nornir 0.4.2

//! Per-repo nornir layout and the source→output render pipeline.
//!
//! Every repo owned by nornir gets a `.nornir/` directory at its root:
//!
//! ```text
//! repo/
//! ├── .nornir/                  ← nornir's namespace
//! │   ├── README.md             ← SOURCE (you edit this)
//! │   ├── CHANGELOG.md          ← SOURCE (you edit this)
//! │   ├── assets/               ← TRACKED media (depgraph.svg, logos, figures)
//! │   ├── warehouse/            ← DATA ONLY: the Iceberg warehouse (gitignored)
//! │   ├── cache/                ← transient: images + the docs index (gitignored)
//! │   └── .gitignore            ← ignores cache/ + warehouse/
//! ├── README.md                 ← GENERATED — DO NOT EDIT (chmod -w)
//! ├── CHANGELOG.md              ← GENERATED — DO NOT EDIT (chmod -w)
//! ├── docs/                     ← GENERATED rendered docs (book.pdf/.md, …); tracked
//! └── ...
//! ```
//!
//! Rendered exports (`docs export` / `docs book`) write the *current* artifact
//! to `<repo>/docs/` and historize the bytes in the Iceberg `doc_exports`
//! table; `.nornir/warehouse/` is data-only.
//!
//! The source files use the same `<!-- nornir:gen:start:NAME -->` markers as
//! [`super::sections`] for dynamic fills (bench tables, callgraphs, ...).
//! Render writes the whole output file (not just marker regions) and prepends
//! a loud header so anyone opening the artifact knows where the truth lives.

use std::path::{Path, PathBuf};

use anyhow::{bail, Context, Result};

use super::sections::{rewrite_str, Ctx};

/// Header prepended to every generated output file. The leading newline keeps
/// the comment on its own line; the warning lands in line 1 of the artifact.
pub const GENERATED_HEADER_PREFIX: &str =
    "<!-- ⚠ GENERATED by nornir from .nornir/";
pub const GENERATED_HEADER_SUFFIX: &str = " — DO NOT EDIT this file -->\n\n";

/// File names nornir manages by default. Adding new ones is a single-line
/// change: extend this list and they automatically get init / render / check.
pub const MANAGED_DOCS: &[&str] = &["README.md", "CHANGELOG.md"];

/// Layout of nornir-owned paths under one repo.
#[derive(Debug, Clone)]
pub struct RepoLayout {
    pub repo_root: PathBuf,
}

impl RepoLayout {
    pub fn new(repo_root: impl Into<PathBuf>) -> Self {
        Self {
            repo_root: repo_root.into(),
        }
    }

    /// `<repo>/.nornir/`
    pub fn nornir_dir(&self) -> PathBuf {
        self.repo_root.join(".nornir")
    }
    /// `<repo>/.nornir/warehouse/`
    pub fn warehouse_dir(&self) -> PathBuf {
        self.nornir_dir().join("warehouse")
    }
    /// `<repo>/.nornir/cache/`
    pub fn cache_dir(&self) -> PathBuf {
        self.nornir_dir().join("cache")
    }
    /// Image-cache subdir used by [`super::export`].
    pub fn image_cache_dir(&self) -> PathBuf {
        self.cache_dir().join("images")
    }
    /// Source path for one managed doc, e.g. `.nornir/README.md`.
    pub fn source_of(&self, doc_name: &str) -> PathBuf {
        self.nornir_dir().join(doc_name)
    }
    /// Output (artifact) path for one managed doc, e.g. `README.md`.
    pub fn output_of(&self, doc_name: &str) -> PathBuf {
        self.repo_root.join(doc_name)
    }
    /// `<repo>/docs/` — the canonical, git-tracked output directory for
    /// nornir-rendered documents (README/book PDF/HTML/MD). README links here.
    pub fn docs_dir(&self) -> PathBuf {
        self.repo_root.join("docs")
    }
    /// Path of a rendered export under `docs/`, e.g. `docs/book.pdf`. Stable
    /// (version-free) so links from the README don't churn per release.
    pub fn export_path(&self, doc_name: &str, ext: &str) -> PathBuf {
        self.docs_dir().join(format!("{doc_name}.{ext}"))
    }
}

/// Per-file render outcome.
#[derive(Debug)]
pub struct RenderReport {
    pub doc_name: String,
    pub source: PathBuf,
    pub output: PathBuf,
    pub sections: Vec<String>,
    pub changed: bool,
    pub bytes: usize,
}

