TurnBasedStrategyCourse/Assets/Scripts/Grid/GridSystemHex.cs

using System;
using System.Collections.Generic;
using UnityEngine;
using Object = UnityEngine.Object;

namespace Grid {
    public class GridSystemHex<TGridObject> {
        private const float hexVerticalOffsetMultiplier = .75f;
        private readonly float cellSize;
        private readonly TGridObject[,] gridObjectArray;

        public GridSystemHex(int width, int height, float cellSize, Func<GridSystemHex<TGridObject>, GridPosition, TGridObject> createGridObject) {
            Width = width;
            Height = height;
            this.cellSize = cellSize;

            gridObjectArray = new TGridObject[width, height];
            for (int x = 0; x < width; x++) {
                for (int z = 0; z < height; z++) {
                    gridObjectArray[x, z] = createGridObject(this, new(x, z));
                }
            }
        }

        public int Height { get; }
        public int Width { get; }

        public Vector3 GetWorldPosition(GridPosition gridPosition) {
            return new Vector3(gridPosition.X, 0, 0) * cellSize + cellSize * hexVerticalOffsetMultiplier * new Vector3(0, 0, gridPosition.Z) + (gridPosition.Z % 2 == 1 ? cellSize * .5f * Vector3.right : Vector3.zero);
        }

        public GridPosition GetGridPosition(Vector3 worldPosition) {
            //Get the rough GridPosition
            GridPosition roughXZ = new(Mathf.RoundToInt(worldPosition.x / cellSize), Mathf.RoundToInt(worldPosition.z / cellSize / hexVerticalOffsetMultiplier));

            //Get all neighbours
            bool oddRow = roughXZ.Z % 2 == 1;
            List<GridPosition> neighbourGridPositionList = new() {
                roughXZ + new GridPosition(-1, 0),
                roughXZ + new GridPosition(+1, 0),

                roughXZ + new GridPosition(0, +1),
                roughXZ + new GridPosition(0, -1),

                roughXZ + new GridPosition(oddRow ? +1 : -1, +1),
                roughXZ + new GridPosition(oddRow ? +1 : -1, -1),
            };

            //Find the closest neighbour
            GridPosition closestGridPosition = roughXZ;
            foreach (GridPosition neighbourGridPosition in neighbourGridPositionList) {
                if (Vector3.Distance(worldPosition, GetWorldPosition(neighbourGridPosition)) < Vector3.Distance(worldPosition, GetWorldPosition(closestGridPosition)))
                    closestGridPosition = neighbourGridPosition;
            }

            return closestGridPosition;
        }

        public void CreateDebugObjects(Transform debugPrefab) {
            for (int x = 0; x < Width; x++) {
                for (int z = 0; z < Height; z++) {
                    GridPosition gridPosition = new(x, z);
                    Transform debugTransform = Object.Instantiate(debugPrefab, GetWorldPosition(gridPosition), Quaternion.identity);
                    GridDebugObject gridDebugObject = debugTransform.GetComponent<GridDebugObject>();
                    gridDebugObject.SetGridObject(GetGridObject(gridPosition));
                }
            }
        }

        public TGridObject GetGridObject(GridPosition gridPosition) => gridObjectArray[gridPosition.X, gridPosition.Z];

        public bool IsValidGridPosition(GridPosition gridPosition) => gridPosition is { X: >= 0, Z: >= 0 } && gridPosition.X < Width && gridPosition.Z < Height;
    }
}