package ui;

import model.asn1.ASN1Object;
import model.asn1.UtcTime;
import model.asn1.exceptions.ParseException;
import model.asn1.parsing.BytesReader;
import model.ca.Template;
import model.csr.CertificationRequest;
import model.pki.cert.Certificate;
import model.pki.crl.Reason;
import model.pki.crl.RevokedCertificate;

import java.io.*;
import java.time.ZoneId;
import java.time.ZonedDateTime;
import java.util.Optional;

public class MainScreen implements UIHandler {
    private final JCA session;

    /**
     * EFFECTS: Init with the parent session.
     */
    public MainScreen(JCA session) {
        this.session = session;
    }

    @Override
    public void help() {
        System.out.print("mgmt\tView and manage the CA certificate\n"
                + "issue\tIssue a certificate\n"
                + "show\tList all issued certificates\n"
                + "export\tExport a certificate to file (DER)\n"
                + "template\tManage templates\n"
                + "revoke\tRevoke a certificate\n"
                + "crl\t\tSign CRL\n"
                + "log\t\tView audit logs\n"
                + "exit\tExit\n"
                + "help\tPrint this message\n");
    }

    @Override
    public void show() {
        session.getCa().getSigned().forEach(cert -> {
            System.out.printf("%s\t%d\t%s\n",
                    cert.getCertificate().getSubject().toString(),
                    cert.getCertificate().getSerialNumber().getLong(),
                    session.getCa().getRevoked().stream().anyMatch(rev -> rev.getSerialNumber().getLong()
                            == cert.getCertificate().getSerialNumber().getLong()) ? "REVOKED" : "OK");
        });
    }

    private CertificationRequest handleIssueInputCSR() {
        try {
            return new CertificationRequest(new BytesReader(session.handleInputPEM("CERTIFICATE REQUEST")),
                    false);
        } catch (ParseException e) {
            System.out.println(e.getMessage());
            return null;
        }
    }

    private void handleIssue(String... args) {
        if (!session.checkCA(true)) {
            return;
        }
        if (args.length <= 1) {
            System.out.println("Usage: issue <template>");
            return;
        }
        Template tmp = session.findTemplate(args[1], true);
        if (tmp == null) {
            System.out.println("Cannot find the template specified");
            return;
        }
        CertificationRequest req = handleIssueInputCSR();
        if (req != null) {
            session.setScreen(Screen.ISSUE, req, new Template(tmp.getName(),
                    true,
                    tmp.getSubject(),
                    tmp.getValidity()));
        }
    }

    /**
     * EFFECTS: Find issued and not revoked certificate by serial. Return null if not found.
     */
    private Certificate findCertBySerial(int serial) {
        Optional<Certificate> c = session.getCa().getSigned()
                .stream()
                .filter(cert -> cert.getCertificate().getSerialNumber().getLong() == serial)
                .findFirst();
        if (c.isEmpty()) {
            System.out.println("Cannot find the certificate specified");
            return null;
        }
        if (session.getCa().getRevoked().stream().anyMatch(rev -> rev.getSerialNumber().getLong() == serial)) {
            System.out.println("The certificate has already been revoked.");
            return null;
        }
        return c.get();
    }

    private void handleRevoke(String... args) {
        if (args.length < 3) {
            System.out.println("Usage: revoke <serial> <reason>");
            return;
        }
        try {
            final Reason reason = Reason.valueOf(args[2]);
            int serial = Integer.parseInt(args[1]);
            Certificate c = findCertBySerial(serial);
            if (c == null) {
                return;
            }
            session.getCa().revoke(new RevokedCertificate(ASN1Object.TAG_SEQUENCE, null,
                    c.getCertificate().getSerialNumber(),
                    new UtcTime(UtcTime.TAG, null, ZonedDateTime.now(ZoneId.of("UTC"))), reason));
            session.log("A certificate has been revoked.");
        } catch (IllegalArgumentException ignored) {
            System.out.println("Illegal serial number or reason");
        }
    }

    private void handleExport(String... args) {
        if (args.length < 3) {
            System.out.println("Usage: export <serial> <path>");
            return;
        }
        try {
            int serial = Integer.parseInt(args[1]);
            Certificate c = findCertBySerial(serial);
            if (c == null) {
                return;
            }
            final File fd = new File(args[2]);
            final OutputStream out = new FileOutputStream(fd);
            out.write(Utils.byteToByte(c.encodeDER()));
            out.close();
        } catch (IllegalArgumentException ignored) {
            System.out.println("Illegal serial number or reason");
        } catch (IOException e) {
            System.out.println(e.getMessage());
        }
    }

    private void handleCRL() {
        if (!session.checkCA(true)) {
            return;
        }
        try {
            System.out.println(Utils.toPEM(session.getCa().signCRL().encodeDER(), "X509 CRL"));
            session.log("A CRL was signed");
        } catch (Throwable e) {
            System.out.println(e.getMessage());
        }
    }

    private void handleLog() {
        session.getLogs().forEach(System.out::println);
    }

    @Override
    public void command(String... args) {
        switch (args[0]) {
            case "mgmt":
                session.setScreen(Screen.MGMT);
                return;
            case "issue":
                handleIssue(args);
                return;
            case "revoke":
                handleRevoke(args);
                return;
            case "export":
                handleExport(args);
                return;
            case "template":
                session.setScreen(Screen.TEMPLATES);
                return;
            case "crl":
                handleCRL();
                return;
            case "log":
                handleLog();
                return;
        }
        help();
    }

    @Override
    public Screen exit() {
        return null;
    }

    @Override
    public String getPS1() {
        return "/ %";
    }
}