// registry-migrate.mjs — One-shot ai-foundry -> foundry URL remap + reserved
// schema migration. Pure functions (no I/O) so they are unit-testable; the
// migrate-ai-foundry.mjs script wires backup + atomic write around them.
//
// Microsoft rebranded "Azure AI Foundry" -> "Microsoft Foundry"; doc URLs moved
// /azure/ai-foundry/ -> /azure/foundry/. Two pages probed in Sesjon 1 are DEAD
// on a naive prefix swap and need explicit targets.

const AI_FOUNDRY_PREFIX = 'https://learn.microsoft.com/azure/ai-foundry/';
const FOUNDRY_PREFIX = 'https://learn.microsoft.com/azure/foundry/';

// Probed DEAD pages (Sesjon 1): naive prefix swap 404s, these are the live targets.
const DEAD_REMAPS = {
  'https://learn.microsoft.com/azure/ai-foundry/concepts/evaluation-evaluators':
    'https://learn.microsoft.com/azure/foundry/concepts/built-in-evaluators',
  'https://learn.microsoft.com/azure/ai-foundry/agent-service':
    'https://learn.microsoft.com/azure/foundry/agents/overview',
};

/**
 * Remap a single registry URL key. DEAD overrides win; otherwise prefix-swap
 * ai-foundry -> foundry; non-ai-foundry URLs are returned unchanged.
 * @param {string} url
 * @returns {string}
 */
export function remapKey(url) {
  if (DEAD_REMAPS[url]) return DEAD_REMAPS[url];
  if (url.startsWith(AI_FOUNDRY_PREFIX)) {
    return FOUNDRY_PREFIX + url.slice(AI_FOUNDRY_PREFIX.length);
  }
  return url;
}

/**
 * Migrate a registry: remap ai-foundry keys (resetting their tracking state so
 * the next poll re-evaluates them), merge any target collisions, and ensure the
 * reserved schema fields (authority_source, course) exist on every entry.
 * Pure — does not mutate the input.
 * @param {object} registry
 * @returns {{registry: object, stats: {remapped: number, deadRemapped: number, collisions: number}}}
 */
export function migrateRegistry(registry) {
  const out = { ...registry, urls: {} };
  const stats = { remapped: 0, deadRemapped: 0, collisions: 0 };

  for (const [url, entry] of Object.entries(registry.urls)) {
    const target = remapKey(url);
    const isRemap = target !== url;

    // Normalize every entry to the full schema (reserved fields included).
    const base = {
      sitemap_lastmod: entry.sitemap_lastmod ?? null,
      reference_files: entry.reference_files ?? [],
      status: entry.status ?? 'unpolled',
      authority_source: entry.authority_source ?? null,
      course: entry.course ?? null,
    };

    let next = base;
    if (isRemap) {
      stats.remapped++;
      if (DEAD_REMAPS[url]) stats.deadRemapped++;
      // The URL changed — old poll state is invalid; let the next poll decide.
      next = { ...base, sitemap_lastmod: null, status: 'unpolled' };
    }

    if (out.urls[target]) {
      // Two source keys collapsed onto one target — union the reference files.
      stats.collisions++;
      const merged = [
        ...new Set([...out.urls[target].reference_files, ...next.reference_files]),
      ].sort();
      out.urls[target] = { ...out.urls[target], ...next, reference_files: merged };
    } else {
      out.urls[target] = next;
    }
  }

  return { registry: out, stats };
}