nova-doc 0.3.2

//! Writing the site to `target/doc/` (spec §4.3, §6.1).

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

use crate::model::Site;
use crate::{render, search, CSS, JS};

/// The file every site holds, so that `nova doc` replaces only a
/// directory it wrote (spec §4.3).
pub const MARKER: &str = ".nova-doc";

const MARKER_TEXT: &str =
    "This directory was written by nova doc, which replaces it on its next run.\n";

/// Why a site was not written.
#[derive(Debug, thiserror::Error)]
pub enum WriteError {
    /// The directory exists, holds files, and has no marker.
    #[error("{} exists and was not written by nova doc; remove it, and nova doc will write its site there", .0.display())]
    NotOurs(PathBuf),
    /// A file or directory could not be removed, read or written.
    #[error("cannot write {}: {}", .0.display(), .1)]
    Io(PathBuf, std::io::Error),
}

/// Write `site` to `dir`, replacing a site written there before (spec
/// §4.3). Returns the start page's path.
///
/// The marker is never removed, and is written before any page, so a
/// write cut short leaves a directory the next `nova doc` replaces.
pub fn write_site(site: &Site, dir: &Path) -> Result<PathBuf, WriteError> {
    let io = |path: &Path| {
        let path = path.to_path_buf();
        move |e| WriteError::Io(path, e)
    };
    if dir.exists() {
        if dir.join(MARKER).is_file() {
            for entry in std::fs::read_dir(dir).map_err(io(dir))? {
                let entry = entry.map_err(io(dir))?;
                if entry.file_name() == MARKER {
                    continue;
                }
                let path = entry.path();
                // `file_type` does not follow a symlink: a link to a
                // directory is removed, not the directory.
                let removed = if entry.file_type().map_err(io(&path))?.is_dir() {
                    std::fs::remove_dir_all(&path)
                } else {
                    std::fs::remove_file(&path)
                };
                removed.map_err(io(&path))?;
            }
        } else if std::fs::read_dir(dir).map_err(io(dir))?.next().is_some() {
            return Err(WriteError::NotOurs(dir.to_path_buf()));
        }
    }
    for (path, text) in &files(site) {
        let full = under(dir, path);
        if let Some(parent) = full.parent() {
            std::fs::create_dir_all(parent).map_err(io(parent))?;
        }
        std::fs::write(&full, text.replace("\r\n", "\n")).map_err(io(&full))?;
    }
    Ok(under(dir, &site.start))
}

/// Every file of `site`'s directory, by its path from the site's root,
/// the marker first.
fn files(site: &Site) -> Vec<(String, String)> {
    let mut files = vec![(MARKER.to_string(), MARKER_TEXT.to_string())];
    files.extend(render::pages(site));
    files.push(("nova.css".to_string(), CSS.to_string()));
    files.push(("nova.js".to_string(), JS.to_string()));
    files.push(("search-index.js".to_string(), search::index(site)));
    files
}

/// `relative`, a `/`-separated path, under `dir`.
fn under(dir: &Path, relative: &str) -> PathBuf {
    relative
        .split('/')
        .fold(dir.to_path_buf(), |path, part| path.join(part))
}

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

    fn fresh(name: &str) -> PathBuf {
        let dir = std::env::temp_dir().join(format!("nova-doc-write-{name}"));
        let _ = std::fs::remove_dir_all(&dir);
        std::fs::create_dir_all(&dir).unwrap();
        dir
    }

    #[test]
    fn the_sample_site_is_written_whole_and_its_links_hold() {
        let dir = fresh("whole").join("doc");
        let start = write_site(&sample_site(), &dir).unwrap();
        assert_eq!(start, dir.join("app").join("index.html"));
        for file in [
            MARKER,
            "index.html",
            "nova.css",
            "nova.js",
            "search-index.js",
            "app/index.html",
            "app/util/index.html",
            "std/index.html",
            "std/core/index.html",
            "std/primitive.Int.html",
        ] {
            assert!(dir.join(file).is_file(), "{file}");
        }
        assert_eq!(crate::check_links(&dir), Vec::new());
    }

    #[test]
    fn a_site_it_wrote_is_replaced_and_another_directory_is_refused() {
        let base = fresh("replace");
        let dir = base.join("doc");
        write_site(&sample_site(), &dir).unwrap();
        std::fs::write(dir.join("stale.html"), "old").unwrap();
        write_site(&sample_site(), &dir).unwrap();
        assert!(!dir.join("stale.html").exists());
        let other = base.join("other");
        std::fs::create_dir_all(&other).unwrap();
        std::fs::write(other.join("keep.txt"), "keep").unwrap();
        assert!(matches!(
            write_site(&sample_site(), &other),
            Err(WriteError::NotOurs(_))
        ));
        assert!(other.join("keep.txt").is_file());
        let empty = base.join("empty");
        std::fs::create_dir_all(&empty).unwrap();
        write_site(&sample_site(), &empty).unwrap();
    }

    #[test]
    fn the_marker_is_written_before_any_page() {
        // A write cut short still leaves a directory `nova doc` replaces.
        let files = files(&sample_site());
        assert_eq!(files[0].0, MARKER);
        assert_eq!(files.iter().filter(|(p, _)| p == MARKER).count(), 1);
    }

    #[test]
    fn the_marker_stays_while_the_old_site_is_removed() {
        // A hard link to the marker sees the new text only if the marker
        // is the same file: it was written over, never removed.
        let base = fresh("marker");
        let dir = base.join("doc");
        write_site(&sample_site(), &dir).unwrap();
        std::fs::write(dir.join(MARKER), "old").unwrap();
        std::fs::hard_link(dir.join(MARKER), base.join("link")).unwrap();
        write_site(&sample_site(), &dir).unwrap();
        assert_eq!(
            std::fs::read_to_string(base.join("link")).unwrap(),
            MARKER_TEXT
        );
    }

    #[test]
    fn a_marker_and_a_partial_site_are_replaced_cleanly() {
        let dir = fresh("partial").join("doc");
        std::fs::create_dir_all(dir.join("app").join("old")).unwrap();
        std::fs::write(dir.join(MARKER), MARKER_TEXT).unwrap();
        std::fs::write(dir.join("app").join("index.html"), "<p>half").unwrap();
        std::fs::write(dir.join("app").join("old").join("index.html"), "x").unwrap();
        std::fs::write(dir.join("stale.html"), "old").unwrap();
        write_site(&sample_site(), &dir).unwrap();
        assert!(!dir.join("stale.html").exists());
        assert!(!dir.join("app").join("old").exists());
        assert!(dir.join(MARKER).is_file());
        let page = std::fs::read_to_string(dir.join("app").join("index.html")).unwrap();
        assert!(page.ends_with("</html>\n"), "{page}");
        assert_eq!(crate::check_links(&dir), Vec::new());
    }

    #[test]
    fn every_file_ends_its_lines_with_a_line_feed() {
        let dir = fresh("endings").join("doc");
        write_site(&sample_site(), &dir).unwrap();
        for file in [
            "index.html",
            "nova.css",
            "nova.js",
            "search-index.js",
            "app/index.html",
        ] {
            let text = std::fs::read_to_string(dir.join(file)).unwrap();
            assert!(!text.contains('\r'), "{file}");
        }
    }
}