jlox/src/main/java/com/craftinginterpreters/lox/Lox.java

/* Copyright (C) 2019-2023 Hangzhou HSH Co. Ltd.
 * All right reserved.*/
package com.craftinginterpreters.lox;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.nio.charset.Charset;
import java.nio.file.Files;
import java.nio.file.Path;
import java.util.List;

/**
 * @author simon
 * @date 2023-06-04 15:21
 * @desc
 */
public class Lox {
  private static final Interpreter interpreter = new Interpreter();
  private static boolean hadError = false;
  private static boolean hadRuntimeError = false;

  public static void main(String[] args) throws IOException {
    if (args.length > 1) {
      System.out.println("Usage: jlox [script]");
      System.exit(64);
    } else if (args.length == 1) {
      runFile(args[0]);
    } else {
      runPrompt();
    }
  }

  /**
   * start jlox from the command line and give it a path to a file, it reads the file and executes
   * it
   *
   * @param path 文件路径
   */
  private static void runFile(String path) throws IOException {
    byte[] bytes = Files.readAllBytes(Path.of(path));
    run(new String(bytes, Charset.defaultCharset()));

    // Indicate an error in the exit code.
    if (hadError) System.exit(65);
    if (hadRuntimeError) System.exit(70);
  }

  /** 提示符里面输入 */
  private static void runPrompt() throws IOException {
    InputStreamReader input = new InputStreamReader(System.in);
    BufferedReader reader = new BufferedReader(input);

    for (; ; ) {
      System.out.print("> ");
      String line = reader.readLine();
      if (line == null) break;
      run(line);

      // reset this flag in the interactive loop. If the user makes a mistake,
      // it shouldn’t kill their entire session.
      // hadError = true;
    }
  }

  private static void run(String source) {
    Scanner scanner = new Scanner(source);
    List<Token> tokens = scanner.scanTokens();

    // for (Token token : tokens) {
    //    System.out.println(token);
    // }
    Parser parser = new Parser(tokens);
    List<Stmt> statements = parser.parse();

    // Stop if there was a syntax error.
    if (hadError) return;

    // System.out.println("  ...AST: " + new AstPrinter().print(statements));
    interpreter.interpret(statements);
  }

  /**
   * 错误处理
   *
   * @param line 行号
   * @param message 消息
   */
  static void error(int line, String message) {
    report(line, "", message);
  }

  private static void report(int line, String where, String message) {
    System.err.println("[line " + line + " ] Error " + where + ": " + message);
    hadError = true;
  }

  static void error(Token token, String message) {
    if (token.type == TokenType.EOF) {
      report(token.line, " at end", message);
    } else {
      report(token.line, " at '" + token.lexeme + "'", message);
    }
  }

  public static void runtimeError(RuntimeError error) {
    System.err.println(error.getMessage() + "\n[line " + error.token.line + "]");
    hadRuntimeError = true;
  }
}