return LinkResolution::Valid(full);
    }
    if let Some(s) = &stripped
        && page_set.contains(s.as_str())
    {
        return LinkResolution::Valid(s.clone());
    }

    let clearly_docs = group_is_validatable(&full, group_counts)
        || stripped
            .as_ref()
            .is_some_and(|s| group_is_validatable(s, group_counts));
    if clearly_docs {
        LinkResolution::Broken
    } else {
        LinkResolution::Skip
    }
}

/// Classify a relative link (e.g. `../guides/foo`) resolved against the current
/// file's directory.
fn classify_relative(
    current_page: &str,
    path: &str,
    page_set: &HashSet<&str>,
    group_counts: &HashMap<&str, usize>,
) -> LinkResolution {
    let Some(resolved) = resolve_relative(current_page, path) else {
        return LinkResolution::Skip;
    };
    let resolved = normalize_page_key(&resolved);
    if resolved.is_empty() {
        return LinkResolution::Skip;
    }
    if page_set.contains(resolved.as_str()) {
        return LinkResolution::Valid(resolved);
    }
    if group_is_validatable(&resolved, group_counts) {
        LinkResolution::Broken
    } else {
        LinkResolution::Skip
    }
}

/// Validate a single link target found in `src`. Emits `cargo:warning` for
/// broken page targets and missing anchors.
fn check_link(
    src: &str,
    current_page: &str,
    target: &str,
    page_set: &HashSet<&str>,
    group_counts: &HashMap<&str, usize>,
    headings: &HashMap<&str, HashSet<String>>,
) {
    let (path_part, fragment) = match target.split_once('#') {
        Some((p, f)) => (p, Some(f)),
        None => (target, None),
    };

    // Same-page anchor (`#heading`).
    if path_part.is_empty() {
        if let Some(frag) = fragment {
            check_anchor(src, current_page, target, frag, headings);
        }
        return;
    }

    // Skip external links (`https:`, `mailto:`, protocol-relative `//host`).
    if path_part.starts_with("//") || has_scheme(path_part) {
        return;
    }

    let resolution = if let Some(rest) = path_part.strip_prefix('/') {
        classify_root_absolute(rest, page_set, group_counts)
    } else {
        classify_relative(current_page, path_part, page_set, group_counts)
    };

    match resolution {
        LinkResolution::Valid(page) => {
            if let Some(frag) = fragment {
                check_anchor(src, &page, target, frag, headings);
            }
        }
        LinkResolution::Broken => {
            println!(
                "cargo:warning={src}: internal link target \"{target}\" does not match any known docs page"
            );
        }
        LinkResolution::Skip => {}
    }
}

/// Validate that `fragment` matches a heading anchor in `page`. Skipped when the
/// target page's headings are unknown (its file was not read).
fn check_anchor(
    src: &str,
    page: &str,
    target: &str,
    fragment: &str,
    headings: &HashMap<&str, HashSet<String>>,
) {
    if fragment.is_empty() {
        return;
    }
    if let Some(anchors) = headings.get(page)
        && !anchors.contains(&slugify(fragment))
    {
        println!(
            "cargo:warning={src}: link \"{target}\" points to \"#{fragment}\" but no heading with that anchor exists in {page}"
        );
    }
}

/// Validate docs frontmatter (build error on malformed) and internal markdown
/// links (warnings only) for every existing nav page.
fn validate_docs(manifest_dir: &str, docs_dir: &str, pages: &[String]) {
    // Read each existing page once.
    let mut contents: Vec<(String, String)> = Vec::new();
    for page in pages {
        let mdx_path = format!("{docs_dir}/{page}.mdx");
        let full_path = include_path(manifest_dir, &mdx_path);
        if let Ok(raw) = fs::read_to_string(&full_path) {
            validate_docs_frontmatter(&mdx_path, &raw);
            contents.push((page.clone(), raw));
        }
    }

    let page_set: HashSet<&str> = pages.iter().map(String::as_str).collect();

    let mut group_counts: HashMap<&str, usize> = HashMap::new();
    for page in pages {
        if let Some((group, _)) = page.split_once('/') {
            *group_counts.entry(group).or_insert(0) += 1;
        }
    }

