import java.sql.*;
import java.util.ArrayList;
import java.util.List;

public class Main {

    private static int[] nestedLoopJoin(List<Professor> profs, List<Vorlesung> vls) {
        int counterMatches = 0;
        int counter = 0;

        for (int i = 0; i < vls.size(); i++) {
            for (int j = 0; j < profs.size(); j++) {
                if (vls.get(i).getGelesenVon() == profs.get(j).getPersNr()) {
                    counterMatches++;
                }
                counter++;
            }
        }

        return new int[]{counter,counterMatches};
    }

    private static int[] mergeJoin(List<Professor> profs, List<Vorlesung> vls) {
        int counterMatches = 0;
        int counter = 0;
        int currentProf = 0;

        for (int i = 0; i < vls.size(); i++) {
            if (vls.get(i).getGelesenVon() == profs.get(currentProf).getPersNr()) {
                counterMatches++;
            } else {
                currentProf++;
            }
            counter++;
        }

        return new int[]{counter,counterMatches};
    }

    /**
     * Führen Sie den kompilierten Code mit
     *   java -cp .:postgresql-9.4.1208.jar Exercise3
     * aus. Passen Sie gegebenenfalls den Pfad zur postgres-jar an.
     */
    public static void main(String[] args) {
        try{
            // setup connection
            Class.forName("org.postgresql.Driver");
            String url = "jdbc:postgresql://localhost/uni?user=postgres&password=Sur.15.Mi";
            Connection conn = DriverManager.getConnection(url);

            // setup lists
            List<Professor> professoren = new ArrayList<Professor>();
            List<Vorlesung> vorlesungen = new ArrayList<Vorlesung>();

            // setup stmt
            Statement stmt = conn.createStatement();

            // Professoren
            ResultSet rsetProf = stmt.executeQuery("select * from Professoren") ;
            while (rsetProf.next()) {
                professoren.add(new Professor(rsetProf));
            }

            // Vorlesungen
            ResultSet rsetVorl = stmt.executeQuery("select * from Vorlesungen ORDER BY gelesenVon") ;
            while (rsetVorl.next()) {
                vorlesungen.add(new Vorlesung(rsetVorl));
            }

            int[] ergNL = nestedLoopJoin(professoren,vorlesungen);
            System.out.println("Vergleiche Nested-Loop-Join: "+ergNL[0]);
            System.out.println("Matches Nested-Loop-Join: "+ergNL[1]);

            int[] ergMerge = mergeJoin(professoren,vorlesungen);
            System.out.println("Vergleiche Merge-Join: "+ergMerge[0]);
            System.out.println("Matches Merge-Join: "+ergMerge[1]);

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

class Professor {
    private String name;
    private int persnr;
    private String rang;
    private int raum;

    public Professor(ResultSet rset) throws SQLException {
        name = rset.getString("name");
        persnr = rset.getInt("persnr");
        rang = rset.getString("rang");
        raum = rset.getInt("raum");
    }

    public String getName() {
        return name;
    }

    public int getPersNr() {
        return persnr;
    }

    public String getRang() {
        return rang;
    }

    public int getRaum() {
        return raum;
    }
}

class Vorlesung {
    private int vorlnr;
    private String titel;
    private int sws;
    private int gelesenVon;

    public Vorlesung(ResultSet rset) throws SQLException {
        vorlnr = rset.getInt("vorlnr");
        titel = rset.getString("titel");
        sws = rset.getInt("sws");
        gelesenVon = rset.getInt("gelesenVon");
    }

    public int getVorlnr() {
        return vorlnr;
    }

    public String getTitel() {
        return titel;
    }

    public int getSws() {
        return sws;
    }

    public int getGelesenVon() {
        return gelesenVon;
    }
}