/// <summary>
/// Remove an item from the <see cref="IPagedDataSet"/> with the specified position
/// </summary>
/// <param name="dataSet">The dataset to modify</param>
/// <param name="offset">The position to remove relative to the dataset's caret</param>
/// <returns></returns>
public static async Task RemoveAtOffset(this IRemovable removable, IPagedDataSet dataSet, int offset)
{
var pi = await dataSet.GetCurrentPageIndex();
var ps = await dataSet.GetPageSize();
var sel = await dataSet.GetSelector();
if (sel == null)
{
throw new InvalidOperationException("The paged data set does not support selecting items that is required for this method to work");
}
await removable.RemoveAt(dataSet, pi *ps + offset + await sel.GetCaretPosition());
}
/// <summary>
/// Add an item into the <see cref="IPagedDataSet"/> with the position relative to the <see cref="ISelectable"/>'s caret
/// </summary>
/// <param name="addable">The adder to perform</param>
/// <param name="item">The item to add</param>
/// <param name="dataSet">the dataset to modify</param>
/// <param name="offset">The position to add relative to the <see cref="IPagedDataSet{TItem, TResult}"/> caret</param>
/// <returns></returns>
public static async Task AddOffset(this IAddable addable, IPagedDataSet dataSet, object item, int offset)
{
var selector = await dataSet.GetSelector();
if (selector == null)
{
throw new InvalidOperationException("PagedDataSet must support selector to use this function!");
}
var pi = await dataSet.GetCurrentPageIndex();
var ps = await dataSet.GetPageSize();
var caret = await selector.GetCaretPosition();
await addable.Add(item, pi *ps + caret + offset);
}
// TODO: BIGTODO Find a better way to move through pages. This is a very smelly code!
/// <summary>
/// Jump the caret to a new position
/// </summary>
/// <param name="offset">the number of item to jump. A positive value will jump forward, a negative value will jump backward</param>
/// <param name="dataSet">The data set to move caret</param>
/// <param name="throughPage">should overflow offset move to a new page</param>
/// <returns></returns>
public static async Task MoveCaretBy(this ISelectable selectable, IPagedDataSet dataSet, int offset, bool throughPage = false)
{
if (throughPage)
{
var pageCount = await dataSet.GetPageCount();
if (offset > 0)
{
var tempCaret = await selectable.GetCaretPosition();
var tempPageIndex = await dataSet.GetCurrentPageIndex();
var currentPageSize = (await dataSet.GetPageItems()).Count();
if (currentPageSize == 0)
{
return;
}
if (currentPageSize - tempCaret - offset <= 0)
{
offset -= currentPageSize - tempCaret;
tempPageIndex = (tempPageIndex + 1).NormalizeIndex(pageCount);
}
else
{
await selectable.SetCaretPosition(tempCaret + offset);
return;
}
while (true)
{
await dataSet.SetCurrentPageIndex(tempPageIndex);
currentPageSize = (await dataSet.GetPageItems()).Count();
if (offset - currentPageSize >= 0)
{
offset -= currentPageSize;
tempPageIndex = (tempPageIndex + 1).NormalizeIndex(pageCount);
}
else
{
break;
}
}
await dataSet.SetCurrentPageIndex(tempPageIndex);
await selectable.SetCaretPosition(offset);
}
else
{
var tempCaret = await selectable.GetCaretPosition();
var tempPageIndex = await dataSet.GetCurrentPageIndex();
int currentPageSize;
if (tempCaret + offset < 0)
{
offset = Math.Abs(offset) - tempCaret - 1;
tempPageIndex = (tempPageIndex - 1).NormalizeIndex(pageCount);
await dataSet.SetCurrentPageIndex(tempPageIndex);
currentPageSize = (await dataSet.GetPageItems()).Count();
if (currentPageSize == 0)
{
return;
}
tempCaret = currentPageSize - 1;
}
else
{
await selectable.SetCaretPosition(tempCaret + offset);
return;
}
while (true)
{
if (offset - currentPageSize >= 0)
{
offset -= currentPageSize;
tempPageIndex = (tempPageIndex - 1).NormalizeIndex(pageCount);
await dataSet.SetCurrentPageIndex(tempPageIndex);
currentPageSize = (await dataSet.GetPageItems()).Count();
tempCaret = currentPageSize - 1;
}
else
{
break;
}
}
await selectable.SetCaretPosition(tempCaret - offset);
}
}
else
{
await selectable.SetCaretPosition(await selectable.GetCaretPosition() + offset);
}
}
