import path from "node:path";
import fs from "fs-extra";
import type { Paths } from "../lib/paths";
import { isDoNotClean } from "../lib/doNotClean-server";
import { readChannelConfig } from "./channels";
import { computeKeptVideoIds } from "./keptVideos";
import { dropSavedVideo, loadSavedVideo } from "../lib/savedVideo-server";

const { pathExists, readdir } = fs;

export type PruneSavedVideosResult = {
  // Dirs carrying a saved-video pointer that were considered.
  scanned: number;
  // Window-persisted containers dropped (rolled out, unpinned).
  pruned: number;
  bytesFreed: number;
};

// Retention prune of the saved-video store. A persisted source video is removed
// from the store only when ALL of these hold:
//   - it was persisted by the rolling keep-latest rule (pointer keepReason
//     "keep-latest") — NOT a manual archive ("override") or a pin ("pin"),
//   - its id has rolled OUT of the channel's current keep-latest window, and
//   - it is not pinned via do-not-clean (a kept video later deleted-from-source
//     is pinned and must survive forever).
// This is what bounds the store's growth as new uploads displace old ones, and it
// is the Phase-3 resolution of the Phase-2 "source media not auto-pruned" caveat.
// Manually-archived and pinned containers are never auto-evicted.
export async function pruneSavedVideos({
  channelSlug,
  paths,
  onLog,
  signal,
}: {
  channelSlug: string;
  paths: Paths;
  onLog?: (msg: string) => void;
  signal?: AbortSignal;
}): Promise<PruneSavedVideosResult> {
  const log = onLog ?? ((m: string) => console.log(m));
  const dataDir = path.join(paths.channelsDir, channelSlug, "data");
  if (!(await pathExists(dataDir))) {
    return { scanned: 0, pruned: 0, bytesFreed: 0 };
  }
  const config = await readChannelConfig(paths, channelSlug);
  const keptIds = await computeKeptVideoIds({
    paths,
    channelSlug,
    keepLatest: config?.keepLatest ?? 0,
  });
  const dirs = await readdir(dataDir);

  let scanned = 0;
  let pruned = 0;
  let bytesFreed = 0;
  for (const id of dirs) {
    if (signal?.aborted) break;
    const videoDir = path.join(dataDir, id);
    const pointer = await loadSavedVideo(videoDir);
    if (!pointer) continue;
    scanned++;
    // Only the rolling keep-latest containers are eligible for auto-eviction.
    if (pointer.keepReason !== "keep-latest") continue;
    if (keptIds.has(id)) continue; // still inside the window
    if (await isDoNotClean(videoDir)) continue; // pinned -> keep forever
    const bytes = await dropSavedVideo(videoDir);
    bytesFreed += bytes;
    pruned++;
    log(
      `Pruned saved video ${id} (rolled out of keep-latest window; freed ${bytes} bytes)`,
    );
  }
  if (pruned > 0) {
    log(
      `Pruned ${pruned} saved video(s) from the store (freed ${bytesFreed} bytes).`,
    );
  }
  return { scanned, pruned, bytesFreed };
}