(** Example using GPX with real Eio effects-based API 
 
    This demonstrates the real Eio-based API with structured concurrency
    and proper resource management.
**)

open Gpx_eio

let main env =
  try
    let fs = Eio.Stdenv.fs env in
    
    (* Create some GPS coordinates *)
    let lat1 = Gpx.latitude 37.7749 |> Result.get_ok in
    let lon1 = Gpx.longitude (-122.4194) |> Result.get_ok in
    let lat2 = Gpx.latitude 37.7849 |> Result.get_ok in
    let lon2 = Gpx.longitude (-122.4094) |> Result.get_ok in
    
    (* Create waypoints *)
    let waypoint1 = make_waypoint ~fs ~lat:(Gpx.latitude_to_float lat1) ~lon:(Gpx.longitude_to_float lon1) ~name:"San Francisco" () in
    let waypoint2 = make_waypoint ~fs ~lat:(Gpx.latitude_to_float lat2) ~lon:(Gpx.longitude_to_float lon2) ~name:"Near SF" () in
    
    (* Create a simple track from coordinates *)
    let track = make_track_from_coords ~fs ~name:"SF Walk" [
      (37.7749, -122.4194);
      (37.7759, -122.4184);
      (37.7769, -122.4174);
      (37.7779, -122.4164);
    ] in
    
    (* Create a route *)
    let route = make_route_from_coords ~fs ~name:"SF Route" [
      (37.7749, -122.4194);
      (37.7849, -122.4094);
    ] in
    
    (* Create GPX document with all elements *)
    let gpx = Gpx.make_gpx ~creator:"eio-example" in
    let gpx = { gpx with 
      waypoints = [waypoint1; waypoint2];
      tracks = [track];
      routes = [route];
    } in
    
    Printf.printf "Created GPX document with:\\n";
    print_stats gpx;
    Printf.printf "\\n";
    
    (* Write to file with validation *)
    write_validated ~fs "example_output.gpx" gpx;
    Printf.printf "Wrote GPX to example_output.gpx\\n";
    
    (* Read it back and verify *)
    let gpx2 = read_validated ~fs "example_output.gpx" in
    Printf.printf "Read back GPX document with %d waypoints, %d tracks, %d routes\\n" 
      (List.length gpx2.waypoints) (List.length gpx2.tracks) (List.length gpx2.routes);
    
    (* Extract coordinates from track *)
    match gpx2.tracks with
    | track :: _ ->
        let coords = track_coords track in
        Printf.printf "Track coordinates: %d points\\n" (List.length coords);
        List.iteri (fun i (lat, lon) ->
          Printf.printf "  Point %d: %.4f, %.4f\\n" i lat lon
        ) coords
    | [] -> Printf.printf "No tracks found\\n";
    
    Printf.printf "\\nEio example completed successfully!\\n"
    
  with
  | Gpx.Gpx_error err ->
      let error_msg = match err with
        | Gpx.Invalid_xml s -> "Invalid XML: " ^ s
        | Gpx.Invalid_coordinate s -> "Invalid coordinate: " ^ s
        | Gpx.Missing_required_attribute (elem, attr) -> 
            Printf.sprintf "Missing required attribute '%s' in element '%s'" attr elem
        | Gpx.Missing_required_element s -> "Missing required element: " ^ s
        | Gpx.Validation_error s -> "Validation error: " ^ s
        | Gpx.Xml_error s -> "XML error: " ^ s
        | Gpx.IO_error s -> "I/O error: " ^ s
      in
      Printf.eprintf "GPX Error: %s\\n" error_msg;
      exit 1
  | exn ->
      Printf.eprintf "Unexpected error: %s\\n" (Printexc.to_string exn);
      exit 1

let () = Eio_main.run main