// Pure logic for autocomplete trigger detection and skill filtering.
// Extracted from SimpleInput.js for testability.

/**
 * Detect if cursor is at a trigger position for autocomplete.
 * Returns trigger info object or null.
 */
export function getTriggerInfo(value, cursorPos, autocompleteConfig) {
  if (!autocompleteConfig) return null;

  const { trigger } = autocompleteConfig;

  // Find the start of the current "word" (after last whitespace before cursor)
  let wordStart = cursorPos;
  while (wordStart > 0 && !/\s/.test(value[wordStart - 1])) {
    wordStart--;
  }

  // Check if word starts with this agent's trigger character
  if (value[wordStart] === trigger) {
    return {
      trigger,
      filterText: value.slice(wordStart + 1, cursorPos).toLowerCase(),
      replaceStart: wordStart,
      replaceEnd: cursorPos,
    };
  }

  return null;
}

/**
 * Filter and sort skills based on trigger info.
 * Returns sorted array of matching skills.
 */
export function filteredSkills(autocompleteConfig, triggerInfo) {
  if (!autocompleteConfig || !triggerInfo) return [];

  const { skills } = autocompleteConfig;
  const { filterText } = triggerInfo;

  let filtered = filterText
    ? skills.filter(s => s.name.toLowerCase().includes(filterText))
    : skills.slice();

  // Server pre-sorts, but re-sort after filtering for stability
  return filtered.sort((a, b) => a.name.localeCompare(b.name));
}