package interpreter;

import environment.RuntimeEnvironment;
import error.LispException;
import parser.LispParser;
import sexpression.SExpression;

import java.io.InputStream;
import java.util.List;

import static function.builtin.EVAL.eval;

public class LispInterpreter {

    protected RuntimeEnvironment environment;
    private LispParser parser;

    public LispInterpreter() {
        this.environment = RuntimeEnvironment.INSTANCE;
    }

    public void interpretLanguageFiles(List<LanguageFile> languageFiles) {
        for (LanguageFile file : languageFiles) {
            LispParser languageParser = new LispParser(file.getInputStream(), file.getName());

            while (!languageParser.isEof())
                eval(languageParser.nextSExpression());
        }
    }

    public void interpret() {
        createParser();

        for (prompt(); !parser.isEof(); prompt())
            evaluateAndPrintNextSExpression();

        applyFinishingTouches();
    }

    private void createParser() {
        parser = new LispParser(environment.getInput(), environment.getInputName());
    }

    protected void prompt() {}

    protected void evaluateAndPrintNextSExpression() {
        try {
            evaluateAndPrintNextSExpressionWithException();
        } catch (LispException e) {
            environment.getErrorManager().handle(e);
        }
    }

    private void evaluateAndPrintNextSExpressionWithException() {
        printSExpression(evaluateNextSExpression());
    }

    protected SExpression evaluateNextSExpression() {
        SExpression sExpression = parser.nextSExpression();

        return eval(sExpression);
    }

    protected void printSExpression(SExpression sExpression) {
        String result = environment.decorateValueOutput(String.valueOf(sExpression));
        environment.getOutput().println(result);
        environment.getOutput().flush();
    }

    protected void applyFinishingTouches() {
        environment.getOutput().println();
        environment.getOutput().flush();
    }

    public static class LanguageFile {

        private InputStream inputStream;
        private String name;

        public LanguageFile(InputStream inputStream, String name) {
            this.inputStream = inputStream;
            this.name = "lang:" + name;
        }

        public InputStream getInputStream() {
            return inputStream;
        }

        public String getName() {
            return name;
        }
    }
}