#if UNITY_EDITOR
using JetBrains.Annotations;
using System.Text;
using UnityEditor;
using UnityEngine;

namespace Phantom.XRMOD.UnityFusion.Editor
{
	internal static class MonoScriptSummaryParser
	{
		private static readonly StringBuilder stringBuilder = new();

		public static bool TryParseSummary([NotNull] MonoBehaviour monoBehaviour, out string summary)
		{
			if(!(MonoScript.FromMonoBehaviour(monoBehaviour) is MonoScript monoScript) || monoScript == null)
			{
				summary = "";
				return false;
			}

			string text = monoScript.text;
			int summaryStart = text.IndexOf("<summary>");
			if(summaryStart == -1)
			{
				summary = "";
				return false;
			}

			int baseClassBeforeSummary = text.LastIndexOf(':', summaryStart);
			if(baseClassBeforeSummary != -1)
			{
				summary = "";
				return false;
			}
			
			int summaryEnd = text.IndexOf("</summary>", summaryStart);
			if(summaryEnd == -1)
			{
				summary = "";
				return false;
			}

			summaryStart += "<summary>".Length;
			ParseSummary(text, summaryStart, summaryEnd);
			summary = stringBuilder.ToString().TrimEnd();
			stringBuilder.Clear();
			return true;
		}

		private static void ParseSummary(string code, int summaryStart, int summaryEnd)
		{
			int tagLength = -1;
			for(int i = summaryStart; i < summaryEnd; i++)
			{
				switch(code[i])
				{
					case '<':
						if(TryParseXMLTag(code, i, ref tagLength))
						{
							i += tagLength - 1;
							break;
						}
						stringBuilder.Append(code[i]);
						break;
					case '/':
						if(SubstringEquals(code, i, "///"))
						{
							i += 2;
							break;
						}
						stringBuilder.Append(code[i]);
						break;
					case '\n':
					case '\r':
					case '\t':
						break;
					case ' ':
						if(stringBuilder.Length > 0)
						{
							char prev = stringBuilder[stringBuilder.Length - 1];
							if(prev != ' ' && prev != '\n')
							{
								stringBuilder.Append(' ');
							}
						}
						break;
					case '{':
						stringBuilder.Append('<');
						break;
					case '}':
						stringBuilder.Append('>');
						break;
					default:
						stringBuilder.Append(code[i]);
						break;
				}
			}
		}

		private static bool TryParseXMLTag(string line, int tagStartIndex, ref int tagLength)
		{
			int firstLetterIndex = tagStartIndex + 1;
			if(line.Length <= firstLetterIndex)
			{
				return false;
			}

			switch(line[firstLetterIndex])
			{
				case 's':
					// Examples:
					// <see cref="Awake"/>
					// <see cref="Awake">Awake function</see>
					if(SubstringEquals(line, firstLetterIndex, "see cref=\""))
					{
						int refStartIndex = firstLetterIndex + "see cref=\"".Length;
						int tagEndIndex = line.IndexOf('>', refStartIndex + 1);
						if(tagEndIndex == -1)
						{
							return false;
						}

						// Example: <see cref="Awake"/>
						if(line[tagEndIndex - 1] == '/')
						{
							int refEndIndex = line.IndexOf('"', refStartIndex + 1);
							if(refEndIndex == -1)
							{
								return false;
							}

							Append(line.Substring(refStartIndex, refEndIndex - refStartIndex));
							tagLength = tagEndIndex - tagStartIndex + 1;
							return true;
						}
						// Example: <see cref="Awake">Awake function</see>
						else
						{
							int contentStartIndex = tagEndIndex + 1;
							int contentEndIndex = line.IndexOf('<', contentStartIndex + 1);
							if(contentEndIndex == -1)
							{
								return false;
							}

							int closingTagEndIndex = line.IndexOf('>', contentEndIndex + 1);

							Append(line.Substring(contentStartIndex, contentEndIndex - contentStartIndex));
							tagLength = closingTagEndIndex - tagStartIndex + 1;
							return true;
						}
					}
					return false;
				case 't':
					// Examples:
					// <typeparamref name="TClient"/>
					// <typeparamref name="TClient">client</typeparamref>
					if(SubstringEquals(line, firstLetterIndex, "typeparamref name=\""))
					{
						int refStartIndex = firstLetterIndex + "typeparamref name=\"".Length;
						int tagEndIndex = line.IndexOf('>', refStartIndex + 1);
						if(tagEndIndex == -1)
						{
							return false;
						}

						// Example: <see cref="Awake"/>
						if(line[tagEndIndex - 1] == '/')
						{
							int refEndIndex = line.IndexOf('"', refStartIndex + 1);
							if(refEndIndex == -1)
							{
								return false;
							}

							Append(line.Substring(refStartIndex, refEndIndex - refStartIndex));
							tagLength = tagEndIndex - tagStartIndex + 1;
							return true;
						}
						// Example: <typeparamref name="TClient">client</typeparamref>
						else
						{
							int contentStartIndex = tagEndIndex + 1;
							int contentEndIndex = line.IndexOf('<', contentStartIndex + 1);
							if(contentEndIndex == -1)
							{
								return false;
							}

							int closingTagEndIndex = line.IndexOf('>', contentEndIndex + 1);

							Append(line.Substring(contentStartIndex, contentEndIndex - contentStartIndex));
							tagLength = closingTagEndIndex - tagStartIndex + 1;
							return true;
						}
					}
					return false;
				case 'e':
					if(SubstringEquals(line, firstLetterIndex, "example>"))
					{
						tagLength = "<example>".Length;
						return true;
					}

					return false;
				case 'c':
					if(SubstringEquals(line, firstLetterIndex, "code>"))
					{
						tagLength = "<code>".Length;
						return true;
					}

					return false;
				case 'p':
					if(SubstringEquals(line, firstLetterIndex, "para>"))
					{
						stringBuilder.Append("\n\n");
						tagLength = "<para>".Length;
						return true;
					}

					return false;
				case '/':
					if(SubstringEquals(line, firstLetterIndex, "/para>"))
					{
						tagLength = "</para>".Length;
						return true;
					}

					if(SubstringEquals(line, firstLetterIndex, "/typeparamref>"))
					{
						tagLength = "</para>".Length;
						return true;
					}

					if(SubstringEquals(line, firstLetterIndex, "/code>"))
					{
						tagLength = "</code>".Length;
						return true;
					}

					if(SubstringEquals(line, firstLetterIndex, "/example>"))
					{
						tagLength = "</example>".Length;
						return true;
					}

					return false;

			}

			int endIndex = line.IndexOf('>', tagStartIndex + 1);
			if(endIndex == -1)
			{
				return false;
			}
			
			tagLength = endIndex - tagStartIndex + 1;
			return true;
		}

		private static void Append(string substring)
			=> stringBuilder.Append(substring.Replace('{', '<').Replace('}', '>'));

		private static bool SubstringEquals(string line, int startIndex, string substring)
		{
			int charCount = substring.Length;
			int lastIndex = startIndex + charCount - 1;
			if(line.Length <= lastIndex)
			{
				return false;
			}

			for(int i = 0; i < charCount; i++)
			{
				if(line[startIndex + i] != substring[i])
				{
					return false;
				}
			}

			return true;
		}
	}
}
#endif