-- The cache of other servers' users' keys.
--
-- A local client about to send an encrypted message asks for the keys of
-- everyone in the room, and asks again whenever a sync says their device
-- list moved. Answering that for a remote user by asking their server
-- every time puts a federation round trip in front of every message, and
-- turns a busy room into a steady stream of identical queries. So the
-- keys of remote users who share a room with somebody here are kept, and
-- kept current by the m.device_list_update and m.signing_key_update EDUs
-- their server sends whenever they change.
--
-- These are tables of their own rather than rows in the local key tables.
-- A local user's keys are the source of truth, and every write to them
-- moves the device list stream and goes out over federation; a cached
-- copy of somebody else's is neither, and keeping them apart means no
-- code path that announces a local change can ever announce a copy.

-- One row per cached user: the marker that the user's device list is held
-- here at all, and the position in their server's device list stream the
-- copy is at. An update names the position before it (prev_id), and is
-- applied only when that is the position held; anything else means an
-- update was missed, and the copy is marked stale until it is fetched
-- again whole.
CREATE TABLE IF NOT EXISTS keyserver_remote_users (
    user_id   TEXT    NOT NULL PRIMARY KEY,
    stream_id BIGINT  NOT NULL,
    stale     BOOLEAN NOT NULL DEFAULT FALSE
);

-- The identity keys of a cached user's devices, as their server sent
-- them, and the display name it gave each.
CREATE TABLE IF NOT EXISTS keyserver_remote_device_keys (
    user_id      TEXT NOT NULL,
    device_id    TEXT NOT NULL,
    display_name TEXT NOT NULL DEFAULT '',
    key_json     TEXT NOT NULL,
    PRIMARY KEY (user_id, device_id)
);

-- A cached user's master and self-signing keys. The user-signing key is
-- never sent over federation, so there is no row for one.
CREATE TABLE IF NOT EXISTS keyserver_remote_cross_signing_keys (
    user_id  TEXT NOT NULL,
    -- master or self_signing.
    purpose  TEXT NOT NULL,
    key_json TEXT NOT NULL,
    PRIMARY KEY (user_id, purpose)
);