use std::fmt::Write as _;
use std::fs;
use std::path::Path;

/// 前端构建产物目录（`pnpm build` 的输出）。
const WEB_DIST: &str = "../../../view/dist";

fn main() {
    let manifest_dir = Path::new(env!("CARGO_MANIFEST_DIR"));
    let out_dir = std::path::PathBuf::from(std::env::var("OUT_DIR").expect("OUT_DIR"));
    build_web_assets(manifest_dir, &out_dir);
}

/// 把根目录 `view/dist` 下的前端产物编进二进制：认证中心自带登录页，不依赖外部静态站点。
fn build_web_assets(manifest_dir: &Path, out_dir: &Path) {
    let root = manifest_dir.join(WEB_DIST);
    println!("cargo:rerun-if-changed={}", root.display());
    println!("cargo:rerun-if-changed=build.rs");
    println!("cargo:rerun-if-env-changed=KENOAUTH_SKIP_WEB_ASSETS");

    if std::env::var_os("KENOAUTH_SKIP_WEB_ASSETS").is_some() {
        // 纯后端编译（未装 pnpm 的环境）跳过前端资产，服务启动后退化为 501 页面。
        let source = "// web assets skipped via KENOAUTH_SKIP_WEB_ASSETS\npub static ASSETS: &[Asset] = &[];\n";
        fs::write(out_dir.join("assets.rs"), source).expect("writing generated asset table");
        return;
    }

    let mut files = Vec::new();
    collect_assets(&root, &root, &mut files);
    files.sort();

    let mut source = String::from(concat!(
        "// generated by build.rs from ",
        "../../../view/dist\n",
        "pub static ASSETS: &[Asset] = &[\n"
    ));
    for file in &files {
        let absolute = root.join(file);
        let absolute = absolute
            .canonicalize()
            .unwrap_or(absolute)
            .to_string_lossy()
            .replace('\\', "/");
        let _ = writeln!(
            source,
            "    Asset {{ path: {file:?}, content_type: {:?}, bytes: include_bytes!({absolute:?}) }},",
            content_type(file)
        );
    }
    source.push_str("];\n");

    fs::write(out_dir.join("assets.rs"), source).expect("writing generated asset table");
}

fn collect_assets(root: &Path, dir: &Path, files: &mut Vec<String>) {
    let Ok(entries) = fs::read_dir(dir) else {
        return;
    };

    for entry in entries.flatten() {
        let path = entry.path();
        if path.is_dir() {
            collect_assets(root, &path, files);
        } else if let Ok(relative) = path.strip_prefix(root) {
            files.push(relative.to_string_lossy().replace('\\', "/"));
        }
    }
}

fn content_type(file: &str) -> &'static str {
    match file.rsplit_once('.').map(|(_, extension)| extension) {
        Some("html" | "htm") => "text/html; charset=utf-8",
        Some("js" | "mjs") => "text/javascript; charset=utf-8",
        Some("css") => "text/css; charset=utf-8",
        Some("json" | "map") => "application/json",
        Some("svg") => "image/svg+xml",
        Some("png") => "image/png",
        Some("jpg" | "jpeg") => "image/jpeg",
        Some("webp") => "image/webp",
        Some("gif") => "image/gif",
        Some("ico") => "image/x-icon",
        Some("txt") => "text/plain; charset=utf-8",
        Some("woff") => "font/woff",
        Some("woff2") => "font/woff2",
        Some("ttf") => "font/ttf",
        Some("otf") => "font/otf",
        Some("wasm") => "application/wasm",
        Some("xml") => "application/xml",
        Some("pdf") => "application/pdf",
        _ => "application/octet-stream",
    }
}