package org.asamk.signal.manager.api;

import org.asamk.signal.manager.groups.GroupLinkPassword;
import org.signal.core.util.Base64;
import org.signal.libsignal.zkgroup.InvalidInputException;
import org.signal.libsignal.zkgroup.groups.GroupMasterKey;
import org.signal.storageservice.protos.groups.GroupInviteLink;
import org.signal.storageservice.protos.groups.local.DecryptedGroup;

import java.io.IOException;
import java.net.URI;
import java.net.URISyntaxException;

import okio.ByteString;

public final class GroupInviteLinkUrl {

    private static final String GROUP_URL_HOST = "signal.group";
    private static final String GROUP_URL_PREFIX = "https://" + GROUP_URL_HOST + "/#";

    private final GroupMasterKey groupMasterKey;
    private final GroupLinkPassword password;
    private final String url;

    public static GroupInviteLinkUrl forGroup(GroupMasterKey groupMasterKey, DecryptedGroup group) {
        return new GroupInviteLinkUrl(groupMasterKey,
                GroupLinkPassword.fromBytes(group.inviteLinkPassword.toByteArray()));
    }

    /**
     * @return null iff not a group url.
     * @throws InvalidGroupLinkException If group url, but cannot be parsed.
     */
    public static GroupInviteLinkUrl fromUri(String urlString) throws InvalidGroupLinkException, UnknownGroupLinkVersionException {
        var uri = getGroupUrl(urlString);

        if (uri == null) {
            return null;
        }

        try {
            if (!"/".equals(uri.getPath()) && !uri.getPath().isEmpty()) {
                throw new InvalidGroupLinkException("No path was expected in uri");
            }

            var encoding = uri.getFragment();

            if (encoding == null || encoding.isEmpty()) {
                throw new InvalidGroupLinkException("No reference was in the uri");
            }

            var bytes = Base64.decode(encoding);
            GroupInviteLink groupInviteLink = GroupInviteLink.ADAPTER.decode(bytes);

            if (groupInviteLink.v1Contents != null) {
                var groupInviteLinkContentsV1 = groupInviteLink.v1Contents;
                var groupMasterKey = new GroupMasterKey(groupInviteLinkContentsV1.groupMasterKey.toByteArray());
                var password = GroupLinkPassword.fromBytes(groupInviteLinkContentsV1.inviteLinkPassword.toByteArray());

                return new GroupInviteLinkUrl(groupMasterKey, password);
            } else {
                throw new UnknownGroupLinkVersionException("Url contains no known group link content");
            }
        } catch (InvalidInputException | IOException e) {
            throw new InvalidGroupLinkException(e);
        }
    }

    /**
     * @return {@link URI} if the host name matches.
     */
    private static URI getGroupUrl(String urlString) {
        try {
            var url = new URI(urlString);

            if (!"https".equalsIgnoreCase(url.getScheme()) && !"sgnl".equalsIgnoreCase(url.getScheme())) {
                return null;
            }

            return GROUP_URL_HOST.equalsIgnoreCase(url.getHost()) ? url : null;
        } catch (URISyntaxException e) {
            return null;
        }
    }

    private GroupInviteLinkUrl(GroupMasterKey groupMasterKey, GroupLinkPassword password) {
        this.groupMasterKey = groupMasterKey;
        this.password = password;
        this.url = createUrl(groupMasterKey, password);
    }

    private static String createUrl(GroupMasterKey groupMasterKey, GroupLinkPassword password) {
        var groupInviteLink = new GroupInviteLink.Builder().v1Contents(new GroupInviteLink.GroupInviteLinkContentsV1.Builder().groupMasterKey(
                        ByteString.of(groupMasterKey.serialize()))
                .inviteLinkPassword(ByteString.of(password.serialize()))
                .build()).build();

        var encoding = Base64.encodeUrlSafeWithoutPadding(groupInviteLink.encode());

        return GROUP_URL_PREFIX + encoding;
    }

    public String getUrl() {
        return url;
    }

    public GroupMasterKey getGroupMasterKey() {
        return groupMasterKey;
    }

    public GroupLinkPassword getPassword() {
        return password;
    }

    public static final class InvalidGroupLinkException extends Exception {

        public InvalidGroupLinkException(String message) {
            super(message);
        }

        public InvalidGroupLinkException(Throwable cause) {
            super(cause);
        }
    }

    public static final class UnknownGroupLinkVersionException extends Exception {

        public UnknownGroupLinkVersionException(String message) {
            super(message);
        }
    }
}