use std::collections::hash_map::DefaultHasher;
use std::hash::{Hash, Hasher};
use std::process::Command;
use std::{fs, path::Path};

fn main() {
    // Set GIT_HASH env var for compile-time inclusion via option_env!()
    let hash = Command::new("git")
        .args(["rev-parse", "--short", "HEAD"])
        .output()
        .ok()
        .filter(|o| o.status.success())
        .and_then(|o| String::from_utf8(o.stdout).ok())
        .map(|s| s.trim().to_string())
        .unwrap_or_default();

    println!("cargo::rustc-env=GIT_HASH={}", hash);
    // Only re-run when HEAD changes
    println!("cargo::rerun-if-changed=.git/HEAD");

    // --- Static asset fingerprinting ---
    // Hash the content of key static files to produce a version suffix.
    // When any watched file changes, URLs in templates get a new ?v= param,
    // busting browser caches automatically.
    let static_files = [
        "static/style.css",
        "static/htmx.min.js",
        "static/upload.js",
        "static/passkey.js",
        "static/insertions.js",
    ];

    let mut hasher = DefaultHasher::new();
    for path in &static_files {
        println!("cargo::rerun-if-changed={}", path);
        if let Ok(content) = fs::read(path) {
            content.hash(&mut hasher);
        }
    }
    let static_hash = format!("{:016x}", hasher.finish());
    let version = &static_hash[..8];

    // Generate a template partial with versioned asset URLs.
    // base.html includes this via {% include "_head_assets.html" %}
    let partial = format!(
        r#"    <link rel="preload" href="/static/fonts/Lato-Regular.woff2" as="font" type="font/woff2" crossorigin>
    <link rel="preload" href="/static/fonts/ysrf.woff2" as="font" type="font/woff2" crossorigin>
    <link rel="stylesheet" href="/static/style.css?v={v}">
    <link rel="icon" href="/static/images/favicon.ico" type="image/x-icon">
    <script src="/static/htmx.min.js"></script>
    <script src="/static/upload.js?v={v}"></script>"#,
        v = version,
    );

    let out_path = Path::new("templates/_head_assets.html");
    // Only write if content changed (avoids unnecessary recompilation)
    let needs_write = fs::read_to_string(out_path)
        .map(|existing| existing != partial)
        .unwrap_or(true);
    if needs_write {
        fs::write(out_path, &partial).expect("failed to write _head_assets.html");
    }
}