Insertion sort - Array Extension in Swift

extension Array where Element: Comparable {
    
    func insertionSort() -> Array<Element> {
        
        //check for trivial case
        guard self.count > 1 else {
            return self
        }
        
        //mutated copy
        var output: Array<Element> = self
        
        for primaryindex in 0..<output.count {
            print("primaryindex: \(primaryindex)")
            let key = output[primaryindex]
            var secondaryindex = primaryindex
            print("secondaryindex: \(secondaryindex),key : \(key)")
            while secondaryindex > -1 {
                if key < output[secondaryindex] {
                    
                    //move to correct position
                    output.remove(at: secondaryindex + 1)
                    print(output)
                    output.insert(key, at: secondaryindex)
                    print(output)
                }
                
                secondaryindex -= 1
                print("secondaryindex : \(secondaryindex)")
            }
        }
        
        return output
    }
}

Sample input - [1,2,8,4,3,-9]

primaryindex: 0
secondaryindex: 0,key : 1
secondaryindex : -1
primaryindex: 1
secondaryindex: 1,key : 2
secondaryindex : 0
secondaryindex : -1
primaryindex: 2
secondaryindex: 2,key : 8
secondaryindex : 1
secondaryindex : 0
secondaryindex : -1
primaryindex: 3
secondaryindex: 3,key : 4
secondaryindex : 2
[1, 2, 8, 3, -9]
[1, 2, 4, 8, 3, -9]
secondaryindex : 1
secondaryindex : 0
secondaryindex : -1
primaryindex: 4
secondaryindex: 4,key : 3
secondaryindex : 3
[1, 2, 4, 8, -9]
[1, 2, 4, 3, 8, -9]
secondaryindex : 2
[1, 2, 4, 8, -9]
[1, 2, 3, 4, 8, -9]
secondaryindex : 1
secondaryindex : 0
secondaryindex : -1
primaryindex: 5
secondaryindex: 5,key : -9
secondaryindex : 4
[1, 2, 3, 4, 8]
[1, 2, 3, 4, -9, 8]
secondaryindex : 3
[1, 2, 3, 4, 8]
[1, 2, 3, -9, 4, 8]
secondaryindex : 2
[1, 2, 3, 4, 8]
[1, 2, -9, 3, 4, 8]
secondaryindex : 1
[1, 2, 3, 4, 8]
[1, -9, 2, 3, 4, 8]
secondaryindex : 0
[1, 2, 3, 4, 8]
[-9, 1, 2, 3, 4, 8]
secondaryindex : -1

Final output - [-9, 1, 2, 3, 4, 8]