import { readdir, readFile } from 'fs/promises';
import { join } from 'path';

/**
 * Walk the outputFolder looking for the pageSummary JSON files
 * produced by sitespeed.io. The structure is:
 *   outputFolder/pages/<hostname>/<urlpath>/<plugin>.pageSummary.json
 */
async function findPageSummaries(outputFolder) {
  const pagesDir = join(outputFolder, 'pages');
  const summaries = {};

  async function walk(dir) {
    let entries;
    try {
      entries = await readdir(dir, { withFileTypes: true });
    } catch {
      return;
    }
    for (const e of entries) {
      const full = join(dir, e.name);
      if (e.isDirectory()) {
        await walk(full);
      } else if (e.name.endsWith('.pageSummary.json')) {
        const plugin = e.name.replace('.pageSummary.json', '');
        if (!summaries[plugin]) summaries[plugin] = [];
        summaries[plugin].push(full);
      }
    }
  }

  await walk(pagesDir);
  return summaries;
}

async function readJson(filePath) {
  const raw = await readFile(filePath, 'utf8');
  return JSON.parse(raw);
}

function safe(obj, ...path) {
  let cur = obj;
  for (const key of path) {
    if (cur == null || typeof cur !== 'object') return null;
    cur = cur[key];
  }
  return cur ?? null;
}

function median(obj) {
  return safe(obj, 'median') ?? safe(obj, 'mean') ?? null;
}

export async function parseResults(outputFolder, _url) {
  const summaries = await findPageSummaries(outputFolder);
  const metrics = {};

  // ─── browsertime.pageSummary ───────────────────────────────────────────────
  const btFiles = summaries['browsertime'] || [];
  if (btFiles.length > 0) {
    const bt = await readJson(btFiles[0]);
    const stats = safe(bt, 'statistics');
    const timings = safe(stats, 'timings');
    const pageTimings = safe(timings, 'pageTimings');
    const userTimings = safe(timings, 'userTimings');
    const visualMetrics = safe(stats, 'visualMetrics');
    const cpu = safe(stats, 'cpu');
    const axe = safe(bt, 'accessibility', 'summary');

    // Core Web Vitals / timings
    if (timings) {
      metrics.ttfb = median(safe(timings, 'timeToFirstByte'));
      metrics.fcp = median(safe(timings, 'firstContentfulPaint'));
      metrics.lcp = median(safe(timings, 'largestContentfulPaint'));
      metrics.cls = median(safe(timings, 'cumulativeLayoutShift'));
      metrics.tbt = median(safe(timings, 'totalBlockingTime'));
      metrics.max_potential_fid = median(safe(timings, 'maxPotentialFID'));
    }

    if (pageTimings) {
      metrics.page_load_time = median(safe(pageTimings, 'pageLoadTime'));
      metrics.fully_loaded = median(safe(pageTimings, 'fullyLoaded'));
      metrics.dom_content_loaded = median(safe(pageTimings, 'domContentLoadedEventEnd'));
      metrics.dom_interactive = median(safe(pageTimings, 'domInteractive'));
      metrics.front_end_time = median(safe(pageTimings, 'frontEndTime'));
      metrics.back_end_time = median(safe(pageTimings, 'backEndTime'));
      metrics.time_to_first_byte = median(safe(pageTimings, 'timeToFirstByte'))
        ?? metrics.ttfb;
    }

    if (visualMetrics) {
      metrics.speed_index = median(safe(visualMetrics, 'SpeedIndex'));
      metrics.first_visual_change = median(safe(visualMetrics, 'FirstVisualChange'));
      metrics.last_visual_change = median(safe(visualMetrics, 'LastVisualChange'));
      metrics.visual_complete_85 = median(safe(visualMetrics, 'VisualComplete85'));
      metrics.perceptual_speed_index = median(safe(visualMetrics, 'PerceptualSpeedIndex'));
    }

    // CPU / Long Tasks
    if (cpu) {
      metrics.long_tasks_count = median(safe(cpu, 'longTasks', 'tasks'));
      metrics.long_tasks_duration = median(safe(cpu, 'longTasks', 'totalDuration'));
    }

    // Axe accessibility
    if (axe) {
      metrics.axe_critical = safe(axe, 'critical') ?? 0;
      metrics.axe_serious = safe(axe, 'serious') ?? 0;
      metrics.axe_moderate = safe(axe, 'moderate') ?? 0;
      metrics.axe_minor = safe(axe, 'minor') ?? 0;
    }
  }

  // ─── coach.pageSummary ─────────────────────────────────────────────────────
  const coachFiles = summaries['coach'] || [];
  if (coachFiles.length > 0) {
    const coach = await readJson(coachFiles[0]);
    const advice = safe(coach, 'advice');
    if (advice) {
      metrics.score_overall = safe(advice, 'score') ?? safe(advice, 'overall', 'score');
      metrics.score_performance = safe(advice, 'performance', 'score');
      metrics.score_accessibility = safe(advice, 'accessibility', 'score');
      metrics.score_bestpractice = safe(advice, 'bestpractice', 'score');
      metrics.score_privacy = safe(advice, 'privacy', 'score');
    }
  }

  // ─── pagexray.pageSummary ──────────────────────────────────────────────────
  const xrayFiles = summaries['pagexray'] || [];
  if (xrayFiles.length > 0) {
    const xray = await readJson(xrayFiles[0]);
    // pagexray has multiple runs — use the first or median-like object
    const page = Array.isArray(xray) ? xray[0] : xray;
    const ct = safe(page, 'contentTypes');

    if (ct) {
      metrics.transfer_total = safe(page, 'transferSize');
      metrics.requests_total = safe(page, 'requests');
      metrics.transfer_html = safe(ct, 'html', 'transferSize');
      metrics.transfer_js = safe(ct, 'javascript', 'transferSize');
      metrics.transfer_css = safe(ct, 'css', 'transferSize');
      metrics.transfer_image = safe(ct, 'image', 'transferSize');
      metrics.transfer_font = safe(ct, 'font', 'transferSize');
      metrics.requests_js = safe(ct, 'javascript', 'requests');
      metrics.requests_css = safe(ct, 'css', 'requests');
      metrics.requests_image = safe(ct, 'image', 'requests');
      metrics.requests_font = safe(ct, 'font', 'requests');
    }

    const tp = safe(page, 'thirdParty');
    if (tp) {
      metrics.third_party_requests = safe(tp, 'requests');
      metrics.third_party_transfer = safe(tp, 'transferSize');
    }
  }

  // ─── sustainable.pageSummary ───────────────────────────────────────────────
  const sustainFiles = summaries['sustainable'] || [];
  if (sustainFiles.length > 0) {
    const sust = await readJson(sustainFiles[0]);
    metrics.co2_per_page_view = safe(sust, 'co2PerPageView')
      ?? safe(sust, 'statistics', 'co2PerPageView', 'median');
    metrics.co2_total = safe(sust, 'totalCO2')
      ?? safe(sust, 'statistics', 'totalCO2', 'median');
    metrics.co2_first_party = safe(sust, 'firstParty', 'co2')
      ?? safe(sust, 'statistics', 'firstParty', 'co2', 'median');
    metrics.co2_third_party = safe(sust, 'thirdParty', 'co2')
      ?? safe(sust, 'statistics', 'thirdParty', 'co2', 'median');
  }

  // Remove null values to avoid overwriting real DB values with NULL
  return Object.fromEntries(
    Object.entries(metrics).filter(([, v]) => v !== null && v !== undefined)
  );
}