//! Serving the built web UI out of the binary.
//!
//! `rust-embed` compiles `web/dist` in for release builds, so a deployment is
//! still one file. In debug builds it reads from disk instead, so `vite build`
//! output is picked up without a `cargo` rebuild.
//!
//! Anything that is not an embedded asset falls back to `index.html`, because the
//! UI routes client-side and a deep link must not 404.

use axum::http::{StatusCode, Uri, header};
use axum::response::{IntoResponse, Response};

#[derive(rust_embed::Embed)]
#[folder = "../../web/dist"]
struct Assets;

/// The message shown when the binary was built without a web UI. Silence here
/// would look like a broken deployment rather than a missing build step.
const NO_BUILD: &str = "the web UI is not built. Run `cd web && bun install && bun run build`.";

pub async fn serve(uri: Uri) -> Response {
    let path = uri.path().trim_start_matches('/');
    if let Some(response) = asset(path) {
        return response;
    }
    // Never fall back for asset-shaped requests: a missing chunk answered with
    // HTML turns a clear 404 into a confusing MIME-type error in the console.
    if path.starts_with("assets/") {
        return (StatusCode::NOT_FOUND, "not found").into_response();
    }
    asset("index.html").unwrap_or_else(|| (StatusCode::NOT_FOUND, NO_BUILD).into_response())
}

fn asset(path: &str) -> Option<Response> {
    let file = Assets::get(path)?;
    let mime = mime_guess::from_path(path).first_or_octet_stream();
    // Vite content-hashes everything under assets/, so those are immutable.
    // index.html must not be, or a deploy would never reach an open tab.
    let cache = if path.starts_with("assets/") {
        "public, max-age=31536000, immutable"
    } else {
        "no-cache"
    };
    Some(
        (
            [
                (header::CONTENT_TYPE, mime.as_ref()),
                (header::CACHE_CONTROL, cache),
            ],
            file.data.into_owned(),
        )
            .into_response(),
    )
}