use std::{
    env, fs,
    path::{Path, PathBuf},
};

fn fnv1a64(parts: &[&[u8]]) -> u64 {
    let mut hash = 0xcbf29ce484222325u64;
    for part in parts {
        for byte in *part {
            hash ^= u64::from(*byte);
            hash = hash.wrapping_mul(0x100000001b3);
        }
    }
    hash
}

fn bundle_manifest(root: &Path, directory: &Path, manifest: &Path, extension: &str) -> String {
    println!("cargo:rerun-if-changed={}", manifest.display());
    let manifest_text = fs::read_to_string(manifest)
        .unwrap_or_else(|error| panic!("{}: {error}", manifest.display()));
    let mut bundle = String::new();

    for raw in manifest_text.lines() {
        let name = raw.trim();
        if name.is_empty() || name.starts_with('#') {
            continue;
        }
        assert!(
            name.ends_with(extension)
                && !name.contains('/')
                && !name.contains('\\')
                && !name.contains(".."),
            "invalid {extension} manifest entry: {name}"
        );
        let path = directory.join(name);
        assert!(
            path.starts_with(root),
            "asset path escaped project root: {}",
            path.display()
        );
        println!("cargo:rerun-if-changed={}", path.display());
        let source =
            fs::read_to_string(&path).unwrap_or_else(|error| panic!("{}: {error}", path.display()));
        if !bundle.is_empty() {
            bundle.push('\n');
        }
        bundle.push_str(&source);
        if !source.ends_with('\n') {
            bundle.push('\n');
        }
    }

    bundle
}

fn main() {
    let root = PathBuf::from(env::var_os("CARGO_MANIFEST_DIR").expect("CARGO_MANIFEST_DIR"));
    let out = PathBuf::from(env::var_os("OUT_DIR").expect("OUT_DIR"));
    let css_dir = root.join("src/web/css");
    let js_dir = root.join("src/web/js");

    for path in [
        root.join("src/web/index.html"),
        root.join("src/web/icons.svg"),
        root.join("src/web/i18n/en.json"),
        root.join("src/web/i18n/pl.json"),
    ] {
        println!("cargo:rerun-if-changed={}", path.display());
    }

    let css_bundle = bundle_manifest(&root, &css_dir, &css_dir.join("manifest.txt"), ".css");
    let js_bundle = bundle_manifest(&root, &js_dir, &js_dir.join("manifest.txt"), ".js");

    let asset_id = fnv1a64(&[css_bundle.as_bytes(), js_bundle.as_bytes()]);
    println!("cargo:rustc-env=RUSTBOX_ASSET_ID={asset_id:016x}");

    fs::write(out.join("rustbox-ui.css"), css_bundle).expect("write RustBox CSS bundle");
    fs::write(out.join("rustbox-ui.js"), js_bundle).expect("write RustBox JavaScript bundle");
}