function UI(async, buttons, dom, screen, session) {
	var lineWidth = 36;
	var textSpeeds = {
		slow: 100,
		medium: 50,
		fast: 20
	};
	var textSpeed = session.get('options').textSpeed;

	return {
		animation: animation,
		ask: ask,
		cinematic: cinematic,
		frame: frame,
		menu: menu,
		text: text,
		setLayout: setLayout,
		setTextSpeed: setTextSpeed
	};

	function animation(frames) {
		var frameCounter = 0;
		var scheduled;
		var step = function() {
			if(frameCounter < frames.length) {
				scheduled = null;
				frames[frameCounter].action();
				if(frames[frameCounter].delay != undefined) {
					scheduled = setTimeout(step, frames[frameCounter].delay);
				}
				frameCounter++
			}
		};
		return {
			run: step,
			pause: function() { if(scheduled != undefined) { clearTimeout(scheduled); } }
		};
	}

	function cinematic(frames, controls) {
		var remote = animation(frames);
		var mapping = {};
		var escaper = function(f) {
			return function() {
				buttons.pop();
				remote.pause();
				f();
			};
		}
		for(var key in controls) {
			mapping[key] = escaper(controls[key]);
		}
		return function(f) {
			buttons.push(mapping);
			remote.run();
			f();
		};
	}

	function close(elem) {
		buttons.pop();
		screen.clear(elem);
	}

	function frame(id) {
		screen.clear();
		screen.frame(id);
	}

	function menu(config) {
		var cursor = config.selected || 0;
    config.direction = config.direction || 'vertical';
		var m = screen.menu(config);
		var sync = function() { screen.select(cursor); };
    var back = function() {
      cursor = (config.entries.length + cursor - 1) % config.entries.length;
      sync();
    };
    var forth = function() {
      cursor = (cursor + 1) % config.entries.length;
      sync();
    };
		var mapping = {
			A: function() {
				var entry = config.entries[cursor];
				if(entry.close) {
					close(m);
				}
				if(entry.action != undefined) {
					entry.action(m);
				}
			}
    };
    mapping[config.direction == 'vertical' ? 'Up' : 'Left'] = back;
    mapping[config.direction == 'vertical' ? 'Down' : 'Right'] = forth;
		if(config.cancel != undefined) {
			mapping['B'] = function() { close(m); config.cancel(); }
		}
		buttons.push(mapping);
	}

	function ask(config) {
		var menuConfig = {
			cancel: config.cancel,
			direction: config.direction,
			entries: [],
			name: config.name,
			selected: config.selected
		};
		var apply = function(f, val) { return function() { return f(val); }; };
		return function(f) {
			for(var i = 0; i < config.entries.length; i++) {
				var entry;
				if(config.entries[i].label != undefined) {
					entry = {label: config.entries[i].label, action: apply(f, config.entries[i].value), close: true};
				} else if(config.entries[i].picto != undefined) {
					entry = {picto: config.entries[i].picto, action: apply(f, config.entries[i].value), close: true};
				} else {
					entry = {label: '___', action: promptValue(config.entries[i].size, f)};
				}
				menuConfig.entries.push(entry);
			}
			menu(menuConfig);
		};
	}

	function promptValue(size, f) {
		return function(m) {
			var input = screen.input(size);
			input.focus();
			buttons.push({});
			input.addEventListener('keydown', function(event) {
				switch(event.key) {
					case 'Escape': close(input); break;
					case 'Enter':
						var value = input.value;
						close(input);
						close(m);
						return f(value);
				}
			});
		};
	}

	function textScreen(message) {
		var characters = message.split('');
		var frames = [];
		var ready = false;
		var append = function(c) { return function() { screen.appendText(c); }; };
		for(var i = 0; i < characters.length; i++) {
			frames.push(
				{action: append(characters[i]), delay: textSpeeds[textSpeed]}
			);
		}
		frames.push({action: function() { ready = true; screen.markAsRead(); }, delay: null});
		var remote = animation(frames);
		return function(f) {
			buttons.push({
				'A': function() {
					if(ready) {
						buttons.pop();
						f();
					} else {
						remote.pause();
						screen.text(message);
						ready = true;
					}
				}
			});
			screen.text('');
			remote.run();
		};
	}

	function text(message) {
		var words = message.split(' ');
		var i = 0;
		var line = '';
		var screen = null;
		var screens = [];
		var width = 0;
		while (i < words.length) {
			if(width == 0) {
				line = words[i];
				width += line.length;
				i++;
			} else {
				if(width + words[i].length + 1 <= lineWidth) {
					line += ' ' + words[i];
					width += 1 + words[i].length;
					i++;
				} else {
					if(screen === null) {
						screen = line;
					} else {
						screens.push(screen + ' ' + line);
						screen = null;
					}
					line = '';
					width = 0;
				}
			}
		}
		screens.push(screen === null ? line : screen + ' ' + line);
		return async.sequence.apply(null,
			screens.map(function(s) { return textScreen(s); })
		);
	}

	function keyPromptLabel(key, button) {
		return button + " : " + (key != undefined ? "[" + key + "]" : "???");
	}

	function setLayout() {
		var layout = session.get('options').layout
		var buttonsMenu = {
			cancel: function() {},
			entries: [],
			name: "layout"
		};
		for(var key in layout) {
			buttonsMenu.entries[buttons.code(layout[key])] = {
				label: keyPromptLabel(key, layout[key]),
				action: setKey(layout[key])
			};
		}
		menu(buttonsMenu);
	}

	function setKey(button) {
		return function(f) {
			buttons.push({});
			var elem = dom.make('div', {
				class: ['framed', 'center'],
				textContent: "Press the key you wanna map to " + button
			});
			screen.currentMenu().getElementsByClassName('selected')[0].textContent = keyPromptLabel(null, button);
			var promptKey = function(event) {
				var assignment = buttons.assign(event.key, button);
				session.update({options: {layout: assignment.layoutDiff}});
				screen.clear(elem);
				screen.currentMenu().getElementsByClassName('selected')[0].textContent = keyPromptLabel(event.key, button);
				document.removeEventListener('keydown', promptKey);
				buttons.pop();
				if(assignment.button != undefined) {
					screen.select(buttons.code(assignment.button));
					return setKey(assignment.button)(function () {
						screen.select(buttons.code(button));
					});
				}
				return f();
			};
			screen.show(elem);
			document.addEventListener('keydown', promptKey);
		}
	}

	function setTextSpeed(choices) {
		var config = {
			entries: [],
			cancel: choices.cancel,
			name: choices.name
		};
		for(var i = 0; i < choices.entries.length; i++) {
			config.entries[i] = choices.entries[i];
			if(choices.entries[i].value == textSpeed) {
				config.selected = i;
			}
		}
		ask(config)(function(value) {
			session.update({options: {textSpeed: value}});
			textSpeed = value;
		});
	}
}