14-paginationhelper.md

Problem:

For this exercise you will be strengthening your page-fu mastery. You will complete the PaginationHelper class, which is a utility class helpful for querying paging information related to an array.

The class is designed to take in an array of values and an integer indicating how many items will be allowed per each page. The types of values contained within the collection/array are not relevant.

The following are some examples of how this class is used:

var helper = new PaginationHelper(['a','b','c','d','e','f'], 4);
helper.pageCount(); //should == 2
helper.itemCount(); //should == 6
helper.pageItemCount(0); //should == 4
helper.pageItemCount(1); // last page - should == 2
helper.pageItemCount(2); // should == -1 since the page is invalid
// pageIndex takes an item index and returns the page that it belongs on
helper.pageIndex(5); //should == 1 (zero based index)
helper.pageIndex(2); //should == 0
helper.pageIndex(20); //should == -1
helper.pageIndex(-10); //should == -1

PaginationHelper<Character> helper = new PaginationHelper(Arrays.asList('a', 'b', 'c', 'd', 'e', 'f'), 4);
helper.pageCount(); //should == 2
helper.itemCount(); //should == 6
helper.pageItemCount(0); //should == 4
helper.pageItemCount(1); // last page - should == 2
helper.pageItemCount(2); // should == -1 since the page is invalid

// pageIndex takes an item index and returns the page that it belongs on
helper.pageIndex(5); //should == 1 (zero based index)
helper.pageIndex(2); //should == 0
helper.pageIndex(20); //should == -1
helper.pageIndex(-10); //should == -1

helper = new PaginationHelper(['a','b','c','d','e','f'], 4)
helper.pageCount() # should == 2
helper.itemCount() # should == 6
helper.pageItemCount(0)  # should == 4
helper.pageItemCount(1) # last page - should == 2
helper.pageItemCount(2) # should == -1 since the page is invalid

# pageIndex takes an item index and returns the page that it belongs on
helper.pageIndex(5) # should == 1 (zero based index)
helper.pageIndex(2) # should == 0
helper.pageIndex(20) # should == -1
helper.pageIndex(-10) # should == -1

helper = PaginationHelper.new(['a','b','c','d','e','f'], 4)
helper.page_count # should == 2
helper.item_count # should == 6
helper.page_item_count(0)  # should == 4
helper.page_item_count(1) # last page - should == 2
helper.page_item_count(2) # should == -1 since the page is invalid

# page_ndex takes an item index and returns the page that it belongs on
helper.page_index(5) # should == 1 (zero based index)
helper.page_index(2) # should == 0
helper.page_index(20) # should == -1
helper.page_index(-10) # should == -1 because negative indexes are invalid

collection   = ['a','b','c','d','e','f']
itemsPerPage = 4

pageCount collection itemsPerPage       `shouldBe` 2
itemCount collection itemsPerPage       `shouldBe` 6

pageItemCount collection itemsPerPage 0 `shouldBe` Just 4 -- four of six items
pageItemCount collection itemsPerPage 1 `shouldBe` Just 2 -- the last two items
pageItemCount collection itemsPerPage 3 `shouldBe` Nothing -- page doesn't exist

pageIndex collection itemsPerPage  0    `shouldBe` Just 0 -- zero based index
pageIndex collection itemsPerPage  5    `shouldBe` Just 1 
pageIndex collection itemsPerPage 20    `shouldBe` Nothing
pageIndex collection itemsPerPage (-20) `shouldBe` Nothing

helper = PaginationHelper(['a','b','c','d','e','f'], 4)
helper.page_count # should == 2
helper.item_count # should == 6
helper.page_item_count(0)  # should == 4
helper.page_item_count(1) # last page - should == 2
helper.page_item_count(2) # should == -1 since the page is invalid

# page_ndex takes an item index and returns the page that it belongs on
helper.page_index(5) # should == 1 (zero based index)
helper.page_index(2) # should == 0
helper.page_index(20) # should == -1
helper.page_index(-10) # should == -1 because negative indexes are invalid

var helper = new PaginationHelper<char>(new List<char>{'a', 'b', 'c', 'd', 'e', 'f'}, 4);
helper.PageCount; //should == 2
helper.ItemCount; //should == 6
helper.PageItemCount(0); //should == 4
helper.PageItemCount(1); // last page - should == 2
helper.PageItemCount(2); // should == -1 since the page is invalid

// pageIndex takes an item index and returns the page that it belongs on
helper.PageIndex(5); //should == 1 (zero based index)
helper.PageIndex(2); //should == 0
helper.PageIndex(20); //should == -1
helper.PageIndex(-10); //should == -1

Solution