max / balanced_breakfast

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1	//! Small helpers the repositories share.
2	//!
3	//! These exist so a repository method reads as one line each, and so the
4	//! [`DbError`] mapping lives in one place instead of on every `?`.
5
6	use rusqlite::{Connection, Params, Row};
7
8	use crate::error::DbError;
9
10	/// Fetch every matching row, mapped by `f`.
11	pub fn query_all<T, P, F>(conn: &Connection, sql: &str, params: P, f: F) -> Result<Vec<T>, DbError>
12	where
13	P: Params,
14	F: FnMut(&Row<'_>) -> rusqlite::Result<T>,
15	{
16	let mut stmt = conn.prepare(sql)?;
17	let rows = stmt.query_map(params, f)?;
18	Ok(rows.collect::<rusqlite::Result<Vec<T>>>()?)
19	}
20
21	/// Fetch at most one row, mapped by `f`. `None` when nothing matched.
22	pub fn query_opt<T, P, F>(
23	conn: &Connection,
24	sql: &str,
25	params: P,
26	f: F,
27	) -> Result<Option<T>, DbError>
28	where
29	P: Params,
30	F: FnOnce(&Row<'_>) -> rusqlite::Result<T>,
31	{
32	use rusqlite::OptionalExtension as _;
33	Ok(conn.query_row(sql, params, f).optional()?)
34	}
35
36	/// Fetch exactly one row, mapped by `f`.
37	///
38	/// For queries that always produce a row -- aggregates, and the `RETURNING *`
39	/// on an insert -- where no rows means something is wrong rather than absent.
40	pub fn query_one<T, P, F>(conn: &Connection, sql: &str, params: P, f: F) -> Result<T, DbError>
41	where
42	P: Params,
43	F: FnOnce(&Row<'_>) -> rusqlite::Result<T>,
44	{
45	Ok(conn.query_row(sql, params, f)?)
46	}
47
48	/// Run a statement, returning the number of rows it changed.
49	///
50	/// The return value is the number of rows affected.
51	pub fn execute<P: Params>(conn: &Connection, sql: &str, params: P) -> Result<usize, DbError> {
52	Ok(conn.execute(sql, params)?)
53	}
54
55	/// Build a comma-separated list of `n` numbered bind placeholders
56	/// (`?1,?2,...,?n`) for an `IN (...)` clause.
57	///
58	/// Callers guard the empty case before building the query (an empty `IN ()` is
59	/// invalid SQL); this returns `""` for `n == 0` so the guard stays their
60	/// responsibility.
61	#[must_use]
62	pub fn bind_placeholders(n: usize) -> String {
63	(1..=n)
64	.map(\|i\| format!("?{i}"))
65	.collect::<Vec<_>>()
66	.join(", ")
67	}
68
69	#[cfg(test)]
70	mod tests {
71	use super::*;
72
73	#[test]
74	fn placeholders_are_numbered_from_one() {
75	assert_eq!(bind_placeholders(0), "");
76	assert_eq!(bind_placeholders(1), "?1");
77	assert_eq!(bind_placeholders(3), "?1, ?2, ?3");
78	}
79	}
80