pomf-rehost/background.js

function getCurrentTabUrl(callback) {
	var queryInfo = {
		active: true,
		currentWindow: true
	};

	chrome.tabs.query(queryInfo, function(tabs) {
		var tab = tabs[0];

		var url = tab.url;

		callback(url);
	});
}

function replaceBookmark(oldUrl, newUrl) {
	chrome.bookmarks.search({url: oldUrl}, function(bookmarks) {
		for(bookmark of bookmarks) {
			chrome.bookmarks.update(bookmark.id, {url: newUrl});	
		}
	});
}

function copyToClipboard(url) {
	document.oncopy = function(event) {
		event.clipboardData.setData("text/plain", url);
		event.preventDefault();
	};
	document.execCommand('Copy', false, null);
}

var blacklist = ["pomf.", "mixtape.moe", "catgirlsare.sexy", "p.fuwafuwa.moe", "/wiki/", "catbox.moe", "fuwa.se"];

chrome.pageAction.onClicked.addListener(function(tab) {
	getCurrentTabUrl(function(url) {
		getBetterUrl(url, function(betterUrl) {
			var filename = betterUrl.substr(betterUrl.lastIndexOf("/"));
			filename = cleanExtension(filename);

			if(filename.indexOf('.') == -1) {
				filename = filename + '.jpg'; //on average, it's probably JPEG if it doesn't have an extension
			}

			chrome.storage.sync.get({url: '', tabbehaviour: '', copytoclipboard: false, replacebookmark: false, disableblacklist: false}, function(config) {
				if(config.url == '') {
					alert("Please select a Pomf clone.");
					chrome.tabs.create({ url: "options.html" });
					return;
				}

				if(!config.disableblacklist) {
					for(black of blacklist) {
						if(url.indexOf(black) != -1) {
							return;
						}
					}
				}

				var worker = new Worker('worker.js');
				worker.onmessage = function(event) {
					var response = JSON.parse(event.data);

					var newUrl = response.files[0].url;

					switch(config.tabbehaviour)
					{
						case "newtab":
							chrome.tabs.create({url: newUrl});
							break;
						case "replacetab":
							chrome.tabs.update(tab.id, {url: newUrl});
							break;
					}

					if(config.copytoclipboard) {
						copyToClipboard(newUrl);	
					}

					if(config.replacebookmark) {
						replaceBookmark(url, newUrl);
					}

					worker.terminate();
				};
				worker.postMessage(JSON.stringify({pomfclone: config.url, url: betterUrl, filename: filename}));	
			});
		});
	});
});

function getBetterUrl(url, callback) {
	var extensionIndex = url.lastIndexOf('.');
	var extension = url.substr(extensionIndex + 1);

	if(extension == "gifv") {
		url = url.replace("gifv", "mp4");
	}

	if(isTwitterUrl(url)) {
		if(url.indexOf(':') != url.lastIndexOf(':')) { //Match if there are occurences of ':' other than the ':' in 'https://', such as in '.jpg:large'
			url = url.substr(0, url.lastIndexOf(':'));
		}

		url = url + ':orig';

		callback(url);
	} else if(isInstagramUrl(url)) {
		var request = new XMLHttpRequest();
		request.open('GET', 'https://api.instagram.com/oembed/?callback=&url=' + url, true);
		request.onload = function () {
			var json = JSON.parse(request.responseText);

			var filename = json.thumbnail_url.substr(json.thumbnail_url.lastIndexOf('/') + 1);
			filename = filename.substr(0, filename.indexOf('?'));

			var baseurl = 'https://scontent-amt2-1.cdninstagram.com/';

			callback(baseurl + '/' + filename);
		};
		request.send();
	} else if(isPixivUrl(url)) {
		//TODO: Use a content script instead of re-fetching the page

		var pageRequest = new XMLHttpRequest();
		pageRequest.open('GET', url, true);
		pageRequest.onload = function () {
			var regex = /<div class="_layout-thumbnail ui-modal-trigger"><img src="[^"]+img-master\/([^"]+)_master[0-9]+(\.[^"]+)".*>/g;

