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import Hint from './hint';
import HintKeyProducer from './hint-key-producer';
const DEFAULT_HINT_CHARSET = 'abcdefghijklmnopqrstuvwxyz';
export default class Follow {
constructor(doc) {
this.doc = doc;
this.hintElements = {};
this.keys = [];
this.onActivatedCallbacks = [];
// TODO activate input elements and push button elements
let links = Follow.getTargetElements(doc);
this.addHints(links);
this.boundKeydown = this.handleKeydown.bind(this);
doc.addEventListener('keydown', this.boundKeydown);
}
addHints(elements) {
let producer = new HintKeyProducer(DEFAULT_HINT_CHARSET);
Array.prototype.forEach.call(elements, (ele) => {
let keys = producer.produce();
let hint = new Hint(ele, keys);
this.hintElements[keys] = hint;
});
}
handleKeydown(e) {
let { keyCode } = e;
if (keyCode === KeyboardEvent.DOM_VK_ESCAPE) {
this.remove();
return;
} else if (keyCode === KeyboardEvent.DOM_VK_ENTER ||
keyCode === KeyboardEvent.DOM_VK_RETURN) {
let chars = Follow.codeChars(this.keys);
this.activate(this.hintElements[chars].target);
return;
} else if (Follow.availableKey(keyCode)) {
this.keys.push(keyCode);
} else if (keyCode === KeyboardEvent.DOM_VK_BACK_SPACE ||
keyCode === KeyboardEvent.DOM_VK_DELETE) {
this.keys.pop();
}
e.stopPropagation();
e.preventDefault();
this.refreshKeys();
}
refreshKeys() {
let chars = Follow.codeChars(this.keys);
let shown = Object.keys(this.hintElements).filter((key) => {
return key.startsWith(chars);
});
let hidden = Object.keys(this.hintElements).filter((key) => {
return !key.startsWith(chars);
});
if (shown.length === 0) {
this.remove();
return;
} else if (shown.length === 1) {
this.remove();
this.activate(this.hintElements[chars].target);
}
shown.forEach((key) => {
this.hintElements[key].show();
});
hidden.forEach((key) => {
this.hintElements[key].hide();
});
}
remove() {
this.doc.removeEventListener('keydown', this.boundKeydown);
Object.keys(this.hintElements).forEach((key) => {
this.hintElements[key].remove();
});
}
activate(element) {
this.onActivatedCallbacks.forEach(f => f(element));
}
onActivated(f) {
this.onActivatedCallbacks.push(f);
}
static availableKey(keyCode) {
return (
KeyboardEvent.DOM_VK_0 <= keyCode && keyCode <= KeyboardEvent.DOM_VK_9 ||
KeyboardEvent.DOM_VK_A <= keyCode && keyCode <= KeyboardEvent.DOM_VK_Z
);
}
static isNumericKey(code) {
return KeyboardEvent.DOM_VK_0 <= code && code <= KeyboardEvent.DOM_VK_9;
}
static isAlphabeticKey(code) {
return KeyboardEvent.DOM_VK_A <= code && code <= KeyboardEvent.DOM_VK_Z;
}
static codeChars(codes) {
const CHARCODE_ZERO = '0'.charCodeAt(0);
const CHARCODE_A = 'a'.charCodeAt(0);
let chars = '';
for (let code of codes) {
if (Follow.isNumericKey(code)) {
chars += String.fromCharCode(
code - KeyboardEvent.DOM_VK_0 + CHARCODE_ZERO);
} else if (Follow.isAlphabeticKey(code)) {
chars += String.fromCharCode(
code - KeyboardEvent.DOM_VK_A + CHARCODE_A);
}
}
return chars;
}
static getTargetElements(doc) {
let all = doc.querySelectorAll('a');
let filtered = Array.prototype.filter.call(all, (e) => {
return Follow.isVisibleElement(e);
});
return filtered;
}
static isVisibleElement(element) {
let style = window.getComputedStyle(element);
if (style.display === 'none') {
return false;
} else if (style.visibility === 'hidden') {
return false;
}
return true;
}
}
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