/*
 * Copyright (C) 2003-2014 eXo Platform SAS.
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program. If not, see <http://www.gnu.org/licenses/>.
 */
package org.exoplatform.social.rest.impl.activity;

import io.swagger.annotations.Api;
import io.swagger.annotations.ApiOperation;
import io.swagger.annotations.ApiParam;
import io.swagger.annotations.ApiResponse;
import io.swagger.annotations.ApiResponses;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

import javax.annotation.security.RolesAllowed;
import javax.ws.rs.DELETE;
import javax.ws.rs.GET;
import javax.ws.rs.POST;
import javax.ws.rs.PUT;
import javax.ws.rs.Path;
import javax.ws.rs.PathParam;
import javax.ws.rs.Produces;
import javax.ws.rs.QueryParam;
import javax.ws.rs.WebApplicationException;
import javax.ws.rs.core.Context;
import javax.ws.rs.core.MediaType;
import javax.ws.rs.core.Response;
import javax.ws.rs.core.UriInfo;

import org.exoplatform.commons.utils.CommonsUtils;
import org.exoplatform.services.security.ConversationState;
import org.exoplatform.social.common.RealtimeListAccess;
import org.exoplatform.social.core.activity.model.ExoSocialActivity;
import org.exoplatform.social.core.activity.model.ExoSocialActivityImpl;
import org.exoplatform.social.core.identity.model.Identity;
import org.exoplatform.social.core.identity.provider.OrganizationIdentityProvider;
import org.exoplatform.social.core.manager.ActivityManager;
import org.exoplatform.social.core.manager.IdentityManager;
import org.exoplatform.social.core.space.model.Space;
import org.exoplatform.social.core.space.spi.SpaceService;
import org.exoplatform.social.rest.api.ActivityRestResources;
import org.exoplatform.social.rest.api.EntityBuilder;
import org.exoplatform.social.rest.api.RestUtils;
import org.exoplatform.social.rest.entity.ActivityEntity;
import org.exoplatform.social.rest.entity.CollectionEntity;
import org.exoplatform.social.rest.entity.CommentEntity;
import org.exoplatform.social.rest.entity.DataEntity;
import org.exoplatform.social.service.rest.Util;
import org.exoplatform.social.service.rest.api.VersionResources;

@Path(VersionResources.VERSION_ONE + "/social/activities")
@Api(tags = VersionResources.VERSION_ONE + "/social/activities", value = VersionResources.VERSION_ONE + "/social/activities", description = "Managing activities together with comments and likes")
public class ActivityRestResourcesV1 implements ActivityRestResources {
  
  private static final String SPACE_PREFIX = "/spaces/";
  private static final String TYPE = "space";

  
  @GET
  @RolesAllowed("users")
  @ApiOperation(value = "Gets all activities",
                httpMethod = "GET",
                response = Response.class,
                notes = "This returns an activity in the list in the following cases: <br/><ul><li>the authenticated user is the super user, so he can see all the activities</li><li>this is a user activity and the owner of the activity is the authenticated user or one of his connections</li><li>this is a space activity and the authenticated user is a member of the space</li></ul>")
  @ApiResponses(value = { 
    @ApiResponse (code = 200, message = "Request fulfilled"),
    @ApiResponse (code = 500, message = "Internal server error"),
    @ApiResponse (code = 400, message = "Invalid query input") })
  public Response getActivitiesOfCurrentUser(@Context UriInfo uriInfo,
                                             @ApiParam(value = "Offset", required = false, defaultValue = "0") @QueryParam("offset") int offset,
                                             @ApiParam(value = "Limit", required = false, defaultValue = "20") @QueryParam("limit") int limit,
                                             @ApiParam(value = "Returning the number of activities or not", defaultValue = "false") @QueryParam("returnSize") boolean returnSize,
                                             @ApiParam(value = "Asking for a full representation of a specific subresource, ex: comments or likes", required = false) @QueryParam("expand") String expand) throws Exception {
    
    offset = offset > 0 ? offset : RestUtils.getOffset(uriInfo);
    limit = limit > 0 ? limit : RestUtils.getLimit(uriInfo);
    
