import java.io.*;
import java.lang.*;

public class Decode{
    public static void main (String[] args) throws IOException{

            String eingabe = args[0];
            String ausgabe = args[1];
            int key = 0;
            boolean makesSense = false;



            if (ausgabe.endsWith(".txt") == false)
                throw new BadFormatException();

        try{

            while (makesSense == false && key <= 26 ){

                System.out.println("mache neue file");
                File entschlusselt = new File(ausgabe);
                FileOutputStream fos = new FileOutputStream(ausgabe);
                FileInputStream fis = new FileInputStream(eingabe);


                while (fis.available() > 0){
                    fos.write(decodeChar((char)fis.read(), key));
                }


                if (understand(ausgabe) == true){
                    makesSense = true;
                } else {
                    System.out.println("erhöhe key");
                    key = key + 1;
                }

                fis.close();
                fos.close();

                System.out.println("key:" + key);


            }

            if (makesSense == true)
                System.out.println("Schlüssel war: " + key);
            else
                System.out.println("Konnte nicht Entschlüsseln");






        }catch(FileNotFoundException a) {
            System.out.println("Datei nicht gefunden.");
        }catch(ArrayIndexOutOfBoundsException b){
            System.out.println("Falsche Anzahl von Eingaben.");
        }catch(NumberFormatException d){
            System.out.println("Falsche Eingabetypen.");
        }
    }

    private static char decodeChar(char c, int key) {
        key = key * -1;
        int cleanKey = key%26;
        if(cleanKey < 0)
                cleanKey += 26;
        if (c >= 'a' && c<='z') {
        if (c + cleanKey > 'z')
            return (char) (c + cleanKey - 26);
        return (char) (c + cleanKey);

        } else return c;

    }

    private static boolean understand(String ausgabe)throws IOException{

        String[] haufig = {"die","der","und","in","zu","den","das","nicht","von","sie","ist","des","sich","mit","dem","dass","er","es","ein","ich","auf","so","eine","auch","als","an","nach","wie","im","fuer"};

        String s = "";
        int worterAnzahl = 1;
        int checkedWorter = 0;
        char c;

        try{
            FileInputStream fis2 = new FileInputStream(ausgabe);

            while(fis2.available() >0){
                c = (char) fis2.read();
                if (c >= 'a' && c <= 'z' ){
                    s = s + c;
                }
                if (c == ' '){
                    for( int i = 0; i<haufig.length; i++){
                        System.out.println("checke durch das array");
                        if (s.equals(haufig[i])){
                            System.out.println("habe wort erkannt");
                            checkedWorter = checkedWorter + 1;
                            break;
                        }
                    }
                    s = "";
                    System.out.println("erhoehe wortanzahl");
                    worterAnzahl += 1;
                }
            }

            System.out.println("string: " + s);




            fis2.close();

        }catch(FileNotFoundException a) {
            System.out.println("Datei nicht gefunden.");
        }catch(ArrayIndexOutOfBoundsException b){
            System.out.println("Falsche Anzahl von Eingaben.");
        }catch(NumberFormatException d){
            System.out.println("Falsche Eingabetypen.");
        }

        System.out.println("wortzahl: " + worterAnzahl);
        System.out.println("checkedWorter: " + checkedWorter);

        if ( ((checkedWorter*100)/worterAnzahl) >= 29){
            System.out.println("ende understand");
            return true;
        }else{
            System.out.println("ende understand");
            return false;
        }

    }
}