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class BookSearchPaginator | |
DEFAULT_CURSOR = { | |
current_query_index: 0, | |
current_page_number: 1, | |
current_item: 0 | |
}.freeze | |
def initialize(ordered_queries, &auth_block) | |
@ordered_queries = ordered_queries | |
@auth_block = auth_block | |
end | |
def next(page_size: 12, cursor: DEFAULT_CURSOR) | |
results = [] | |
new_cursor = cursor | |
auth_block.call do | |
(page_results, new_cursor) = fetch_results_from_cursor(number_needed: page_size, cursor:) | |
results += page_results | |
while results.size < page_size | |
break if ordered_queries[new_cursor.fetch(:current_query_index)].nil? | |
(page_results, new_cursor) = fetch_results_from_cursor(number_needed: page_size - results.size, cursor: new_cursor) | |
break if results.empty? | |
results += page_results | |
end | |
end | |
[results, new_cursor] | |
end | |
private | |
attr_reader :ordered_queries, :auth_block | |
def fetch_results_from_cursor(number_needed:, cursor:) | |
current_query_index = cursor.fetch(:current_query_index) | |
current_item = cursor.fetch(:current_item) | |
current_page = ordered_queries[current_query_index] | |
.page(cursor.fetch(:current_page_number)) | |
.all | |
results = current_page.slice(cursor.fetch(:current_item), number_needed) || [] | |
new_cursor = if results.size < number_needed | |
if current_page.pages.next_page | |
{ | |
current_query_index:, | |
current_page_number: current_page.pages.next_page, | |
current_item: 0 | |
} | |
else | |
{ | |
current_query_index: current_query_index + 1, | |
current_page_number: 1, | |
current_item: 0 | |
} | |
end | |
else | |
{ | |
current_query_index:, | |
current_page_number: current_page.pages.current_page, | |
current_item: current_item + results.size | |
} | |
end | |
[results, new_cursor] | |
end | |
end |
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