max / makenotwork

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1	use super::{PgPool, Uuid};
2
3	/// Track a thread (upsert).
4	#[tracing::instrument(skip_all)]
5	pub async fn track_thread(
6	pool: &PgPool,
7	user_id: Uuid,
8	thread_id: Uuid,
9	) -> Result<(), sqlx::Error> {
10	sqlx::query!(
11	"INSERT INTO tracked_threads (user_id, thread_id)
12	VALUES ($1, $2)
13	ON CONFLICT (user_id, thread_id) DO NOTHING",
14	user_id,
15	thread_id,
16	)
17	.execute(pool)
18	.await?;
19	Ok(())
20	}
21
22	/// Untrack a thread.
23	#[tracing::instrument(skip_all)]
24	pub async fn untrack_thread(
25	pool: &PgPool,
26	user_id: Uuid,
27	thread_id: Uuid,
28	) -> Result<(), sqlx::Error> {
29	sqlx::query!(
30	"DELETE FROM tracked_threads WHERE user_id = $1 AND thread_id = $2",
31	user_id,
32	thread_id,
33	)
34	.execute(pool)
35	.await?;
36	Ok(())
37	}
38
39	/// Stop tracking all threads for a user.
40	#[tracing::instrument(skip_all)]
41	pub async fn untrack_all(pool: &PgPool, user_id: Uuid) -> Result<(), sqlx::Error> {
42	sqlx::query!("DELETE FROM tracked_threads WHERE user_id = $1", user_id)
43	.execute(pool)
44	.await?;
45	Ok(())
46	}
47
48	/// Advance the read position for a tracked thread to `last_post_id`.
49	///
50	/// Monotonic: the position only ever moves forward in thread order. The caller
51	/// (`routes::forum::thread`) bumps to the last post on the page being viewed,
52	/// so an unguarded write would drag the position backward whenever a reader
53	/// revisits an earlier page, and `list_tracked_threads` would then re-count
54	/// already-read posts as unread. The two writes are also spawned off the
55	/// response path, so concurrent views of different pages race; keeping the
56	/// comparison in SQL means Postgres re-evaluates it against the winning row
57	/// under read-committed rather than letting the last writer win.
58	///
59	/// A `last_post_id` that names no row leaves the position untouched: the
60	/// scalar subquery yields NULL, the comparison is not true, and the guard
61	/// fails closed.
62	#[tracing::instrument(skip_all)]
63	pub async fn update_read_position(
64	pool: &PgPool,
65	user_id: Uuid,
66	thread_id: Uuid,
67	last_post_id: Uuid,
68	) -> Result<(), sqlx::Error> {
69	sqlx::query!(
70	"UPDATE tracked_threads SET last_read_post_id = $3
71	WHERE user_id = $1 AND thread_id = $2
72	AND (last_read_post_id IS NULL
73	OR (SELECT np.created_at FROM posts np WHERE np.id = $3)
74	> (SELECT cp.created_at FROM posts cp WHERE cp.id = last_read_post_id))",
75	user_id,
76	thread_id,
77	last_post_id,
78	)
79	.execute(pool)
80	.await?;
81	Ok(())
82	}
83