-- Rooms, events and room state: the roomserver tables.
--
-- Events are keyed by their event ID rather than by a numeric surrogate.
-- An event ID is 44 bytes of base64 and appears in prev_events,
-- auth_events, state snapshots and client requests alike, so a surrogate
-- would have to be translated at every one of those boundaries; the
-- indexes below are what make the text key cheap enough.
--
-- Timestamps are milliseconds since the Unix epoch, as everywhere else in
-- Warp.

CREATE TABLE IF NOT EXISTS roomserver_rooms (
    room_id       TEXT    NOT NULL PRIMARY KEY,
    -- Fixed at creation. Nothing can read an event without it: the room
    -- version decides the event format, the redaction algorithm and the
    -- authorisation rules.
    room_version  TEXT    NOT NULL,
    creator       TEXT    NOT NULL,
    is_published  BOOLEAN NOT NULL DEFAULT 0,
    created_at_ms BIGINT  NOT NULL,

    -- The denormalised room listing columns. Everything below is derivable
    -- from the room's current state and is kept here anyway, because the
    -- public room directory orders every published room by member count
    -- and pages the result: that cannot be done by reading each room's
    -- state in turn. The roomserver recomputes them when the state behind
    -- them changes; joined_members the store counts for itself.
    name               TEXT   NOT NULL DEFAULT '',
    topic              TEXT   NOT NULL DEFAULT '',
    avatar_url         TEXT   NOT NULL DEFAULT '',
    canonical_alias    TEXT   NOT NULL DEFAULT '',
    join_rule          TEXT   NOT NULL DEFAULT '',
    history_visibility TEXT   NOT NULL DEFAULT '',
    guest_access       TEXT   NOT NULL DEFAULT '',
    room_type          TEXT   NOT NULL DEFAULT '',
    joined_members     BIGINT NOT NULL DEFAULT 0
);

-- The public room directory's own ordering: published rooms, biggest first.
CREATE INDEX IF NOT EXISTS roomserver_rooms_published_idx
    ON roomserver_rooms (is_published, joined_members);

-- One counter row per stream, incremented inside the write transaction.
--
-- Neither AUTOINCREMENT nor a sequence would do: SQLite and PostgreSQL
-- spell those differently, and a PostgreSQL sequence is explicitly not
-- transactional, so a rolled-back write would leave a hole in the stream
-- that /sync would have to be taught to skip. An UPDATE on this row takes
-- a row lock in both engines and gives out positions with no gaps.
CREATE TABLE IF NOT EXISTS roomserver_sequences (
    name  TEXT   NOT NULL PRIMARY KEY,
    value BIGINT NOT NULL
);

INSERT INTO roomserver_sequences (name, value) VALUES ('stream_ordering', 0)
    ON CONFLICT (name) DO NOTHING;
INSERT INTO roomserver_sequences (name, value) VALUES ('state_snapshot', 0)
    ON CONFLICT (name) DO NOTHING;

-- A state snapshot is the complete state of a room at one point, stored
-- once and shared by every event it applies to. Consecutive messages in a
-- room whose state is not changing all point at the same snapshot, so the
-- cost is one snapshot per state change rather than one per event.
CREATE TABLE IF NOT EXISTS roomserver_state_snapshots (
    snapshot_id BIGINT NOT NULL PRIMARY KEY,
    room_id     TEXT   NOT NULL REFERENCES roomserver_rooms (room_id) ON DELETE CASCADE,
    -- SHA-256 over the sorted (type, state_key, event_id) triples: the
    -- identity of the snapshot's contents, which is what lets two
    -- identical states share a row.
    state_hash  TEXT   NOT NULL,
    UNIQUE (room_id, state_hash)
);

CREATE TABLE IF NOT EXISTS roomserver_state_entries (
    snapshot_id BIGINT NOT NULL REFERENCES roomserver_state_snapshots (snapshot_id) ON DELETE CASCADE,
    event_type  TEXT   NOT NULL,
    state_key   TEXT   NOT NULL,
    event_id    TEXT   NOT NULL,
    PRIMARY KEY (snapshot_id, event_type, state_key)
);

