use anyhow::{Context, Result};
use axum::body::Body;
use axum::extract::Path;
use axum::http::{header, HeaderValue, StatusCode};
use axum::response::{IntoResponse, Response};
use axum::routing::get;
use axum::Router;
use mime_guess::from_path;
use rust_embed::RustEmbed;

#[derive(RustEmbed)]
#[folder = "../backchannel-web/dist"]
struct WebAssets;

pub async fn serve(bind_addr: &str) -> Result<()> {
    let app = Router::new()
        .route("/", get(index))
        .route("/*path", get(asset_or_index));

    let listener = tokio::net::TcpListener::bind(bind_addr)
        .await
        .with_context(|| format!("Failed to bind HTTP server to {bind_addr}"))?;

    tracing::info!("BackChannel web UI listening on http://{bind_addr}");
    axum::serve(listener, app).await.context("HTTP server failed")
}

async fn index() -> Response {
    render_asset("index.html")
}

async fn asset_or_index(Path(path): Path<String>) -> Response {
    if path.is_empty() {
        return render_asset("index.html");
    }

    render_asset(&path)
}

fn render_asset(path: &str) -> Response {
    let canonical = path.trim_start_matches('/');

    if let Some(content) = WebAssets::get(canonical) {
        return build_response(canonical, content.data.as_ref(), StatusCode::OK);
    }

    if let Some(index) = WebAssets::get("index.html") {
        return build_response("index.html", index.data.as_ref(), StatusCode::OK);
    }

    (StatusCode::NOT_FOUND, "Web UI asset not found").into_response()
}

fn build_response(path: &str, body: &[u8], status: StatusCode) -> Response {
    let mime = from_path(path).first_or_octet_stream();

    let mut response = Response::new(Body::from(body.to_vec()));
    *response.status_mut() = status;
    response.headers_mut().insert(
        header::CONTENT_TYPE,
        HeaderValue::from_str(mime.as_ref()).unwrap_or(HeaderValue::from_static("application/octet-stream")),
    );

    response
}