create table users (
    id integer primary key not null,
    username text unique not null,
    password_hash text not null
);

create table sessions (
    id bigint primary key not null,
    user_id bigint not null
        references users (id)
        on delete cascade,
    unique (id, user_id)
);

create table devices (
    id integer primary key not null,

    device_id text not null,
    user_id bigint not null
        references users (id)
        on delete cascade,

    caption text not null,
    type text not null,

    unique (user_id, device_id)
);

create table subscriptions (
    id integer primary key not null,
    device_id bigint not null
        references devices (id)
        on delete cascade,
    url text not null,

    time_changed bigint not null default 0,
    deleted boolean not null default false,

    unique (device_id, url)
);

create table episode_actions (
    id integer primary key not null,

    subscription_id bigint not null
        references subscriptions (id)
        on delete cascade,

    -- Can be null, as the device is not always provided
    device_id bigint
        references devices (id)
        on delete set null,

    episode text not null,
    timestamp bigint,
    action text not null,
    started integer,
    position integer,
    total integer,

    -- Position should be set if the action type is "Play" and null otherwise
    check ((action = "Play") = (position is not null)),

    -- Started and position can only be set if the action type is "Play"
    check (action = "Play" or (started is null and position is null)),

    -- Started and position should be provided together
    check ((started is null) = (total is null))
);