CREATE TABLE IF NOT EXISTS roomserver_events (
    event_id         TEXT    NOT NULL PRIMARY KEY,
    room_id          TEXT    NOT NULL REFERENCES roomserver_rooms (room_id) ON DELETE CASCADE,
    -- This server's own monotonic position for the event: the order it was
    -- persisted in, which is the order clients are shown it in.
    stream_ordering  BIGINT  NOT NULL,
    event_type       TEXT    NOT NULL,
    -- NULL for a message event. The empty string is a valid state key, so
    -- "no state key" cannot be spelled as ''.
    state_key        TEXT,
    sender           TEXT    NOT NULL,
    depth            BIGINT  NOT NULL,
    origin_server_ts BIGINT  NOT NULL,
    -- The event as canonical JSON, byte for byte as it was signed. Every
    -- other column here is a projection of it, written out to be indexed.
    event_json       TEXT    NOT NULL,
    -- The state of the room as of this event's prev_events, 0 for the
    -- create event. Keeping it per event is what lets the state after a
    -- forward extremity be worked out, which state resolution needs when a
    -- room has more than one.
    state_before_id  BIGINT  NOT NULL DEFAULT 0,
    -- The redaction that applies to this event, or ''. The JSON above is
    -- rewritten to its redacted form at the same time; this records which
    -- event did it so that unsigned.redacted_because can be filled in.
    redacted_by      TEXT    NOT NULL DEFAULT ''
);

CREATE UNIQUE INDEX IF NOT EXISTS roomserver_events_stream_idx
    ON roomserver_events (stream_ordering);

-- Paging a room's timeline, which is what /messages and /sync do.
CREATE INDEX IF NOT EXISTS roomserver_events_room_stream_idx
    ON roomserver_events (room_id, stream_ordering);

-- The forward extremities: the events with no children, and so the
-- prev_events of whatever is sent next.
CREATE TABLE IF NOT EXISTS roomserver_extremities (
    room_id  TEXT NOT NULL REFERENCES roomserver_rooms (room_id) ON DELETE CASCADE,
    event_id TEXT NOT NULL,
    PRIMARY KEY (room_id, event_id)
);

-- The room's resolved current state: the state after its extremities.
--
-- It is derivable from the events, and is stored anyway because every
-- authorisation decision reads it. The membership column is a denormalised
-- copy of content.membership on m.room.member rows, so that "the rooms
-- @alice is joined to" is an index lookup rather than a scan that parses
-- JSON.
CREATE TABLE IF NOT EXISTS roomserver_current_state (
    room_id    TEXT NOT NULL REFERENCES roomserver_rooms (room_id) ON DELETE CASCADE,
    event_type TEXT NOT NULL,
    state_key  TEXT NOT NULL,
    event_id   TEXT NOT NULL,
    membership TEXT NOT NULL DEFAULT '',
    PRIMARY KEY (room_id, event_type, state_key)
);

CREATE INDEX IF NOT EXISTS roomserver_current_state_membership_idx
    ON roomserver_current_state (event_type, state_key, membership);

-- Client transaction IDs, so that a retried request returns the event the
-- first attempt created instead of sending a second one.
CREATE TABLE IF NOT EXISTS roomserver_transactions (
    localpart TEXT   NOT NULL,
    device_id TEXT   NOT NULL,
    txn_id    TEXT   NOT NULL,
    event_id  TEXT   NOT NULL,
    room_id   TEXT   NOT NULL,
    sent_at_ms BIGINT NOT NULL,
    PRIMARY KEY (localpart, device_id, txn_id)
);

-- Local room aliases. Remote aliases are never stored: they are resolved
-- over federation every time, because the other server may have moved them.
CREATE TABLE IF NOT EXISTS roomserver_aliases (
    alias         TEXT   NOT NULL PRIMARY KEY,
    room_id       TEXT   NOT NULL REFERENCES roomserver_rooms (room_id) ON DELETE CASCADE,
    creator       TEXT   NOT NULL,
    created_at_ms BIGINT NOT NULL
);

CREATE INDEX IF NOT EXISTS roomserver_aliases_room_idx
    ON roomserver_aliases (room_id);