import Foundation

extension Array {

    /// move items at indices to index (insert them at index in the order of indices)
    ///
    /// could be useful for dragging and dropping in a table view
    ///
    /// - Parameters:
    ///   - indices: the indices to move
    ///   - index: the index to move them to
    mutating func move(indices: [Int], to index: Index) {
        var values: [Element] = []
        for i in indices {
            values.append(self[i])
        }
        // need to remove in reverse order so we don't change
        let sortedIndices = indices.sorted(by: >)
        for i in sortedIndices {
            self.remove(at: i)
        }
        // if we are removing elements before the index, then the insertion point needs to move backwards for each one
        var position = index - (indices.filter { $0 < index }).count
        for value in values {
            self.insert(value, at: position)
            position += 1
        }
    }
}

var items = [0, 10, 20, 30, 40, 50, 60, 70, 80, 90]
items.move(indices: [7, 3, 5, 4], to: 2)
print(items)