# Personalised user segments (Phase-I)

## Overview
Merchant Segment Service (MSS) is responsible for
1. Storing user segments (merchant, segment-definition)->customer_ids.
2. While creating a promotion: If the merchant requests to target specific audience for that promo, MPS will talk with MSS to sync segments for that merchant, for that segment definition with CP/segmentation-service.
3. MSS will also keep a counter against each customer_id to keep track of how many segments have been synced for that customer

## DE <-> MSS
We have decided to setup an actor for this. We also need to setup an internal endpoint on MSS to write/update segments to. We can split this part in two cards

1. Setup an "internal" endpoint on MSS to write/update segments
1. Create up the DB schema for storing segments
3. Setup Lambda actor, Kafka topic
1. Create a kafka topic
2. Setup actor to read from the topic
3. post segments to endpoint from #1 above

## Merchant Segment Service
APIs:
1. Internet endpoint to sync up user segments
2. Sync-segments:
MPS will call this endpoint while creating a promotion to sync segments
1. MPS will call with <merchant_id, segment_type, promo.end_date>
2. MSS will fetch the customer_ids for given segment, filter out those customer_ids which have more segments synced that set threshold. For the remaining ones, call CP/segment-service to create/update segments.
3. Update user_id thresholds

NOTE: CP is yet to setup segment expiry field on create endpoint. We need them to do it in this iteration only. Expiry date would be promo.end_date

## Merchant Promotions Service

2. Sync segments if target_audience is set on create-request
1. After request validation, call MSS with <merchant_id, segment_type, end_date>
2. On success: share the segment info with markdown
3. On failure: we return error response

NOTE: Food/markdown is yet to expose segment field on create-campaign endpoint

## Stories
1. Setup proto, kafka topic
2. Setup Elixir kafka consumer (segments->db)
3. API to sync segments (MPS->MSS)
5. Maintain thresholds
6. Add validations to the API
7. Update create-promo endpoint to accept target-audience
8. Call MSS to sync segments