background.js

let bangs = [];

// Get current list of Bangs from DuckDuckGo
(async () => {
  const res = await fetch("https://duckduckgo.com/bang.js");
  bangs = await res.json();
})();

chrome.webRequest.onBeforeRequest.addListener(({ url }) => {
  // Get search query from URL
  const urlObj = new URL(url);
  const query = urlObj.searchParams.get('q');

  // Check if query has a bang anywhere in it
  if (query && query.includes('!') && bangs.some((bang) => {
    const bangStartIdx = query.indexOf(`!${bang.t}`);
    const prevCharIdx = bangStartIdx - 1;
    const nextCharIdx = bangStartIdx + bang.t.length + 1;
    return bangStartIdx > -1 && (nextCharIdx === query.length || query[nextCharIdx] === ' ') && (prevCharIdx === -1 || query[prevCharIdx] === ' ');
  })) {
    // Redirect to DuckDuckGo
    return {
      redirectUrl: `https://www.duckduckgo.com/?q=${encodeURIComponent(query)}`,
    };
  }
}, {
  urls: [
    "http://www.google.com/search*", "http://www.google.co.jp/search*", "http://www.google.co.uk/search*", "http://www.google.es/search*", "http://www.google.ca/search*", "http://www.google.de/search*", "http://www.google.it/search*", "http://www.google.fr/search*", "http://www.google.com.au/search*", "http://www.google.com.tw/search*", "http://www.google.nl/search*", "http://www.google.com.br/search*", "http://www.google.com.tr/search*", "http://www.google.be/search*", "http://www.google.com.gr/search*", "http://www.google.co.in/search*", "http://www.google.com.mx/search*", "http://www.google.dk/search*", "http://www.google.com.ar/search*", "http://www.google.ch/search*", "http://www.google.cl/search*", "http://www.google.at/search*", "http://www.google.co.kr/search*", "http://www.google.ie/search*", "http://www.google.com.co/search*", "http://www.google.pl/search*", "http://www.google.pt/search*", "http://www.google.com.pk/search*", "https://www.google.com/search*", "https://www.google.co.jp/search*", "https://www.google.co.uk/search*", "https://www.google.es/search*", "https://www.google.ca/search*", "https://www.google.de/search*", "https://www.google.it/search*", "https://www.google.fr/search*", "https://www.google.com.au/search*", "https://www.google.com.tw/search*", "https://www.google.nl/search*", "https://www.google.com.br/search*", "https://www.google.com.tr/search*", "https://www.google.be/search*", "https://www.google.com.gr/search*", "https://www.google.co.in/search*", "https://www.google.com.mx/search*", "https://www.google.dk/search*", "https://www.google.com.ar/search*", "https://www.google.ch/search*", "https://www.google.cl/search*", "https://www.google.at/search*", "https://www.google.co.kr/search*", "https://www.google.ie/search*", "https://www.google.com.co/search*", "https://www.google.pl/search*", "https://www.google.pt/search*", "https://www.google.com.pk/search*"
  ],
}, [
  "blocking" // Needed so we can redirect the request to DuckDuckGo - we aren't really blocking anything
]);

// Omnibox Auto-Complete
chrome.omnibox.onInputChanged.addListener((text, addSuggestions) => {
  let filterText = text.trim();
  if (filterText.indexOf("!") === 0) {
      filterText = filterText.substr(1)
  }

  chrome.omnibox.setDefaultSuggestion({
    description: 'Use Bang'
  });

  let results = [];

  for (let bang of bangs) {
    if (
      bang.t.startsWith(filterText) ||
      bang.s.includes(filterText) ||
      bang.d.includes(filterText)
    ) {
      // Shorter Bang => More relevant
      let lengthRelevance = (10 - bang.t.length);
      if (lengthRelevance > 0){
        lengthRelevance = 0;
      }

      // Relevance based on the type of match
      let typeRelevance = 0;
      if (bang.t === filterText) {
        // Exact match - set as default suggestion
        chrome.omnibox.setDefaultSuggestion({
          description: `!${bang.t} (${bang.s})`
        });
        continue;
      } else if (bang.t.startsWith(filterText)) {
        typeRelevance = 100;
      } else if (bang.s.includes(filterText)) {
        typeRelevance = 2;
      }

      const relevance = lengthRelevance + typeRelevance + bang.r;

      results.push({
        content: bang.t,
        description: `!${bang.t} (${bang.s}), Rel: ${relevance}`,
        relevance,
      });
    }
  }

  // Sort based on relevance
  results = results.sort((a, b) => b.relevance - a.relevance).slice(0, 10).map((item) => {
    return {
      content: item.content,
      description: item.description,
    };
  });

  addSuggestions(results);
});

chrome.omnibox.onInputEntered.addListener((text, disposition) => {
  let bang = text.trim();
  if (bang.indexOf("!") === 0) {
      bang = bang.substr(1)
  }

  const url = `https://www.duckduckgo.com/?q=${encodeURIComponent(`!${bang}`)}`;

  switch (disposition) {
    case "currentTab":
      chrome.tabs.update({url});
      break;
    case "newForegroundTab":
      chrome.tabs.create({url});
      break;
    case "newBackgroundTab":
      chrome.tabs.create({url, active: false});
      break;
  }
});