package eu.siacs.conversations.xmpp.jid;

import java.net.IDN;

import gnu.inet.encoding.Stringprep;
import gnu.inet.encoding.StringprepException;

/**
 * The `Jid' class provides an immutable representation of a JID.
 */
public final class Jid {

    private final String localpart;
    private final String domainpart;
    private final String resourcepart;

    // It's much more efficient to store the ful JID as well as the parts instead of figuring them
    // all out every time (since some characters are displayed but aren't used for comparisons).
    private final String displayjid;

    public String getLocalpart() {
        return IDN.toUnicode(localpart);
    }

    public String getDomainpart() {
        return IDN.toUnicode(domainpart);
    }

    public String getResourcepart() {
        return IDN.toUnicode(resourcepart);
    }

    // Special private constructor that doesn't do any checking...
    private Jid(final String localpart, final String domainpart) {
        this.localpart = localpart;
        this.domainpart = domainpart;
        this.resourcepart = "";
        if (localpart.isEmpty()) {
            this.displayjid = domainpart;
        } else {
            this.displayjid = localpart + "@" + domainpart;
        }
    }

    // Note: If introducing a mutable instance variable for some reason, make the constructor
    // private and add a factory method to ensure thread safety and hash-cach-ability (tm).
    public Jid(final String jid) throws InvalidJidException {

        // Hackish Android way to count the number of chars in a string... should work everywhere.
        final int atCount = jid.length() - jid.replace("@", "").length();
        final int slashCount = jid.length() - jid.replace("/", "").length();

        // Throw an error if there's anything obvious wrong with the JID...
        if (jid.isEmpty() || jid.length() > 3071) {
            throw new InvalidJidException(InvalidJidException.INVALID_LENGTH);
        }
        if (atCount > 1 || slashCount > 1 ||
                jid.startsWith("@") || jid.endsWith("@") ||
                jid.startsWith("/") || jid.endsWith("/")) {
            throw new InvalidJidException(InvalidJidException.INVALID_CHARACTER);
        }

        String finaljid;

        final int domainpartStart;
        if (atCount == 1) {
            final int atLoc = jid.indexOf("@");
            final String lp = jid.substring(0, atLoc);
            try {
                localpart = Stringprep.nodeprep(lp);
            } catch (final StringprepException e) {
                throw new InvalidJidException(InvalidJidException.STRINGPREP_FAIL, e);
            }
            if (localpart.isEmpty() || localpart.length() > 1023) {
                throw new InvalidJidException(InvalidJidException.INVALID_PART_LENGTH);
            }
            domainpartStart = atLoc;
            finaljid = lp + "@";
        } else {
            localpart = "";
            finaljid = "";
            domainpartStart = 0;
        }

        final String dp;
        if (slashCount == 1) {
            final int slashLoc = jid.indexOf("/");
            final String rp = jid.substring(slashLoc + 1, jid.length());
            try {
                resourcepart = Stringprep.resourceprep(rp);
            } catch (final StringprepException e) {
                throw new InvalidJidException(InvalidJidException.STRINGPREP_FAIL, e);
            }
            if (resourcepart.isEmpty() || resourcepart.length() > 1023) {
                throw new InvalidJidException(InvalidJidException.INVALID_PART_LENGTH);
            }
            dp = jid.substring(domainpartStart, slashLoc);
            finaljid = finaljid + dp + "/" + rp;
        } else {
            resourcepart = "";
            dp = jid.substring(domainpartStart, jid.length());
            finaljid = finaljid + dp;
        }

        // Remove trailling "." before storing the domain part.
        if (dp.endsWith(".")) {
            domainpart = IDN.toASCII(dp.substring(0, dp.length() - 1), IDN.USE_STD3_ASCII_RULES);
        } else {
            domainpart = IDN.toASCII(dp, IDN.USE_STD3_ASCII_RULES);
        }

        // TODO: Find a proper domain validation library; validate individual parts, separators, etc.
        if (domainpart.isEmpty() || domainpart.length() > 1023) {
            throw new InvalidJidException(InvalidJidException.INVALID_PART_LENGTH);
        }

        this.displayjid = finaljid;
    }

    public Jid getBareJid() {
        return displayjid.contains("/") ? new Jid(localpart, domainpart) : this;
    }

    @Override
    public String toString() {
        return displayjid;
    }

    @Override
    public boolean equals(final Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;

        final Jid jid = (Jid) o;

        // Since we're immutable, the JVM will cache hashcodes, making this very fast.
        // I'm assuming Dalvik does the same sorts of optimizations...
        // Since the hashcode does not include the displayJID it can be used for IDN comparison as
        // well.
        return jid.hashCode() == this.hashCode();

    }

    @Override
    public int hashCode() {
        int result = localpart.hashCode();
        result = 31 * result + domainpart.hashCode();
        result = 31 * result + resourcepart.hashCode();
        return result;
    }
}