package backtype.storm.security.auth.authorizer;

import java.lang.reflect.Field;
import java.security.Principal;
import java.util.Collection;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;

import backtype.storm.Config;
import backtype.storm.security.auth.ReqContext;
import backtype.storm.security.auth.authorizer.DRPCAuthorizerBase;
import backtype.storm.security.auth.AuthUtils;
import backtype.storm.security.auth.IPrincipalToLocal;
import backtype.storm.utils.Utils;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class DRPCSimpleACLAuthorizer extends DRPCAuthorizerBase {
    public static Logger LOG = LoggerFactory.getLogger(DRPCSimpleACLAuthorizer.class);

    public static final String CLIENT_USERS_KEY = "client.users";
    public static final String INVOCATION_USER_KEY = "invocation.user";
    public static final String FUNCTION_KEY = "function.name";

    protected String _aclFileName = "";
    protected IPrincipalToLocal _ptol;
    protected boolean _permitWhenMissingFunctionEntry = false;

    protected class AclFunctionEntry {
        final public Set<String> clientUsers;
        final public String invocationUser;

        public AclFunctionEntry(Collection<String> clientUsers, String invocationUser) {
            this.clientUsers = (clientUsers != null) ? new HashSet<String>(clientUsers) : new HashSet<String>();
            this.invocationUser = invocationUser;
        }
    }

    private volatile Map<String, AclFunctionEntry> _acl = null;
    private volatile long _lastUpdate = 0;

    protected Map<String, AclFunctionEntry> readAclFromConfig() {
        // Thread safety is mostly around _acl. If _acl needs to be updated it is changed atomically
        // More then one thread may be trying to update it at a time, but that is OK, because the
        // change is atomic
        long now = System.currentTimeMillis();
        if ((now - 5000) > _lastUpdate || _acl == null) {
            Map<String, AclFunctionEntry> acl = new HashMap<String, AclFunctionEntry>();
            Map conf = Utils.findAndReadConfigFile(_aclFileName);
            if (conf.containsKey(Config.DRPC_AUTHORIZER_ACL)) {
                Map<String, Map<String, ?>> confAcl = (Map<String, Map<String, ?>>) conf.get(Config.DRPC_AUTHORIZER_ACL);

                for (String function : confAcl.keySet()) {
                    Map<String, ?> val = confAcl.get(function);
                    Collection<String> clientUsers = val.containsKey(CLIENT_USERS_KEY) ? (Collection<String>) val.get(CLIENT_USERS_KEY) : null;
                    String invocationUser = val.containsKey(INVOCATION_USER_KEY) ? (String) val.get(INVOCATION_USER_KEY) : null;
                    acl.put(function, new AclFunctionEntry(clientUsers, invocationUser));
                }
            } else if (!_permitWhenMissingFunctionEntry) {
                LOG.warn("Requiring explicit ACL entries, but none given. " + "Therefore, all operiations will be denied.");
            }
            _acl = acl;
            _lastUpdate = System.currentTimeMillis();
        }
        return _acl;
    }

    @Override
    public void prepare(Map conf) {
        Boolean isStrict = (Boolean) conf.get(Config.DRPC_AUTHORIZER_ACL_STRICT);
        _permitWhenMissingFunctionEntry = (isStrict != null && !isStrict) ? true : false;
        _aclFileName = (String) conf.get(Config.DRPC_AUTHORIZER_ACL_FILENAME);
        _ptol = AuthUtils.GetPrincipalToLocalPlugin(conf);
    }

    private String getUserFromContext(ReqContext context) {
        if (context != null) {
            Principal princ = context.principal();
            if (princ != null) {
                return princ.getName();
            }
        }
        return null;
    }

    private String getLocalUserFromContext(ReqContext context) {
        if (context != null) {
            return _ptol.toLocal(context.principal());
        }
        return null;
    }

    protected boolean permitClientOrInvocationRequest(ReqContext context, Map params, String fieldName) {
        Map<String, AclFunctionEntry> acl = readAclFromConfig();
        String function = (String) params.get(FUNCTION_KEY);
        if (function != null && !function.isEmpty()) {
            AclFunctionEntry entry = acl.get(function);
            if (entry == null && _permitWhenMissingFunctionEntry) {
                return true;
            }
            if (entry != null) {
                Object value;
                try {
                    Field field = AclFunctionEntry.class.getDeclaredField(fieldName);
                    value = field.get(entry);
                } catch (Exception ex) {
                    LOG.warn("Caught Exception while accessing ACL", ex);
                    return false;
                }
                String principal = getUserFromContext(context);
                String user = getLocalUserFromContext(context);
                if (value == null) {
                    LOG.warn("Configuration for function '" + function + "' is " + "invalid: it should have both an invocation user "
                            + "and a list of client users defined.");
                } else if (value instanceof Set && (((Set<String>) value).contains(principal) || ((Set<String>) value).contains(user))) {
                    return true;
                } else if (value instanceof String && (value.equals(principal) || value.equals(user))) {
                    return true;
                }
            }
        }
        return false;
    }

    @Override
    protected boolean permitClientRequest(ReqContext context, String operation, Map params) {
        return permitClientOrInvocationRequest(context, params, "clientUsers");
    }

    @Override
    protected boolean permitInvocationRequest(ReqContext context, String operation, Map params) {
        return permitClientOrInvocationRequest(context, params, "invocationUser");
    }
}