/**
 * DOM utility helpers — safe element lookup with missing-element warnings and telemetry.
 */
import { telemetry } from './app-telemetry.js';

const warned = new Set();

export const warnOnce = (code, message, details = {}) => {
  const normalizedCode = String(code ?? '').trim() || 'UI_WARN';
  const normalizedMessage = String(message ?? '').trim();
  const key = `${normalizedCode}:${normalizedMessage}`;
  if (warned.has(key)) {return;}
  warned.add(key);
  console.warn(`[${normalizedCode}] ${normalizedMessage}`, details);

  const warnMeta = {
    source: 'warn_once',
    code: normalizedCode,
  };

  if (details && typeof details === 'object' && !Array.isArray(details)) {
    if (typeof details.module === 'string' && details.module.trim() !== '') {
      warnMeta.module = details.module.trim();
    }
    if (typeof details.component === 'string' && details.component.trim() !== '') {
      warnMeta.component = details.component.trim();
    }
    if (typeof details.feature === 'string' && details.feature.trim() !== '') {
      warnMeta.feature = details.feature.trim();
    }
  }

  telemetry.capture('frontend.warn_once', {
    severity: 'warning',
    message: `[${normalizedCode}] ${normalizedMessage}`,
    meta: warnMeta,
  });
};

export const requireEl = (selector, details = {}) => {
  const el = document.querySelector(selector);
  if (!el) {
    warnOnce('UI_EL_MISSING', `Missing element: ${selector}`, details);
    return null;
  }
  return el;
};

export const requireAll = (selector, details = {}) => {
  const list = Array.from(document.querySelectorAll(selector));
  if (!list.length) {
    warnOnce('UI_EL_MISSING', `Missing elements: ${selector}`, details);
  }
  return list;
};

export const optionalEl = (selector) => document.querySelector(selector);

/**
 * Resolve a mount root to a valid query host.
 * Components receive a `root` parameter that may be document, an element, or undefined.
 * Returns the root if it supports querySelectorAll, otherwise falls back to document.
 */
export const resolveHost = (root) =>
  root && typeof root.querySelectorAll === 'function' ? root : document;