Add Omnibox API example (#164)

* Add Omnibox API example

* Add an example for the omnibox api

* Resolved pull request comments and did some minor refactoring

* Resolved pull request comments and did some minor refactoring

* Fix error when handling default suggestion

* Fix error when handling default suggestion

* Require Firefox 52, update version to 1.0, and update match pattern to be more specific

firefox-code-search/README.md

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+# firefox-code-search
+
+## What it does
+
+This extension allows you to search the Firefox codebase using the awesome bar.
+
+To test it out, type 'cs' into the awesome bar followed by a search string (e.g. `cs hello world`). The results will be shown as suggestions, and clicking on a suggestion will navigate to the file where the result was found.
+
+To search a specific file, use the "path:" prefix (e.g. `cs hello path:omnibox.js`)
+
+## What it shows
+
+How to use the omnibox API to add custom suggestions to the awesome bar.

firefox-code-search/background.js

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+const BASE_URL = "https://searchfox.org/mozilla-central";
+const SEARCH_URL = `${BASE_URL}/search`;
+const SOURCE_URL = `${BASE_URL}/source`;
+
+// Provide help text to the user.
+browser.omnibox.setDefaultSuggestion({
+  description: `Search the firefox codebase
+    (e.g. "hello world" | "path:omnibox.js onInputChanged")`
+});
+
+// Update the suggestions whenever the input is changed.
+browser.omnibox.onInputChanged.addListener((text, addSuggestions) => {
+  let headers = new Headers({"Accept": "application/json"});
+  let init = {method: 'GET', headers};
+  let url = buildSearchURL(text);
+  let request = new Request(url, init);
+
+  fetch(request)
+    .then(createSuggestionsFromResponse)
+    .then(addSuggestions);
+});
+
+// Open the page based on how the user clicks on a suggestion.
+browser.omnibox.onInputEntered.addListener((text, disposition) => {
+  let url = text;
+  if (!text.startsWith(SOURCE_URL)) {
+    // Update the url if the user clicks on the default suggestion.
+    url = `${SEARCH_URL}?q=${text}`;
+  }
+  switch (disposition) {
+    case "currentTab":
+      browser.tabs.update({url});
+      break;
+    case "newForegroundTab":
+      browser.tabs.create({url});
+      break;
+    case "newBackgroundTab":
+      browser.tabs.create({url, active: false});
+      break;
+  }
+});
+
+function buildSearchURL(text) {
+  let path = '';
+  let queryParts = [];
+  let query = '';
+  let parts = text.split(' ');
+
+  parts.forEach(part => {
+    if (part.startsWith("path:")) {
+      path = part.slice(5);
+    } else {
+      queryParts.push(part);
+    }
+  });
+
+  query = queryParts.join(' ');
+  return `${SEARCH_URL}?q=${query}&path=${path}`;
+}
+
+function createSuggestionsFromResponse(response) {
+  return new Promise(resolve => {
+    let suggestions = [];
+    let suggestionsOnEmptyResults = [{
+      content: SOURCE_URL,
+      description: "no results found"
+    }];
+    response.json().then(json => {
+      if (!json.normal) {
+        return resolve(suggestionsOnEmptyResults);
+      }
+
+      let occurrences = json.normal["Textual Occurrences"];
+      let files = json.normal["Files"];
+
+      if (!occurrences && !files) {
+        return resolve(suggestionsOnEmptyResults);
+      }
+
+      if (occurrences) {
+        occurrences.forEach(({path, lines}) => {
+          suggestions.push({
+            content: `${SOURCE_URL}/${path}#${lines[0].lno}`,
+            description: lines[0].line,
+          });
+        });
+        return resolve(suggestions);
+      }
+
+      // There won't be any textual occurrences if the "path:" prefix is used.
+      files.forEach(({path}) => {
+        suggestions.push({
+          content: `${SOURCE_URL}/${path}`,
+          description: path,
+        });
+      });
+      return resolve(suggestions);
+    });
+  });
+}
+

firefox-code-search/manifest.json

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+{
+  "name": "Firefox Code Search",
+  "description" : "To use, type 'cs' plus a search term into the url bar.",
+  "version": "1.0",
+  "applications": {
+    "gecko": {
+      "strict_min_version": "52.0a1"
+    }
+  },
+  "background": {
+    "scripts": ["background.js"]
+  },
+  "omnibox": { "keyword" : "cs" },
+  "manifest_version": 2,
+  "permissions": [
+    "https://searchfox.org/"
+  ]
+}