    String authenticatedUser = ConversationState.getCurrent().getIdentity().getUserId();
    
    Identity currentUser = CommonsUtils.getService(IdentityManager.class).getOrCreateIdentity(OrganizationIdentityProvider.NAME, authenticatedUser, true);

    ActivityManager activityManager = CommonsUtils.getService(ActivityManager.class);
    RealtimeListAccess<ExoSocialActivity> listAccess = activityManager.getActivityFeedWithListAccess(currentUser);
    List<ExoSocialActivity> activities = listAccess.loadAsList(offset, limit);
    
    List<DataEntity> activityEntities = new ArrayList<DataEntity>();
    for (ExoSocialActivity activity : activities) {
      DataEntity as = EntityBuilder.getActivityStream(activity, currentUser);
      if (as == null && !Util.hasMentioned(activity, currentUser.getRemoteId())) continue;
      ActivityEntity activityEntity = EntityBuilder.buildEntityFromActivity(activity, uriInfo.getPath(), expand);
      activityEntity.setActivityStream(as);
      //
      activityEntities.add(activityEntity.getDataEntity()); 
    }
    CollectionEntity collectionActivity = new CollectionEntity(activityEntities, EntityBuilder.ACTIVITIES_TYPE,  offset, limit);
    if(returnSize) {
      collectionActivity.setSize(listAccess.getSize());
    }

    return EntityBuilder.getResponse(collectionActivity, uriInfo, RestUtils.getJsonMediaType(), Response.Status.OK);
  }
  
  @GET
  @Path("{id}")
  @RolesAllowed("users")
  @ApiOperation(value = "Gets a specific activity by id",
                httpMethod = "GET",
                response = Response.class,
				notes = "This returns the activity in the following cases: <br/><ul><li>this is a user activity and the owner of the activity is the authenticated user or one of his connections</li><li>this is a space activity and the authenticated user is a member of the space</li><li>the authenticated user is the super user</li></ul>")
  @ApiResponses(value = { 
    @ApiResponse (code = 200, message = "Request fulfilled"),
    @ApiResponse (code = 500, message = "Internal server error"),
    @ApiResponse (code = 400, message = "Invalid query input") })
  public Response getActivityById(@Context UriInfo uriInfo,
                                  @ApiParam(value = "Activity id", required = true) @PathParam("id") String id,
                                  @ApiParam(value = "Asking for a full representation of a specific subresource, ex: comments or likes", required = false) @QueryParam("expand") String expand) throws Exception {

    String authenticatedUser = ConversationState.getCurrent().getIdentity().getUserId();
    Identity currentUser = CommonsUtils.getService(IdentityManager.class).getOrCreateIdentity(OrganizationIdentityProvider.NAME, authenticatedUser, true);
    
    ActivityManager activityManager = CommonsUtils.getService(ActivityManager.class);
    ExoSocialActivity activity = activityManager.getActivity(id);
    if (activity == null) {
      throw new WebApplicationException(Response.Status.NOT_FOUND);
    }
    
    DataEntity as = EntityBuilder.getActivityStream(activity.isComment() ? activityManager.getParentActivity(activity) : activity, currentUser);
    if (as == null && !Util.hasMentioned(activity, currentUser.getRemoteId())) { //current user doesn't have permission to view activity
      throw new WebApplicationException(Response.Status.UNAUTHORIZED);
    }
    ActivityEntity activityEntity = EntityBuilder.buildEntityFromActivity(activity, uriInfo.getPath(), expand);
    if (!activity.isComment()) {
      activityEntity.setActivityStream(as);
    }

    return EntityBuilder.getResponse(activityEntity.getDataEntity(), uriInfo, RestUtils.getJsonMediaType(), Response.Status.OK);
  }

