import { useEffect, useState } from "react";
import { Coordinates, Track } from "@mt/common-types";

import { getDistance, getPointDeviation } from "../utils";

const APPROXIMATE_DISTANCE = 15; // [meters] half of tramway length (~30 meters)

export function usePassedTrackIndex(
  track: Track | null,
  currentPosition: Coordinates | null
) {
  const [passedTrackIndex, setPassedTrackIndex] = useState<number>(0);

  useEffect(() => {
    if (!track || !currentPosition) {
      return;
    }

    let minDistance = getDistance(track[0], currentPosition);
    let newPassedIndex = 0;

    for (let i = 1; i < track.length; i++) {
      const distance = getDistance(track[i], currentPosition);

      if (distance < minDistance) {
        newPassedIndex = i;
        minDistance = distance;
      }
    }

    /**
     * Is current position more than APPROXIMATE_DISTANCE far from found track point
     * we need to check that we really reach newPassedIndex. If not — should decrement index
     */
    if (
      getDistance(track[newPassedIndex], currentPosition) > APPROXIMATE_DISTANCE
    ) {
      const prevIndex = Math.max(newPassedIndex - 1, 0);
      const nextIndex = Math.min(newPassedIndex + 1, track.length - 1);

      const leftDeviation = getPointDeviation(
        track[prevIndex],
        track[newPassedIndex], // Ближайшая точка трека
        currentPosition
      );
      const rightDeviation = getPointDeviation(
        track[newPassedIndex], // Ближайшая точка трека
        track[nextIndex],
        currentPosition
      );

      if (leftDeviation >= rightDeviation) {
        newPassedIndex--;
      }
    }

    setPassedTrackIndex(newPassedIndex);
  }, [track, currentPosition]);

  return { passedTrackIndex };
}