Displaying chat by punished users only to themselves (db fiddle attached)

[Alexander Farber]

Hello,

I have developed a complete SQL fiddle for my question:

https://dbfiddle.uk/?rdbms=postgres_14&fiddle=dcf063ba1615b392cc3cfa347a32c97b

The context is that I run an online game for two players using a PostgreSQL
14.2 backend.

I would like to make my game more friendly by hiding chat messages of
misbehaving users.

However, to prevent the punished users from noticing it and registering new
game accounts, I would like to still show them all messages :->

So here are the 4 tables used in my reduced test case:

CREATE TABLE words_users (
    uid SERIAL PRIMARY KEY,
    muted BOOLEAN NOT NULL DEFAULT false
);

CREATE TABLE words_social (
    sid     text     NOT NULL CHECK (sid ~ '\S'),
    social  integer  NOT NULL CHECK (0 < social AND social <= 256),
    given   text     NOT NULL CHECK (given ~ '\S'),
    uid     integer  NOT NULL REFERENCES words_users ON DELETE CASCADE,
    PRIMARY KEY(sid, social)
);

CREATE TABLE words_games (
    gid      SERIAL PRIMARY KEY,
    player1  integer REFERENCES words_users(uid) ON DELETE CASCADE NOT NULL
CHECK (player1 <> player2),
    player2  integer REFERENCES words_users(uid) ON DELETE CASCADE
);

CREATE TABLE words_chat (
        cid     BIGSERIAL PRIMARY KEY,
        created timestamptz NOT NULL,
        gid     integer NOT NULL REFERENCES words_games ON DELETE CASCADE,
        uid     integer NOT NULL REFERENCES words_users ON DELETE CASCADE,
        msg     text    NOT NULL
);

Then I put 2 users into the game #10 and they start chatting:

-- create 2 users: one is ok, while the other is muted (punished)
INSERT INTO words_users (uid, muted) VALUES (1, false), (2, true);
INSERT INTO words_social (sid, social, given, uid) VALUES ('abc', 100,
'Nice user', 1), ('def', 200, 'Bad user', 2);

-- put these 2 users into a game #10
INSERT INTO words_games (gid, player1, player2) VALUES (10, 1, 2);

-- both users in the game #10 start chatting
INSERT INTO words_chat (gid, uid, created, msg) VALUES
(10, 1, CURRENT_TIMESTAMP + INTERVAL '1 min', 'Hi how are you doing?'),
(10, 1, CURRENT_TIMESTAMP + INTERVAL '2 min', 'I am a nice user'),
(10, 2, CURRENT_TIMESTAMP + INTERVAL '3 min', 'F*** ***!!'),
(10, 2, CURRENT_TIMESTAMP + INTERVAL '4 min', 'I am a bad user'),
(10, 1, CURRENT_TIMESTAMP + INTERVAL '5 min','Are you there??');

Here is my custom stored function (in SQL, I would prefer not to switch to
PL/pgSQL):

CREATE OR REPLACE FUNCTION words_get_chat(
                in_gid    integer,
                in_social integer,
                in_sid    text
        ) RETURNS TABLE (
                out_mine  integer,
                out_msg   text
        ) AS
$func$
        SELECT
                CASE WHEN c.uid = s.uid THEN 1 ELSE 0 END,
                c.msg
        FROM    words_chat c
        JOIN    words_games g USING (gid)
        JOIN    words_users u ON (u.uid IN (g.player1, g.player2)
                -- The condition below is broken if both users are not muted
                AND (u.muted OR (c.uid = u.uid AND NOT u.muted)))
        JOIN    words_social s ON (s.uid = u.uid)
        WHERE   c.gid    = in_gid
        AND     s.social = in_social
        AND     s.sid    = in_sid
        ORDER BY c.CREATED ASC;

$func$ LANGUAGE sql;

For a chat of a bad and a nice user it seemingly works:

SELECT words_get_chat(10, 100, 'abc') AS nice_user;
SELECT words_get_chat(10, 200, 'def') AS muted_user;

But if you change both users to be not muted - it will break and they only
will see their own messages.

I have tinkered a lot with my db fiddle... but still cannot figure it out

Thank you!
Alex