fix(pagination): guard against division by zero when Size is 0 (#59)

- Clamp pagination.Size to minimum of 1 before division operations
- Add regression tests for Size=0 edge case

Author: erlendellefsen

JsonApiToolkit.Tests/Extensions/QueryableExtensionTests.cs

@@ -371,6 +371,32 @@ public async Task Issue_Scenario_PageTwoOfOneTotal_ReturnsLastPageDataAsync()
         Assert.Equal(1, result.First().Id);
     }
 
+    [Fact]
+    public void ApplyPagination_WithSizeZero_TreatsAsSize1()
+    {
+        var query = GetTestData();
+        var pagination = new PaginationParameters { Number = 1, Size = 0 };
+
+        var result = query.ApplyPagination(pagination).ToList();
+
+        Assert.Single(result);
+        Assert.Equal(1, result[0].Id);
+    }
+
+    [Fact]
+    public async Task CreatePaginationMetaAsync_WithSizeZero_TreatsAsSize1Async()
+    {
+        var query = GetTestData();
+        var pagination = new PaginationParameters { Number = 1, Size = 0 };
+
+        var meta = await query.CreatePaginationMetaAsync(pagination);
+
+        Assert.Equal(5, meta.TotalResources);
+        Assert.Equal(5, meta.TotalPages); // 5 items / size 1 = 5 pages
+        Assert.Equal(1, meta.CurrentPage);
+        Assert.Equal(1, meta.PageSize); // Clamped to 1
+    }
+
     [Fact]
     public void ApplyFilters_WithInFilter_FiltersCorrectly()
     {

JsonApiToolkit/Extensions/Querying/Handlers/PaginationHandler.cs

@@ -18,12 +18,13 @@ public static IQueryable<T> ApplyPagination<T>(
         PaginationParameters pagination
     )
     {
+        int size = Math.Max(1, pagination.Size);
         int totalCount = query.Count();
-        int totalPages = (int)Math.Ceiling(totalCount / (double)pagination.Size);
+        int totalPages = (int)Math.Ceiling(totalCount / (double)size);
         int effectivePage = Math.Max(1, Math.Min(pagination.Number, Math.Max(totalPages, 1)));
 
-        int skip = (effectivePage - 1) * pagination.Size;
-        return query.Skip(skip).Take(pagination.Size);
+        int skip = (effectivePage - 1) * size;
+        return query.Skip(skip).Take(size);
     }
 
     /// <summary>
@@ -44,15 +45,16 @@ PaginationParameters pagination
             totalCount = query.Count(); // Fallback for in-memory queryables
         }
 
-        int totalPages = (int)Math.Ceiling(totalCount / (double)pagination.Size);
+        int size = Math.Max(1, pagination.Size);
+        int totalPages = (int)Math.Ceiling(totalCount / (double)size);
         int effectivePage = Math.Max(1, Math.Min(pagination.Number, Math.Max(totalPages, 1)));
 
         return new PaginationMeta
         {
             TotalResources = totalCount,
             TotalPages = totalPages,
             CurrentPage = effectivePage,
-            PageSize = pagination.Size,
+            PageSize = size,
         };
     }
 }