comunicapiv2/src/helpers/PostsHelper.ts

import { PostKind, PostVisibilityLevel, Post, PostPageKind, PostFile, PostLink, PostAccessLevel } from "../entities/Post";
import { FriendsHelper } from "./FriendsHelper";
import { DatabaseHelper } from "./DatabaseHelper";
import { UserHelper } from "./UserHelper";
import { GroupsHelper } from "./GroupsHelper";
import { GroupMembershipLevels } from "../entities/GroupMember";

/**
 * Posts helper
 * 
 * @author Pierre HUBERT
 */

/**
 * Table name
 */
const TABLE_NAME = "texte";

/**
 * Database mapping
 */
const PostDBTypes : Record<string, PostKind> = {
	"texte": PostKind.POST_KIND_TEXT,
	"image": PostKind.POST_KIND_IMAGE,
	"webpage_link": PostKind.POST_KIND_WEBLINK,
	"pdf": PostKind.POST_KIND_PDF,
	"video": PostKind.POST_KIND_MOVIE,
	"count_down": PostKind.POST_KIND_COUNTDOWN,
	"sondage": PostKind.POST_KIND_SURVEY,
	"youtube": PostKind.POST_KIND_YOUTUBE
}

/**
 * Posts helper
 */
export class PostsHelper {

	/**
	 * Get the posts of a user
	 * 
	 * @param userID The ID of the user making the request
	 * @param targetID The ID of the target user
	 * @param startFrom Start point (0 = none)
	 * @param limit Maximum number of messages to fetch
	 */
	public static async GetUserPosts(userID: number, targetID: number, 
		startFrom: number = 0, limit: number = 10) : Promise<Array<Post>> {
		
		if(limit < 1) 
			throw Error("Limit of post query must be greater or equal to one!");

		
		// Determine max user visibility
		let level : PostVisibilityLevel = PostVisibilityLevel.VISIBILITY_PUBLIC;

		if(userID == targetID)
			level = PostVisibilityLevel.VISIBILITY_USER;
		
		else if(userID > 0 && await FriendsHelper.AreFriend(userID, targetID))
			level = PostVisibilityLevel.VISIBILITY_FRIENDS;
		
		

		// Preprocess conditions
		
		/// ============= PERMISSION CONDITIONS =================
		// Visibility level
		let customWhere = "((niveau_visibilite <= ?) ";
		let customWhereArgs =  [level.toString()];

		// Add user post (if user signed in)
		if(userID > 0) {
			customWhere += " OR (ID_amis = ?) ";
			customWhereArgs.push(userID.toString());
		}

		customWhere += ")"
		/// ============= /PERMISSION CONDITIONS ================



		// ============== START POINT CONDITION =================
		if(startFrom != 0) {
			customWhere += " AND ID <= ?";
			customWhereArgs.push(startFrom.toString());
		}
		// ============== /START POINT CONDITION ================



		// Perform the request
		const entries = await DatabaseHelper.Query({
			table: TABLE_NAME,
			
			// Base conditions
			where: {
				ID_personne: targetID,
				group_id: 0
			},

			customWhere: customWhere,
			customWhereArgs: customWhereArgs,

			order: "ID DESC",
			limit: limit,
		});

		return entries.map((r) => this.DBToPost(r));
	}

	/**
	 * Get the posts of a group
	 * 
	 * @param userID The ID of the user making the request
	 * @param groupID The ID of the target group
	 * @param startFrom Start point. 0 for none
	 */
	public static async GetGroupPosts(userID: number, groupID: number, 
		startFrom: number = 0, limit: number = 10) : Promise<Array<Post>> {

		if(limit < 1)
			throw new Error("Limit (" + limit +") is invalid!");

		// Check membership of the user
		const membership = await GroupsHelper.GetMembershipLevel(groupID, userID);
		const canSeeAllPosts = membership <= GroupMembershipLevels.MEMBER;

		const visibilityLevel = canSeeAllPosts ? PostVisibilityLevel.VISIBILITY_GROUP_MEMBERS : PostVisibilityLevel.VISIBILITY_PUBLIC;
		

		// Prepare request

		// === VISIBILITY RESTRICTION ===
		let customWhere = "(niveau_visibilite <= ?)";
		let customWhereArgs = [visibilityLevel.toString()];
		// == /VISIBILITY RESTRICTION ===


