import {
  type ChannelPriority,
  type FocusSummary,
  type PendingByLeaf,
  focusSummary,
} from "../lib/channelPriority";

// THE STATUS PAYLOAD'S HALF OF CHANNEL PRIORITY — the shape of "which tree does
// this lane dispatch from", and the focus banner's numbers off it.
//
// The RESOLUTION of that shape is a read (a channel listing, and for a site
// focus a sites read), so it stays in the editor as `readPriorityView`. What
// lives here is everything downstream of it: the view type the four lanes are
// compiled against, and the two pure folds the payload applies to it.

export type PriorityView = {
  model: ChannelPriority;
  // The model says something, so the four trees are compiled rather than
  // stored. The lane consoles read this to go read-only on the tree.
  compiled: boolean;
  // Every channel slug, the population `compileLaneRoot` filters per lane.
  // Empty when nothing is compiled — it is never read in that case.
  slugs: string[];
  focusSlugs: string[];
  // A display name for the focus: the site's title for a site focus, the slugs
  // for a channel focus. Resolved by the reader because the model stores a
  // siteId and the banner does no I/O.
  name: string | null;
};

// `focusSummary` reads nothing but each leaf's COUNT, and `computeLeafPending`
// throws the arrays away before this layer sees them (it returns counts plus a
// truncated head). Rather than widen that return type — which would put the
// whole pending set of every leaf on a three-second poll's heap — the counts are
// re-presented as arrays of the right length. `new Array(n)` allocates no
// elements; only `.length` is ever read.
export function pendingByLeafFromCounts(
  counts: Record<string, number>,
): PendingByLeaf {
  const out: Record<string, readonly string[]> = {};
  for (const [id, n] of Object.entries(counts)) out[id] = new Array<string>(n);
  return out;
}

export function laneFocusSummary(
  view: PriorityView,
  counts: Record<string, number>,
): FocusSummary {
  return focusSummary(
    view.model,
    view.focusSlugs,
    pendingByLeafFromCounts(counts),
  );
}