    // Strip fenced code once and reuse for both headings and link scanning.
    let stripped: Vec<(String, String)> = contents
        .iter()
        .map(|(page, raw)| (page.clone(), strip_code_fences(raw)))
        .collect();

    let mut headings: HashMap<&str, HashSet<String>> = HashMap::new();
    for (page, body) in &stripped {
        headings.insert(
            page.as_str(),
            extract_heading_slugs(body).into_iter().collect(),
        );
    }

    for (page, body) in &stripped {
        let src = format!("{docs_dir}/{page}.mdx");
        for target in extract_links(body) {
            check_link(&src, page, &target, &page_set, &group_counts, &headings);
        }
    }
}

/// A docs page's frontmatter block (if present) must parse as a YAML mapping.
/// No particular fields are required for docs pages.
fn validate_docs_frontmatter(path: &str, content: &str) {
    let content = content.trim();
    if !content.starts_with("---") {
        return;
    }
    let after = &content[3..];
    // No closing delimiter → not a frontmatter block (matches runtime behavior).
    let Some(end) = after.find("\n---") else {
        return;
    };
    let yaml = after[..end].trim();
    if yaml.is_empty() {
        return; // an empty frontmatter block is valid
    }
    match serde_yaml::from_str::<serde_yaml::Value>(yaml) {
        Ok(serde_yaml::Value::Mapping(_)) => {}
        // The runtime treats an unparseable leading block as page content and
        // still renders the page (a `---`-fenced paragraph is legal markdown),
        // so a hard build failure here would reject pages that work. Warn only.
        Ok(_) => println!(
            "cargo:warning={path}: leading --- block is not a YAML mapping and will render as page content, not frontmatter"
        ),
        Err(e) => println!(
            "cargo:warning={path}: leading --- block is not valid YAML ({e}) and will render as page content, not frontmatter"
        ),
    }
}

/// Blog frontmatter fields, mirroring
/// `dioxus_docs_kit::blog::types::BlogFrontmatter` (which a build crate cannot
/// depend on). ALL fields are mirrored, including optional ones: a
/// present-but-wrong-typed optional field (e.g. `tags: rust` instead of a
/// sequence) is a hard deserialize error at runtime that silently drops the
/// post, so it must fail the build here too.
#[derive(Deserialize)]
#[allow(dead_code)]
struct BlogFrontmatterCheck {
    title: String,
    #[serde(default)]
    description: Option<String>,
    date: String,
    author: String,
    #[serde(default)]
    tags: Vec<String>,
    #[serde(default, rename = "coverImage")]
    cover_image: Option<String>,
    #[serde(default)]
    draft: bool,
    #[serde(default)]
    featured: bool,
}

/// A blog post must have a valid frontmatter block carrying the required
/// fields, or the build fails (the post would otherwise silently vanish from
/// the site at runtime). The extraction mirrors `extract_blog_frontmatter`.
fn validate_blog_frontmatter(path: &str, content: &str) {
    let content = content.trim();
    if !content.starts_with("---") {
        panic!("{path}: missing frontmatter block (expected leading ---)");
    }
    let after = &content[3..];
    let Some(end) = after.find("\n---") else {
        panic!("{path}: unclosed frontmatter block (missing closing ---)");
    };
    let yaml = after[..end].trim();
    if let Err(e) = serde_yaml::from_str::<BlogFrontmatterCheck>(yaml) {
        panic!("{path}: malformed frontmatter: {e}");
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn include_path_joins_with_forward_slash() {
        assert_eq!(
            include_path("/home/me/project", "docs/intro.mdx"),
            "/home/me/project/docs/intro.mdx"
        );
    }

    #[test]
    fn include_path_normalizes_windows_backslashes() {
        assert_eq!(
            include_path("C:\\Users\\me\\project", "docs\\intro.mdx"),
            "C:/Users/me/project/docs/intro.mdx"
        );
    }

