define(["jquery", "core", "async-runner"], function($, core, asyncRunner) {

	var connected = undefined;
	var github = undefined;

	var githubHelper = {};

	// Try to connect github by downloading js file
	function connect(task) {
		task.onRun(function() {
			if(core.isOffline === true) {
				connected = false;
				task.error(new Error("Operation not available in offline mode.|stopPublish"));
				return;
			}
			if (connected === true) {
				task.chain();
				return;
			}
			$.ajax({
				url : "lib/github.js",
				dataType : "script", timeout : AJAX_TIMEOUT
			}).done(function() {
				connected = true;
				task.chain();
			}).fail(function(jqXHR) {
				var error = {
					error: jqXHR.status,
					message: jqXHR.statusText
				};
				handleError(error, task);
			});
		});
	}

	// Try to authenticate with Oauth
	function authenticate(task) {
		var authWindow = undefined;
		var intervalId = undefined;
		task.onRun(function() {
			if (github !== undefined) {
				task.chain();
				return;
			}
			var token = localStorage["githubToken"];
			if(token !== undefined) {
				github = new Github({
					  token: token,
					  auth: "oauth"
					});
				task.chain();
				return;
			}
			core.showMessage("Please make sure the Github authorization popup is not blocked by your browser.");
			var errorMsg = "Failed to retrieve a token from GitHub.";
			// We add time for user to enter his credentials
			task.timeout = ASYNC_TASK_LONG_TIMEOUT;
			var code = undefined;
			function getCode() {
				localStorage.removeItem("githubCode");
				authWindow = core.popupWindow(
					'github-oauth-client.html?client_id=' + GITHUB_CLIENT_ID,
					'stackedit-github-oauth', 960, 600);
				authWindow.focus();
				intervalId = setInterval(function() {
					if(authWindow.closed === true) {
						clearInterval(intervalId);
						authWindow = undefined;
						intervalId = undefined;
						code = localStorage["githubCode"];
						if(code === undefined) {
							task.error(new Error(errorMsg));
							return;
						}
						localStorage.removeItem("githubCode");
						task.chain(getToken);
					}
				}, 500);
			}
			function getToken() {
				$.getJSON(GATEKEEPER_URL + "authenticate/" + code, function(data) {
					if(data.token !== undefined) {
						token = data.token;
						localStorage["githubToken"] = token;
						github = new Github({
							  token: token,
							  auth: "oauth"
							});
						task.chain();
					}
					else {
						task.error(new Error(errorMsg));
					}
				});
			}
			task.chain(getCode);
		});
		task.onError(function() {
			if(intervalId !== undefined) {
				clearInterval(intervalId);
			}
			if(authWindow !== undefined) {
				authWindow.close();
			}
		});
	}

	githubHelper.upload = function(reponame, branch, path, content, commitMsg, callback) {
		callback = callback || core.doNothing;
		var task = asyncRunner.createTask();
		connect(task);
		authenticate(task);
		task.onRun(function() {
			var userLogin = undefined;
			function getUserLogin() {
				var user = github.getUser();
				user.show(undefined, function(err, result) {
					if(err) {
						handleError(err, task);
						return;
					}
					userLogin = result.login;
					task.chain(write);
				});
			}
			function write() {
				var repo = github.getRepo(userLogin, reponame);
				repo.write(branch, path, content, commitMsg, function(err) {
					if(err) {
						handleError(err, task);
						return;
					}
					task.chain();
				});
			}
			task.chain(getUserLogin);
		});
		task.onSuccess(function() {
			callback();
		});
		task.onError(function(error) {
			callback(error);
		});
		asyncRunner.addTask(task);
	};
	
	githubHelper.uploadGist = function(gistId, filename, isPublic, title, content, callback) {
		callback = callback || core.doNothing;
		var task = asyncRunner.createTask();
		connect(task);
		authenticate(task);
		task.onRun(function() {
			var gist = github.getGist(gistId);
			var files = {};
			files[filename] = {content: content};
			githubFunction = gist.update;
			if(gistId === undefined) {
				githubFunction = gist.create;
			}
			githubFunction({
				description: title,
				"public": isPublic,
				files: files
			}, function(err, gist) {
				if(err) {
					// Handle error
					if(err.error === 404 && gistId !== undefined) {
						err = 'Gist ' + gistId + ' not found on GitHub.|removePublish';
					}
					handleError(err, task);
					return;
				}
				gistId = gist.id;
				task.chain();
			});
		});
		task.onSuccess(function() {
			callback(undefined, gistId);
		});
		task.onError(function(error) {
			callback(error);
		});
		asyncRunner.addTask(task);
	};
	
	githubHelper.downloadGist = function(gistId, filename, callback) {
		callback = callback || core.doNothing;
		var task = asyncRunner.createTask();
		connect(task);
		// No need for authentication
		var title = undefined;
		var content = undefined;
		task.onRun(function() {
			var github = new Github({});
			var gist = github.getGist(gistId);
			gist.read(function(err, gist) {
				if(err) {
					// Handle error
					task.error(new Error('Error trying to access Gist ' + gistId + '.'));
					return;
				}
				title = gist.description;
				var file = gist.files[filename];
				if(file === undefined) {
					task.error(new Error('Gist ' + gistId + ' does not contain "' + filename + '".'));
					return;
				}
				content = file.content;
				task.chain();
			});
		});
		task.onSuccess(function() {
			callback(undefined, title, content);
		});
		task.onError(function(error) {
			callback(error);
		});
		asyncRunner.addTask(task);
	};
	
	function handleError(error, task) {
		var errorMsg = undefined;
		if (error) {
			console.error(error);
			// Try to analyze the error
			if (typeof error === "string") {
				errorMsg = error;
			}
			else {
				errorMsg = "Could not publish on GitHub.";
				if (error.error === 401 || error.error === 403) {
					github = undefined;
					localStorage.removeItem("githubToken");
					errorMsg = "Access to GitHub account is not authorized.";
					task.retry(new Error(errorMsg), 1);
					return;
				} else if (error.error <= 0) {
					connected = false;
					github = undefined;
					core.setOffline();
					errorMsg = "|stopPublish";
				}
			}
		}
		task.error(new Error(errorMsg));
	}

	return githubHelper;
});