[Unity] UniRxを使ってアナログスティックで十字キーのGetKeyDownをエミュレートする

NewBehaviourScript.cs

using System.Collections.Generic;
using UniRx;
using UniRx.Triggers;
using UnityEngine;

public class NewBehaviourScript : MonoBehaviour
{
    private enum DPadDirection
    {
        None,
        Up,
        Down,
        Left,
        Right,
        UpRight,
        UpLeft,
        DownRight,
        DownLeft,
    }

    private const float Threshold = 0.3f;

    // 4方向にエミュレートするので4で割る
    private const float Direct4 = 360f / 4;
    private static readonly IReadOnlyDictionary<int, DPadDirection> DirectionMap4 = new Dictionary<int, DPadDirection>()
    {
        {0, DPadDirection.Right},
        {4 / 4, DPadDirection.Up},
        {4 / 2, DPadDirection.Left},
        {4 / -4, DPadDirection.Down},
        {4 / -2, DPadDirection.Left},
    };

    // 8方向にエミュレートするので8で割る
    private const float Direct8 = 360f / 8;
    private static readonly IReadOnlyDictionary<int, DPadDirection> DirectionMap8 = new Dictionary<int, DPadDirection>()
    {
        {0, DPadDirection.Right},
        {8 / 4, DPadDirection.Up},
        {8 / 2, DPadDirection.Left},
        {8 / -4, DPadDirection.Down},
        {8 / -2, DPadDirection.Left},
        {1, DPadDirection.UpRight},
        {3, DPadDirection.UpLeft},
        {-1, DPadDirection.DownRight},
        {-3, DPadDirection.DownLeft},
    };

    private DPadDirection GetDirection(float nums, IReadOnlyDictionary<int, DPadDirection> map)
    {
        // references
        // - https://forum.unity.com/threads/8-way-direction-joystick-only.438758/#post-3513040
        // - https://stickpan.hatenablog.com/entry/2014/05/13/172026
        var result = DPadDirection.None;
        var inputDirection = new Vector2(Input.GetAxis("Horizontal"), Input.GetAxis("Vertical"));
        if (inputDirection.magnitude >= Threshold)
        {
            var angle = Mathf.Atan2(inputDirection.y, inputDirection.x) * Mathf.Rad2Deg;
            var direction = Mathf.RoundToInt(angle / nums);
            map.TryGetValue(direction, out result);
        }

        return result;
    }

    private DPadDirection GetDirection4()
    {
        return GetDirection(Direct4, DirectionMap4);
    }


    private DPadDirection GetDirection8()
    {
        return GetDirection(Direct8, DirectionMap8);
    }

    private void Start()
    {
        // 4分割の場合
        this.UpdateAsObservable()
            .Select(_ => GetDirection4())
            .DistinctUntilChanged()
            .Where(d => d != DPadDirection.None)
            .Subscribe(d => { Debug.Log(d); })
            .AddTo(gameObject);

        // 8分割の場合
        this.UpdateAsObservable()
            .Select(_ => GetDirection8())
            .DistinctUntilChanged()
            .Where(d => d != DPadDirection.None)
            .Subscribe(d => { Debug.Log(d); })
            .AddTo(gameObject);
    }
}