using System;
using System.Collections;
using System.Collections.Generic;
using UnityEditor;
using UnityEngine;
public class DrawGraphWindow : EditorWindow
{
    private static DrawGraphWindow _window;
    private static float _minZoom = 0.4f;
    private static float _maxZoom = 7.0f;
    private static float _zoonSpeed = 0.1f;
    private Color bgColor = new Color(0.15f, 0.15f, 0.15f);
    private Color gridColor = new Color(0.85f, 0.85f, 0.85f);
    private Rect graphRect;
    private Vector2 drag;
    private Vector2 offset;
    private float zoom = 1.0f;
    private Vector2 dragStart;
    private float dragSpeed = 0.1f;
  
    [MenuItem("Tools/Draw")]
    public static void PopUp()
    {
        _window = GetWindow<DrawGraphWindow>("Draw");
        _window.minSize = new Vector2(400, 300);
        _window.Show();
    }
    private void OnGUI()
    {
        SetupSize();
        ProcessEvents(Event.current);
        DrawBackground();
        DrawGrid(10 * zoom, 0.2f);
        DrawGrid(50 * zoom, 0.4f);
    }
    private void SetupSize()
    {
        graphRect = new Rect(0, 0, position.width, position.height);
    }
    private void ProcessEvents(Event e)
    {
        if (e.type == EventType.MouseDown && e.button == 1)
        {
            dragStart = e.mousePosition;
        }
        if (e.type == EventType.MouseDrag && e.button == 1)
        {
            drag = e.mousePosition - dragStart;
            dragStart = e.mousePosition;
            GUI.changed = true;
        }
        if (e.type == EventType.ScrollWheel)
        {
            zoom -= _zoonSpeed * e.delta.y;
            zoom = Mathf.Clamp(zoom, _minZoom, _maxZoom);
            e.Use();
        }
    }
    private void DrawBackground()
    {
        EditorGUI.DrawRect(graphRect, bgColor);
    }
    private void DrawGrid(float gridSpacing, float gridOpacity)
    {
        int widthDivs = Mathf.CeilToInt(position.width / gridSpacing);
        int heightDivs = Mathf.CeilToInt(position.height / gridSpacing);
        Handles.BeginGUI();
        Handles.color = new Color(gridColor.r, gridColor.g, gridColor.b, gridOpacity);
        offset += drag * dragSpeed;
        Vector3 newOffset = new Vector3(offset.x % gridSpacing, offset.y % gridSpacing, 0);
        for (int i = 0; i < widthDivs; i++)
        {
            Handles.DrawLine(new Vector3(gridSpacing * i, -gridSpacing, 0) + newOffset, new Vector3(gridSpacing * i, position.height, 0f) + newOffset);
        }
        for(int i = 0; i < heightDivs; i++)
        {
            Handles.DrawLine(new Vector3(-gridSpacing, gridSpacing * i, 0) + newOffset, new Vector3(position.width, gridSpacing * i, 0) + newOffset);
        }
        Handles.color = Color.white;
        Handles.EndGUI();
    }
}