import { createHash } from "node:crypto";
import { statSync } from "node:fs";
import { getPaths } from "yt-dlp-transcript-common/lib/paths";
import { getSettings } from "yt-dlp-transcript-common/lib/settings";
import { getRegistry } from "yt-dlp-transcript-common/jobs/registry";
import { getScheduler } from "yt-dlp-transcript-common/jobs/scheduler";
import { getWorkerPool } from "yt-dlp-transcript-common/jobs/workerPool";
import type {
  LiveInputs,
  ObserveInputs,
} from "yt-dlp-transcript-common/views/inputs";

// THE ONE CONSTRUCTOR.
//
// Every view-model lives in `common/views/` and takes its live state as an
// argument (`views/inputs.ts` is the shape). Something has to actually fetch
// that state, and this is the only file in the editor allowed to fetch all of
// it at once. Concentrating it here is the point: the getters below are LAZY
// SINGLETONS — calling one CREATES it — so "who may construct?" is a question
// worth being able to answer by reading one file.
//
// Per-view extras (a disk gate, a log tail, a channel-brief list) are assembled
// in each noun's own shell next to the page that needs them, never here.

export function liveInputs(): LiveInputs {
  return {
    paths: getPaths(),
    settings: getSettings(),
    registry: getRegistry(),
    scheduler: getScheduler(),
    pool: getWorkerPool(),
    // A function, not a timestamp: a view that folds "is this cooldown over?"
    // should read the clock when it looks, and a test should be able to freeze
    // it. `Date.now` is banned inside views/ so this is the only way in.
    now: Date.now,
  };
}

// THE OBSERVER'S HALF, AND WHY IT IS DIFFERENT.
//
// `/api/pulse` runs every few seconds on every open tab and must never CREATE
// anything: `/api/test/invalidate-cache` clears exactly these globals between
// e2e specs, and a poll landing a moment later used to rebuild them — re-seeding
// a worker pool from settings mid-reset, which took out ~16 unrelated specs in
// non-deterministic combinations. So read the globals directly and treat "not
// created yet" as "nothing to report": a pulse must be able to say the system
// is idle without making a system to ask.
//
// (The globals are declared by the modules that own them —
// `common/jobs/{registry,scheduler,workerPool,snapshotScheduler}.ts`.)
//
// Everything gathered here is either in-memory or a stat(). No readdir, no
// corpus contact, no large JSON parse — asserted by e2e/pulse.spec.ts.
export function observeInputs(): ObserveInputs {
  const paths = getPaths();
  return {
    registry: globalThis.__yttJobRegistry__ ?? null,
    scheduler: globalThis.__yttScheduler__ ?? null,
    pool: globalThis.__yttWorkerPool__ ?? null,
    // One integer meaning "a report was rewritten", so the pages whose counts
    // come from snapshots notice without this endpoint stat-ing 65 files. The
    // scheduler's state type is not exported, so read the number off it here
    // rather than passing the object down.
    snapshotGeneration: globalThis.__yttSnapshotScheduler__?.generation ?? 0,
    // Files the layout renders from. mtime only — neither is read.
    settingsMtime: mtime(paths.settingsFile),
    changelogMtime: mtime(paths.editorChangelogFile),
    // Injected so the view never imports node:crypto.
    digest: (s: string) => createHash("sha1").update(s).digest("base64url"),
  };
}

function mtime(file: string): number {
  try {
    return statSync(file).mtimeMs;
  } catch {
    return 0;
  }
}