necessary changes for EXDSchema generation

src/Lumina/Excel/LazyRow.cs

@@ -1,4 +1,8 @@
+using System;
+using System.Linq;
 using Lumina.Data;
+using Lumina.Data.Files.Excel;
+using Lumina.Data.Structs.Excel;
 
 namespace Lumina.Excel
 {
@@ -22,6 +26,40 @@ public interface ILazyRow
         public ExcelRow? RawRow { get; }
     }
 
+    public class EmptyLazyRow : ILazyRow
+    {
+        private static readonly ExcelDataPagination _blankPagination = new();
+
+        public uint Row { get; set; }
+        public bool IsValueCreated => false;
+        public Language Language => Language.None;
+        public ExcelRow? RawRow => null;
+
+        public EmptyLazyRow( uint rowId )
+        {
+            Row = rowId;
+        }
+
+        public static ILazyRow GetFirstLazyRowOrEmpty( GameData gameData, uint row, params string[] sheetNames )
+        {
+            return GetFirstLazyRowOrEmpty( gameData, row, Language.None, sheetNames );
+        }
+
+        public static ILazyRow GetFirstLazyRowOrEmpty( GameData gameData, uint row, Language language, params string[] sheetNames )
+        {
+            foreach( var sheetName in sheetNames )
+            {
+                var exh = gameData.GetFile<ExcelHeaderFile>( $"exd/{sheetName}.exh" );
+                if( exh == null ) continue;
+                var page = exh.DataPages.FirstOrDefault( s => row >= s.StartId && row <= s.StartId + s.RowCount, _blankPagination );
+                if( page.Equals( _blankPagination ) ) continue; 
+
+                return new LazyRow<ExcelRow>(gameData, row, language);
+            }
+            return new EmptyLazyRow( row );
+        }
+    }
+
     /// <summary>
     /// Allows for sheet definitions to contain entries which will lazily load the referenced sheet row
     /// </summary>