Generate book from readme (#1155)

bin/generate-book/Cargo.toml

@@ -0,0 +1,9 @@
+[package]
+name = "generate-book"
+version = "0.0.0"
+edition = "2018"
+publish = false
+
+[dependencies]
+pulldown-cmark = "0.9.1"
+pulldown-cmark-to-cmark = "10.0.1"

bin/generate-book/src/main.rs

@@ -0,0 +1,51 @@
+use {
+  pulldown_cmark::{
+    Event,
+    HeadingLevel::{H2, H3},
+    Options, Parser, Tag,
+  },
+  pulldown_cmark_to_cmark::cmark,
+  std::{error::Error, fs},
+};
+
+fn main() -> Result<(), Box<dyn Error>> {
+  fs::remove_dir_all("book/src").ok();
+  fs::create_dir("book/src")?;
+
+  let txt = fs::read_to_string("README.md")?;
+
+  let mut chapters = vec![(1usize, Vec::new())];
+
+  for event in Parser::new_ext(&txt, Options::all()) {
+    if let Event::Start(Tag::Heading(level @ (H2 | H3), ..)) = event {
+      chapters.push((if level == H2 { 2 } else { 3 }, Vec::new()));
+    }
+    chapters.last_mut().unwrap().1.push(event);
+  }
+
+  let mut summary = String::new();
+
+  for (i, (level, chapter)) in chapters.into_iter().enumerate() {
+    let mut txt = String::new();
+    cmark(chapter.iter(), &mut txt)?;
+    let title = if i == 0 {
+      txt = txt.split_inclusive('\n').skip(1).collect::<String>();
+      "Introduction"
+    } else {
+      txt.lines().next().unwrap().split_once(' ').unwrap().1
+    };
+
+    let path = format!("book/src/chapter_{}.md", i + 1);
+    fs::write(&path, &txt)?;
+    summary.push_str(&format!(
+      "{}- [{}](chapter_{}.md)\n",
+      " ".repeat((level.saturating_sub(1)) * 4),
+      title,
+      i + 1
+    ));
+  }
+
+  fs::write("book/src/SUMMARY.md", summary)?;
+
+  Ok(())
+}