let fs = require('fs');
let path = require('path');let babylon = require('babylon'); // Babylon 把源码转换为AST
let t = require('@babel/types'); // @babel-types 替换节点
let traverse = require('@babel/traverse').default; // @babel-traverse 遍历节点
let generator = require('@babel/generator').default; // @babel/generator 生成let ejs = require('ejs'); // js模版class Compiler {// 构造函数constructor(config) {// entry outthis.config = config;// 1、保存入口文件的路径this.entryId;// 2、博阿村所有的模块依赖this.modules = {};// 入口路径this.entry = config.entry;// 工作路径this.root = process.cwd();}// 获取文件源码getSource(modulePath){let content = fs.readFileSync(modulePath,'utf8');return content;}// 解析源码parse(source,parentPath){// AST解析语法树let ast = babylon.parse(source);let dependencies = [];traverse(ast,{CallExpression(p){let node = p.node; // 对应的节点if(node.callee.name === 'require'){node.callee.name = '__webpack_require__';let moduleName = node.arguments[0].value; // 取到的就是模块的引用名字moduleName = moduleName + (path.extname(moduleName)?'':'.js');moduleName = './'+path.join(parentPath,moduleName);dependencies.push(moduleName);node.arguments = [t.stringLiteral(moduleName)];}}});let sourceCode = generator(ast).code;return { sourceCode, dependencies }}// 建立模块buildModule(modulePath,isEntry){// 拿到模块的内容let source = this.getSource(modulePath);// 模块id modulePath modulePath-this.root  =  src/index.jslet moduleName = './'+path.relative(this.root,modulePath);if(isEntry){// 保存入口的名字this.entryId = moduleName;}// 解析需要把source源码进行改造，返回一个依赖列表let {sourceCode,dependencies} = this.parse(source,path.dirname(moduleName));this.modules[moduleName] = sourceCode;dependencies.forEach(// 父模块的加载，递归加载(dep)=>{this.buildModule(path.join(this.root,dep),false)});}emitFile(){// 发射文件// 用数据渲染// 输出路径let main = path.join(this.config.output.path,this.config.output.filename);// 模板的路径let tempateStr = this.getSource(path.join(__dirname,'main.ejs'));let code = ejs.render(tempateStr,{entryId:this.entryId,modules: this.modules});// this.assets = {};// // 路径对应的代码// this.assets[main] = code;// fs.writeFileSync(main,this.assets[main]);fs.writeFileSync(main,code);}run() {// 执行并创建模块依赖关系this.buildModule(path.resolve(this.root, this.entry),true);// 发射一个打包后的文件this.emitFile();}
}module.exports = Compiler;