/**
 * Shared stop words and key refinement for causal breadcrumb extraction.
 *
 * Used by both brief.ts (turn summary key generation) and format.ts
 * (breadcrumb extraction from capped lines) to ensure consistent key output.
 */

// Stop words filtered out when building breadcrumb keys.
// These carry no causal signal and would bloat the key.
export const KEY_STOPS = new Set([
  // Articles, pronouns, demonstratives
  'the',
  'a',
  'an',
  'this',
  'that',
  'these',
  'those',
  'it',
  'its',
  // Be-verbs, auxiliaries
  'is',
  'was',
  'are',
  'were',
  'been',
  'being',
  'has',
  'have',
  'had',
  'does',
  'do',
  'did',
  'will',
  'would',
  'could',
  'should',
  'may',
  'might',
  'shall',
  'can',
  // Prepositions
  'to',
  'of',
  'in',
  'for',
  'on',
  'with',
  'at',
  'by',
  'from',
  'as',
  'into',
  'through',
  'before',
  'after',
  'above',
  'below',
  // Conjunctions, adverbs
  'and',
  'but',
  'or',
  'not',
  'so',
  'yet',
  'before',
  'after',
  'when',
  'where',
  'while',
  'during',
  // Contextual filler that doesn't carry causal signal
  'against',
  'into',
  'around',
  'before',
  'all',
  // Marker remnant words: verbs from resolution markers that survive
  // the extraction because the fragment starts right after the marker.
  // E.g. "added session check" → we want "session-check", not "added-session-check".
  'added',
  'adding',
  'created',
  'creating',
  'applied',
  'applying',
  'inserted',
  'inserting',
  'implemented',
  'implementing',
  'introduced',
  'introducing',
  'using',
  'swapped',
  'swapping',
  'split',
  'splitting',
  'migrated',
  'migrating',
  'isolated',
  'isolating',
  'removed',
  'removing',
  'extracted',
  'extracting',
  'replaced',
  'replacing',
  'refactored',
  'refactoring',
  'wrapped',
  'wrapping',
  'guarded',
  'guarding',
  'moved',
  'moving',
  'updated',
  'configured',
  'enabled',
  'switched',
]);

/** Maximum content words in a breadcrumb key. */
const KEY_MAX_WORDS = 3;

/**
 * Build a compact breadcrumb key from a raw fragment.
 * Takes up to KEY_MAX_WORDS content words (skipping stop words), joined with "-".
 */
export const refineBreadcrumbKey = (fragment: string, maxChars = 40): string => {
  const words = fragment.split(/\s+/);
  const content: string[] = [];
  for (const w of words) {
    if (KEY_STOPS.has(w.toLowerCase())) continue;
    content.push(w);
    if (content.length >= KEY_MAX_WORDS) break;
  }
  return content.join('-') || fragment.slice(0, maxChars);
};