			var match = regex.exec(pageRequest.responseText);

			var imageUrl = 'http://i3.pixiv.net/img-original/' + match[1];

			var onload = function (imageRequest, extension) {
				if(imageRequest.status == 404 && extension == "jpg") {
					makerequest("png");
				} else {
					callback(imageUrl + "." + extension);
				}
			};

			var makerequest = function(extension) {
				var imageRequest = new XMLHttpRequest();
				imageRequest.open('GET', imageUrl + "." + extension, true); 
				imageRequest.setRequestHeader('X-Pixiv-Referer', url);
				imageRequest.onload = function() { onload(imageRequest, extension); };				
				imageRequest.send();
			};

			makerequest("jpg");
		};
		pageRequest.send();
	} else if(isSkypeUrl(url)) {
		url = url.substr(0, url.lastIndexOf('/'));
		url = url + '/imgpsh_fullsize';

		callback(url);
	} else {
		callback(url);
	}
}

chrome.webRequest.onBeforeSendHeaders.addListener(
	function(details) {
		if(details.url.indexOf('pixiv') != -1) {
			for (var i = 0; i < details.requestHeaders.length; ++i) {
            	if (details.requestHeaders[i].name === 'X-Pixiv-Referer') {
        			var referer = details.requestHeaders[i].value;
					details.requestHeaders.splice(i, 1);
            		break;
            	}
			}

			details.requestHeaders.push({
				name: 'Referer',
				value: referer
			});
		}
  	
		return {requestHeaders: details.requestHeaders};
  	},
	{urls: ["*://*/*"], types: ["xmlhttprequest"]},
	["blocking", "requestHeaders"]
);

function cleanExtension(url) {
	var trailingStrings = ["?", ":orig", ":large", ":small", ":thumb", ":medium"];

	for(trailingString of trailingStrings) {
		if(url.indexOf(trailingString) != -1) {
			url = url.substr(0, url.indexOf(trailingString));
		}
	}

	return url;
}

function isTwitterUrl(url) {
	return url.indexOf('pbs.twimg.com/media/') != -1;	
}

function isInstagramUrl(url) {
	return url.indexOf('instagram.com/p') != -1;
}

function isPixivUrl(url) {
	return url.indexOf('pixiv.net/member_illust.php') != -1;
}

function isSkypeUrl(url) {
	return url.indexOf('api.asm.skype.com/v1/objects/') != -1;
}

function isCoolUrl(url, callback) {
	url = url.toLowerCase();

	var extensionIndex = url.lastIndexOf('.');
	var extension = cleanExtension(url.substr(extensionIndex + 1));
	
	var validExtensions = ["jpg", "jpeg", "png", "gif", "webm", "gifv", "mp4", "mp3", "ogg", "opus", "pdf", "mkv", "ogv", "swf", "flv"];

	chrome.storage.sync.get({ disableblacklist: false }, function(config) {
		if(!config.disableblacklist) {
			for(black of blacklist) {
				if(url.indexOf(black) != -1) {
					return false;
				}
			}
		} else {
			console.log('blacklist disabled!');
		}

		callback(validExtensions.indexOf(extension) != -1 || isInstagramUrl(url) || isPixivUrl(url) || isSkypeUrl(url));
	});
}

chrome.tabs.onUpdated.addListener(function(tabId, changeInfo, tab) {
	if(tab.active) {	
		isCoolUrl(tab.url, function (cool) {	
			if(cool) {
				chrome.pageAction.show(tabId);
			}
		});
	}
}); 

chrome.tabs.onActivated.addListener(function(activeInfo) {
	chrome.tabs.get(activeInfo.tabId, function(tab) {
		isCoolUrl(tab.url, function(cool) {
			if (cool) {
				chrome.pageAction.show(activeInfo.tabId);
			}
		});
	});
});