-- migrate:up

-- Lifecycle of a reservation:
--
--     requested ──▶ refused
--         │
--         ▼
--     approved ──▶ cancelled
--         │            ▲
--         ▼            │
--      ongoing ────────┘
--         │
--         ▼
--     archived
--
-- `refused`, `cancelled` and `archived` are final. The transitions are enforced
-- in the controller (`ReservationStatus::can_transition_to`), not by a trigger,
-- so the rule stays with the rest of the business logic.
CREATE TYPE reservation_status AS ENUM (
    'requested',
    'refused',
    'approved',
    'cancelled',
    'ongoing',
    'archived'
);

CREATE TABLE reservations (
    id SERIAL PRIMARY KEY,
    -- Exactly one unit borrows the bikes. Free text for the same reason as
    -- `units_users.unit_name`: the value comes from Whiskey.
    unit TEXT NOT NULL,
    start_time TIMESTAMPTZ NOT NULL,
    end_time TIMESTAMPTZ NOT NULL,
    -- Who filed the request; also part of `reservations_users`
    requester_id INTEGER NOT NULL REFERENCES users (id),
    -- Telegram handle to reach the group, stored with its leading '@'
    telegram TEXT NOT NULL,
    "description" TEXT NOT NULL DEFAULT '',
    status reservation_status NOT NULL DEFAULT 'requested',
    CONSTRAINT reservations_time_order CHECK (end_time > start_time),
    CONSTRAINT reservations_telegram_handle CHECK (
        telegram ~ '^@[A-Za-z][A-Za-z0-9_]{4,31}$'
    )
);

CREATE INDEX reservations_unit_idx ON reservations (unit);
CREATE INDEX reservations_status_idx ON reservations (status);
CREATE INDEX reservations_period_idx ON reservations (start_time, end_time);

-- People allowed to pick the bikes up for this reservation
CREATE TABLE reservations_users (
    reservation_id INTEGER NOT NULL REFERENCES reservations (id) ON DELETE CASCADE,
    user_id INTEGER NOT NULL REFERENCES users (id) ON DELETE CASCADE,
    PRIMARY KEY (reservation_id, user_id)
);

-- Bikes booked by this reservation. A bike that has been booked cannot be
-- deleted (ON DELETE RESTRICT): take it out of the fleet with
-- `status = 'out_of_service'` instead.
CREATE TABLE reservations_bikes (
    reservation_id INTEGER NOT NULL REFERENCES reservations (id) ON DELETE CASCADE,
    bike_id INTEGER NOT NULL REFERENCES bikes (id) ON DELETE RESTRICT,
    PRIMARY KEY (reservation_id, bike_id)
);

CREATE INDEX reservations_bikes_bike_id_idx ON reservations_bikes (bike_id);

-- migrate:down
DROP TABLE IF EXISTS reservations_bikes;
DROP TABLE IF EXISTS reservations_users;
DROP TABLE IF EXISTS reservations;
DROP TYPE IF EXISTS reservation_status;