/** Projects the pane todo snapshot into a herdr pane header/sidebar (M22, D62/D68); the pi session
 *  JSONL stays authoritative and herdr truncates title/state_label at 80 chars, so truncate locally
 *  to avoid cutting an emoji in half. */
import { countTodos, PI_HERDR_META_KEY, type TodoItem } from './vocab.ts';
import { formatAge, isArchived } from './stale-core.ts';

/** herdr's character limit for title/state_label (from official documentation and schema measurements). */
const TITLE_MAX = 80;
/** Valid state_labels keys are only idle|working|blocked|done|unknown (herdr socket-api). */
export const BLOCKED_LABEL_KEY = 'blocked';

/** D93: custom sidebar token for the todo summary, referenced as `$pi-todo` by herdr
 *  `[ui.sidebar.agents]`; its value keeps the pane-title format (`▶i ○p ■b ✓c (N/M) · activity`). */
const SIDEBAR_TODO_TOKEN = 'pi-todo';
/** D95: token marking an ask_user_question wait (the workbench heat scale uses it to distinguish ask from block). */
export const SIDEBAR_ASK_TOKEN = 'pi-ask';

/** D93: build the pi-todo token patch for report_metadata (no todo = an empty string, because herdr's
 *  patch semantics remove empty keys). D96: never merge the stale cleanup in here — stale(16) +
 *  pi-todo(1) exceeds herdr's tokens maxProperties=16 and the rejected request would drop both the
 *  title and the tokens. */
export function sidebarTodoTokens(title: string | null): Record<string, string> {
  return { [SIDEBAR_TODO_TOKEN]: title ?? '' };
}

const STALE_CHUNK_COUNT = 15;

function clipTitle(s: string): string {
  return s.length <= TITLE_MAX ? s : s.slice(0, TITLE_MAX);
}

/**
 * `▶i ○p ■b ✓c (N/M [~eta]) · <activity>` (D91 unifies the four status glyphs). activity is the
 * first in_progress item, then fallbackDescription, then only the counts. Empty list → null, which
 * callers translate into clear_title; progressSuffix (M16) comes from formatProgressSuffix.
 * Anti-freeze (stale-core D): once all work completed and the wall clock expired (archived), the
 * dead list degrades to `✓N done <age>` instead of presenting itself as a current-state view.
 */
export function formatPaneTitle(
  items: readonly TodoItem[],
  fallbackDescription?: string | null,
  opts?: { progressSuffix?: string | null; lastWriteAt?: number | null; now?: number },
): string | null {
  if (items.length === 0) return null;
  const c = countTodos(items);
  const now = opts?.now ?? Date.now();
  if (isArchived(items, opts?.lastWriteAt ?? null, now)) {
    const age = formatAge(now - (opts?.lastWriteAt as number));
    return clipTitle(`✓${c.completed} done ${age}`);
  }
  const activity =
    items.find((it) => it.status === 'in_progress')?.content
    ?? (fallbackDescription?.trim() ? fallbackDescription.trim() : null);
  const head = `▶${c.inProgress} ○${c.pending} ■${c.blocked} ✓${c.completed}`;
  const suffix = opts?.progressSuffix?.trim();
  const withProgress = suffix ? `${head} (${suffix})` : head;
  return clipTitle(activity ? `${withProgress} · ${activity}` : withProgress);
}

/** First blocked item's blocker (fall back to content); no blocked item → null. */
export function formatBlockedLabel(items: readonly TodoItem[]): string | null {
  const blocked = items.find((it) => it.status === 'blocked');
  if (!blocked) return null;
  const text = blocked.blocker?.trim() || blocked.content;
  return clipTitle(text);
}

/** The first post-upgrade report clears the old 16-key chunks (herdr merges tokens by key, so omitted nulls would otherwise remain — M13b). */
export function staleTokenClearance(): Record<string, null> {
  const tokens: Record<string, null> = { [PI_HERDR_META_KEY]: null };
  for (let i = 0; i < STALE_CHUNK_COUNT; i++) {
    tokens[`${PI_HERDR_META_KEY}-${i}`] = null;
  }
  return tokens;
}