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| import { closeSync, existsSync, openSync, readFileSync, readSync } from "node:fs"; | |
| import { join } from "node:path"; | |
| import type { DecisionCase, Family } from "./types"; | |
| /** a case's head (everything but the conversation) and where its line sits in the family file */ | |
| export interface CaseRow { | |
| head: Omit<DecisionCase, "conversation">; | |
| offset: number; | |
| length: number; | |
| } | |
| /** reads only each line's head, the conversation is last and can be megabytes */ | |
| export function indexCases(dir: string, family: Family): CaseRow[] { | |
| const path = join(dir, `${family}.jsonl`); | |
| if (!existsSync(path)) return []; | |
| const buffer = readFileSync(path); | |
| const marker = Buffer.from(',"conversation":'); | |
| const rows: CaseRow[] = []; | |
| let start = 0; | |
| while (start < buffer.length) { | |
| let end = buffer.indexOf(10, start); | |
| if (end === -1) end = buffer.length; | |
| const cut = buffer.indexOf(marker, start); | |
| if (cut !== -1 && cut < end) { | |
| const head = JSON.parse(`${buffer.subarray(start, cut).toString("utf8")}}`); | |
| rows.push({ head, offset: start, length: end - start }); | |
| } | |
| start = end + 1; | |
| } | |
| return rows; | |
| } | |
| export function readCaseAt( | |
| dir: string, | |
| family: Family, | |
| row: Pick<CaseRow, "offset" | "length"> | |
| ): DecisionCase { | |
| const fd = openSync(join(dir, `${family}.jsonl`), "r"); | |
| try { | |
| const buffer = Buffer.alloc(row.length); | |
| readSync(fd, buffer, 0, row.length, row.offset); | |
| return JSON.parse(buffer.toString("utf8")) as DecisionCase; | |
| } finally { | |
| closeSync(fd); | |
| } | |
| } | |