background.js

const webExt = typeof browser !== 'undefined' ? browser : chrome;
const MAX_HISTORY_RESULTS = 100000;

function toTimeString(lastVisitTime) {
  return new Date(lastVisitTime).toLocaleTimeString('en-GB', {
    hour12: false,
    hour: '2-digit',
    minute: '2-digit'
  });
}

function generateId(item) {
  const safeUrl = typeof item.url === 'string' ? item.url : '';
  const seconds = Number.isFinite(item.lastVisitTime)
    ? Math.floor(item.lastVisitTime / 1000)
    : 0;

  let hash = 2166136261;
  const input = `${safeUrl}|${seconds}`;

  for (let i = 0; i < input.length; i++) {
    hash ^= input.charCodeAt(i);
    hash = Math.imul(hash, 16777619);
  }

  return hash >>> 0;
}

function hostnameOf(url) {
  try {
    return new URL(url).hostname;
  } catch {
    return null;
  }
}

function mapItem(item, parentId = null) {
  return {
    id: generateId(item),
    time: toTimeString(item.lastVisitTime),
    url: item.url,
    title: item.title || item.url,
    type: 'visit',
    parent: parentId
  };
}

async function buildHistoryExport() {
  const results = await webExt.history.search({
    text: '',
    startTime: 0,
    maxResults: MAX_HISTORY_RESULTS
  });

  results.sort((a, b) => a.lastVisitTime - b.lastVisitTime);

  const output = [];
  const lastIdByDomain = new Map();

  for (const item of results) {
    if (!item || typeof item.url !== 'string' || !item.url) {
      continue;
    }

    const domain = hostnameOf(item.url);
    const parentId = domain ? (lastIdByDomain.get(domain) ?? null) : null;
    const mapped = mapItem(item, parentId);
    output.push(mapped);

    if (domain) {
      lastIdByDomain.set(domain, mapped.id);
    }
  }

  return output;
}

async function triggerDownload() {
  const output = await buildHistoryExport();
  const json = JSON.stringify(output, null, 2);
  let blobUrl = null;

  try {
    blobUrl = URL.createObjectURL(new Blob([json], { type: 'application/json' }));

    await webExt.downloads.download({
      url: blobUrl,
      filename: 'history-export.json',
      saveAs: true
    });
  } catch (firstError) {
    const dataUrl = `data:application/json;charset=utf-8,${encodeURIComponent(json)}`;

    await webExt.downloads.download({
      url: dataUrl,
      filename: 'history-export.json',
      saveAs: true
    }).catch((secondError) => {
      throw new Error(
        `Primary download failed (${firstError?.message || String(firstError)}); fallback failed (${secondError?.message || String(secondError)})`
      );
    });
  } finally {
    if (blobUrl) {
      setTimeout(() => URL.revokeObjectURL(blobUrl), 5000);
    }
  }

  return { ok: true, count: output.length };
}

webExt.runtime.onMessage.addListener((message) => {
  if (!message || message.action !== 'exportHistory') {
    return undefined;
  }

  return triggerDownload().catch((error) => ({
    ok: false,
    error: error?.message || String(error)
  }));
});