package linq

// Skip bypasses a specified number of elements in a collection
// and then returns the remaining elements.
func (q Query) Skip(count int) Query {
	return Query{
		Iterate: func() Iterator {
			next := q.Iterate()
			n := count

			return func() (item interface{}, ok bool) {
				for ; n > 0; n-- {
					item, ok = next()
					if !ok {
						return
					}
				}

				return next()
			}
		},
	}
}

// SkipWhile bypasses elements in a collection as long as a specified condition is true
// and then returns the remaining elements.
//
// This method tests each element by using predicate and skips the element
// if the result is true. After the predicate function returns false for an element,
// that element and the remaining elements in source are returned
// and there are no more invocations of predicate.
func (q Query) SkipWhile(predicate func(interface{}) bool) Query {
	return Query{
		Iterate: func() Iterator {
			next := q.Iterate()
			ready := false

			return func() (item interface{}, ok bool) {
				for !ready {
					item, ok = next()
					if !ok {
						return
					}

					ready = !predicate(item)
					if ready {
						return
					}
				}

				return next()
			}
		},
	}
}

// SkipWhileIndexed bypasses elements in a collection as long as a specified condition
// is true and then returns the remaining elements. The element's index is used
// in the logic of the predicate function.
//
// This method tests each element by using predicate and skips the element
// if the result is true. After the predicate function returns false for an element,
// that element and the remaining elements in source are returned
// and there are no more invocations of predicate.
func (q Query) SkipWhileIndexed(predicate func(int, interface{}) bool) Query {
	return Query{
		Iterate: func() Iterator {
			next := q.Iterate()
			ready := false
			index := 0

			return func() (item interface{}, ok bool) {
				for !ready {
					item, ok = next()
					if !ok {
						return
					}

					ready = !predicate(index, item)
					if ready {
						return
					}

					index++
				}

				return next()
			}
		},
	}
}