//! Compiles style/main.scss into OUT_DIR and emits FORGE_BUILD_SHA for the binary. Each static
//! asset also gets a content hash (FORGE_MAIN_CSS_V, FORGE_NAV_JS_V) that the page links use as
//! their cache-busting query, so an unchanged file keeps its URL and a changed one gets a new one.

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

use hex::encode;
use sha2::{Digest, Sha256};

/// First 12 hex characters of the SHA-256 of `bytes`.
fn content_version(bytes: &[u8]) -> String {
    encode(Sha256::digest(bytes))[..12].to_string()
}

fn main() {
    println!("cargo:rerun-if-env-changed=FORGE_BUILD_SHA");
    println!("cargo:rerun-if-changed=../../style");
    println!("cargo:rerun-if-changed=assets/nav.js");

    let sha = env::var("FORGE_BUILD_SHA").unwrap_or_else(|_| "dev".to_string());
    println!("cargo:rustc-env=FORGE_BUILD_SHA={sha}");

    let manifest =
        PathBuf::from(env::var("CARGO_MANIFEST_DIR").expect("CARGO_MANIFEST_DIR is set by cargo"));
    let out = PathBuf::from(env::var("OUT_DIR").expect("OUT_DIR is set by cargo"));
    let css = grass::from_path(
        manifest.join("../../style/main.scss"),
        &grass::Options::default(),
    )
    .unwrap_or_else(|e| panic!("compiling style/main.scss: {e}"));
    println!(
        "cargo:rustc-env=FORGE_MAIN_CSS_V={}",
        content_version(css.as_bytes())
    );
    fs::write(out.join("main.css"), css).expect("writing compiled stylesheet to OUT_DIR");

    let nav = fs::read(manifest.join("assets/nav.js")).expect("reading assets/nav.js");
    println!("cargo:rustc-env=FORGE_NAV_JS_V={}", content_version(&nav));
}