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background.js
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background.js
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var currentTab;
function updateIcon(previewing) {
chrome.browserAction.setIcon({
path: previewing ? {
19: "/icons/black-bg.svg",
38: "/icons/black-bg.svg"
} : {
19: "/icons/white-bg.svg",
38: "/icons/white-bg.svg"
},
tabId: currentTab.id
});
chrome.browserAction.setTitle({
title: previewing ? 'Hide Preview' : 'Show Preview',
tabId: currentTab.id
});
}
function togglePreview() {
// tell content to render preview
chrome.tabs.sendMessage(currentTab.id, {preview: true}, (result) => {
// if content responds with preview being active
// clear the preview instead
if (result && result.preview) {
chrome.tabs.sendMessage(currentTab.id, {preview: false});
updateIcon(false);
} else if (result && !result.preview) {
updateIcon(true);
}
});
}
// listen for clicks on browser extension icon
chrome.browserAction.onClicked.addListener(togglePreview);
function disableExtension() {
// when the content script reports back that there
// are no supported text areas we should disable action
chrome.browserAction.disable(currentTab.id);
chrome.browserAction.setTitle({
title: 'No Preview Available',
tabId: currentTab.id
});
}
function updateActiveTab() {
// don't try to inject the script on pages that
// are not webpages, i.e. chrome:// or about://
function isSupportedProtocol(urlString) {
var supportedProtocols = ["https:", "http:", "file:"];
var url = document.createElement('a');
url.href = urlString;
return supportedProtocols.indexOf(url.protocol) != -1;
}
chrome.tabs.query({active: true, currentWindow: true}, (tabs) => {
if (tabs[0]) {
currentTab = tabs[0];
if (isSupportedProtocol(currentTab.url)) {
// check state first, if error execute script?
chrome.tabs.sendMessage(currentTab.id, {state: true}, (result) => {
if (chrome.runtime.lastError) {
console.log(chrome.runtime.lastError.message);
disableExtension();
console.log(`Could not detect previewable content.`);
} else if (result && result.supported) {
// when there is supported content we should enable action
// and update the icon state, which also updates the tooltip
chrome.browserAction.enable(currentTab.id);
updateIcon(result.preview);
} else {
disableExtension();
console.log(`No previewable content detected at '${currentTab.url}'`);
}
});
} else {
console.log(`Markdown Preview does not support the '${currentTab.url}' URL.`);
disableExtension();
}
}
});
}
// update the extension icon for any tab, when switching and updating
chrome.tabs.onCreated.addListener(updateActiveTab);
chrome.tabs.onUpdated.addListener(updateActiveTab);
chrome.tabs.onActivated.addListener(updateActiveTab);
chrome.windows.onFocusChanged.addListener(() => {
updateActiveTab();
});
chrome.runtime.onMessage.addListener((request, sender, sendResponse) => {
if (request.endpoint && request.data) {
var params = {
body: JSON.stringify(request.data),
method: 'POST',
headers: {
'Content-Type': 'application/json'
}
};
fetch(request.endpoint, params).then(function(response) {
return response.text().then(function(text) {
sendResponse([{
body: text,
status: response.status,
statusText: response.statusText,
}, null]);
});
}, function(error) {
sendResponse([null, error]);
});
}
return true;
});
chrome.runtime.onMessage.addListener((request, sender, sendResponse) => {
if (request.toggle) {
togglePreview();
}
});