build.rs

use std::{io::Write, iter};

fn main() {
    println!("cargo::rerun-if-changed=spec.processed.md");

    // Generates tests out of spec.clear.md and spec.processed.md files
    let test_in = String::from_utf8(std::fs::read("spec.clear.md").unwrap()).unwrap();
    let iter_in = prepare_test_md_file(&test_in);

    let test_out = String::from_utf8(std::fs::read("spec.processed.md").unwrap()).unwrap();
    let out_tests = prepare_test_md_file(&test_out);

    let mut f = std::fs::File::create("src/tests.rs").unwrap();

    writeln!(f, "//! Generated by build.rs, do not modify.").unwrap();
    writeln!(f, "//! See spec.clear.md and spec.processed.md.\n").unwrap();
    writeln!(f, "use crate::test::{{process, assert_process_eq}};\n").unwrap();

    iter_in
        .zip(out_tests.chain(iter::repeat(("none".to_owned(), ""))))
        .for_each(|((name, input_data), (out_name, output_data))| {
            (name == out_name).then_some(()).unwrap_or_else(|| {
                panic!("expected {name} test case section spec.processed.md, got {out_name}")
            });
            writeln!(f, "#[test]").unwrap();
            writeln!(f, "fn {name}() {{").unwrap();
            writeln!(f, "    assert_process_eq!(").unwrap();
            writeln!(f, "        {input_data:?},").unwrap();
            writeln!(f, "        {output_data:?}").unwrap();
            writeln!(f, "    );").unwrap();
            writeln!(f, "}}\n").unwrap();
        })
}

fn prepare_test_md_file(input: &str) -> impl Iterator<Item = (String, &str)> {
    let mut iter = input.split("#### ");
    iter.next(); // skipping first section
    iter.map(|section| section.split_once('\n').unwrap())
        .map(|(name, code)| {
            let name = name.replace([' ', '-', '(', ')'], "_").to_ascii_lowercase();
            (name, code)
        })
}