max / makenotwork

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1	//! Database-error helpers: unique-violation (23505) detection/mapping and the
2	//! auto-suffixing unique-slug insert loop.
3
4	/// Maximum auto-suffix attempts when allocating a unique slug before giving up.
5	pub const SLUG_SUFFIX_CAP: u32 = 100;
6
7	/// Whether `e` is a Postgres unique-violation (SQLSTATE 23505), the slug
8	/// collision backstop every [`insert_with_unique_slug`] caller relies on.
9	pub fn is_unique_violation(e: &crate::error::AppError) -> bool {
10	matches!(
11	e,
12	crate::error::AppError::Database(sqlx::Error::Database(db_err))
13	if db_err.code().as_deref() == Some("23505")
14	)
15	}
16
17	/// Map a Postgres unique-violation (23505) into a clean `AppError::Conflict(msg)`;
18	/// pass any other error through unchanged. A create/insert on a deterministic or
19	/// user-supplied unique key that legitimately re-runs (a retry, a duplicate the
20	/// user can fix) should surface a 409 with a helpful message, not a raw 500.
21	/// Use only where the INSERT has a single relevant unique constraint.
22	pub fn map_unique_violation(e: crate::error::AppError, msg: &str) -> crate::error::AppError {
23	if is_unique_violation(&e) {
24	crate::error::AppError::Conflict(msg.to_string())
25	} else {
26	e
27	}
28	}
29
30	/// Insert a row whose slug must be unique under a per-parent `UNIQUE` index,
31	/// auto-suffixing the slug (`base`, `base-2`, `base-3`, ...) on collision.
32	///
33	/// The `UNIQUE` index is the race-safe source of truth: `insert` is retried on a
34	/// 23505 unique violation, up to [`SLUG_SUFFIX_CAP`] attempts, so a concurrent
35	/// insert racing between any pre-check and this one can never surface a raw 500.
36	/// `insert` receives the candidate slug and performs the actual row insert.
37	/// Use it for every slug insert (blog posts, items, item/project sections, the
38	/// internal content route) rather than pre-checking and hoping.
39	pub async fn insert_with_unique_slug<T, F, Fut>(
40	base: &str,
41	mut insert: F,
42	) -> crate::error::Result<T>
43	where
44	F: FnMut(String) -> Fut,
45	Fut: std::future::Future<Output = crate::error::Result<T>>,
46	{
47	let mut slug = base.to_string();
48	let mut suffix = 1u32;
49	loop {
50	match insert(slug.clone()).await {
51	Ok(value) => return Ok(value),
52	Err(e) if is_unique_violation(&e) && suffix < SLUG_SUFFIX_CAP => {
53	suffix += 1;
54	slug = format!("{base}-{suffix}");
55	}
56	Err(e) => return Err(e),
57	}
58	}
59	}
60