import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.HashMap;

/**
 * 一个简单的脚本解释器。
 * 所支持的语法，请参见SimpleParser.java
 *
 * 运行脚本：
 * 在命令行下，键入：java SimpleScript
 * 则进入一个REPL界面。你可以依次敲入命令。比如：
 * > 2+3;
 * > int age = 10;
 * > int b;
 * > b = 10*2;
 * > age = age + b;
 * > exit();  //退出REPL界面。
 *
 * 你还可以使用一个参数 -v，让每次执行脚本的时候，都输出AST和整个计算过程。
 *
 */
public class SimpleScript {
    private HashMap<String, Integer> variables = new HashMap<String, Integer>();
    private static boolean verbose = false;

    /**
     * 实现一个简单的REPL
     * @param args
     */
    public static void main(String[] args) {
        if (args.length > 0 && args[0].equals("-v")) {
            verbose = true;
            System.out.println("verbose mode");
        }
        System.out.println("Simple script language!");

        SimpleParser parser = new SimpleParser();
        SimpleScript script = new SimpleScript();
        BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));

        String scriptText = "";
        System.out.print("\n>");   //提示符

        while (true) {
            try {
                String line = reader.readLine().trim();
                if (line.equals("exit();")) {
                    System.out.println("good bye!");
                    break;
                }
                scriptText += line + "\n";
                if (line.endsWith(";")) {
                    ASTNode tree = parser.parse(scriptText);
                    if (verbose) {
                        parser.dumpAST(tree, "");
                    }

                    script.evaluate(tree, "");

                    System.out.print("\n>");   //提示符

                    scriptText = "";
                }

            } catch (Exception e) {
                // e.printStackTrace();

                System.out.println(e.getLocalizedMessage());
                System.out.print("\n>");   //提示符
                scriptText = "";
            } 
        }
    }


    /**
     * 遍历AST，计算值。
     * @param node
     * @param indent
     * @return
     * @throws Exception
     */
    private Integer evaluate(ASTNode node, String indent) throws Exception {
        Integer result = null;   
        if (verbose) {
            System.out.println(indent + "Calculating: " + node.getType());
        }

        switch (node.getType()) {
        case Programm:
            for (ASTNode child : node.getChildren()) {
                result = evaluate(child, indent);
            }
            break;
        case Additive:
            ASTNode child1 = node.getChildren().get(0);
            Integer value1 = evaluate(child1, indent + "\t");
            ASTNode child2 = node.getChildren().get(1);
            Integer value2 = evaluate(child2, indent + "\t");
            if (node.getText().equals("+")) {
                result = value1 + value2;
            } else {
                result = value1 - value2;
            }
            break;
        case Multiplicative:
            child1 = node.getChildren().get(0);
            value1 = evaluate(child1, indent + "\t");
            child2 = node.getChildren().get(1);
            value2 = evaluate(child2, indent + "\t");
            if (node.getText().equals("*")) {
                result = value1 * value2;
            } else {
                result = value1 / value2;
            }
            break;
        case IntLiteral:
            result = Integer.valueOf(node.getText()).intValue();
            break;
        case Identifier:
            String varName = node.getText();
            if (variables.containsKey(varName)) {
                Integer value = variables.get(varName);
                if (value != null) {
                    result = value.intValue();
                } else {
                    throw new Exception("variable " + varName + " has not been set any value");
                }
            }
            else{
                throw new Exception("unknown variable: " + varName);
            }
            break;
        case AssignmentStmt:
            varName = node.getText();
            if (!variables.containsKey(varName)){
                throw new Exception("unknown variable: " + varName);
            }   //接着执行下面的代码
        case IntDeclaration:
            varName = node.getText();
            Integer varValue = null;
            if (node.getChildren().size() > 0) {
                ASTNode child = node.getChildren().get(0);
                result = evaluate(child, indent + "\t");
                varValue = Integer.valueOf(result);
            }
            variables.put(varName, varValue);
            break;

        default:
        }

        if (verbose) {
            System.out.println(indent + "Result: " + result);
        } else if (indent.equals("")) { // 顶层的语句
            if (node.getType() == ASTNodeType.IntDeclaration || node.getType() == ASTNodeType.AssignmentStmt) {
                System.out.println(node.getText() + ": " + result);
            }else if (node.getType() != ASTNodeType.Programm){
                System.out.println(result);
            }
        }
        return result;
    }

}