  @PUT
  @Path("{id}")
  @Produces(MediaType.APPLICATION_JSON)
  @RolesAllowed("users")
  @ApiOperation(value = "Updates a specific activity by id",
                httpMethod = "PUT",
                response = Response.class,
				notes = "This updates the activity in the following cases: <br/><ul><li>this is a user activity and the owner of the activity is the authenticated user</li><li>the authenticated user is the super user</li></ul>")
  @ApiResponses(value = { 
    @ApiResponse (code = 200, message = "Request fulfilled"),
    @ApiResponse (code = 500, message = "Internal server error"),
    @ApiResponse (code = 400, message = "Invalid query input") })
  public Response updateActivityById(@Context UriInfo uriInfo,
                                     @ApiParam(value = "Activity id", required = true) @PathParam("id") String id,
                                     @ApiParam(value = "Asking for a full representation of a specific subresource, ex: comments or likes", required = false) @QueryParam("expand") String expand,
                                     @ApiParam(value = "Activity object to be updated, ex: <br/>{<br/>\"title\" : \"My activity\"<br/>}", required = true) ActivityEntity model) throws Exception {
  
    if (model == null || model.getTitle() == null || model.getTitle().length() == 0) {
      throw new WebApplicationException(Response.Status.BAD_REQUEST);
    }
    //
    String authenticatedUser = ConversationState.getCurrent().getIdentity().getUserId();
    Identity currentUser = CommonsUtils.getService(IdentityManager.class).getOrCreateIdentity(OrganizationIdentityProvider.NAME, authenticatedUser, true);
    
    ActivityManager activityManager = CommonsUtils.getService(ActivityManager.class);
    ExoSocialActivity activity = activityManager.getActivity(id);
    if (activity == null) {
      throw new WebApplicationException(Response.Status.UNAUTHORIZED);
    }
    checkPermissionToModifyActivity(activity, currentUser);
    //update activity's title
    activity.setTitle(model.getTitle());
    activityManager.updateActivity(activity);
    
    DataEntity as = EntityBuilder.getActivityStream(activity, currentUser);
    ActivityEntity activityInfo = EntityBuilder.buildEntityFromActivity(activity, uriInfo.getPath(), expand);
    activityInfo.setActivityStream(as);
    
    return EntityBuilder.getResponse(activityInfo.getDataEntity(), uriInfo, RestUtils.getJsonMediaType(), Response.Status.OK);
  }
  
  @DELETE
  @Path("{id}")
  @RolesAllowed("users")
  @ApiOperation(value = "Deletes a specific activity by id",
                httpMethod = "DELETE",
                response = Response.class,
				notes = "This deletes the activity in the following cases: <br/><ul><li>this is a user activity and the owner of the activity is the authenticated user</li><li>the authenticated user is the super user</li></ul>")
  @ApiResponses(value = { 
    @ApiResponse (code = 200, message = "Request fulfilled"),
    @ApiResponse (code = 500, message = "Internal server error"),
    @ApiResponse (code = 400, message = "Invalid query input") })
  public Response deleteActivityById(@Context UriInfo uriInfo,
                                     @ApiParam(value = "Activity id", required = true) @PathParam("id") String id,
                                     @ApiParam(value = "Asking for a full representation of a specific subresource if any", required = false) @QueryParam("expand") String expand) throws Exception {
    
    String authenticatedUser = ConversationState.getCurrent().getIdentity().getUserId();
    Identity currentUser = CommonsUtils.getService(IdentityManager.class).getOrCreateIdentity(OrganizationIdentityProvider.NAME, authenticatedUser, true);
    
    ActivityManager activityManager = CommonsUtils.getService(ActivityManager.class);
    ExoSocialActivity activity = activityManager.getActivity(id);
    if (activity == null) {
      throw new WebApplicationException(Response.Status.UNAUTHORIZED);
    }
    checkPermissionToModifyActivity(activity, currentUser);
    //
    DataEntity as = EntityBuilder.getActivityStream(activity, currentUser);
    ActivityEntity activityEntity = EntityBuilder.buildEntityFromActivity(activity, uriInfo.getPath(), expand);
    activityEntity.setActivityStream(as);
    //Delete activity
    activityManager.deleteActivity(activity);
    return EntityBuilder.getResponse(activityEntity.getDataEntity(), uriInfo, RestUtils.getJsonMediaType(), Response.Status.OK);
  }
  
