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import { closeSync, fsyncSync, openSync, renameSync, statSync, writeSync } from "node:fs";
import type { LogRecord, LogSink } from "@dispatch/kernel";
// --- Pure core (no I/O) ---
/**
* Serialize a LogRecord to exactly one NDJSON line (record JSON + newline).
* Pure function — no I/O, no side effects.
*/
export function serialize(record: LogRecord): string {
return `${JSON.stringify(record)}\n`;
}
// --- Imperative shell (fs edge) ---
/** Injectable fs operations — confined to the edge. */
export interface FsOps {
readonly open: (path: string) => number;
readonly write: (fd: number, data: string) => void;
readonly close: (fd: number) => void;
readonly rename: (oldPath: string, newPath: string) => void;
readonly statSize: (path: string) => number;
readonly fsync: (fd: number) => void;
}
/** Clock injection for fsync interval. */
export interface ClockOps {
readonly now: () => number;
}
export interface JournalSinkOpts {
readonly path: string;
readonly maxBytes?: number;
readonly fsync?: "periodic" | "none";
readonly fs?: FsOps;
readonly clock?: ClockOps;
}
const DEFAULT_MAX_BYTES = 50 * 1024 * 1024; // 50 MB
const FSYNC_INTERVAL_MS = 5_000; // 5 seconds
/**
* Create a LogSink that durably appends each record to the journal file
* as one NDJSON line. Fail-safe: write errors drop + warn, never throw.
* Rotates when file exceeds maxBytes (rename → .1, reopen fresh).
*/
export function createJournalSink(opts: JournalSinkOpts): LogSink {
const filePath = opts.path;
const maxBytes = opts.maxBytes ?? DEFAULT_MAX_BYTES;
const syncMode = opts.fsync ?? "periodic";
const fs = opts.fs ?? createDefaultFsOps();
const clock = opts.clock ?? { now: () => Date.now() };
const NO_FD = -1;
let fd: number;
let bytesWritten: number;
try {
fd = fs.open(filePath);
bytesWritten = fs.statSize(filePath);
} catch {
fd = NO_FD;
bytesWritten = 0;
}
let lastFsyncAt = clock.now();
function tryOpen(): boolean {
if (fd !== NO_FD) return true;
try {
fd = fs.open(filePath);
bytesWritten = 0;
return true;
} catch {
return false;
}
}
function rotate(): void {
if (fd !== NO_FD) {
try {
fs.close(fd);
} catch {
// Ignore close errors during rotation.
}
}
const rotatedPath = `${filePath}.1`;
try {
fs.rename(filePath, rotatedPath);
} catch {
// If rename fails, just truncate by reopening.
}
try {
fd = fs.open(filePath);
} catch {
fd = NO_FD;
}
bytesWritten = 0;
}
function maybeFsync(): void {
if (syncMode !== "periodic" || fd === NO_FD) return;
const now = clock.now();
if (now - lastFsyncAt >= FSYNC_INTERVAL_MS) {
try {
fs.fsync(fd);
} catch {
// Swallow — fail-safe.
}
lastFsyncAt = now;
}
}
const sink: LogSink = {
emit(record: LogRecord): void {
try {
if (!tryOpen()) {
console.warn("[journal-sink] cannot open journal, dropping record");
return;
}
const line = serialize(record);
const lineBytes = Buffer.byteLength(line, "utf8");
if (bytesWritten + lineBytes > maxBytes) {
rotate();
if (fd === NO_FD) {
console.warn("[journal-sink] rotation failed, dropping record");
return;
}
}
fs.write(fd, line);
bytesWritten += lineBytes;
maybeFsync();
} catch (err) {
// Fail-safe: drop + warn, never throw to the caller (D3/D7).
console.warn("[journal-sink] write failed, dropping record:", err);
}
},
};
return sink;
}
// --- Default fs ops (real Bun/Node I/O) ---
function createDefaultFsOps(): FsOps {
return {
open(path: string): number {
return openSync(path, "a");
},
write(fd: number, data: string): void {
writeSync(fd, data);
},
close(fd: number): void {
closeSync(fd);
},
rename(oldPath: string, newPath: string): void {
renameSync(oldPath, newPath);
},
statSize(path: string): number {
try {
return statSync(path).size;
} catch {
return 0;
}
},
fsync(fd: number): void {
fsyncSync(fd);
},
};
}
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