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import { z } from "zod";
import { randomBytes } from "crypto";
export namespace Identifier {
const prefixes = {
session: "ses",
message: "msg",
} as const;
export function schema(prefix: keyof typeof prefixes) {
return z.string().startsWith(prefixes[prefix]);
}
const LENGTH = 26;
// State for monotonic ID generation
let lastTimestamp = 0;
let counter = 0;
export function ascending(prefix: keyof typeof prefixes, given?: string) {
return generateID(prefix, false, given);
}
export function descending(prefix: keyof typeof prefixes, given?: string) {
return generateID(prefix, true, given);
}
function generateID(
prefix: keyof typeof prefixes,
descending: boolean,
given?: string,
): string {
if (!given) {
return generateNewID(prefix, descending);
}
if (!given.startsWith(prefixes[prefix])) {
throw new Error(`ID ${given} does not start with ${prefixes[prefix]}`);
}
return given;
}
function generateNewID(
prefix: keyof typeof prefixes,
descending: boolean,
): string {
const currentTimestamp = Date.now();
if (currentTimestamp !== lastTimestamp) {
lastTimestamp = currentTimestamp;
counter = 0;
}
counter++;
let now = BigInt(currentTimestamp) * BigInt(0x1000) + BigInt(counter);
now = descending ? ~now : now;
const timeBytes = Buffer.alloc(6);
for (let i = 0; i < 6; i++) {
timeBytes[i] = Number((now >> BigInt(40 - 8 * i)) & BigInt(0xff));
}
const randLength = (LENGTH - 12) / 2;
const random = randomBytes(randLength);
return (
prefixes[prefix] +
"_" +
timeBytes.toString("hex") +
random.toString("hex")
);
}
}
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