/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.storm.blobstore;

import org.apache.storm.Config;
import org.apache.storm.generated.AccessControl;
import org.apache.storm.generated.AccessControlType;
import org.apache.storm.generated.AuthorizationException;
import org.apache.storm.generated.SettableBlobMeta;
import org.apache.storm.security.auth.AuthUtils;
import org.apache.storm.security.auth.IPrincipalToLocal;
import org.apache.storm.security.auth.NimbusPrincipal;
import org.apache.commons.lang.StringUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import javax.security.auth.Subject;
import java.security.Principal;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;

/**
 * Provides common handling of acls for Blobstores.
 * Also contains some static utility functions related to Blobstores.
 */
public class BlobStoreAclHandler {
    public static final Logger LOG = LoggerFactory.getLogger(BlobStoreAclHandler.class);
    private final IPrincipalToLocal _ptol;

    public static final int READ = 0x01;
    public static final int WRITE = 0x02;
    public static final int ADMIN = 0x04;
    public static final List<AccessControl> WORLD_EVERYTHING =
            Arrays.asList(new AccessControl(AccessControlType.OTHER, READ | WRITE | ADMIN));
    public static final List<AccessControl> DEFAULT = new ArrayList<AccessControl>();
    private Set<String> _supervisors;
    private Set<String> _admins;
    private boolean doAclValidation;

    public BlobStoreAclHandler(Map conf) {
        _ptol = AuthUtils.GetPrincipalToLocalPlugin(conf);
        _supervisors = new HashSet<String>();
        _admins = new HashSet<String>();
        if (conf.containsKey(Config.NIMBUS_SUPERVISOR_USERS)) {
            _supervisors.addAll((List<String>)conf.get(Config.NIMBUS_SUPERVISOR_USERS));
        }
        if (conf.containsKey(Config.NIMBUS_ADMINS)) {
            _admins.addAll((List<String>)conf.get(Config.NIMBUS_ADMINS));
        }
        if (conf.containsKey(Config.STORM_BLOBSTORE_ACL_VALIDATION_ENABLED)) {
           doAclValidation = (boolean)conf.get(Config.STORM_BLOBSTORE_ACL_VALIDATION_ENABLED);
        }
    }

    private static AccessControlType parseACLType(String type) {
        if ("other".equalsIgnoreCase(type) || "o".equalsIgnoreCase(type)) {
            return AccessControlType.OTHER;
        } else if ("user".equalsIgnoreCase(type) || "u".equalsIgnoreCase(type)) {
            return AccessControlType.USER;
        }
        throw new IllegalArgumentException(type+" is not a valid access control type");
    }

    private static int parseAccess(String access) {
        int ret = 0;
        for (char c: access.toCharArray()) {
            if ('r' == c) {
                ret = ret | READ;
            } else if ('w' == c) {
                ret = ret | WRITE;
            } else if ('a' == c) {
                ret = ret | ADMIN;
            } else if ('-' == c) {
                //ignored
            } else {
                throw new IllegalArgumentException("");
            }
        }
        return ret;
    }

    public static AccessControl parseAccessControl(String str) {
        String[] parts = str.split(":");
        String type = "other";
        String name = "";
        String access = "-";
        if (parts.length > 3) {
            throw new IllegalArgumentException("Don't know how to parse "+str+" into an ACL value");
        } else if (parts.length == 1) {
            type = "other";
            name = "";
            access = parts[0];
        } else if (parts.length == 2) {
            type = "user";
            name = parts[0];
            access = parts[1];
        } else if (parts.length == 3) {
            type = parts[0];
            name = parts[1];
            access = parts[2];
        }
        AccessControl ret = new AccessControl();
        ret.set_type(parseACLType(type));
        ret.set_name(name);
        ret.set_access(parseAccess(access));
        return ret;
    }

    private static String accessToString(int access) {
        StringBuilder ret = new StringBuilder();
        ret.append(((access & READ) > 0) ? "r" : "-");
        ret.append(((access & WRITE) > 0) ? "w" : "-");
        ret.append(((access & ADMIN) > 0) ? "a" : "-");
        return ret.toString();
    }

    public static String accessControlToString(AccessControl ac) {
        StringBuilder ret = new StringBuilder();
        switch(ac.get_type()) {
            case OTHER:
                ret.append("o");
                break;
            case USER:
                ret.append("u");
                break;
            default:
                throw new IllegalArgumentException("Don't know what a type of "+ac.get_type()+" means ");
        }
        ret.append(":");
        if (ac.is_set_name()) {
            ret.append(ac.get_name());
        }
        ret.append(":");
        ret.append(accessToString(ac.get_access()));
        return ret.toString();
    }