  @GET
  @Path("{id}/comments")
  @RolesAllowed("users")
  @ApiOperation(value = "Gets comments of a specific activity",
                httpMethod = "GET",
                response = Response.class,
				notes = "This returns a list of comments if the authenticated user has permissions to see the activity.")
  @ApiResponses(value = { 
    @ApiResponse (code = 200, message = "Request fulfilled"),
    @ApiResponse (code = 500, message = "Internal server error"),
    @ApiResponse (code = 400, message = "Invalid query input") })
  public Response getCommentsOfActivity(@Context UriInfo uriInfo,
                                        @ApiParam(value = "Activity id", required = true) @PathParam("id") String id,
                                        @ApiParam(value = "Offset", required = false, defaultValue = "0") @QueryParam("offset") int offset,
                                        @ApiParam(value = "Limit", required = false, defaultValue = "20") @QueryParam("limit") int limit,
                                        @ApiParam(value = "Returning the number of activities or not", defaultValue = "false") @QueryParam("returnSize") boolean returnSize,
                                        @ApiParam(value = "Asking for a full representation of a specific subresource if any", required = false) @QueryParam("expand") String expand) throws Exception {

    offset = offset > 0 ? offset : RestUtils.getOffset(uriInfo);
    limit = limit > 0 ? limit : RestUtils.getLimit(uriInfo);
    
    String authenticatedUser = ConversationState.getCurrent().getIdentity().getUserId();
    Identity currentUser = CommonsUtils.getService(IdentityManager.class).getOrCreateIdentity(OrganizationIdentityProvider.NAME, authenticatedUser, true);
    
    ActivityManager activityManager = CommonsUtils.getService(ActivityManager.class);
    ExoSocialActivity activity = activityManager.getActivity(id);
    if (activity == null) {
      throw new WebApplicationException(Response.Status.UNAUTHORIZED);
    }
    
    if (EntityBuilder.getActivityStream(activity, currentUser) == null && !Util.hasMentioned(activity, currentUser.getRemoteId())) { //current user doesn't have permission to view activity
      throw new WebApplicationException(Response.Status.UNAUTHORIZED);
    }
    
    List<DataEntity> commentsEntity = new ArrayList<DataEntity>();
    RealtimeListAccess<ExoSocialActivity> listAccess = activityManager.getCommentsWithListAccess(activity, EntityBuilder.expandSubComments(expand));
    List<ExoSocialActivity> comments = listAccess.loadAsList(offset, limit);
    for (ExoSocialActivity comment : comments) {
      CommentEntity commentInfo = EntityBuilder.buildEntityFromComment(comment, uriInfo.getPath(), expand, true);
      commentsEntity.add(commentInfo.getDataEntity());
    }
    
    CollectionEntity collectionComment = new CollectionEntity(commentsEntity, EntityBuilder.COMMENTS_TYPE, offset, limit);    
    if(returnSize) {
      collectionComment.setSize(listAccess.getSize());
    }
    //
    return EntityBuilder.getResponse(collectionComment, uriInfo, RestUtils.getJsonMediaType(), Response.Status.OK);
  }
  
