import { closeSync, openSync, readSync, statSync } from "node:fs";

const DEFAULT_TAIL_BYTES = 1_048_576;

// #1571 — bounded tail read for potentially large log files: reads at most `maxBytes` from the
// end of the file instead of the whole thing, since callers only ever want the last N lines and
// agent session/mirror logs can grow unbounded over a long-running process.
export function readLogTail(path: string, maxBytes = DEFAULT_TAIL_BYTES): string {
  const size = statSync(path).size;
  const readSize = Math.min(size, maxBytes);
  if (readSize === 0) return "";
  const buffer = Buffer.alloc(readSize);
  const fd = openSync(path, "r");
  try {
    readSync(fd, buffer, 0, readSize, size - readSize);
  } finally {
    closeSync(fd);
  }
  return buffer.toString("utf8");
}

export function logLines(content: string, sanitize = true): string[] {
  const text = sanitize ? sanitizeLogText(content) : content.replace(/\r\n/g, "\n").replace(/\r/g, "\n");
  return text
    .split("\n")
    .map((line) => line.trimEnd())
    .filter((line) => line.trim().length > 0);
}

export function sanitizeLogText(content: string): string {
  return content
    .replace(/\x1B\][^\x07\x1B]*(?:\x07|\x1B\\)/g, "")
    .replace(/\x1B[PX^_][\s\S]*?\x1B\\/g, "")
    .replace(/\x1B\[(\d*)C/g, (_match, count: string) => " ".repeat(Math.min(Number(count || "1"), 120)))
    .replace(/\x1B\[[0-?]*[ -/]*[@-~]/g, "")
    .replace(/\x1B[()#%*+\-.\/ ][ -~]/g, "")
    .replace(/\x1B[ -/]*[@-~]/g, "")
    .replace(/\x9B[0-?]*[ -/]*[@-~]/g, "")
    .replace(/\x1B.?/g, "")
    .replace(/\r\n/g, "\n")
    .replace(/\r/g, "\n")
    .replace(/[\x00-\x08\x0B\x0C\x0E-\x1F\x7F]/g, "");
}