    public static void validateSettableACLs(String key, List<AccessControl> acls) throws AuthorizationException {
        Set<String> aclUsers = new HashSet<>();
        List<String> duplicateUsers = new ArrayList<>();
        for (AccessControl acl : acls) {
            String aclUser = acl.get_name();
            if (!StringUtils.isEmpty(aclUser) && !aclUsers.add(aclUser)) {
                LOG.error("'{}' user can't appear more than once in the ACLs", aclUser);
                duplicateUsers.add(aclUser);
            }
        }
        if (duplicateUsers.size() > 0) {
            String errorMessage  = "user " + Arrays.toString(duplicateUsers.toArray())
                    + " can't appear more than once in the ACLs for key [" + key +"].";
            throw new AuthorizationException(errorMessage);
        }
    }

    private Set<String> constructUserFromPrincipals(Subject who) {
        Set<String> user = new HashSet<String>();
        if (who != null) {
            for (Principal p : who.getPrincipals()) {
                user.add(_ptol.toLocal(p));
            }
        }
        return user;
    }

    private boolean isAdmin(Subject who) {
        Set<String> user = constructUserFromPrincipals(who);
        for (String u : user) {
            if (_admins.contains(u)) {
                return true;
            }
        }
        return false;
    }

    private boolean isReadOperation(int operation) {
        if (operation == 1) {
            return true;
        }
        return false;
    }

    private boolean isSupervisor(Subject who, int operation) {
        Set<String> user = constructUserFromPrincipals(who);
        if (isReadOperation(operation)) {
            for (String u : user) {
                if (_supervisors.contains(u)) {
                    return true;
                }
            }
        }
        return false;
    }

    private boolean isNimbus(Subject who) {
        Set<Principal> principals;
        boolean isNimbusInstance = false;
        if (who != null) {
            principals = who.getPrincipals();
            for (Principal principal : principals) {
                if (principal instanceof NimbusPrincipal) {
                    isNimbusInstance = true;
                }
            }
        }
        return isNimbusInstance;
    }

    public boolean checkForValidUsers(Subject who, int mask) {
        return isNimbus(who) || isAdmin(who) || isSupervisor(who,mask);
    }

    /**
     * The user should be able to see the metadata if and only if they have any of READ, WRITE, or ADMIN
     */
    public void validateUserCanReadMeta(List<AccessControl> acl, Subject who, String key) throws AuthorizationException {
        hasAnyPermissions(acl, (READ|WRITE|ADMIN), who, key);
    }

    /**
     * Validates if the user has any of the permissions
     * mentioned in the mask.
     * @param acl ACL for the key.
     * @param mask mask holds the cumulative value of
     * READ = 1, WRITE = 2 or ADMIN = 4 permissions.
     * mask = 1 implies READ privilege.
     * mask = 5 implies READ and ADMIN privileges.
     * @param who Is the user against whom the permissions
     * are validated for a key using the ACL and the mask.
     * @param key Key used to identify the blob.
     * @throws AuthorizationException
     */
    public void hasAnyPermissions(List<AccessControl> acl, int mask, Subject who, String key) throws AuthorizationException {
        if (!doAclValidation) {
            return;
        }
        Set<String> user = constructUserFromPrincipals(who);
        LOG.debug("user {}", user);
        if (checkForValidUsers(who, mask)) {
            return;
        }
        for (AccessControl ac : acl) {
            int allowed = getAllowed(ac, user);
            LOG.debug(" user: {} allowed: {} key: {}", user, allowed, key);
            if ((allowed & mask) > 0) {
                return;
            }
        }
        throw new AuthorizationException(
                user + " does not have access to " + key);
    }

    /**
     * Validates if the user has at least the set of permissions
     * mentioned in the mask.
     * @param acl ACL for the key.
     * @param mask mask holds the cumulative value of
     * READ = 1, WRITE = 2 or ADMIN = 4 permissions.
     * mask = 1 implies READ privilege.
     * mask = 5 implies READ and ADMIN privileges.
     * @param who Is the user against whom the permissions
     * are validated for a key using the ACL and the mask.
     * @param key Key used to identify the blob.
     * @throws AuthorizationException
     */
    public void hasPermissions(List<AccessControl> acl, int mask, Subject who, String key) throws AuthorizationException {
        if (!doAclValidation) {
            return;
        }
        Set<String> user = constructUserFromPrincipals(who);
        LOG.debug("user {}", user);
        if (checkForValidUsers(who, mask)) {
            return;
        }
        for (AccessControl ac : acl) {
            int allowed = getAllowed(ac, user);
            mask = ~allowed & mask;
            LOG.debug(" user: {} allowed: {} disallowed: {} key: {}", user, allowed, mask, key);
        }
        if (mask == 0) {
            return;
        }
        throw new AuthorizationException(
                user + " does not have " + namedPerms(mask) + " access to " + key);
    }