  @POST
  @Path("{id}/comments")
  @Produces(MediaType.APPLICATION_JSON)
  @RolesAllowed("users")
  @ApiOperation(value = "Posts a comment on a specific activity",
                httpMethod = "POST",
                response = Response.class,
				notes = "This posts the comment if the authenticated user has permissions to see the activity.")
  @ApiResponses(value = { 
    @ApiResponse (code = 200, message = "Request fulfilled"),
    @ApiResponse (code = 500, message = "Internal server error"),
    @ApiResponse (code = 400, message = "Invalid query input") })
  public Response postComment(@Context UriInfo uriInfo,
                              @ApiParam(value = "Activity id", required = true) @PathParam("id") String id,
                              @ApiParam(value = "Asking for a full representation of a specific subresource if any", required = false) @QueryParam("expand") String expand,
                              @ApiParam(value = "Comment object to be posted, ex: <br/>{<br/>\"title\" : \"My comment\"<br/>}", required = true) CommentEntity model) throws Exception {
    
    if (model == null || model.getTitle() == null || model.getTitle().length() == 0) {
      throw new WebApplicationException(Response.Status.BAD_REQUEST);
    }
    
    String authenticatedUser = ConversationState.getCurrent().getIdentity().getUserId();
    Identity currentUser = CommonsUtils.getService(IdentityManager.class).getOrCreateIdentity(OrganizationIdentityProvider.NAME, authenticatedUser, true);
    
    ActivityManager activityManager = CommonsUtils.getService(ActivityManager.class);
    ExoSocialActivity activity = activityManager.getActivity(id);
    if (activity == null) {
      throw new WebApplicationException(Response.Status.UNAUTHORIZED);
    }
    
    if (EntityBuilder.getActivityStream(activity, currentUser) == null && !Util.hasMentioned(activity, currentUser.getRemoteId())) { //current user doesn't have permission to view activity
      throw new WebApplicationException(Response.Status.UNAUTHORIZED);
    }
    
    ExoSocialActivity comment = new ExoSocialActivityImpl();
    comment.setBody(model.getBody());
    comment.setTitle(model.getTitle());
    comment.setParentCommentId(model.getParentCommentId());
    comment.setUserId(currentUser.getId());
    activityManager.saveComment(activity, comment);
    
    return EntityBuilder.getResponse(EntityBuilder.buildEntityFromComment(activityManager.getActivity(comment.getId()), uriInfo.getPath(), expand, false), uriInfo, RestUtils.getJsonMediaType(), Response.Status.OK);
  }
  
  @GET
  @Path("{id}/likes")
  @RolesAllowed("users")
  @ApiOperation(value = "Gets likes of a specific activity",
                httpMethod = "GET",
                response = Response.class,
				notes = "This returns a list of likes if the authenticated user has permissions to see the activity.")
  @ApiResponses(value = { 
    @ApiResponse (code = 200, message = "Request fulfilled"),
    @ApiResponse (code = 500, message = "Internal server error"),
    @ApiResponse (code = 400, message = "Invalid query input") })
  public Response getLikesOfActivity(@Context UriInfo uriInfo,
                                     @ApiParam(value = "Activity id", required = true) @PathParam("id") String id,
                                     @ApiParam(value = "Offset", required = false, defaultValue = "0") @QueryParam("offset") int offset,
                                     @ApiParam(value = "Limit", required = false, defaultValue = "20") @QueryParam("limit") int limit,
                                     @ApiParam(value = "Asking for a full representation of a specific subresource if any", required = false) @QueryParam("expand") String expand) throws Exception {
    
    offset = offset > 0 ? offset : RestUtils.getOffset(uriInfo);
    limit = limit > 0 ? limit : RestUtils.getLimit(uriInfo);
    
    String authenticatedUser = ConversationState.getCurrent().getIdentity().getUserId();
    Identity currentUser = CommonsUtils.getService(IdentityManager.class).getOrCreateIdentity(OrganizationIdentityProvider.NAME, authenticatedUser, true);
    
    ActivityManager activityManager = CommonsUtils.getService(ActivityManager.class);
    ExoSocialActivity activity = activityManager.getActivity(id);
    if (activity == null) {
      throw new WebApplicationException(Response.Status.UNAUTHORIZED);
    }
    
    if (EntityBuilder.getActivityStream(activity, currentUser) == null && !Util.hasMentioned(activity, currentUser.getRemoteId())) { //current user doesn't have permission to view activity
      throw new WebApplicationException(Response.Status.UNAUTHORIZED);
    }
    List<DataEntity> likesEntity = EntityBuilder.buildEntityFromLike(activity, uriInfo.getPath(), expand, offset, limit);
    CollectionEntity collectionLike = new CollectionEntity(likesEntity, EntityBuilder.LIKES_TYPE, offset, limit);    
    //
    return EntityBuilder.getResponse(collectionLike, uriInfo, RestUtils.getJsonMediaType(), Response.Status.OK);
  }
  
