// ONE SEARCH PIPELINE — result ordering.
//
// Two orderings exist in this corpus and both were written inline at their one
// call site:
//
//   newest-first over uploadDate   the search result list
//     (`components/SearchSessionContext.tsx`), which sorts videos and social
//     posts into ONE list so a unified search reads as one result set rather
//     than videos-then-posts.
//   oldest-first over createdAt    a social thread
//     (`mcp/src/search.ts` getThread), tie-broken by id so a thread whose posts
//     share a timestamp still has a stable order.
//
// They are comparators, not policies: a caller picks one, and the point of
// naming them is that the next consumer (an MCP tool that wants the viewer's
// order, say) reaches for the same function instead of re-deriving a
// three-branch ternary with its own idea of which way "newest" points.
//
// Deliberately NOT here: relevance ranking. Nothing in this repo ranks by
// score today — the scanner emits in corpus scan order and the viewer emits in
// date order — and inventing one under cover of a refactor would change what
// every caller returns.

export type UploadDated = { uploadDate: string };
export type Threaded = { createdAt: string; id: string };

// Newest upload first. Dates are "YYYYMMDD", so a lexicographic compare is a
// chronological one. Equal dates keep their input order (Array#sort is stable),
// which is what preserves the summaries index's own ordering within a day.
export function byUploadDateDesc(a: UploadDated, b: UploadDated): number {
  return a.uploadDate === b.uploadDate ? 0 : a.uploadDate < b.uploadDate ? 1 : -1;
}

// Sorts IN PLACE and returns the same array — matching the call site this
// replaced, where the array is freshly built and nobody else holds it.
export function rankByUploadDateDesc<T extends UploadDated>(items: T[]): T[] {
  return items.sort(byUploadDateDesc);
}

// Oldest post first within a thread; ties broken by id so the order is total.
export function byCreatedAtThenId(a: Threaded, b: Threaded): number {
  return a.createdAt === b.createdAt
    ? a.id.localeCompare(b.id)
    : a.createdAt.localeCompare(b.createdAt);
}

export function rankThread<T extends Threaded>(items: T[]): T[] {
  return items.sort(byCreatedAtThenId);
}