/// Render a single managed doc: read source → fill markers → prepend warning
/// → atomically write output → restore read-only bit if file was previously
/// locked. Returns `Ok(None)` when no source exists for that doc (so a repo
/// can opt into only README and not CHANGELOG, etc.).
pub fn render_doc(layout: &RepoLayout, doc_name: &str, ctx: &Ctx) -> Result<Option<RenderReport>> {
    let src = layout.source_of(doc_name);
    if !src.exists() {
        return Ok(None);
    }
    let raw = std::fs::read_to_string(&src)
        .with_context(|| format!("read {}", src.display()))?;
    let (filled, sections) = rewrite_str(&raw, ctx)?;
    let header = format!("{GENERATED_HEADER_PREFIX}{doc_name}{GENERATED_HEADER_SUFFIX}");
    let mut output = String::with_capacity(header.len() + filled.len());
    output.push_str(&header);
    output.push_str(&filled);

    let dst = layout.output_of(doc_name);
    let prev = std::fs::read_to_string(&dst).ok();
    let changed = prev.as_deref() != Some(output.as_str());
    if changed {
        write_atomic(&dst, &output)?;
    }
    Ok(Some(RenderReport {
        doc_name: doc_name.to_string(),
        source: src,
        output: dst,
        sections,
        changed,
        bytes: output.len(),
    }))
}

/// Render every managed doc found under `.nornir/`.
pub fn render_all(layout: &RepoLayout, ctx: &Ctx) -> Result<Vec<RenderReport>> {
    let mut reports = Vec::new();
    for &doc in MANAGED_DOCS {
        if let Some(r) = render_doc(layout, doc, ctx)? {
            reports.push(r);
        }
    }
    Ok(reports)
}

/// In-memory dry-run of [`render_doc`] — bails if rendering would change
/// the output file. Use as a CI gate.
pub fn check_doc(layout: &RepoLayout, doc_name: &str, ctx: &Ctx) -> Result<Option<bool>> {
    let src = layout.source_of(doc_name);
    if !src.exists() {
        return Ok(None);
    }
    let raw = std::fs::read_to_string(&src)?;
    let (filled, _) = rewrite_str(&raw, ctx)?;
    let header = format!("{GENERATED_HEADER_PREFIX}{doc_name}{GENERATED_HEADER_SUFFIX}");
    let expected = format!("{header}{filled}");
    let dst = layout.output_of(doc_name);
    let prev = std::fs::read_to_string(&dst).unwrap_or_default();
    if prev != expected {
        bail!(
            "{} is out of date with {} — run `nornir docs render <repo>` to regenerate",
            dst.display(),
            src.display()
        );
    }
    Ok(Some(true))
}

/// Check every managed doc.
pub fn check_all(layout: &RepoLayout, ctx: &Ctx) -> Result<()> {
    for &doc in MANAGED_DOCS {
        check_doc(layout, doc, ctx)?;
    }
    Ok(())
}

/// Scaffold `.nornir/` for a repo:
///   - create `.nornir/`, `.nornir/cache/`, `.nornir/warehouse/`
///   - migrate any existing top-level managed docs (README.md, CHANGELOG.md)
///     into `.nornir/` as the source
///   - if no managed doc exists, write a minimal scaffold for README.md
///   - write `.nornir/.gitignore` (ignores cache/)
///
/// Returns the list of source files now present in `.nornir/`.
pub fn init_repo(layout: &RepoLayout) -> Result<Vec<PathBuf>> {
    std::fs::create_dir_all(layout.nornir_dir())?;
    std::fs::create_dir_all(layout.cache_dir())?;
    std::fs::create_dir_all(layout.warehouse_dir())?;
    std::fs::create_dir_all(layout.image_cache_dir())?;

    let gi = layout.nornir_dir().join(".gitignore");
    if !gi.exists() {
        std::fs::write(&gi, "cache/\n")?;
    }

