iOS- Chatto framework chat deletion - ios

Question

I have been using the Chatto framework for working in a chat application. Everything works fine. Now I want to delete a chat message from DataSource which is SlidingDataSource class. The indexing of the array is being handled with some properties like windowOffset itemsOffset windowCount along with the array's count. If anyone has used delete operation in Chatto, Please explain the properties or provide a simple function to delete will be helpful.
Thank you. I am attaching the data source code here..
import Foundation
import Chatto
public enum InsertPosition {
case top
case bottom
}
public class SlidingDataSource<Element> {
private var pageSize: Int
private var windowOffset: Int
private var windowCount: Int
private var itemGenerator: (() -> Element)?
private var items = [Element]()
private var itemsOffset: Int
public var itemsInWindow: [Element] {
let offset = self.windowOffset - self.itemsOffset
return Array(items[offset..<offset+self.windowCount])
}
public init(count: Int, pageSize: Int, itemGenerator: (() -> Element)?) {
self.windowOffset = count
self.itemsOffset = count
self.windowCount = 0
self.pageSize = pageSize
self.itemGenerator = itemGenerator
self.generateItems(min(pageSize, count), position: .top)
}
public convenience init(items: [Element], pageSize: Int) {
var iterator = items.makeIterator()
self.init(count: items.count, pageSize: pageSize) { iterator.next()! }
}
private func generateItems(_ count: Int, position: InsertPosition) {
// swiftlint:disable:next empty_count
guard count > 0 else { return }
guard let itemGenerator = self.itemGenerator else {
fatalError("Can't create messages without a generator")
}
for _ in 0..<count {
self.insertItem(itemGenerator(), position: .top)
}
}
public func insertItem(_ item: Element, position: InsertPosition) {
if position == .top {
self.items.insert(item, at: 0)
let shouldExpandWindow = self.itemsOffset == self.windowOffset
self.itemsOffset -= 1
if shouldExpandWindow {
self.windowOffset -= 1
self.windowCount += 1
}
} else {
let shouldExpandWindow = self.itemsOffset + self.items.count == self.windowOffset + self.windowCount
if shouldExpandWindow {
self.windowCount += 1
}
self.items.append(item)
}
}
public func hasPrevious() -> Bool {
return self.windowOffset > 0
}
public func hasMore() -> Bool {
return self.windowOffset + self.windowCount < self.itemsOffset + self.items.count
}
public func loadPrevious() {
let previousWindowOffset = self.windowOffset
let previousWindowCount = self.windowCount
let nextWindowOffset = max(0, self.windowOffset - self.pageSize)
let messagesNeeded = self.itemsOffset - nextWindowOffset
if messagesNeeded > 0 {
self.generateItems(messagesNeeded, position: .top)
}
let newItemsCount = previousWindowOffset - nextWindowOffset
self.windowOffset = nextWindowOffset
self.windowCount = previousWindowCount + newItemsCount
}
public func loadNext() {
guard !self.items.isEmpty else { return }
let itemCountAfterWindow = self.itemsOffset + self.items.count - self.windowOffset - self.windowCount
self.windowCount += min(self.pageSize, itemCountAfterWindow)
}
#discardableResult
public func adjustWindow(focusPosition: Double, maxWindowSize: Int) -> Bool {
assert(0 <= focusPosition && focusPosition <= 1, "")
guard 0 <= focusPosition && focusPosition <= 1 else {
assert(false, "focus should be in the [0, 1] interval")
return false
}
let sizeDiff = self.windowCount - maxWindowSize
guard sizeDiff > 0 else { return false }
self.windowOffset += Int(focusPosition * Double(sizeDiff))
self.windowCount = maxWindowSize
return true
}
#discardableResult
func replaceItem(withNewItem item: Element, where predicate: (Element) -> Bool) -> Bool {
guard let index = self.items.firstIndex(where: predicate) else { return false }
self.items[index] = item
return true
}
func contains(item: Element, where predicate: (Element) -> Bool ) -> Bool {
guard let _ = self.items.firstIndex(where: predicate) else { return false }
return true
}
//FIXME: Add delete method here, don't know the use off itemOffset, windowOffset, windowCount
// func delete(item: Element, where predicate: (Element) -> Bool ) {
// self.items.removeAll(where: predicate)
// }
}

Answer 1

I have raised a question in their Github repo. Here is the solution they answered.
when delete or add a new element in data source you need to -1 or +1 to offset. If offset is 0 - do nothing.
Originial answer link