build.rs

/*!
# pxsum: Build Script
*/

use argyle::KeyWordsBuilder;
use dactyl::NiceU32;
use image::ImageFormat;
use std::{
	collections::BTreeSet,
	io::Write,
	path::PathBuf,
};



/// # Pre-Compute CLI keys and Extensions.
pub fn main() {
	println!("cargo:rerun-if-env-changed=CARGO_PKG_VERSION");

	build_cli();
	build_ext();
}

/// # Build CLI Keys.
fn build_cli() {
	let mut builder = KeyWordsBuilder::default();
	builder.push_keys([
		"--bench",
		"-c", "--check",
		"-g", "--group-by-checksum",
		"-h", "--help",
		"--no-warnings",
		"--only-dupes",
		"-q", "--quiet",
		"--strict",
		"-V", "--version",
	]);
	builder.push_keys_with_values([
		"-d", "--dir",
		"-j"
	]);
	builder.save(out_path("argyle.rs"));
}

/// # Build Extensions.
fn build_ext() {
	// Collect the supported formats.
	let formats: Vec<ImageFormat> = ImageFormat::all()
		.filter(|f| f.can_read() && f.reading_enabled())
		.collect();

	// Build up a list of matching file extensions by length.
	let mut ext3: BTreeSet<u32> = BTreeSet::new();
	let mut ext4: BTreeSet<u32> = BTreeSet::new();
	for f in formats {
		for ext in f.extensions_str() {
			assert!(ext.is_ascii(), "Bug: extension is non-ascii: {ext}");

			match ext.as_bytes() {
				[a, b, c] => {
					ext3.insert(u32::from_le_bytes([
						b'.',
						a.to_ascii_lowercase(),
						b.to_ascii_lowercase(),
						c.to_ascii_lowercase(),
					]));
				},
				[a, b, c, d] => {
					ext4.insert(u32::from_le_bytes([
						a.to_ascii_lowercase(),
						b.to_ascii_lowercase(),
						c.to_ascii_lowercase(),
						d.to_ascii_lowercase(),
					]));
				},
				_ => panic!("Bug: file extension has unexpected length: {ext}"),
			}
		}
	}

	// Formats not in the image crate.
	ext3.insert(u32::from_le_bytes(*b".j2c"));
	ext3.insert(u32::from_le_bytes(*b".j2k"));
	ext3.insert(u32::from_le_bytes(*b".jp2"));
	ext3.insert(u32::from_le_bytes(*b".jpc"));
	ext3.insert(u32::from_le_bytes(*b".jxl"));
	ext4.insert(u32::from_le_bytes(*b"avif"));
	ext4.insert(u32::from_le_bytes(*b"jpg2"));

	// Build up a matching method we can use at runtime.
	let out = format!(
		r"
/// # Match Image Extension.
const fn check_extension(bytes: &[u8]) -> bool {{
	if let [.., 0..=46 | 48..=91 | 93..=255, b'.', a, b, c] = bytes {{
		matches!(
			u32::from_le_bytes([b'.', a.to_ascii_lowercase(), b.to_ascii_lowercase(), c.to_ascii_lowercase()]),
			{}
		)
	}}
	else if let [.., 0..=46 | 48..=91 | 93..=255, b'.', a, b, c, d] = bytes {{
		matches!(
			u32::from_le_bytes([a.to_ascii_lowercase(), b.to_ascii_lowercase(), c.to_ascii_lowercase(), d.to_ascii_lowercase()]),
			{}
		)
	}}
	else {{ false }}
}}",
		ext3.into_iter()
			.map(|n| NiceU32::with_separator(n, b'_'))
			.collect::<Vec<_>>()
			.join(" | "),
		ext4.into_iter()
			.map(|n| NiceU32::with_separator(n, b'_'))
			.collect::<Vec<_>>()
			.join(" | "),
	);

	std::fs::File::create(out_path("pxsum-ext.rs"))
		.and_then(|mut f| f.write_all(out.as_bytes()).and_then(|_| f.flush()))
		.expect("Unable to write file.");
}

/// # Output Path.
///
/// Append the sub-path to OUT_DIR and return it.
fn out_path(stub: &str) -> PathBuf {
	std::fs::canonicalize(std::env::var("OUT_DIR").expect("Missing OUT_DIR."))
		.expect("Missing OUT_DIR.")
		.join(stub)
}