    // ---- link validation ---------------------------------------------------

    // Mirrors `dioxus_mdx`'s own `slugify` test cases.
    #[test]
    fn slugify_matches_mdx() {
        assert_eq!(slugify("Hello World"), "hello-world");
        assert_eq!(slugify("Getting Started!"), "getting-started");
        assert_eq!(slugify("API v1.0"), "api-v1-0");
        assert_eq!(slugify("Tips & Tricks"), "tips-tricks");
        assert_eq!(slugify("Tips &amp; Tricks"), "tips-tricks");
        assert_eq!(slugify("Q&A"), "qa");
        assert_eq!(slugify("a &lt; b"), "a-b");
        assert_eq!(slugify("See [the docs](https://x.y/z)"), "see-the-docs");
    }

    #[test]
    fn extract_links_skips_images() {
        let md = "see ![alt](/img/logo.png) and [Quickstart](/docs/getting-started/quickstart)";
        assert_eq!(
            extract_links(md),
            vec!["/docs/getting-started/quickstart".to_string()]
        );
    }

    #[test]
    fn extract_links_strips_title_and_angle_brackets() {
        let md = "[a](/docs/x \"the title\") and [b](</docs/y>)";
        assert_eq!(
            extract_links(md),
            vec!["/docs/x".to_string(), "/docs/y".to_string()]
        );
    }

    #[test]
    fn strip_code_fences_removes_fenced_links() {
        let md = "before\n```\n[not a link](/docs/nope)\n```\nafter [real](/docs/real)";
        let body = strip_code_fences(md);
        assert!(!body.contains("nope"));
        assert_eq!(extract_links(&body), vec!["/docs/real".to_string()]);
    }

    #[test]
    fn has_scheme_detects_external() {
        assert!(has_scheme("https://example.com"));
        assert!(has_scheme("mailto:me@example.com"));
        assert!(!has_scheme("/docs/guides/x"));
        assert!(!has_scheme("guides/x"));
        assert!(!has_scheme("../guides/x"));
    }

    #[test]
    fn resolve_relative_resolves_against_dir() {
        assert_eq!(
            resolve_relative("guides/blog", "customization").as_deref(),
            Some("guides/customization")
        );
        assert_eq!(
            resolve_relative("guides/blog", "../guides/customization").as_deref(),
            Some("guides/customization")
        );
        assert_eq!(
            resolve_relative("getting-started/introduction", "../guides/basic-usage").as_deref(),
            Some("guides/basic-usage")
        );
        // Escapes the docs root.
        assert_eq!(resolve_relative("changelog", "../../x"), None);
    }

    #[test]
    fn extract_heading_slugs_covers_h2_to_h4_only() {
        let md = "# Title\n## Section One\n### Sub Section\n##### Too Deep\ntext\n";
        assert_eq!(
            extract_heading_slugs(md),
            vec!["section-one".to_string(), "sub-section".to_string()]
        );
    }

    fn sample_page_data() -> (Vec<&'static str>, HashMap<&'static str, usize>) {
        let pages = vec![
            "getting-started/introduction",
            "getting-started/quickstart",
            "guides/basic-usage",
            "guides/customization",
            "guides/integration",
            "guides/blog",
            "api-reference/overview",
            "changelog",
        ];
        let mut group_counts: HashMap<&str, usize> = HashMap::new();
        for p in &pages {
            if let Some((g, _)) = p.split_once('/') {
                *group_counts.entry(g).or_insert(0) += 1;
            }
        }
        (pages, group_counts)
    }

    #[test]
    fn root_absolute_heuristic() {
        let (pages, group_counts) = sample_page_data();
        let page_set: HashSet<&str> = pages.iter().copied().collect();

