util.ts53 lines · main

1	/**
2	* LLMs sometimes emit MySQL-style `\'` escapes in SQL. PostgreSQL doesn't
3	* treat backslash as an escape character, so replace `\'` → `''`.
4	* Dollar-quoted strings (e.g. `$$...$$`) are left untouched.
5	*/
6	export function fixSqlBackslashEscapes(sql: string): string {
7	return sql.replace(/\$([^$]*)\$[\s\S]*?\$\1\$|\\'/g, (match, dollarTag) =>
8	dollarTag !== undefined ? match : "''"
9	)
10	}
11
12	/**
13	* Selects a key from weighted choices using consistent hashing
14	* on an input string.
15	*
16	* The same input always returns the same key, with distribution
17	* proportional to the provided weights.
18	*
19	* @example
20	* const region = await selectWeightedKey('my-unique-id', {
21	* use1: 40,
22	* use2: 10,
23	* usw2: 10,
24	* euc1: 10,
25	* })
26	* // Returns one of the keys based on the input and weights
27	*/
28	export async function selectWeightedKey<T extends string>(
29	input: string,
30	weights: Record<T, number>
31	): Promise<T> {
32	const keys = Object.keys(weights) as T[]
33	const encoder = new TextEncoder()
34	const data = encoder.encode(input)
35	const hashBuffer = await crypto.subtle.digest('SHA-256', data)
36
37	// Use first 4 bytes (32 bit integer)
38	const hashInt = new DataView(hashBuffer).getUint32(0)
39
40	const totalWeight = keys.reduce((sum, key) => sum + weights[key], 0)
41
42	let cumulativeWeight = 0
43	const targetWeight = hashInt % totalWeight
44
45	for (const key of keys) {
46	cumulativeWeight += weights[key]
47	if (cumulativeWeight > targetWeight) {
48	return key
49	}
50	}
51
52	return keys[0]
53	}