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

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

/**
 * @author simon
 * @date 2023-06-05 13:19
 * @desc
 */
public class AstPrinter implements Expr.Visitor<String> {
    String print(Expr expr) {
        return expr.accept(this);
    }

    @Override
    public String visitAssignExpr(Expr.Assign expr) {
        return parenthesize("assign", expr.value);
    }

    @Override
    public String visitBinaryExpr(Expr.Binary expr) {
        return parenthesize(expr.operator.lexeme, expr.left, expr.right);
    }

    @Override
    public String visitCallExpr(Expr.Call expr) {
        return null;
    }

    @Override
    public String visitGroupingExpr(Expr.Grouping expr) {
        return parenthesize("group", expr.expression);
    }

    @Override
    public String visitLiteralExpr(Expr.Literal expr) {
        if (expr.value == null) return "nil";
        return expr.value.toString();
    }

    @Override
    public String visitLogicalExpr(Expr.Logical expr) {
        return parenthesize(null, expr.left)
                + " "
                + expr.operator.lexeme.toUpperCase()
                + " "
                + parenthesize(null, expr.right);
    }

    @Override
    public String visitUnaryExpr(Expr.Unary expr) {
        return parenthesize(expr.operator.lexeme, expr.right);
    }

    @Override
    public String visitVariableExpr(Expr.Variable expr) {
        return parenthesize(expr.name.lexeme);
    }

    private String parenthesize(String name, Expr... exprs) {
        StringBuilder builder = new StringBuilder();
        builder.append("(").append(name == null ? "" : name);
        for (Expr expr : exprs) {
            builder.append(" ");
            builder.append(expr.accept(this));
        }
        builder.append(")");
        return builder.toString();
    }
}