pgs/Assets/Scripts/NpcMovementController.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class NpcMovementController : MonoBehaviour {

    [SerializeField] private SpriteRenderer spriteRenderer;
    [SerializeField] private Animator animator;
    [SerializeField] private Rigidbody2D rigidBody;
    [SerializeField] private float walkSpeed;
    [Range(0f, 1f)] [SerializeField] private float walkProbability;
    [Range(0f, 3f)] [SerializeField] private float smoothTime;

    [SerializeField] private float minTimeIdle;
    [SerializeField] private float maxTimeIdle;
    [SerializeField] private float minTimeWalk;
    [SerializeField] private float maxTimeWalk;

    public Vector2 boundsX;

    public bool isFacingRight;
    public bool isWalking;
    private Vector2 targetVelocity;
    private Vector2 referenceVelocity = Vector2.zero;

    private Vector2 myBounds;

    // Start is called before the first frame update
    void Awake() {
        animator = gameObject.GetComponent<Animator>();
        rigidBody = gameObject.GetComponent<Rigidbody2D>();
        isFacingRight = true;
        isWalking = false;
        StartCoroutine("IdleWalkCoroutine");

        myBounds = new Vector2(transform.position.x - boundsX.x, transform.position.x + boundsX.y);
    }

    private void FixedUpdate() {
        // If you're about to walk off a ledge, don't.
        bool isMoving = Mathf.Abs(rigidBody.velocity.x) > 0.001;
        bool isMovingRight = rigidBody.velocity.x > 0;
        if (isMoving && !CheckBounds(isMovingRight)) {
            rigidBody.velocity = new Vector2(0f, rigidBody.velocity.y);
            targetVelocity = new Vector2(0f, rigidBody.velocity.y);
        } else if (Mathf.Abs(rigidBody.velocity.y) < 0.01f) {
            Vector2 newVelocity = new Vector2(Vector2.SmoothDamp(rigidBody.velocity, targetVelocity, ref referenceVelocity, smoothTime).x,
                                              rigidBody.velocity.y);
            rigidBody.velocity = newVelocity;
        }

        animator.SetFloat("Speed", Mathf.Abs(rigidBody.velocity.x));
    }

    private bool TryToWalk(bool right, bool chase = false) {
        if (CheckBounds(right)) {
            if (right) {
                targetVelocity = new Vector3(walkSpeed, 0, 0);
            } else {
                targetVelocity = new Vector3(-1 * walkSpeed, 0, 0);
            }
            if (isFacingRight != right) {
                Flip();
            }
            return true;
        }
        return false;
    }

    private bool CheckBounds(bool right) {
        if ((right && transform.position.x > myBounds.y) ||
            (!right && transform.position.x < myBounds.x)) {
            return false;
        }
        return true;
    }

    private IEnumerator IdleWalkCoroutine() {
        while (true) {
            if (ShouldWalk() && !isWalking) {
                // Walk in a random direction.
                isWalking = true;
                if (Random.Range(0f, 1f) < 0.5f) {
                    // Walk left.
                    if (!TryToWalk(false)) {
                        TryToWalk(true);
                    }
                } else {
                    // Walk right.
                    if (!TryToWalk(true)) {
                        TryToWalk(false);
                    }
                }
                yield return new WaitForSeconds(RandomWalkSeconds());
            } else {
                // Idle.
                isWalking = false;
                targetVelocity = Vector3.zero;
                yield return new WaitForSeconds(RandomIdleSeconds());
            }
        }
    }

    private bool ShouldWalk() {
        return Random.Range(0f, 1f) < walkProbability;
    }

    private float RandomIdleSeconds() {
        return Random.Range(0f, 1f) * (maxTimeIdle - minTimeIdle) + minTimeIdle;
    }

    private float RandomWalkSeconds() {
        return Random.Range(0f, 1f) * (maxTimeWalk - minTimeWalk) + minTimeWalk;
    }

    private void Flip() {
        isFacingRight = !isFacingRight;
        Vector3 scale = transform.localScale;
        scale.x *= -1;
        transform.localScale = scale;
    }
}