    public void normalizeSettableBlobMeta(String key, SettableBlobMeta meta, Subject who, int opMask) {
        meta.set_acl(normalizeSettableACLs(key, meta.get_acl(), who, opMask));
    }

    private String namedPerms(int mask) {
        StringBuilder b = new StringBuilder();
        b.append("[");
        if ((mask & READ) > 0) {
            b.append("READ ");
        }
        if ((mask & WRITE) > 0) {
            b.append("WRITE ");
        }
        if ((mask & ADMIN) > 0) {
            b.append("ADMIN ");
        }
        b.append("]");
        return b.toString();
    }

    private int getAllowed(AccessControl ac, Set<String> users) {
        switch (ac.get_type()) {
            case OTHER:
                return ac.get_access();
            case USER:
                if (users.contains(ac.get_name())) {
                    return ac.get_access();
                }
                return 0;
            default:
                return 0;
        }
    }

    private List<AccessControl> removeBadACLs(List<AccessControl> accessControls) {
        List<AccessControl> resultAcl = new ArrayList<AccessControl>();
        for (AccessControl control : accessControls) {
            if(control.get_type().equals(AccessControlType.OTHER) && (control.get_access() == 0 )) {
                LOG.debug("Removing invalid blobstore world ACL " +
                        BlobStoreAclHandler.accessControlToString(control));
                continue;
            }
            resultAcl.add(control);
        }
        return resultAcl;
    }

    private final List<AccessControl> normalizeSettableACLs(String key, List<AccessControl> acls, Subject who,
                                                            int opMask) {
        List<AccessControl> cleanAcls = removeBadACLs(acls);
        Set<String> userNames = getUserNamesFromSubject(who);
        for (String user : userNames) {
            fixACLsForUser(cleanAcls, user, opMask);
        }
        fixEmptyNameACLForUsers(cleanAcls, userNames, opMask);
        if ((who == null || userNames.isEmpty()) && !worldEverything(acls)) {
            cleanAcls.addAll(BlobStoreAclHandler.WORLD_EVERYTHING);
            LOG.debug("Access Control for key {} is normalized to world everything {}", key, cleanAcls);
            if (!acls.isEmpty())
                LOG.warn("Access control for blob with key {} is normalized to WORLD_EVERYTHING", key);
        }
        return cleanAcls;
    }

    private boolean worldEverything(List<AccessControl> acls) {
        boolean isWorldEverything = false;
        for (AccessControl acl : acls) {
            if (acl.get_type() == AccessControlType.OTHER && acl.get_access() == (READ|WRITE|ADMIN)) {
                isWorldEverything = true;
                break;
            }
        }
        return isWorldEverything;
    }

    private void fixACLsForUser(List<AccessControl> acls, String user, int mask) {
        boolean foundUserACL = false;
        List<AccessControl> emptyUserACLs = new ArrayList<>();

        for (AccessControl control : acls) {
            if (control.get_type() == AccessControlType.USER) {
                if (!control.is_set_name()) {
                    emptyUserACLs.add(control);
                } else if (control.get_name().equals(user)) {
                    int currentAccess = control.get_access();
                    if ((currentAccess & mask) != mask) {
                        control.set_access(currentAccess | mask);
                    }
                    foundUserACL = true;
                }
            }
        }

        // if ACLs have two user ACLs for empty user and principal, discard empty user ACL
        if (!emptyUserACLs.isEmpty() && foundUserACL) {
            acls.removeAll(emptyUserACLs);
        }

        // add default user ACL when only empty user ACL is not present
        if (emptyUserACLs.isEmpty() && !foundUserACL) {
            AccessControl userACL = new AccessControl();
            userACL.set_type(AccessControlType.USER);
            userACL.set_name(user);
            userACL.set_access(mask);
            acls.add(userACL);
        }
    }

    private void fixEmptyNameACLForUsers(List<AccessControl> acls, Set<String> users, int mask) {
        List<AccessControl> aclsToAdd = new ArrayList<>();
        List<AccessControl> aclsToRemove = new ArrayList<>();

        for (AccessControl control : acls) {
            if (control.get_type() == AccessControlType.USER && !control.is_set_name()) {
                aclsToRemove.add(control);

                int currentAccess = control.get_access();
                if ((currentAccess & mask) != mask) {
                    control.set_access(currentAccess | mask);
                }

                for (String user : users) {
                    AccessControl copiedControl = new AccessControl(control);
                    copiedControl.set_name(user);
                    aclsToAdd.add(copiedControl);
                }
            }
        }

        acls.removeAll(aclsToRemove);
        acls.addAll(aclsToAdd);
    }

    private Set<String> getUserNamesFromSubject(Subject who) {
        Set<String> user = new HashSet<String>();
        if (who != null) {
            for(Principal p: who.getPrincipals()) {
                user.add(_ptol.toLocal(p));
            }
        }
        return user;
    }
}