WIP

AuroraSignal/Src/Cursor/Cursor.cs

@@ -0,0 +1,112 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+
+#nullable enable
+namespace Aurora.Cursor
+{
+    public enum SortDirection
+    {
+        Asc,
+        Desc,
+    }
+
+    public class Cursor<T> where T : ICursorObject
+    {
+        private CursorList<T> _list;
+
+        private string? _previousPageToken;
+        private string? _nextPageToken;
+        private int _pageSize;
+        private Func<KeyValuePair<string, T>, string> _sortDelgate;
+        private SortDirection _direction;
+        public Cursor(ref CursorList<T> list)
+        {
+            this._list = list;
+            this._previousPageToken = string.Empty;
+            this._nextPageToken = string.Empty;
+            this._pageSize = 10;
+            this._sortDelgate = delegate (KeyValuePair<string, T> item)
+            {
+                return item.Value.Id;
+            };
+        }
+
+        public CursorResult<T> GetNextPage()
+        {
+            List<KeyValuePair<string, T>> tmpList;
+
+            // Sort reference list
+            if (this._direction == SortDirection.Desc)
+            {
+                tmpList = this._list.OrderByDescending(this._sortDelgate).ToList();
+
+            }
+            else
+            {
+                tmpList = this._list.OrderBy(this._sortDelgate).ToList();
+            }
+
+            if (tmpList == null)
+            {
+                throw new System.NullReferenceException();
+            }
+
+            int startIdx = 0;
+            if (!string.IsNullOrEmpty(this._nextPageToken))
+            {
+                // TODO find another way to index into the list that's not a regular array search
+                startIdx = tmpList.FindIndex(item => item.Key == this._nextPageToken);
+            }
+
+            int endIdx = startIdx + this._pageSize;
+
+            List<T> selection = new List<T>();
+
+            // Get page
+            for (int i = startIdx; i < tmpList.Count && i < endIdx; i++)
+            {
+                selection.Add(tmpList.ElementAt(i).Value);
+            }
+
+            return new CursorResult<T>
+            {
+                NextPageToken = selection[selection.Count - 1].Id,
+                PrevPageToken = selection[0].Id,
+                Count = this._list.Count,
+                Result = selection
+            };
+        }
+
+        public CursorResult<T> GetPreviousPage()
+        {
+            throw new NotImplementedException();
+        }
+
+        public Cursor<T> WithNextPage(string nextPageToken)
+        {
+            this._nextPageToken = nextPageToken;
+            return this;
+        }
+
+        public Cursor<T> WithPreviousPage(string prevPageToken)
+        {
+            this._previousPageToken = prevPageToken;
+            return this;
+        }
+
+        public Cursor<T> WithSort(Func<KeyValuePair<string, T>, string> sortDelegate, SortDirection direction)
+        {
+            this._sortDelgate = sortDelegate;
+            this._direction = direction;
+            return this;
+        }
+
+        public Cursor<T> WithSize(int size)
+        {
+            this._pageSize = size;
+            return this;
+        }
+    }
+
+}

AuroraSignal/Src/Cursor/CursorList.cs

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+using System.Collections.Generic;
+using System.Collections;
+using System;
+using System.Linq;
+using Aurora.Utils;
+
+#nullable enable
+namespace Aurora.Cursor
+{
+
+    public class CursorList<T> : SortedList<string, T> where T : ICursorObject
+    {
+
+        public CursorList()
+        {
+        }
+
+        public CursorList<T> Add(T item)
+        {
+            string itemHashId = HashUtil.GetHash(new string[] { item.Id, item.GetHashCode().ToString() }).ToString();
+            bool res = this.TryAdd(itemHashId, item);
+
+            if (res == false)
+            {
+                throw new System.Exception("Failed to add item to cursor list");
+            }
+            return this;
+        }
+
+
+    }
+}

AuroraSignal/Src/Cursor/CursorObject.cs

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+using System.Collections.Generic;
+
+namespace Aurora.Cursor
+{
+    public interface ICursorObject
+    {
+        string Id { get; set; }
+    }
+}

AuroraSignal/Src/Cursor/CursorResult.cs

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+using System.Collections.Generic;
+
+namespace Aurora.Cursor
+{
+    public class CursorResult<T>
+    {
+        public CursorResult()
+        {
+            Result = new List<T>();
+        }
+
+        public CursorResult(CursorResult<T> cpy)
+        {
+            NextPageToken = cpy.NextPageToken;
+            PrevPageToken = cpy.PrevPageToken;
+            Result = cpy.Result;
+            Count = cpy.Count;
+        }
+
+        public string NextPageToken { get; set; }
+        public string PrevPageToken { get; set; }
+        public List<T> Result { get; set; }
+        public int Count { get; set; }
+    }
+}