  @POST
  @Path("{id}/likes")
  @Produces(MediaType.APPLICATION_JSON)
  @RolesAllowed("users")
  @ApiOperation(value = "Adds a like to a specific activity",
                httpMethod = "POST",
                response = Response.class,
				notes = "This adds the like if the authenticated user has permissions to see the activity.")
  @ApiResponses(value = { 
    @ApiResponse (code = 200, message = "Request fulfilled"),
    @ApiResponse (code = 500, message = "Internal server error"),
    @ApiResponse (code = 400, message = "Invalid query input") })
  public Response addLike(@Context UriInfo uriInfo,
                          @ApiParam(value = "Activity id", required = true) @PathParam("id") String id,
                          @ApiParam(value = "Asking for a full representation of a subresource if any", required = false) @QueryParam("expand") String expand) throws Exception {
    
    String authenticatedUser = ConversationState.getCurrent().getIdentity().getUserId();
    Identity currentUser = CommonsUtils.getService(IdentityManager.class).getOrCreateIdentity(OrganizationIdentityProvider.NAME, authenticatedUser, true);
    
    ActivityManager activityManager = CommonsUtils.getService(ActivityManager.class);
    ExoSocialActivity activity = activityManager.getActivity(id);
    if (activity == null) {
      throw new WebApplicationException(Response.Status.UNAUTHORIZED);
    }
    
    if (EntityBuilder.getActivityStream(activity, currentUser) == null && !Util.hasMentioned(activity, currentUser.getRemoteId())) { //current user doesn't have permission to view activity
      throw new WebApplicationException(Response.Status.UNAUTHORIZED);
    }
    List<String> likerIds = new ArrayList<String>(Arrays.asList(activity.getLikeIdentityIds()));
    if (!likerIds.contains(currentUser.getId())) {
      likerIds.add(currentUser.getId());
      String[] identityIds = new String[likerIds.size()];
      activity.setLikeIdentityIds(likerIds.toArray(identityIds));
      activityManager.updateActivity(activity);
    }
    return EntityBuilder.getResponse(EntityBuilder.buildEntityFromActivity(activityManager.getActivity(id), uriInfo.getPath(), expand), uriInfo, RestUtils.getJsonMediaType(), Response.Status.OK);
  }
  
  @GET
  @Path("{id}/likes/{username}")
  @RolesAllowed("users")
  @ApiOperation(value = "Gets a like of a specific user for a given activity",
                httpMethod = "GET",
                response = Response.class,
                notes = "This returns the like if the authenticated user has permissions to see the activity.")
  @ApiResponses(value = { 
    @ApiResponse (code = 200, message = "Request fulfilled"),
    @ApiResponse (code = 500, message = "Internal server error"),
    @ApiResponse (code = 400, message = "Invalid query input") })
  public Response getLikesActivityOfUser(@Context UriInfo uriInfo,
                                         @ApiParam(value = "Activity id", required = true) @PathParam("id") String id,
                                         @ApiParam(value = "User name", required = true) @PathParam("username") String username,
                                         @ApiParam(value = "Asking for a full representation of a specific subresource if any", required = false) @QueryParam("expand") String expand) throws Exception {
    
    Identity userToGetLike = CommonsUtils.getService(IdentityManager.class).getOrCreateIdentity(OrganizationIdentityProvider.NAME, username, true);
    
