/**
 * @fileoverview Periodic GC for paste-image files.
 *
 * Without cleanup, /api/sessions/:id/paste-image accumulates files indefinitely
 * under {workingDir}/.claude-images/. The route only triggers cleanup on
 * killMux=true session deletion, so long-lived sessions can fill disk under
 * heavy pasting. This sweeper bounds disk use by deleting `paste-*` files
 * older than MAX_AGE_MS from each live session's image dir on an interval.
 *
 * Conservative defaults — only files matching the `paste-` prefix are
 * considered, and we lstat (not stat) so a planted symlink cannot escape the
 * image dir.
 */
import fs from 'node:fs/promises';
import { join } from 'node:path';
import type { SessionPort } from './ports/index.js';

const MAX_AGE_MS = 7 * 24 * 60 * 60 * 1000; // 7 days
const SWEEP_INTERVAL_MS = 60 * 60 * 1000; // 1 hour
const INITIAL_DELAY_MS = 30 * 1000; // 30s after startup

export async function sweepPasteImagesOnce(
  ctx: Pick<SessionPort, 'sessions'>,
  now: number = Date.now()
): Promise<{ scanned: number; deleted: number }> {
  const cutoff = now - MAX_AGE_MS;
  let scanned = 0;
  let deleted = 0;
  for (const session of ctx.sessions.values()) {
    const dir = join(session.workingDir, '.claude-images');
    let entries: string[];
    try {
      entries = await fs.readdir(dir);
    } catch {
      continue; // dir absent — nothing to do
    }
    for (const name of entries) {
      if (!name.startsWith('paste-')) continue;
      const p = join(dir, name);
      scanned += 1;
      try {
        const st = await fs.lstat(p);
        if (!st.isFile()) continue;
        if (st.mtimeMs < cutoff) {
          await fs.unlink(p);
          deleted += 1;
        }
      } catch {
        // best-effort: skip permission/race errors silently
      }
    }
  }
  return { scanned, deleted };
}

export function startPasteImageGc(ctx: Pick<SessionPort, 'sessions'>): () => void {
  const initial = setTimeout(() => {
    void sweepPasteImagesOnce(ctx);
  }, INITIAL_DELAY_MS);
  const interval = setInterval(() => {
    void sweepPasteImagesOnce(ctx);
  }, SWEEP_INTERVAL_MS);
  if (typeof initial.unref === 'function') initial.unref();
  if (typeof interval.unref === 'function') interval.unref();
  return (): void => {
    clearTimeout(initial);
    clearInterval(interval);
  };
}