var library = {
  book1: {
    name: "",
  },
  book2: "",
};
observe(library);
library.book1.name = "vue權(quán)威指南"; // 屬性name已經(jīng)被監(jiān)聽(tīng)了，現(xiàn)在值為：“vue權(quán)威指南”
library.book2 = "沒(méi)有此書(shū)籍"; // 屬性book2已經(jīng)被監(jiān)聽(tīng)了，現(xiàn)在值為：“沒(méi)有此書(shū)籍”

// 為數(shù)據(jù)添加檢測(cè)
function defineReactive(data, key, val) {
  observe(val); // 遞歸遍歷所有子屬性
  let dep = new Dep(); // 新建一個(gè)dep
  Object.defineProperty(data, key, {
    enumerable: true,
    configurable: true,
    get: function() {
      if (Dep.target) {
        // 判斷是否需要添加訂閱者，僅第一次需要添加，之后就不用了，詳細(xì)看Watcher函數(shù)
        dep.addSub(Dep.target); // 添加一個(gè)訂閱者
      }
      return val;
    },
    set: function(newVal) {
      if (val == newVal) return; // 如果值未發(fā)生改變就return
      val = newVal;
      console.log(
        "屬性" + key + "已經(jīng)被監(jiān)聽(tīng)了，現(xiàn)在值為：“" + newVal.toString() + "”"
      );
      dep.notify(); // 如果數(shù)據(jù)發(fā)生變化，就通知所有的訂閱者。
    },
  });
}

// 監(jiān)聽(tīng)對(duì)象的所有屬性
function observe(data) {
  if (!data || typeof data !== "object") {
    return; // 如果不是對(duì)象就return
  }
  Object.keys(data).forEach(function(key) {
    defineReactive(data, key, data[key]);
  });
}
// Dep 負(fù)責(zé)收集訂閱者，當(dāng)屬性發(fā)生變化時(shí)，觸發(fā)更新函數(shù)。
function Dep() {
  this.subs = {};
}
Dep.prototype = {
  addSub: function(sub) {
    this.subs.push(sub);
  },
  notify: function() {
    this.subs.forEach((sub) => sub.update());
  },
};

function Watcher(vm, exp, cb) {
  this.cb = cb;
  this.vm = vm;
  this.exp = exp;
  this.value = this.get(); // 將自己添加到訂閱器的操作
}

Watcher.prototype = {
  update: function() {
    this.run();
  },
  run: function() {
    var value = this.vm.data[this.exp];
    var oldVal = this.value;
    if (value !== oldVal) {
      this.value = value;
      this.cb.call(this.vm, value, oldVal);
    }
  },
  get: function() {
    Dep.target = this; // 緩存自己，用于判斷是否添加watcher。
    var value = this.vm.data[this.exp]; // 強(qiáng)制執(zhí)行監(jiān)聽(tīng)器里的get函數(shù)
    Dep.target = null; // 釋放自己
    return value;
  },
};

// MyVue
proxyKeys(key) {
    var self = this;
    Object.defineProperty(this, key, {
        enumerable: false,
        configurable: true,
        get: function proxyGetter() {
            return self.data[key];
        },
        set: function proxySetter(newVal) {
            self.data[key] = newVal;
        }
    });
}

function nodeToFragment(el) {
  var fragment = document.createDocumentFragment();
  var child = el.firstChild;
  while (child) {
    // 將Dom元素移入fragment中
    fragment.appendChild(child);
    child = el.firstChild;
  }
  return fragment;
}

function compileElement (el) {
    var childNodes = el.childNodes;
    var self = this;
    [].slice.call(childNodes).forEach(function(node) {
        var reg = /\{\{(.*)\}\}/; // 匹配{{xx}}
        var text = node.textContent;
        if (self.isTextNode(node) && reg.test(text)) {  // 判斷是否是符合這種形式{{}}的指令
            self.compileText(node, reg.exec(text)[1]);
        }
        if (node.childNodes && node.childNodes.length) {
            self.compileElement(node);  // 繼續(xù)遞歸遍歷子節(jié)點(diǎn)
        }
    });
},
function compileText (node, exp) {
    var self = this;
    var initText = this.vm[exp];
    updateText(node, initText);  // 將初始化的數(shù)據(jù)初始化到視圖中
    new Watcher(this.vm, exp, function (value) {  // 生成訂閱器并綁定更新函數(shù)
        self.updateText(node, value);
    });
},
function updateText (node, value) {
    node.textContent = typeof value == 'undefined' ? '' : value;
}

function compile(node) {
  var nodeAttrs = node.attributes;
  var self = this;
  Array.prototype.forEach.call(nodeAttrs, function(attr) {
    var attrName = attr.name;
    if (isDirective(attrName)) {
      var exp = attr.value;
      var dir = attrName.substring(2);
      if (isEventDirective(dir)) {
        // 事件指令
        self.compileEvent(node, self.vm, exp, dir);
      } else {
        // v-model 指令
        self.compileModel(node, self.vm, exp, dir);
      }
      node.removeAttribute(attrName); // 解析完畢，移除屬性
    }
  });
}
// v-指令解析
function isDirective(attr) {
  return attr.indexOf("v-") == 0;
}
// on: 指令解析
function isEventDirective(dir) {
  return dir.indexOf("on:") === 0;
}

class MyVue {
  constructor(options) {
    var self = this;
    this.data = options.data;
    this.methods = options.methods;
    Object.keys(this.data).forEach(function(key) {
      self.proxyKeys(key);
    });
    observe(this.data);
    new Compile(options.el, this);
    options.mounted.call(this); // 所有事情處理好后執(zhí)行mounted函數(shù)
  }
  proxyKeys(key) {
    // 將this.data屬性代理到this上
    var self = this;
    Object.defineProperty(this, key, {
      enumerable: false,
      configurable: true,
      get: function getter() {
        return self.data[key];
      },
      set: function setter(newVal) {
        self.data[key] = newVal;
      },
    });
  }
}