    ActivityManager activityManager = CommonsUtils.getService(ActivityManager.class);
    ExoSocialActivity activity = activityManager.getActivity(id);
    if (activity == null) {
      throw new WebApplicationException(Response.Status.UNAUTHORIZED);
    }
    List<String> likerIds = Arrays.asList(activity.getLikeIdentityIds());
    List<DataEntity> likesEntity = new ArrayList<DataEntity>();
    if (likerIds.contains(userToGetLike.getId())) {
      likesEntity.add(EntityBuilder.buildEntityProfile(username, uriInfo.getPath(), expand).getDataEntity());
    }

    CollectionEntity collectionLike = new CollectionEntity(likesEntity, EntityBuilder.LIKES_TYPE, 0, 1);
    
    //
    return EntityBuilder.getResponse(collectionLike, uriInfo, RestUtils.getJsonMediaType(), Response.Status.OK);
  }
  
  @DELETE
  @Path("{id}/likes/{username}")
  @RolesAllowed("users")
  @ApiOperation(value = "Deletes a like of a specific user for a given activity",
                httpMethod = "DELETE",
                response = Response.class,
                notes = "This deletes the like if the authenticated user is the given user or the super user.")
  @ApiResponses(value = { 
    @ApiResponse (code = 200, message = "Request fulfilled"),
    @ApiResponse (code = 500, message = "Internal server error"),
    @ApiResponse (code = 400, message = "Invalid query input") })
  public Response deleteLike(@Context UriInfo uriInfo,
                                     @ApiParam(value = "Activity id", required = true) @PathParam("id") String id,
                                     @ApiParam(value = "User name", required = true) @PathParam("username") String username,
                                     @ApiParam(value = "Asking for a full representation of a specific subresource if any", required = false) @QueryParam("expand") String expand) throws Exception {
    
    String authenticatedUser = ConversationState.getCurrent().getIdentity().getUserId();
    if (!authenticatedUser.equals(username)) {
      throw new WebApplicationException(Response.Status.UNAUTHORIZED);
    }
    Identity currentUser = CommonsUtils.getService(IdentityManager.class).getOrCreateIdentity(OrganizationIdentityProvider.NAME, authenticatedUser, true);

    ActivityManager activityManager = CommonsUtils.getService(ActivityManager.class);
    ExoSocialActivity activity = activityManager.getActivity(id);
    if (activity == null
            || (EntityBuilder.getActivityStream(activity, currentUser) == null && !Util.hasMentioned(activity, currentUser.getRemoteId()))) {
      throw new WebApplicationException(Response.Status.UNAUTHORIZED);
    }
    
    List<String> likerIds = new ArrayList<String>(Arrays.asList(activity.getLikeIdentityIds()));
    if (likerIds.contains(currentUser.getId())) {
      likerIds.remove(currentUser.getId());
      String[] identityIds = new String[likerIds.size()];
      activity.setLikeIdentityIds(likerIds.toArray(identityIds));
      activityManager.updateActivity(activity);
    }
    return EntityBuilder.getResponse(EntityBuilder.buildEntityFromActivity(activityManager.getActivity(id), uriInfo.getPath(), expand), uriInfo, RestUtils.getJsonMediaType(), Response.Status.OK);
  }
  private void checkPermissionToModifyActivity(ExoSocialActivity activity, Identity currentUser) {
    if (activity.getActivityStream().getType().toString().equalsIgnoreCase(TYPE)) {
      SpaceService spaceService = CommonsUtils.getService(SpaceService.class);
      String spaceGroupId = SPACE_PREFIX + activity.getActivityStream().getPrettyId();;
      Space space = spaceService.getSpaceByGroupId(spaceGroupId);
      if (space == null) {
        throw new WebApplicationException(Response.Status.UNAUTHORIZED);
      }
      if(!activity.getPosterId().equals(currentUser.getId()) && !spaceService.isManager(space, currentUser.getRemoteId())) {
        throw new WebApplicationException(Response.Status.UNAUTHORIZED);
      }
    }else {
      if(!activity.getPosterId().equals(currentUser.getId())) {
        throw new WebApplicationException(Response.Status.UNAUTHORIZED);
      }
    }
  }
}