when-am-i / files / scripts / usage.mts
usage.mts
091a00cb 2026-06-20 Pavel Safronov | 1 | // Print the session usage trailer for commit messages. |
| 2 | // | |
| 3 | // npm run usage | |
| 4 | // | |
| 5 | // Emits the two-line trailer this project appends to commit messages — a session | |
| 6 | // token tally (summed from the Claude Code transcript JSONL for this repo) and | |
| 7 | // rtk's lifetime savings — already formatted in human units (K/M/G). Copy-paste | |
| 8 | // the output straight into the message shown for commit approval. | |
| 9 | ||
| 10 | import { readFileSync, readdirSync, statSync } from 'node:fs'; | |
| 11 | import { execSync } from 'node:child_process'; | |
| 12 | import os from 'node:os'; | |
| 13 | import path from 'node:path'; | |
| 14 | ||
| 15 | /** 26594 -> "26.6K", 5_110_043 -> "5.1M". */ | |
| 16 | function human(n: number): string { | |
| 17 | if (n >= 1e9) return `${(n / 1e9).toFixed(1)}G`; | |
| 18 | if (n >= 1e6) return `${(n / 1e6).toFixed(1)}M`; | |
| 19 | if (n >= 1e3) return `${(n / 1e3).toFixed(1)}K`; | |
| 20 | return String(n); | |
| 21 | } | |
| 22 | ||
| 23 | // The transcript dir mirrors the cwd with every non-alphanumeric char as '-'. | |
| 24 | function transcriptDir(): string { | |
| 25 | const slug = process.cwd().replace(/[^a-zA-Z0-9]/g, '-'); | |
| 26 | return path.join(os.homedir(), '.claude', 'projects', slug); | |
| 27 | } | |
| 28 | ||
| 29 | function latestTranscript(dir: string): string | null { | |
| 30 | let files: string[]; | |
| 31 | try { | |
| 32 | files = readdirSync(dir).filter((f) => f.endsWith('.jsonl')); | |
| 33 | } catch { | |
| 34 | return null; | |
| 35 | } | |
| 36 | if (files.length === 0) return null; | |
| 37 | return files | |
| 38 | .map((f) => path.join(dir, f)) | |
| 39 | .sort((a, b) => statSync(b).mtimeMs - statSync(a).mtimeMs)[0]; | |
| 40 | } | |
| 41 | ||
| 42 | function sessionTally(file: string): { in: number; out: number; cached: number } { | |
| 43 | const totals = { in: 0, out: 0, cached: 0 }; | |
| 44 | for (const line of readFileSync(file, 'utf-8').split('\n')) { | |
| 45 | if (!line.trim()) continue; | |
| 46 | try { | |
| 47 | const u = JSON.parse(line)?.message?.usage; | |
| 48 | if (!u) continue; | |
| 49 | totals.in += u.input_tokens ?? 0; | |
| 50 | totals.out += u.output_tokens ?? 0; | |
| 51 | totals.cached += u.cache_read_input_tokens ?? 0; | |
| 52 | } catch { | |
| 53 | // Skip any non-JSON / partial line. | |
| 54 | } | |
| 55 | } | |
| 56 | return totals; | |
| 57 | } | |
| 58 | ||
| 59 | // Parse `rtk gain` for "Total commands:" and "Tokens saved: 81.1K (90.9%)". | |
| 60 | function rtkLine(): string { | |
| 61 | try { | |
| 62 | const out = execSync('rtk gain', { encoding: 'utf-8' }); | |
| 63 | const cmds = /Total commands:\s*([\d,]+)/.exec(out)?.[1]?.replace(/,/g, '') ?? '?'; | |
| 64 | const saved = /Tokens saved:\s*([\d.]+[KMG]?)\s*\(([\d.]+)%\)/.exec(out); | |
| 65 | const amount = saved?.[1] ?? '?'; | |
| 66 | const pct = saved?.[2] ?? '?'; | |
| 67 | return `rtk: ${amount} saved, ${pct}% over ${cmds} cmds (global/lifetime)`; | |
| 68 | } catch { | |
| 69 | return 'rtk: (rtk gain unavailable)'; | |
| 70 | } | |
| 71 | } | |
| 72 | ||
| 73 | const dir = transcriptDir(); | |
| 74 | const file = latestTranscript(dir); | |
| 75 | if (!file) { | |
| 76 | console.error(`No transcript JSONL found in ${dir}`); | |
| 77 | process.exit(1); | |
| 78 | } | |
| 79 | ||
| 80 | const t = sessionTally(file); | |
| 81 | console.log(`Usage: ${human(t.in)} in / ${human(t.out)} out / ${human(t.cached)} cached (session tally)`); | |
| 82 | console.log(rtkLine()); |