build.rs

use std::env;
use regex::{Regex, Captures};

fn proc<A : AsRef<str>>(re : &str, str : A) -> String {
    let need_to_escape = Regex::new(r"([_*\\])").unwrap();
    Regex::new(re).unwrap().replace_all(str.as_ref(), |caps : &Captures| {
        format!("{}{}{}",
            caps.get(1).unwrap().as_str(),
            need_to_escape.replace_all(caps.get(2).unwrap().as_str(), "\\$1"),
            caps.get(3).unwrap().as_str()
        )
    }).to_string()
}

fn main() {
    let out_dir = env::var("OUT_DIR").unwrap();
    
    // Since rust is stuck in 80's 7-bit gringo ASCII world, so that rustdoc does not support
    // markdown KaTeX mathematics, we have to process the README to include horrible horrible
    // horrible escapes for the math, and then use an vomit-inducingly ugly javasccript
    // workaround to process the math on the fly.

    println!("cargo:rerun-if-changed=README.md");

    let readme = std::fs::read_to_string("README.md")
        .expect("Error reading README");

    // Escape _, *, and \ in equations.
    let readme_uglified = proc(r"(?m)([^$]\$)([^$]+)(\$[^$])",
                               proc(r"([^$]\$\$)([^$]+)(\$\$[^$])", readme));
    // Remove the instructions for building the documentation
    let readme_cut = Regex::new("## Internals(.*|\n)*")
        .unwrap()
        .replace_all(&readme_uglified, "");

    std::fs::write(out_dir + "/README_uglified.md", readme_cut.as_bytes())
        .expect("Error saving uglified README");
}