build.rs

extern crate glob;

use glob::glob;
use std::env;
use std::fmt;
use std::fs::File;
use std::io::prelude::*;
use std::io::BufReader;
use std::path::Path;

fn main() {
    let mut output = String::new();

    fmt::write(
        &mut output,
        format_args!("static PATTERNS: &[(&str, &str)] = &[\n"),
    )
    .unwrap();

    for line in glob("patterns/*.pattern")
        .unwrap() // load filepaths
        // extract the filepath
        .map(|e| e.unwrap())
        // open file for path
        .map(|path| File::open(path).unwrap())
        // flatten to actual lines
        .flat_map(|f| BufReader::new(f).lines())
        .map(|line| line.unwrap())
        // filter comments
        .filter(|line| !line.starts_with('#'))
        // filter empty lines
        .filter(|line| !line.is_empty())
    {
        let (key, value) = line.split_at(line.find(' ').unwrap());
        fmt::write(
            &mut output,
            format_args!("\t(\"{}\", r#\"{}\"#),\n", key, &value[1..]),
        )
        .unwrap();
    }

    fmt::write(&mut output, format_args!("];\n")).unwrap();

    let out_dir = env::var("OUT_DIR").unwrap();
    let dest_path = Path::new(&out_dir).join("default_patterns.rs");
    let mut file = File::create(&dest_path).unwrap();
    file.write_all(output.as_bytes()).unwrap();
}