# Abgabe - PaginationHelper Aufgabe von Codewars
# Link dazu: https://www.codewars.com/kata/54bf1c2cd5b56cc47f0007a1
# Leart Ramushi

# TODO: complete this class
import math


class PaginationHelper:

    # The constructor takes in an array of items and an integer indicating
    # how many items fit within a single page
    def __init__(self, collection, items_per_page):
        self.collection = collection
        self.items_per_page = items_per_page

    # returns the number of items within the entire collection
    def item_count(self):
        return len(self.collection)

    # returns the number of pages
    def page_count(self):
        return math.ceil(len(self.collection) / self.items_per_page)

    # returns the number of items on the given page. page_index is zero based
    # this method should return -1 for page_index values that are out of range
    def page_item_count(self, page_index):
        if page_index < 0 or page_index >= self.page_count():
            return -1
        if page_index == self.page_count() - 1:
            rest = len(self.collection) % self.items_per_page
            if rest == 0:
                return self.items_per_page
            else:
                return rest
        return self.items_per_page

    # determines what page an item at the given index is on. Zero based indexes.
    # this method should return -1 for item_index values that are out of range
    def page_index(self, item_index):
        if item_index < 0 or item_index >= len(self.collection):
            return -1
        return item_index // self.items_per_page