Writing a store

tilttek/advent-calendar

An application keeps the openings in its own storage by implementing Contract\OpeningStore:

Method	Does
`find($calendar, $member, $day)`	The opening of that box by that member, or null
`add($opening)`	Keeps the opening unless one is there for the same calendar, member and day; true when kept
`openingsOf($calendar, $member)`	The member's openings of the calendar, by day
`eraseMember($member)`	Removes every opening of the member, in every calendar; how many were removed

add() is the guard of idempotence: it must keep at most one opening per calendar, member and day even when two requests write at once. In SQL, a unique key on the three columns and an insert that ignores a duplicate do it:

CREATE TABLE advent_opening (
    calendar VARCHAR(64) NOT NULL,
    member VARCHAR(320) NOT NULL,
    day SMALLINT NOT NULL,
    opened_at TIMESTAMP NOT NULL,
    PRIMARY KEY (calendar, member, day)
);

INSERT INTO advent_opening (calendar, member, day, opened_at) VALUES (?, ?, ?, ?) ON CONFLICT DO NOTHING;

The member is kept as ResourceReference::toString() and read back with ResourceReference::fromString(); the moment keeps its offset. Opening::toArray() gives the four columns.

The library's tests hold OpeningStoreTestCase, the contract every store passes; copy it into the application's tests and extend it with the store to check.