package nouritsu;

import fi.iki.elonen.NanoHTTPD;
import fi.iki.elonen.NanoHTTPD.Response.Status;
import io.vavr.Tuple2;
import io.vavr.collection.HashMap;
import io.vavr.collection.List;
import io.vavr.collection.Map;
import io.vavr.control.Either;
import io.vavr.control.Try;
import nouritsu.types.Message;

import java.io.IOException;
import java.util.function.Function;

public class Nouritsu extends NanoHTTPD {
  private final Dao dao;

  public Nouritsu(int port, Dao dao) throws IOException {
    super(port);
    start(10_000, false);
    this.dao = dao;
  }

  @Override
  public Response serve(IHTTPSession session) {
    return Try.of(() -> processRequest(session, dao))
      .fold(
        err -> newFixedLengthResponse(Status.INTERNAL_ERROR, MIME_PLAINTEXT, err.getMessage()),
        response -> newFixedLengthResponse(response.status(), MIME_PLAINTEXT, response.text())
      );
  }

  private static final String HELP = """
    Valid endpoints are (not case sensitive):
    /addStore/?name=storeName&sections=first,second,third
    /addItem/?name=itemName&category=itemCategory
    /addToList/?user=userId&itemName
    /getList/?user=userId&store=optionalStoreName
    /clearList/?user=userId
    """;

  private static Message processRequest(IHTTPSession session, Dao dao) {
    var params = extractParams(session);
    return switch (session.getUri().replaceAll("/", "").toLowerCase()) {
      case "", "index.html" -> new Message(HELP, Status.OK);
      case "addstore" -> addStore(params, dao);
      case "additem" -> addItem(params, dao);
      case "addtolist" -> addToList(params, dao);
      case "getlist" -> getList(params, dao);
      case "clearlist" -> clearList(params, dao);
      default -> new Message(HELP, Status.NOT_FOUND);
    };
  }

  // Repack the parameters into vavr collections.
  private static Map<String, List<String>> extractParams(IHTTPSession session) {
    return session.getParameters()
      .entrySet()
      .stream()
      .map(e -> new Tuple2<>(e.getKey(), List.ofAll(e.getValue())))
      .collect(HashMap.collector());
  }

  private static Message clearList(Map<String, List<String>> params, Dao dao) {
    return getFromParams(params, "user")
      .map(List::head) // save, the list can’t be empty
      .flatMap(dao::clearList)
      .fold(Function.identity(), Message.OK);
  }

  private static Message getList(Map<String, List<String>> params, Dao dao) {
    return getFromParams(params, "user")
      .map(List::head) // save, the list can’t be empty
      .flatMap(dao::getList)
      .fold(Function.identity(), Message.OK);
  }

  private static Message addToList(Map<String, List<String>> params, Dao dao) {
    return new Message("", Status.NOT_IMPLEMENTED);
  }

  private static Message addItem(Map<String, List<String>> params, Dao dao) {
    return new Message("", Status.NOT_IMPLEMENTED);
  }

  private static Message addStore(Map<String, List<String>> params, Dao dao) {
    return new Message("", Status.NOT_IMPLEMENTED);
  }

  private static Either<Message, List<String>> getFromParams(Map<String, List<String>> params, String key) {
    return params.get(key).toEither(new Message("Parameter “%s” not found".formatted(key), Status.NOT_FOUND));
  }

  public static void main(String[] args) {
    try {
      new Nouritsu(14523, new Dao());
    } catch (IOException e) {
      e.printStackTrace();
    }
  }
}