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//! Takes [`Post`] objects created by the [`crate::post`] module and turns them
//! into index and post HTML files on the file system.
use crate::post::*;
use gtmpl::{Template, Value};
use std::fmt;
use std::io;
use std::path::{Path, PathBuf};
use url::Url;
/// Responsible for indexing, templating, and writing HTML pages to disk from
/// [`Post`] sources.
pub struct Writer<'a> {
/// The template for post pages.
pub posts_template: &'a Template,
/// The template for index pages.
pub index_template: &'a Template,
/// The base URL for index pages. The main index pages will be located at
/// `{index_base_url}/index.html`, `{index_base_url/1.html}`, etc. The tag
/// index pages will be located at
/// `{index_base_url}/{tag_name}/index.html`, `{index_base_url}/
/// {tag_name}/1.html`, etc.
pub index_base_url: &'a Url,
/// The directory in which the index HTML files will be written. The main
/// index page files will be located at
/// `{index_output_directory}/index.html`,
/// `{index_output_directory}/1.html`, etc. The tag index page files
/// will be located at `{index_output_directory}/{tag_name}/index.
/// html`, `{index_output_directory}/{tag_name}/1.html`,
pub index_output_directory: &'a Path,
/// The number of posts per index page.
pub index_page_size: usize,
/// The URL for the site's home page. This is made available to both post
/// and index templates, typically as the destination for the
/// site-header link.
pub home_page: &'a Url,
/// The URL for the static assets. This is made available to both post and
/// index templates, typically for the theme's stylesheet.
pub static_url: &'a Url,
/// The URL for the atom feed. This is made available to both post and
/// index templates, although typically it is only used by the index
/// templates to link to the atom feed.
pub atom_url: &'a Url,
}
impl Writer<'_> {
/// Takes a single [`Page`], templates it, and writes it to disk.
fn write_page(&self, page: &Page) -> Result<()> {
let mut value = page.to_value();
if let Value::Object(obj) = &mut value {
obj.insert(
"home_page".to_owned(),
Value::String(self.home_page.to_string()),
);
obj.insert(
"static_url".to_owned(),
Value::String(self.static_url.to_string()),
);
obj.insert(
"atom_url".to_owned(),
Value::String(self.atom_url.to_string()),
);
}
page.template.execute(
&mut std::fs::File::create(&page.file_path)?,
>mpl::Context::from(value).unwrap(),
)?;
Ok(())
}
/// Takes a slice of [`Post`], indexes it by tag, and writes post and index
/// pages to disk.
pub fn write_posts(&self, posts: &[Post]) -> Result<()> {
use std::collections::HashSet;
let mut seen_dirs: HashSet<PathBuf> = HashSet::new();
pages(
posts,
self.index_base_url,
self.index_output_directory,
self.index_page_size,
self.posts_template,
self.index_template,
)
.try_for_each(|page| {
let dir = page.file_path.parent().unwrap(); // there should always be a dir
if seen_dirs.insert(dir.to_owned()) {
std::fs::create_dir_all(dir)?;
}
self.write_page(&page)
})
}
}
/// An object representing an output HTML file. A [`Page`] can be converted to
/// a [`Value`] and thus rendered in a template via [`Page::to_value`].
struct Page<'a> {
/// The main item for the page.
item: Value,
/// The target location on disk for the output file.
file_path: PathBuf,
/// The URL for the previous page, if any.
prev: Option<Url>,
/// The URL for the next page, if any.
next: Option<Url>,
/// The template with which the page will be rendered.
template: &'a Template,
}
impl Page<'_> {
/// Converts a [`Page`] into a [`Value`]. The result is a [`Value::Object`]
/// with fields `item`, `prev`, and `next` (see [`Page`] for descriptions).
fn to_value(&self) -> Value {
use std::collections::HashMap;
let option_to_value = |opt: &Option<Url>| match opt {
Some(url) => Value::from(url.to_string()),
None => Value::Nil,
};
let mut m: HashMap<String, Value> = HashMap::new();
m.insert("item".to_owned(), self.item.clone());
m.insert("prev".to_owned(), option_to_value(&self.prev));
m.insert("next".to_owned(), option_to_value(&self.next));
Value::Object(m)
}
}
/// Creates all of the index and post [`Page`]s for a set of `[Post]`s. See
/// `[Writer]` for a description of arguments. Calls [`index_pages`] and
/// [`post_pages`] and returns the union of their results as a single stream of
/// [`Page`]s.
fn pages<'a>(
posts: &'a [Post],
index_base_url: &Url,
index_output_directory: &Path,
index_page_size: usize,
posts_template: &'a Template,
index_template: &'a Template,
) -> impl Iterator<Item = Page<'a>> {
index_pages(
posts,
index_base_url,
index_output_directory,
index_page_size,
index_template,
)
.chain(post_pages(posts, posts_template))
}
/// Creates all of the post [`Page`]s for a set of [`Post`]s. Takes the posts
/// and the post template as arguments.
