/**
 * String utilities for config-audit scanners.
 * Zero external dependencies.
 */

/**
 * Count lines in a string.
 * @param {string} s
 * @returns {number}
 */
export function lineCount(s) {
  if (!s) return 0;
  return s.split('\n').length;
}

/**
 * Truncate a string to maxLen chars with ellipsis.
 * @param {string} s
 * @param {number} [maxLen=100]
 * @returns {string}
 */
export function truncate(s, maxLen = 100) {
  if (!s || s.length <= maxLen) return s || '';
  return s.slice(0, maxLen - 3) + '...';
}

/**
 * Check if two strings have >threshold% content similarity (word overlap).
 * @param {string} a
 * @param {string} b
 * @param {number} [threshold=0.8]
 * @returns {boolean}
 */
export function isSimilar(a, b, threshold = 0.8) {
  const wordsA = new Set(a.toLowerCase().split(/\s+/).filter(w => w.length > 2));
  const wordsB = new Set(b.toLowerCase().split(/\s+/).filter(w => w.length > 2));
  if (wordsA.size === 0 || wordsB.size === 0) return false;
  let overlap = 0;
  for (const w of wordsA) {
    if (wordsB.has(w)) overlap++;
  }
  const similarity = overlap / Math.min(wordsA.size, wordsB.size);
  return similarity >= threshold;
}

/**
 * Levenshtein edit distance between two strings (insertions, deletions,
 * substitutions; a transposition counts as 2). Used for typo detection on
 * settings keys. Zero external dependencies, O(a*b) with two rolling rows.
 * @param {string} a
 * @param {string} b
 * @returns {number}
 */
export function levenshtein(a, b) {
  if (a === b) return 0;
  const al = a.length;
  const bl = b.length;
  if (al === 0) return bl;
  if (bl === 0) return al;
  let prev = new Array(bl + 1);
  let curr = new Array(bl + 1);
  for (let j = 0; j <= bl; j++) prev[j] = j;
  for (let i = 1; i <= al; i++) {
    curr[0] = i;
    const ac = a.charCodeAt(i - 1);
    for (let j = 1; j <= bl; j++) {
      const cost = ac === b.charCodeAt(j - 1) ? 0 : 1;
      curr[j] = Math.min(
        prev[j] + 1,        // deletion
        curr[j - 1] + 1,    // insertion
        prev[j - 1] + cost, // substitution
      );
    }
    const tmp = prev;
    prev = curr;
    curr = tmp;
  }
  return prev[bl];
}

/**
 * Extract all key-like patterns from a settings.json or similar config.
 * @param {object} obj
 * @param {string} [prefix='']
 * @returns {string[]}
 */
export function extractKeys(obj, prefix = '') {
  const keys = [];
  for (const [key, value] of Object.entries(obj)) {
    const fullKey = prefix ? `${prefix}.${key}` : key;
    keys.push(fullKey);
    if (value && typeof value === 'object' && !Array.isArray(value)) {
      keys.push(...extractKeys(value, fullKey));
    }
  }
  return keys;
}

/**
 * Normalize a file path for comparison (resolve ~, handle trailing slashes).
 * @param {string} p
 * @returns {string}
 */
export function normalizePath(p) {
  const home = process.env.HOME || process.env.USERPROFILE || '';
  let normalized = p.replace(/^~/, home);
  normalized = normalized.replace(/[/\\]+$/, '');
  return normalized;
}