labeling node backend

[itang06]

What?

Implemented backend for label node feature. It includes a new database table to store event labels and 2 new api endpoints:

• POST /api/sessions/:session_id/time-label - stores a batch of timestamped event labels after a session ends

• GET /api/sessions/:session_id/eeg-data?start=...&end=... - retrieves EEG data rows within a given time range for a specific session

• this branch also includes a cherry-picked commit from a teammate that adds session_id to the eeg_data table (required to filter EEG data by session). That commit brought an export endpoint along with it (not part of this feature, just a side effect of the cherry-pick)

Additional endpoint added to get time labels:

• GET /api/sessions/:session_id/time-label?start=...&end=... - retrieves time labels within a given time range

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How?

Migration (add_time_labels.sql): creates time_labels table with id, session_id, timestamp, and label

Models added (models.rs):

• TimeLabel (db output + used for GET response)
• NewTimeLabel (api input)
• EegDataRow (db output)
• EegDataQuery (query parameters)

DB functions (db.rs):

• added insert_time_labels() for batch insert
• get_eeg_data_by_range() to filter by session_id and time range, ordered by time
• added get_time_labels_by_range() to filter time labels by session_id and time range

handlers + routes (main.rs):
3 new handler functions

• store_time_labels (POST) returns 201
• get_eeg_data (GET) returns JSON array of EEG rows
• get_time_labels (GET) returns JSON array of TimeLabel rows

Import cleanup:

• Brought get_eeg_data_by_range and get_earliest_eeg_timestamp into scope via use statement, instead of using shared_logic::db:: path

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Testing

• cargo build passed with no new warnings other than pre-existing ones

Postman Testing:

1. POST /api/sessions - created session with id of 2

2. POST /api/sessions/2/time-label - 201 response created, batch of labels stored

3. GET /api/sessions/2/time-label?start=...&end=... - returns the inserted labels filtered by time range

4. GET /api/sessions/2/eeg-data?start=...&end=... - returns eeg rows filtered by session and time range

• note: eeg data was inserted directly via psql to verify this endpoint returned data correctly since the websocket server wasn't running

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Notes

the task board specified using timestamp as a foreign key to eeg_data but we stored it as a value instead, since a hard foreign key would require exact timestamp matches but it won't actually always match. The label timestamp is used as a reference point for the GET endpoint's time range query, which would better match the actual use case

[github-actions]

✅ PR approval conditions satisfied (1 lead OR 2 team members approved).
[Last checked: 2026-03-05T02:20:40.017Z]

[HeisSteve]

Also add a Get for the time-label as well, and similar to the get_eeg_data, allow the frontend to pass in a range

[HeisSteve]

not a big issue, use add a use shared_logic::db::{get_earliest_eeg_timestamp,}; at the top so we don't need the shared_logic::db:: in shared_logic::db::get_eeg_data_by_range