const babelParser = require("@babel/parser");
const babelTraverse = require("@babel/traverse").default;

// 执行引擎
class ExecutionEngine {
  constructor() {
    this.globalScope = {}; // 全局作用域
  }

  // 执行语法树
  execute(ast) {
    babelTraverse(ast, {
      enter: (path) => {
        const node = path.node;
        switch (node.type) {
          case 'Program':
            this.executeProgram(node);
            break;
          case 'VariableDeclaration':
            this.executeVariableDeclaration(node);
            break;
          case 'Identifier':
            return this.executeIdentifier(node);
          case 'NumericLiteral':
            return this.executeNumericLiteral(node);
          case 'BinaryExpression':
            return this.executeBinaryExpression(node);
          // 处理其他类型的语法树节点
          // ...
        }
      }
    });
  }

  // 执行 Program 节点
  executeProgram(node) {
    for (const statement of node.body) {
      this.execute(statement);
    }
  }

  // 执行 VariableDeclaration 节点
  executeVariableDeclaration(node) {
    const variableName = node.declarations[0].id.name;
    const variableValue = this.execute(node.declarations[0].init);
    this.globalScope[variableName] = variableValue;
  }

  // 执行 Identifier 节点
  executeIdentifier(node) {
    const variableName = node.name;
    return this.globalScope[variableName];
  }

  // 执行 NumericLiteral 节点
  executeNumericLiteral(node) {
    return node.value;
  }

  // 执行 BinaryExpression 节点
  executeBinaryExpression(node) {
    const leftValue = this.execute(node.left);
    const operator = node.operator;
    const rightValue = this.execute(node.right);

    // 执行二元运算
    switch (operator) {
      case '+':
        return leftValue + rightValue;
      case '-':
        return leftValue - rightValue;
      case '*':
        return leftValue * rightValue;
      case '/':
        return leftValue / rightValue;
      // 处理其他运算符
      // ...
    }
  }
}

// 输入 JavaScript 代码
const code = `
  let x = 5;
  x + 10;
`;

// 使用 Babel 解析代码为 AST
const ast = babelParser.parse(code, {
  sourceType: "module",
});

// 创建执行引擎并执行语法树
const engine = new ExecutionEngine();
engine.execute(ast);
console.log(engine.globalScope['x']); // 输出：5