    let mut sources = Vec::new();
    let mut had_any = false;
    for &doc in MANAGED_DOCS {
        let src = layout.source_of(doc);
        let dst = layout.output_of(doc);
        if src.exists() {
            sources.push(src);
            had_any = true;
            continue;
        }
        if dst.exists() {
            // Migrate the existing artifact into .nornir/ as the source.
            // The artifact will be re-rendered (with the GENERATED warning)
            // on the next `nornir docs render`.
            let existing = std::fs::read_to_string(&dst)
                .with_context(|| format!("read {}", dst.display()))?;
            // Strip any pre-existing GENERATED header so a re-init is a no-op.
            let cleaned = strip_generated_header(&existing);
            std::fs::write(&src, cleaned)
                .with_context(|| format!("write {}", src.display()))?;
            sources.push(src);
            had_any = true;
        }
    }
    if !had_any {
        // No README anywhere — scaffold a starter.
        let starter = scaffold_readme(&layout.repo_root);
        let src = layout.source_of("README.md");
        std::fs::write(&src, starter)?;
        sources.push(src);
    }
    Ok(sources)
}

/// Strip a pre-existing GENERATED-by-nornir header (if any) from the start
/// of `text`. Idempotent.
fn strip_generated_header(text: &str) -> String {
    if let Some(rest) = text.strip_prefix(GENERATED_HEADER_PREFIX) {
        // Find the matching suffix `-->` and the following blank line.
        if let Some(end) = rest.find("-->") {
            let after = &rest[end + 3..];
            let after = after.trim_start_matches(['\n', '\r']);
            return after.to_string();
        }
    }
    text.to_string()
}

fn scaffold_readme(repo_root: &Path) -> String {
    let name = repo_root
        .file_name()
        .and_then(|n| n.to_str())
        .unwrap_or("project");
    format!(
        r#"# {name}

> One-line description of {name}.

<!-- Headline: paste your single most meaningful benchmark number here, e.g.
     **9,950 MB/s decompress · 32 cores**. The full table renders below. -->

<!-- Write any intro prose here. Anything outside the marker blocks below
     is preserved verbatim on every render. -->

## Benchmarks

<!-- The `benches` renderer pivots the latest run into a table and bolds the
     winning cell per row (e.g. ours vs a legacy tool). Direction is inferred
     from the metric unit (`_mbs` higher-better, `_ms` lower-better); override
     odd cases with `benches best=metric:low`. -->
<!-- nornir:gen:start:benches -->
<!-- nornir:gen:end:benches -->

## Tests

<!-- Unit / integration / doc tests, enumerated from source via syn. -->
<!-- nornir:gen:start:tests -->
<!-- nornir:gen:end:tests -->

## Dependency graph

<!-- nornir:gen:start:depgraph -->
<!-- nornir:gen:end:depgraph -->

## License

MIT OR Apache-2.0.
"#
    )
}

/// Write `content` to `dst` atomically (write to tmp, fsync, rename),
/// honouring a previous read-only bit by clearing it before write and
/// restoring it after.
fn write_atomic(dst: &Path, content: &str) -> Result<()> {
    use std::io::Write;
    if let Some(parent) = dst.parent() {
        std::fs::create_dir_all(parent)?;
    }
    // Capture & clear any read-only bit so we can overwrite.
    let prev_readonly = match std::fs::metadata(dst) {
        Ok(m) => {
            let ro = m.permissions().readonly();
            if ro {
                let mut p = m.permissions();
                #[allow(clippy::permissions_set_readonly_false)]
                p.set_readonly(false);
                std::fs::set_permissions(dst, p)?;
            }
            ro
        }
        Err(_) => false,
    };

    let tmp = dst.with_extension(format!(
        "{}.nornir-tmp",
        dst.extension()
            .and_then(|e| e.to_str())
            .unwrap_or("tmp")
    ));
    {
        let mut f = std::fs::File::create(&tmp)
            .with_context(|| format!("create {}", tmp.display()))?;
        f.write_all(content.as_bytes())?;
        f.sync_all().ok();
    }
    std::fs::rename(&tmp, dst)
        .with_context(|| format!("rename {} -> {}", tmp.display(), dst.display()))?;

    if prev_readonly {
        let mut p = std::fs::metadata(dst)?.permissions();
        p.set_readonly(true);
        std::fs::set_permissions(dst, p)?;
    }
    Ok(())
}

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

    fn layout() -> (TempDir, RepoLayout) {
        let t = TempDir::new().unwrap();
        let l = RepoLayout::new(t.path());
        (t, l)
    }

