#!/usr/bin/env node
// report-changes.mjs — Compare sitemap lastmod to reference file "Last updated:" headers.
// Generates change-report.json and prints human-readable summary.
// Usage: node report-changes.mjs [--json]

import { readFileSync, existsSync } from 'node:fs';
import { join, dirname } from 'node:path';
import { fileURLToPath } from 'node:url';
import { loadRegistry, saveReport } from './lib/registry-io.mjs';

const __dirname = dirname(fileURLToPath(import.meta.url));
const PLUGIN_ROOT = join(__dirname, '..', '..');
const DATA_DIR = join(__dirname, 'data');
const jsonOnly = process.argv.includes('--json');

// Priority classification by file path patterns
function getFilePriority(filePath) {
  const lower = filePath.toLowerCase();
  if (/cost|pricing|pris/.test(lower)) return 'critical';
  if (/responsible-ai|governance|ai-security-(?:engineering|scoring)/.test(lower)) return 'high';
  if (/platforms|copilot|azure-ai-services|agent-orchestration|rag|mlops|prompt-engineering|monitoring|performance/.test(lower)) return 'medium';
  return 'low';
}

// Parse "Last updated:" header from a reference file
const LAST_UPDATED_PATTERNS = [
  /\*\*Last updated:\*\*\s*([\d-]+)/i,
  /\*\*Sist (?:oppdatert|verifisert):\*\*\s*([\d-]+)/i,
  /\*\*Dato:\*\*\s*([\d-]+)/i,
];

function parseLastUpdated(filePath) {
  const fullPath = join(PLUGIN_ROOT, filePath);
  if (!existsSync(fullPath)) return null;

  // Only read first 500 bytes — header is always at the top
  const content = readFileSync(fullPath, 'utf8').slice(0, 500);
  for (const pattern of LAST_UPDATED_PATTERNS) {
    const match = content.match(pattern);
    if (match) {
      const raw = match[1].trim();
      // YYYY-MM → YYYY-MM-01, YYYY-MM-DD → as-is
      return raw.length === 7 ? raw + '-01' : raw;
    }
  }
  return null; // No date found — treat as always stale
}

// Priority sort order
const PRIORITY_ORDER = { critical: 0, high: 1, medium: 2, low: 3 };

// --- Main ---
const registry = loadRegistry(DATA_DIR);

if (!registry.last_poll) {
  console.error('Registry has not been polled yet. Run poll-sitemaps.mjs first.');
  process.exit(1);
}

// Group changed URLs by reference file
const fileChanges = new Map(); // filePath → { changedUrls, newestChange }

for (const [url, entry] of Object.entries(registry.urls)) {
  if (!entry.sitemap_lastmod || entry.status !== 'tracked') continue;

  for (const refFile of entry.reference_files) {
    const fileDate = parseLastUpdated(refFile);
    // If no date found, treat as always stale (date "0000-01-01")
    const effectiveDate = fileDate || '0000-01-01';

    if (entry.sitemap_lastmod > effectiveDate) {
      if (!fileChanges.has(refFile)) {
        fileChanges.set(refFile, { changedUrls: [], newestChange: entry.sitemap_lastmod, fileDate });
      }
      const fc = fileChanges.get(refFile);
      fc.changedUrls.push({ url, sitemap_lastmod: entry.sitemap_lastmod });
      if (entry.sitemap_lastmod > fc.newestChange) {
        fc.newestChange = entry.sitemap_lastmod;
      }
    }
  }
}

// Build report entries
const files = [];
for (const [path, changes] of fileChanges) {
  const priority = getFilePriority(path);
  const pathParts = path.split('/');
  files.push({
    path,
    priority,
    file_last_updated: changes.fileDate || 'unknown',
    newest_source_change: changes.newestChange,
    changed_url_count: changes.changedUrls.length,
    changed_urls: changes.changedUrls.map(u => u.url),
    skill: pathParts[1] || 'unknown',
    category: pathParts[3] || 'unknown',
  });
}

// Sort: priority first, then newest source change descending
files.sort((a, b) => {
  const pDiff = PRIORITY_ORDER[a.priority] - PRIORITY_ORDER[b.priority];
  if (pDiff !== 0) return pDiff;
  return b.newest_source_change.localeCompare(a.newest_source_change);
});

// Count by priority
const byPriority = { critical: 0, high: 0, medium: 0, low: 0 };
for (const f of files) byPriority[f.priority]++;

const report = {
  generated_at: new Date().toISOString().split('T')[0],
  last_poll: registry.last_poll,
  total_tracked: Object.values(registry.urls).filter(u => u.status === 'tracked').length,
  total_not_in_sitemap: Object.values(registry.urls).filter(u => u.status === 'not_in_sitemap').length,
  total_files_needing_update: files.length,
  by_priority: byPriority,
  files,
};

saveReport('change-report.json', report, DATA_DIR);

if (jsonOnly) {
  process.stdout.write(JSON.stringify(report, null, 2) + '\n');
} else {
  console.log(`\n=== KB Change Report (${report.generated_at}) ===`);
  console.log(`Sources last polled: ${registry.last_poll}`);
  console.log(`URLs tracked: ${report.total_tracked}/${Object.keys(registry.urls).length} (${report.total_not_in_sitemap} not in sitemap)`);
  console.log(`Files needing update: ${files.length} (Critical: ${byPriority.critical}, High: ${byPriority.high}, Medium: ${byPriority.medium}, Low: ${byPriority.low})`);

  if (files.length > 0) {
    console.log('\nTop 20 by priority:');
    for (const f of files.slice(0, 20)) {
      console.log(`  [${f.priority.toUpperCase()}] ${f.path}`);
      console.log(`    ${f.changed_url_count} source(s) changed. Latest: ${f.newest_source_change}. File: ${f.file_last_updated}`);
    }
    if (files.length > 20) {
      console.log(`  ... and ${files.length - 20} more`);
    }
  }

  console.log('\nRun: /architect:generate-skills --update to process updates');
}