// https://github.com/ShadowIgnition/Unity-Note-Attribute

using System;
using UnityEditor;
using UnityEngine;

namespace Nullframes.Intrigues
{
	[CustomPropertyDrawer(typeof(NoteAttribute))]
	public class NoteDrawer : DecoratorDrawer
	{
		// <summary>
		/// Overrides OnGUI() to draw the note attribute in the Inspector.
		/// </summary>
		/// <param name="position">The position of the drawer in the Inspector.</param>
		public override void OnGUI(Rect position)
		{
			CachePreviewHeight(Attribute.Description, position.width);

			if (Math.Abs(m_Height - m_ScrollViewHeight) > double.Epsilon)
			{
				Rect scrollArea = GetRect(position, true);
				Rect content = scrollArea;

				// Adjust xMax to account for vertical scrollbar
				content.xMax -= 14;

				using (var scrollScope = new GUI.ScrollViewScope(position, scrollPos, content))
				{
					scrollPos = scrollScope.scrollPosition;
					GUI.Box(content, Attribute.Description, GetNoteStyle());
				}
			}
			else
			{
				GUI.Box(GetRect(position, false), Attribute.Description, GetNoteStyle());
			}
		}

		/// <summary>
		/// Gets the height of the drawer.
		/// </summary>
		/// <returns>The height of the drawer.</returns>
		public override float GetHeight()
		{
			return m_Height;
		}

		/// <summary>
		/// Gets the cached note style.
		/// </summary>
		/// <returns>The GUIStyle for the note.</returns>
		static GUIStyle GetNoteStyle()
		{
			if (Style == null)
			{
				GUIStyle style = GUI.skin.box;
				style.padding = new RectOffset(4, 16, 4, 4);
				style.normal.background = Texture2D.grayTexture;
				style.wordWrap = true;
				style.alignment = TextAnchor.UpperLeft;
				style.richText = true;
				Style = style;
			}

			return Style;
		}

		/// <summary>
		/// Caches the height of the note text area.
		/// </summary>
		/// <param name="note">The note string.</param>
		/// <param name="width">The width of the text area.</param>
		void CachePreviewHeight(string note, float width)
		{
			if (Attribute.LineHeight > 0)
			{
				// If a custom line height is specified, use it
				m_Height = GetPaddedLineHeight(Attribute.LineHeight);
				m_ScrollViewHeight = m_Height;
			}
			else
			{
				// Calculate the height of the text area
				m_Height = GUI.skin.textArea.CalcHeight(new GUIContent(note), width) +
				           (GUI.skin.textArea.lineHeight / 2);

				// Store the unclamped height, so we can use for a scroll view later if needed
				m_ScrollViewHeight = m_Height;

				// Clamp the height within the specified range (Don't want to be able to make the editor preview too big)
				m_Height = Mathf.Clamp(m_Height, GetPaddedLineHeight(AUTO_MIN_HEIGHT),
					GetPaddedLineHeight(AUTO_MAX_HEIGHT));
			}
		}

		/// <summary>
		/// Gets the rect for drawing the note area.
		/// </summary>
		/// <param name="position">The position of the drawer in the Inspector.</param>
		/// <param name="isScrollView">Flag indicating if the drawer is part of a scroll view.</param>
		/// <returns>The rect for drawing the note area.</returns>
		Rect GetRect(Rect position, bool isScrollView)
		{
			return new Rect(position.x, position.y, position.width, isScrollView ? m_ScrollViewHeight : m_Height);
		}

		/// <summary>
		/// Gets the padded line height based on the number of lines.
		/// </summary>
		/// <param name="lineCount">The number of lines.</param>
		/// <returns>The padded line height.</returns>
		float GetPaddedLineHeight(uint lineCount)
		{
			return (GUI.skin.textArea.lineHeight * lineCount) + (GUI.skin.textArea.lineHeight / 2);
		}

		/// <summary>
		/// Gets the <see cref="NoteAttribute"/> associated with this drawer.
		/// </summary>
		NoteAttribute Attribute
		{
			get { return attribute as NoteAttribute; }
		}

		static GUIStyle Style;

		Vector2 scrollPos; // Current Scroll position
		float m_Height; // Height of the note text area
		float m_ScrollViewHeight; // Height of the note text area

		const uint AUTO_MAX_HEIGHT = 5; // Maximum number of lines for the text area
		const uint AUTO_MIN_HEIGHT = 2; // Minimum number of lines for the text area
	}
}