        // Valid under a `/docs` base path.
        assert!(matches!(
            classify_root_absolute("docs/guides/basic-usage", &page_set, &group_counts),
            LinkResolution::Valid(_)
        ));
        // Valid under an empty (`/`) base path.
        assert!(matches!(
            classify_root_absolute("getting-started/introduction", &page_set, &group_counts),
            LinkResolution::Valid(_)
        ));
        // Broken: a dense group, but no such page.
        assert!(matches!(
            classify_root_absolute("docs/guides/nope", &page_set, &group_counts),
            LinkResolution::Broken
        ));
        // Skip: api-reference has a single static page; the rest are runtime
        // OpenAPI operations the build crate cannot see.
        assert!(matches!(
            classify_root_absolute("docs/api-reference/getUser", &page_set, &group_counts),
            LinkResolution::Skip
        ));
        // Skip: non-docs routes.
        assert!(matches!(
            classify_root_absolute("blog/hello", &page_set, &group_counts),
            LinkResolution::Skip
        ));
    }

    #[test]
    fn relative_heuristic() {
        let (pages, group_counts) = sample_page_data();
        let page_set: HashSet<&str> = pages.iter().copied().collect();

        assert!(matches!(
            classify_relative(
                "guides/basic-usage",
                "customization",
                &page_set,
                &group_counts
            ),
            LinkResolution::Valid(_)
        ));
        assert!(matches!(
            classify_relative("guides/basic-usage", "nope", &page_set, &group_counts),
            LinkResolution::Broken
        ));
        // Relative link into the single-page (OpenAPI) group is skipped.
        assert!(matches!(
            classify_relative(
                "api-reference/overview",
                "get-user",
                &page_set,
                &group_counts
            ),
            LinkResolution::Skip
        ));
    }

    // ---- frontmatter validation --------------------------------------------

    #[test]
    fn docs_frontmatter_valid_and_empty_ok() {
        validate_docs_frontmatter("x.mdx", "---\ntitle: Hi\n---\nbody");
        validate_docs_frontmatter("x.mdx", "---\n---\nbody");
        validate_docs_frontmatter("x.mdx", "no frontmatter here");
    }

    #[test]
    fn docs_frontmatter_unparseable_block_warns_but_does_not_panic() {
        // The runtime renders these pages (the block is treated as content),
        // so the build must not reject them — it only emits cargo:warning.
        validate_docs_frontmatter("x.mdx", "---\ntitle: [unclosed\n---\nbody");
        validate_docs_frontmatter("x.mdx", "---\n- a\n- b\n---\nbody");
        validate_docs_frontmatter("x.mdx", "---\nJust a fenced paragraph.\n---\nbody");
    }

    #[test]
    fn blog_frontmatter_valid_ok() {
        validate_blog_frontmatter(
            "p.mdx",
            "---\ntitle: Hi\ndate: \"2026-01-01\"\nauthor: jane\n---\nbody",
        );
    }

    #[test]
    #[should_panic(expected = "malformed frontmatter")]
    fn blog_frontmatter_bad_yaml_panics() {
        validate_blog_frontmatter(
            "p.mdx",
            "---\ntitle: [x\ndate: \"2026\"\nauthor: jane\n---\nbody",
        );
    }

    #[test]
    #[should_panic(expected = "missing field")]
    fn blog_frontmatter_missing_field_panics() {
        // No `date` field.
        validate_blog_frontmatter("p.mdx", "---\ntitle: Hi\nauthor: jane\n---\nbody");
    }

    #[test]
    #[should_panic(expected = "missing frontmatter")]
    fn blog_frontmatter_no_block_panics() {
        validate_blog_frontmatter("p.mdx", "just body, no frontmatter");
    }

    #[test]
    #[should_panic(expected = "invalid type")]
    fn blog_frontmatter_wrong_typed_optional_field_panics() {
        // `tags` must be a sequence; a scalar fails deserialization at runtime
        // and would silently drop the post, so it must fail the build.
        validate_blog_frontmatter(
            "p.mdx",
            "---\ntitle: Hi\ndate: \"2026-01-01\"\nauthor: jane\ntags: rust\n---\nbody",
        );
    }

    #[test]
    fn blog_frontmatter_optional_fields_ok() {
        validate_blog_frontmatter(
            "p.mdx",
            "---\ntitle: Hi\ndate: \"2026-01-01\"\nauthor: jane\ntags: [rust, web]\ndraft: true\ncoverImage: cover.png\n---\nbody",
        );
    }
}