		// === START POINT ===
		if(startFrom != 0) {
			customWhere += " AND ID <= ?";
			customWhereArgs.push(startFrom.toString());
		}
		// == /START POINT ===


		const results = await DatabaseHelper.Query({
			table: TABLE_NAME,
			where: {
				group_id: groupID
			},
			customWhere: customWhere,
			customWhereArgs: customWhereArgs,
			order: "ID DESC",
			limit: limit
		});

		return results.map((r) => this.DBToPost(r));
	}

	/**
	 * Get the access level of a user over a post
	 * 
	 * @param userID Target user ID
	 * @param post Target post
	 */
	public static async GetAccessLevel(userID: number, post: Post) : Promise<PostAccessLevel> {

		// User is the owner of the post
		if(userID == post.userID)
			return PostAccessLevel.FULL_ACCESS;
		
		
		// User page
		if(post.kindPage == PostPageKind.PAGE_KIND_USER) {

			// Post made on user page
			if(post.pageID == userID)
				return PostAccessLevel.INTERMEDIATE_ACCESS;
			
			// Check if the post is private
			if(post.visibilityLevel == PostVisibilityLevel.VISIBILITY_USER)
				return PostAccessLevel.NO_ACCESS;
			
			// In case the post is only for friends
			else if(post.visibilityLevel == PostVisibilityLevel.VISIBILITY_FRIENDS) {
				
				if(userID < 1 /* user not signed in */
					|| !await FriendsHelper.AreFriend(userID, post.pageID) /* not a friend */)
					return PostAccessLevel.NO_ACCESS;
				
				else
					return PostAccessLevel.BASIC_ACCESS;
			}

			// In case of public post
			else if(post.visibilityLevel == PostVisibilityLevel.VISIBILITY_PUBLIC) {
				
				// Check if the user can see the page
				if(await UserHelper.CanSeeUserPage(userID, post.userPageID))
					return PostAccessLevel.BASIC_ACCESS;
				
				// Else no access to the user
				return PostAccessLevel.NO_ACCESS;
			}
		}

		// Group page
		else if(post.kindPage == PostPageKind.PAGE_KIND_GROUP) {
			// TODO : check this code
			
			const accessLevel = await GroupsHelper.GetMembershipLevel(userID, post.groupID);

			// Moderator & admin = intermediate access
			if(accessLevel < GroupMembershipLevels.MEMBER)
				return PostAccessLevel.INTERMEDIATE_ACCESS;
			
			// Members can see all the posts of a group
			if(accessLevel == GroupMembershipLevels.MEMBER)
				return PostAccessLevel.BASIC_ACCESS;
			
			// Now we check if the post is public & the group is open
			if(post.visibilityLevel != PostVisibilityLevel.VISIBILITY_PUBLIC
				|| !await GroupsHelper.IsOpen(post.groupID))
				return PostAccessLevel.NO_ACCESS;
			
			// Public post + open group = basic access
			return PostAccessLevel.BASIC_ACCESS;
		}

		throw Error("GetAccessLevel reached an unimplemented status!");
	}

	/**
	 * Check out whether comments are allowed on a post or not
	 * 
	 * @param post The post to check
	 */
	public static async AllowCommentsOnPost(post: Post) : Promise<boolean> {
		return !post.isUserPage || await UserHelper.AllowComments(post.userPageID);
	}

	/**
	 * Turn a database entry into a row object
	 * 
	 * @param row The database entry
	 */
	private static DBToPost(row: any) : Post {

		const postPageKind = row.group_id == 0 ? PostPageKind.PAGE_KIND_USER : PostPageKind.PAGE_KIND_GROUP;

		const postType = PostDBTypes[row.type];

		return new Post({
			// General info
			id: row.ID,
			userID: row.ID_amis == 0 ? row.ID_personne : row.ID_amis,


			// Kind of target of the page and its ID
			kindPage: postPageKind,
			pageID: postPageKind == PostPageKind.PAGE_KIND_USER ? row.ID_personne : row.group_id,

			// Basic info
			timeCreate: row.time_insert == null ? (new Date(row.date_envoi).getTime() / 1000) : row.time_insert,
			content: row.texte,
			visibilityLevel: row.niveau_visibilite,
			kind: postType,

			// Files specific
			file: row.path == null ? undefined : new PostFile({
				size: Number(row.size),
				type: row.file_type,
				path: row.path
			}),

			// Movies specific
			movieID: row.idvideo == null ? undefined : row.idvideo,

			// Coutdown timer specific
			timeEnd: (row.time_end && row.time_end) > 0 ? row.time_end

				// Coutdown legacy support
				: (row.annee_fin && row.annee_fin > 2010 ? new Date(row.annee_fin + "/" + row.mois_fin + "/" + row.jour_fin).getTime() / 1000 : undefined),

			
			// Weblink - specific
			link: row.url_page == null ? undefined :
				new PostLink({
					url: row.url_page,
					title: row.titre_page,
					description: row.description_page,
					image: row.image_page
				}), 
		});
	}
}