package ui;

import model.asn1.exceptions.InvalidCAException;
import model.asn1.exceptions.ParseException;
import model.asn1.parsing.BytesReader;
import model.csr.CertificationRequest;
import model.pki.cert.Certificate;
import model.pki.cert.TbsCertificate;

import java.security.NoSuchAlgorithmException;
import java.util.Base64;

/**
 * Manage the private key and CA certificate. It can print the public key, generate CSR, and install CA cert.
 */
public class MgmtScreen implements UIHandler {
    private final JCA session;

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

    /**
     * EFFECTS: Print help
     */
    @Override
    public void help() {
        System.out.print("show\tView the public key and CA certificate\n"
                + "genkey\tGenerate a RSA private key\n"
                + "csr\tGenerate a CSR for a upper-level CA to sign\n"
                + "install\tInstall a CA certificate\n"
                + "exit\tGo to main menu\n"
                + "help\tPrint this message\n");
    }

    /**
     * EFFECTS: Format the public key and CA
     */
    @Override
    public void show() {
        if (session.getCa().getPublicKey() == null) {
            System.out.println("No private key installed");
        } else {
            System.out.println("Public Key (RSA2048):");
            System.out.printf("\tModules:\t\t%s\n", session.getCa().getPublicKey().getModulus().toString(10));
            System.out.printf("\tPublic Exponent:\t%s\n",
                    session.getCa().getPublicKey().getPublicExponent().toString(16));
        }
        if (!session.checkCA(true)) {
            return;
        }
        final TbsCertificate info = session.getCa().getCertificate().getCertificate();
        System.out.printf("Subject:\t%s\n", info.getSubject().toString());
        System.out.printf("Issuer:\t%s\n", info.getIssuer().toString());
        System.out.printf("Not Before:\t%s\n", info.getValidity().getNotBefore().getTimestamp());
        System.out.printf("Not After:\t%s\n", info.getValidity().getNotAfter().getTimestamp());
        System.out.printf("Signature:\t%s\n",
                Base64.getEncoder().encodeToString(Utils.byteToByte(info.getSubjectPublicKeyInfo()
                        .getSubjectPublicKey().getConvertedVal())));
    }

    /**
     * EFFECT: Generate a CSR
     * MODIFIES: session
     */
    private void handleCSR() {
        if (!session.checkCA(false)) {
            return;
        }
        try {
            CertificationRequest req = session.getCa().signCSR();
            System.out.println(Utils.toPEM(req.encodeDER(), "CERTIFICATE REQUEST"));
            session.setUnsaved(true);
        } catch (Throwable e) {
            System.out.println(e.getMessage());
        }
    }

    /**
     * EFFECTS: Handle the 'install' command. Read incoming certificate and validate it.
     * MODIFIES: session
     */
    private void handleInstall() {
        if (!session.checkCA(false)) {
            return;
        }
        try {
            final Byte[] in = session.handleInputPEM("CERTIFICATE");
            final Certificate cert = new Certificate(new BytesReader(in), false);
            session.getCa().installCertificate(cert);
            session.setUnsaved(true);
        } catch (InvalidCAException | ParseException e) {
            System.out.println(e.getMessage());
        }
    }

    /**
     * EFFECTS: Handle the 'genkey' command. Generate a RSA2048 private key.
     * MODIFIES: session
     */
    private void handleGenKey() {
        if (session.getCa().getPublicKey() != null) {
            System.out.println("A private key is already installed.");
        }
        try {
            session.getCa().generateKey();
            session.setUnsaved(true);
        } catch (NoSuchAlgorithmException e) {
            System.out.println(e.getMessage());
        }
    }

    /**
     * EFFECTS: Handle commands.
     */
    @Override
    public void command(String... args) {
        switch (args[0]) {
            case "genkey":
                handleGenKey();
                break;
            case "csr":
                handleCSR();
                break;
            case "install":
                handleInstall();
                break;
            default:
                help();
                break;
        }
    }

    /**
     * EFFECTS: Go to main menu
     */
    @Override
    public Screen exit() {
        return Screen.MAIN;
    }

    /**
     * EFFECTS: return "/ca/ #"
     */
    @Override
    public String getPS1() {
        return "/ca/ #";
    }
}