package net.curisit.securis.utils;

import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.math.BigInteger;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.Date;

import javax.enterprise.context.ApplicationScoped;
import javax.inject.Inject;

import net.curisit.integrity.commons.Utils;
import net.curisit.securis.services.ApiResource;

import org.apache.commons.lang3.StringUtils;
import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
import org.jboss.resteasy.util.Base64;

@ApplicationScoped
public class TokenHelper {

    private static final Logger LOG = LogManager.getLogger(TokenHelper.class);

    /**
     * Period before token expires, set in hours.
     */
    private static int VALID_TOKEN_PERIOD = 24;
    public static final String TOKEN_HEADER_PÀRAM = "X-SECURIS-TOKEN";

    @Inject
    public TokenHelper() {
    }

    private static byte[] seed = "S3Cur15S33dForT0k3nG3n3r@tion".getBytes();

    /**
     * Generate a token encoded in Base64 for user passed as parameter and
     * taking the current moment as token timestamp
     * 
     * @param user
     * @return
     */
    public String generateToken(String user) {

        return generateToken(user, new Date());
    }

    public String generateToken(String user, Date date) {
        try {
            String secret = generateSecret(user, date);
            StringBuffer sb = new StringBuffer();
            sb.append(secret);
            sb.append(' ');
            sb.append(user);
            sb.append(' ');
            sb.append(Utils.toIsoFormat(date));
            return Base64.encodeBytes(sb.toString().getBytes("utf-8"));
        } catch (NoSuchAlgorithmException e) {
            LOG.error("Error generating SHA-256 hash", e);
        } catch (UnsupportedEncodingException e) {
            LOG.error("Error generating SHA-256 hash", e);
        }
        return null;
    }

    private String generateSecret(String user, Date date) throws UnsupportedEncodingException, NoSuchAlgorithmException {
        MessageDigest mDigest = MessageDigest.getInstance("SHA-256");
        mDigest.update(seed, 0, seed.length);
        byte[] userbytes = user.getBytes("utf-8");
        mDigest.update(userbytes, 0, userbytes.length);
        byte[] isodate = Utils.toIsoFormat(date).getBytes();
        mDigest.update(isodate, 0, isodate.length);
        BigInteger i = new BigInteger(1, mDigest.digest());
        String secret = String.format("%1$064x", i);
        return secret;
    }

    /**
     * Check if passed token is still valid, It use to check if token is expired
     * the attribute VALID_TOKEN_PERIOD (in hours)
     * 
     * @param token
     * @return
     */
    public boolean isTokenValid(String token) {
        try {
            String tokenDecoded = new String(Base64.decode(token));
            String[] parts = StringUtils.split(tokenDecoded, ' ');
            if (parts == null || parts.length < 3) {
                return false;
            }
            String secret = parts[0];
            String user = parts[1];
            Date date = Utils.toDateFromIso(parts[2]);
            if (date.getTime() > 0 || !user.equals(ApiResource.API_CLIENT_USERNAME)) {
                if (new Date().after(new Date(date.getTime() + VALID_TOKEN_PERIOD * 60 * 60 * 1000))) {
                    return false;
                }
            } // else: It's a securis-client API call
            String newSecret = generateSecret(user, date);
            return newSecret.equals(secret);
        } catch (IOException e) {
            LOG.error("Error decoding Base64 token", e);
        } catch (NoSuchAlgorithmException e) {
            LOG.error("Error generation secret to compare with", e);
        }
        return false;
    }

    public String extractUserFromToken(String token) {
        try {
            if (token == null) {
                return null;
            }
            String tokenDecoded = new String(Base64.decode(token));
            String[] parts = StringUtils.split(tokenDecoded, ' ');
            if (parts == null || parts.length < 3) {
                return null;
            }
            String user = parts[1];
            return user;
        } catch (IOException e) {
            LOG.error("Error decoding Base64 token", e);
        }
        return null;
    }

    public Date extractDateCreationFromToken(String token) {
        try {
            String tokenDecoded = new String(Base64.decode(token));
            String[] parts = StringUtils.split(tokenDecoded, ' ');
            if (parts == null || parts.length < 3) {
                return null;
            }
            Date date = Utils.toDateFromIso(parts[2]);
            return date;
        } catch (IOException e) {
            LOG.error("Error decoding Base64 token", e);
        }
        return null;
    }

    public static void main(String[] args) throws IOException {
        // client token:
        // OTk3ODRiMzY5NzQ5MWI5NmYyZGQyODRiYjY2ZTU2YzdmMTZjYzM3YTY3N2ExM2M3ODI2MjU5ZTMzOTIyYjUzNSBfY2xpZW50IDE5NzAtMDEtMDFUMDA6NTk6NTkuOTk5KzAxMDA=
        // OTk3ODRiMzY5NzQ5MWI5NmYyZGQyODRiYjY2ZTU2YzdmMTZjYzM3YTY3N2ExM2M3ODI2MjU5ZTMzOTIyYjUzNSBfY2xpZW50IDE5NzAtMDEtMDFUMDA6NTk6NTkuOTk5KzAxMDA=
        String t = new TokenHelper().generateToken("_client", new Date(-1));
        System.out.println("client token: " + t);
        System.out.println("client token: " + new String(Base64.decode(t)));

        System.out.println("is valid client token: " + new TokenHelper().isTokenValid(t));
    }
}