    #[test]
    fn init_creates_skeleton_when_empty() {
        let (_t, l) = layout();
        let srcs = init_repo(&l).unwrap();
        assert!(l.nornir_dir().exists());
        assert!(l.cache_dir().exists());
        assert!(l.warehouse_dir().exists());
        assert!(l.nornir_dir().join(".gitignore").exists());
        assert_eq!(srcs.len(), 1);
        assert!(srcs[0].ends_with("README.md"));
        let scaffold = std::fs::read_to_string(&srcs[0]).unwrap();
        assert!(scaffold.contains("nornir:gen:start:benches"));
        assert!(scaffold.contains("nornir:gen:start:tests"));
        assert!(scaffold.contains("nornir:gen:start:depgraph"));
    }

    #[test]
    fn init_migrates_existing_readme() {
        let (t, l) = layout();
        std::fs::write(t.path().join("README.md"), "# already here\n\nbody\n").unwrap();
        let srcs = init_repo(&l).unwrap();
        assert_eq!(srcs.len(), 1);
        let s = std::fs::read_to_string(&srcs[0]).unwrap();
        assert!(s.contains("# already here"));
    }

    #[test]
    fn init_strips_old_header_on_remigrate() {
        let (t, l) = layout();
        let body = "# x\n\nbody\n";
        let with_header = format!(
            "{}README.md{}{}",
            GENERATED_HEADER_PREFIX, GENERATED_HEADER_SUFFIX, body
        );
        std::fs::write(t.path().join("README.md"), &with_header).unwrap();
        init_repo(&l).unwrap();
        let s = std::fs::read_to_string(l.source_of("README.md")).unwrap();
        assert!(!s.contains("GENERATED"));
        assert!(s.starts_with("# x"));
    }

    #[test]
    fn render_writes_header_and_preserves_source() {
        let (t, l) = layout();
        let src = l.source_of("README.md");
        std::fs::create_dir_all(l.nornir_dir()).unwrap();
        std::fs::write(&src, "# title\n\nhello\n").unwrap();
        let ctx = Ctx::new(t.path(), t.path(), None);
        let r = render_doc(&l, "README.md", &ctx).unwrap().unwrap();
        assert!(r.changed);
        let out = std::fs::read_to_string(&r.output).unwrap();
        assert!(out.starts_with(GENERATED_HEADER_PREFIX));
        assert!(out.contains("# title"));
    }

    #[test]
    fn render_is_idempotent() {
        let (t, l) = layout();
        std::fs::create_dir_all(l.nornir_dir()).unwrap();
        std::fs::write(l.source_of("README.md"), "# x\n").unwrap();
        let ctx = Ctx::new(t.path(), t.path(), None);
        let r1 = render_doc(&l, "README.md", &ctx).unwrap().unwrap();
        assert!(r1.changed);
        let r2 = render_doc(&l, "README.md", &ctx).unwrap().unwrap();
        assert!(!r2.changed);
    }

    #[test]
    fn check_fails_on_drift() {
        let (t, l) = layout();
        std::fs::create_dir_all(l.nornir_dir()).unwrap();
        std::fs::write(l.source_of("README.md"), "# original\n").unwrap();
        let ctx = Ctx::new(t.path(), t.path(), None);
        render_doc(&l, "README.md", &ctx).unwrap();
        // Mutate source so the output is now stale.
        std::fs::write(l.source_of("README.md"), "# changed\n").unwrap();
        assert!(check_doc(&l, "README.md", &ctx).is_err());
    }

    #[test]
    fn render_respects_readonly_bit() {
        let (t, l) = layout();
        std::fs::create_dir_all(l.nornir_dir()).unwrap();
        std::fs::write(l.source_of("README.md"), "# v1\n").unwrap();
        let ctx = Ctx::new(t.path(), t.path(), None);
        render_doc(&l, "README.md", &ctx).unwrap();
        // Lock the output, then mutate source and re-render. write_atomic
        // should clear+restore the bit.
        let out = l.output_of("README.md");
        let mut p = std::fs::metadata(&out).unwrap().permissions();
        p.set_readonly(true);
        std::fs::set_permissions(&out, p).unwrap();
        std::fs::write(l.source_of("README.md"), "# v2\n").unwrap();
        render_doc(&l, "README.md", &ctx).unwrap();
        let new = std::fs::read_to_string(&out).unwrap();
        assert!(new.contains("# v2"));
        assert!(std::fs::metadata(&out).unwrap().permissions().readonly());
    }
}