fn post_pages<'a>(
posts: &'a [Post],
template: &'a Template,
) -> impl Iterator<Item = Page<'a>> {
posts.iter().enumerate().map(move |(i, post)| Page {
item: post.to_value(),
file_path: post.file_path.clone(),
prev: match i < 1 {
true => None,
false => Some(posts[i - 1].url.clone()),
},
next: match i >= posts.len() - 1 {
true => None,
false => Some(posts[i + 1].url.clone()),
},
template,
})
}
/// Creates all of the index [`Page`]s for a set of [`Post`]s. Takes the posts
/// and various `index_` parameters. See [`Writer`] for descriptions of the
/// `index_` parameters.
fn index_pages<'a>(
posts: &'a [Post],
index_base_url: &Url,
index_output_directory: &Path,
index_page_size: usize,
index_template: &'a Template,
) -> impl Iterator<Item = Page<'a>> {
let indices = index_posts(index_base_url, index_output_directory, posts);
indices
.into_iter()
.flat_map(move |i| i.to_pages(index_page_size, index_template))
}
/// `Index` represents a collection of [`Post`]s associated with tag (including
/// the empty tag, which is the main index containing all posts).
struct Index<'a> {
/// The base URL for all posts in the index.
url: Url,
/// The output directory for all posts in the index.
output_directory: PathBuf,
/// The posts associated with the index.
posts: Vec<&'a Post>,
}
impl<'a, 't> Index<'a> {
/// Converts the index to a list of index pages. `index_page_size` and
/// `index_template` represent the number of posts per page and the
/// template to apply to the pages respectively.
fn to_pages(
&self,
index_page_size: usize,
index_template: &'t Template,
) -> Vec<Page<'t>> {
let total_pages = match self.posts.len() % index_page_size {
0 => self.posts.len() / index_page_size,
_ => self.posts.len() / index_page_size + 1,
};
self.posts
.chunks(index_page_size)
.enumerate()
.map(|(i, chunk)| {
let file_name = match i > 0 {
false => String::from("index.html"),
true => format!("{}.html", i),
};
Page {
item: Value::Array(
chunk.iter().map(|p| p.summarize()).collect(),
),
file_path: self.output_directory.join(file_name),
prev: match i {
0 => None,
// unwrap: `"index.html"` and `"<int>.html"` should
// always be URL-safe.
1 => Some(self.url.join("index.html").unwrap()),
_ => Some(
self.url.join(&format!("{}.html", i - 1)).unwrap(),
),
},
next: match i < total_pages - 1 {
false => None,
// unwrap: `"<int>.html"` should always be URL-safe.
true => Some(
self.url.join(&format!("{}.html", i + 1)).unwrap(),
),
},
template: index_template,
}
})
.collect()
}
}
/// Indexes a list of [`Post`] objects.
///
/// Arguments:
///
/// * `base_url` is the base URL for index pages. See
/// [`Writer::index_base_url`] for more details.
/// * `base_directory` is the base directory for index pages. See
/// [`Writer::index_output_directory`] for more details.
/// * `posts` is the collection of [`Post`] objects to index.
fn index_posts<'a>(
base_url: &Url,
base_directory: &Path,
posts: &'a [Post],
) -> Vec<Index<'a>> {
use std::collections::HashMap;
let mut indices: HashMap<String, Index> = HashMap::new();
indices.insert(
String::default(),
Index {
url: base_url.to_owned(),
output_directory: base_directory.to_owned(),
posts: posts.iter().collect(),
},
);
for post in posts {
for tag in post.tags.iter() {
match indices.get_mut(&tag.name) {
None => {
indices.insert(
tag.name.to_owned(),
Index {
// unwrap: `tag.name` and `"index.html"` should
// both be guaranteed to be URL-safe.
url: base_url
.join(&tag.name)
.unwrap()
.join("index.html")
.unwrap(),
output_directory: base_directory.join(&tag.name),
posts: vec![post],
},
);
}
Some(index) => {
index.posts.push(post);
}
}
}
}
indices.into_values().collect()
}
/// The result of a fallible page-writing operation.
type Result<T> = std::result::Result<T, Error>;
/// Represents an error in a page-writing operation.
#[derive(Debug)]
pub enum Error {
/// An error during templating.
Template(String),
/// An error writing the output files.
Io(io::Error),
}
impl From<io::Error> for Error {
/// Converts an [`io::Error`] into an [`Error`]. This allows us to use the
/// `?` operator for fallible I/O operations.
fn from(err: io::Error) -> Error {
Error::Io(err)
}
}
impl From<String> for Error {
/// Converts a template error message ([`String`]) into an [`Error`]. This
/// allows us to use the `?` operator for fallible template operations.
fn from(err: String) -> Error {
Error::Template(err)
}
}
impl fmt::Display for Error {
/// Displays an [`Error`] as presentable text.
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
match self {
Error::Template(err) => err.fmt(f),
Error::Io(err) => err.fmt(f),
}
}
}
impl std::error::Error for Error {
/// Implements the [`std::error::Error`] trait for [`Error`].
fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
match self {
Error::Template(_) => None,
Error::Io(err) => Some(err),
}
}
}