use std::path::PathBuf;

use axum::Router;
use axum::extract::Path;
use axum::response::IntoResponse;
use axum::routing::get;
use reqwest::StatusCode;
use tokio::fs;
use tower_http::cors::CorsLayer;

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    let app = Router::new()
        .route("/{*path}", get(get_file))
        .layer(CorsLayer::permissive());

    let listener = tokio::net::TcpListener::bind("127.0.0.1:3000")
        .await
        .unwrap();

    axum::serve(listener, app.into_make_service()).await?;

    Ok(())
}

async fn get_file(Path(path): Path<String>) -> Result<impl IntoResponse, StatusCode> {
    let local_path = PathBuf::from("static").join(&path);

    // Check if file exists
    if fs::metadata(&local_path).await.is_err() {
        // Build remote URL
        let remote_url = format!("https://osm.rrze.fau.de/osmhd/{}", path);

        // Download file
        let response = reqwest::get(&remote_url)
            .await
            .map_err(|_| StatusCode::BAD_GATEWAY)?;

        if !response.status().is_success() {
            return Err(StatusCode::NOT_FOUND);
        }

        let bytes = response
            .bytes()
            .await
            .map_err(|_| StatusCode::BAD_GATEWAY)?;

        // Ensure directory exists
        if let Some(parent) = local_path.parent() {
            fs::create_dir_all(parent)
                .await
                .map_err(|_| StatusCode::INTERNAL_SERVER_ERROR)?;
        }

        // Save file
        fs::write(&local_path, &bytes)
            .await
            .map_err(|_| StatusCode::INTERNAL_SERVER_ERROR)?;
    }

    // Serve file
    let bytes = fs::read(&local_path)
        .await
        .map_err(|_| StatusCode::INTERNAL_SERVER_ERROR)?;

    Ok(([(axum::http::header::CONTENT_TYPE, "image/png")], bytes))
}