iref 4.0.0

Uniform & Internationalized Resource Identifiers (URIs/IRIs), borrowed and owned.
Documentation 
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use std::{env, fs, io, path::Path};

fn main() {
	let out_dir = env::var("OUT_DIR").unwrap();
	let output = Path::new(&out_dir).join("iri.rs");
	let content = inline_file("src/uri/mod.rs").unwrap();
	fs::write(output, add_header(replace(content))).unwrap();
}

/// Read a file and return its content with all `mod foo;`
/// declarations replaced by `mod foo { <contents> }`.
fn inline_file(path: impl AsRef<Path>) -> Result<String, io::Error> {
	let path = path.as_ref();
	let content = fs::read_to_string(path)?;
	println!("cargo::rerun-if-changed={}", path.display());
	let dir = path.parent().unwrap();
	inline_mod_declarations(dir, content)
}

fn inline_mod_declarations(dir: &Path, content: String) -> Result<String, io::Error> {
	let mut result = String::with_capacity(content.len());
	let mut skip_until_grammar = false;

	for line in content.lines() {
		// Skip the `#[grammar(...)] pub(crate) mod grammar {}` block,
		// which is defined statically in `src/iri/mod.rs`.
		if line.trim().starts_with("#[grammar(") {
			skip_until_grammar = true;
			continue;
		}
		if skip_until_grammar {
			if line.trim().starts_with("pub(crate) mod grammar") {
				skip_until_grammar = false;
			}
			continue;
		}

		if let Some(name) = parse_mod_declaration(line) {
			let inlined = resolve_and_inline(dir, name)?;
			result.push_str("mod ");
			result.push_str(name);
			result.push_str(" {\n");
			result.push_str(&inlined);
			result.push_str("}\n");
		} else {
			result.push_str(line);
			result.push('\n');
		}
	}

	Ok(result)
}

/// Parse `mod foo;` or `mod r#foo;`, returning the module name.
fn parse_mod_declaration(line: &str) -> Option<&str> {
	let name = line.trim().strip_prefix("mod ")?.strip_suffix(';')?;
	Some(name)
}

/// Resolve a module name to a file or directory and inline it.
fn resolve_and_inline(dir: &Path, name: &str) -> Result<String, io::Error> {
	let file_name = name.strip_prefix("r#").unwrap_or(name);
	let subdir = dir.join(file_name);
	if subdir.is_dir() {
		inline_file(subdir.join("mod.rs"))
	} else {
		inline_file(dir.join(format!("{file_name}.rs")))
	}
}

fn replace(s: impl AsRef<str>) -> String {
	s.as_ref()
		.replace("URI", "IRI")
		.replace("Uri", "Iri")
		.replace("uri", "iri")
		.replace("macro_rules! ", "macro_rules! i")
		.replace("macro_rules! iiri", "macro_rules! iri")
}

fn add_header(content: String) -> String {
	format!(
		"// DO NOT EDIT THIS FILE.\n// It is auto-generated by `build.rs` from its URI counterpart.\n\n{content}"
	)
}