using System;
using Foundation;
using ObjCRuntime;
using UIKit;
 
namespace Microsoft.Maui.Platform
{
	public static class AttributedStringExtensions
	{
		public static NSMutableAttributedString? WithCharacterSpacing(this NSAttributedString attributedString, double characterSpacing)
		{
			if (attributedString == null || attributedString.Length == 0)
				return null;
 
			var attribute = attributedString.GetAttribute(UIStringAttributeKey.KerningAdjustment, 0, out _);
 
			// if we are going to un-set, but there is no adjustment, then bail out
			if (characterSpacing == 0 && attribute == null)
				return null;
 
			var mutableAttributedString = new NSMutableAttributedString(attributedString);
			mutableAttributedString.AddAttribute
			(
				UIStringAttributeKey.KerningAdjustment,
				NSObject.FromObject(characterSpacing),
				new NSRange(0, mutableAttributedString.Length)
			);
			return mutableAttributedString;
		}
 
		internal static NSMutableAttributedString? WithTextColor(this NSAttributedString attributedString, Graphics.Color color)
		{
			if (attributedString == null || attributedString.Length == 0)
				return null;
 
			var mutableAttributedString = new NSMutableAttributedString(attributedString);
			mutableAttributedString.AddAttribute
			(
				UIStringAttributeKey.ForegroundColor,
				Foundation.NSObject.FromObject(color.ToPlatform().CGColor),
				new NSRange(0, mutableAttributedString.Length)
			);
			return mutableAttributedString;
 
		}
 
		public static NSMutableAttributedString? WithLineHeight(this NSAttributedString attributedString, double lineHeight)
		{
			if (attributedString == null || attributedString.Length == 0)
				return null;
 
			var attribute = (NSParagraphStyle)attributedString.GetAttribute(UIStringAttributeKey.ParagraphStyle, 0, out _);
 
			// if we need to un-set the line height but there is no attribute to modify then we do nothing
			if (lineHeight == -1 && attribute == null)
				return null;
 
			var mutableParagraphStyle = new NSMutableParagraphStyle();
			if (attribute != null)
				mutableParagraphStyle.SetParagraphStyle(attribute);
 
			mutableParagraphStyle.LineHeightMultiple = new nfloat(lineHeight >= 0 ? lineHeight : -1);
 
			var mutableAttributedString = new NSMutableAttributedString(attributedString);
			mutableAttributedString.AddAttribute
			(
				UIStringAttributeKey.ParagraphStyle,
				mutableParagraphStyle,
				new NSRange(0, mutableAttributedString.Length)
			);
 
			return mutableAttributedString;
		}
 
		public static NSMutableAttributedString? WithDecorations(this NSAttributedString attributedString, TextDecorations decorations)
		{
			if (attributedString == null || attributedString.Length == 0)
				return null;
 
			var mutable = new NSMutableAttributedString(attributedString);
 
			var range = new NSRange(0, mutable.Length);
 
			UpdateDecoration(mutable, UIStringAttributeKey.StrikethroughStyle, range,
				decorations & TextDecorations.Strikethrough);
 
			UpdateDecoration(mutable, UIStringAttributeKey.UnderlineStyle, range,
				decorations & TextDecorations.Underline);
 
			return mutable;
		}
 
		public static NSAttributedString? TrimToMaxLength(this NSAttributedString? attributedString, int maxLength) =>
			maxLength >= 0 && attributedString?.Length > maxLength
				? attributedString.Substring(0, maxLength)
				: attributedString;
 
		static void UpdateDecoration(NSMutableAttributedString attributedString, NSString key,
			NSRange range, TextDecorations decorations)
		{
			if (decorations == 0)
			{
				attributedString.RemoveAttribute(key, range);
			}
			else
			{
				attributedString.AddAttribute(key, NSNumber.FromInt32((int)NSUnderlineStyle.Single), range);
			}
		}
	}
}