Backend Components

Chatroom Manager

Primarily handled in API endpoint logic, holds one function to return chatroom stats.

return_stats(chatroom_id) - Returns a dict of stats for any given chatroom, ideal for displaying on the map screen.

Database Manager

Handles interfacing with the PSQL database as well as first-boot DB population.

_get_db_config() - Returns the config file for use in connecting to the Chatlus PSQL database.

queryDB(sql_query) - Executes SQL on the database, fetches all results and returns them.

executeOnDB(sql_query) - Executes SQL on the database but returns no results, ideal for POST-style functions.

firstBoot() - Resets the database to the schema depicted in database_create.sql, adds test_inserts.sql as well, and runs databaseSampleGenerator() ensure equal database on first-boot.

seedIfEmpty() - Populates the database with the bundled sample data only when no users exist.

databaseSampleGenerator() - Generates some dummy data for testing purposes.

databaseConnect() - Helper function, returns a connection, only really used by other database_connector functions.

Location Manager

Handles interfacing with Google Maps Tile API, as well as caching results for faster access.

initialiseMapAPI() - Creates a session key based on pre-defined parameters and API key found in /backend/.env file. Returns this key.

returnMap(coordinates,zoom) - Returns image (file) if cached, fetches from Google API if not found.

cacheMapData(coordinates,zoom) - Calls coordsToTile, then calls the Google Maps Tile API to get a tile with the proper parameters.

roundCoordinates(coordinates,zoom) - Coordinates can be rounded when the resulting image would be equal regardless, allowing for more efficient caching.

coordsToTile(coordinates,zoom) - Converts coordinates to Google API Tile Coordinates (their own projection, the code snippet is adapted from their JS example code.)

User Manager

Handles user settings and manages user blocks.

is_block_relationship_present(blocker_id,blocked_id) - Checks if block exists one way. Used in has_block_between_users() to check two-way block.

has_block_between_users(user_a_id,user_b_id) - Runs is_block_relationship_present on both sides to check if a block exists at all.

get_chatroom_type(chatroom_id) - Checks chatroom type - if it exists! Returns none if not.

get_chatroom_member_ids(chatroom_id) - Gets IDs of all members in a chatroom.

chatroom_membership_exists(chatroom_id, user_id) - Check if user is part of chatroom.

get_dm_request(request_id) - returns a dict version of a DM request, used in the API route for accepting or rejecting requests.

is_dm_access_accepted(chatroom_id, sender_id) - Check if DM is allowed to be accessed (does not check for blocks. that is the function below)

is_blocked_dm_message(chatroom_id, sender_id) - Check if DM is blocked from being accessed

set_notifications_enabled(user_id, enabled: bool) - Enables or disables notifications.

get_notifications_enabled(user_id) - Return whether the user has chosen to enable notifications (defaults True).

set_presence_visibility(user_id, visible: bool) - Persist the user’s preference for showing online status to others.

get_presence_visibility(user_id) - Return whether the user has chosen to show their online status (defaults True).

set_user_online(user_id) - Mark user as online by setting account_status to ‘Online’ and updating timestamp.

set_user_offline(user_id) - Mark user as offline by setting account_status to ‘Offline’ and updating timestamp.

is_user_online(user_id) - Return True if user’s account_status is ‘Online’.

is_presence_visible_to(viewer_id, subject_user_id) - Return True if subject’s presence should be visible to viewer.

• Rules: - If subject has show_online_status = false -> not visible

  • If either party has blocked the other -> not visible

  • Otherwise visible

Validation Manager

Validates changes to user profile based on Regex and rules.

validateUsername(username, current_user_id=None) - Validates username based on regex, returns bool

REGEX: ^[A-Za-z0-9_-]{5,25}$

validateAvatarUrl(avatar_url) - Validates url based on regex, returns bool

REGEX: ^(https?://|/|.?./)?.+.(png|jpe?g)$

validateBio(bio) - Validates bio based on conditions, returns bool

Conditions: Must be a string, 150 characters or less, no “<script” or other injection methods.