using System;
using Smooth.Foundations.PatternMatching.GeneralMatcher;
using UniRx;
using UnityEngine;

public enum SwipeDirection
{
    Up,
    Down,
    Left,
    Right
}

public class Swipe : MonoBehaviour
{
    public static IObservable<SwipeDirection> SwipeStream => _swipeSubject;
    private static readonly Subject<SwipeDirection> _swipeSubject = new Subject<SwipeDirection>();

    private void Awake()
    {
        var baseStream = Observable
            // Do on every update.
            .EveryUpdate()
            // Until this component will be destroyed.
            .TakeUntilDestroy(this)
            // Only when component is enabled and gameObject is active in hierarchy.
            .Where(_ => enabled && gameObject.activeInHierarchy);

        // All that was mentioned in baseStream.
        var onMouseDownStream = baseStream
            // When left mouse button is pressed.
            .Where(_ => Input.GetMouseButtonDown(0))
            // Save its position.
            .Select(_ => (Vector2) Input.mousePosition);

        // All that was mentioned in baseStream.
        var onMouseUpStream = baseStream
            // When left mouse button is released.
            .Where(_ => Input.GetMouseButtonUp(0))
            // Save its position.
            .Select(_ => (Vector2) Input.mousePosition);

        var swipeDirectionStream = Observable
            // Combine into the tuple values that will be emitted by onMouseDownStream and onMouseUpStream streams.
            .Zip(onMouseDownStream, onMouseUpStream, Tuple.Create)
            // Get vector that represents swipe direction.
            .Select(firstAndSecondPos => (firstAndSecondPos.Item2 - firstAndSecondPos.Item1).normalized)
            // Check that first mouse press position are not equal to release position so the length of swipe direction
            // vector must be greater than 0.
            .Where(dir => dir.magnitude > 0f)
            // Match the direction vector to enum parameter that represents it.
            .Select(swipeDirection => swipeDirection.Match().To<SwipeDirection>()
                .Where(swipe => swipe.y > 0 && Mathf.Abs(swipe.x) <= 0.7f).Return(SwipeDirection.Up)
                .Where(swipe => swipe.y < 0 && Mathf.Abs(swipe.x) <= 0.7f).Return(SwipeDirection.Down)
                .Where(swipe => swipe.x < 0 && Mathf.Abs(swipe.y) <= 0.7f).Return(SwipeDirection.Left)
                .Where(swipe => swipe.x > 0 && Mathf.Abs(swipe.y) <= 0.7f).Return(SwipeDirection.Right)
                .Result())
            // Finally emit the swipe direction by the subject.
            .Do(direction => _swipeSubject.OnNext(direction));
    }
}