NexGate Location Service — Implementation Spec

For the implementer (Claude Code): read this whole file before writing code. Follow the existing conventions of the NexGate codebase (package layout, REST path style, auth/security, error format, ID type, DTO style, tests). Where this spec and the codebase conventions differ on style, follow the codebase. Where they differ on behaviour/rules, follow this spec. Keep it simple — no approval workflows, no extra services, no over-engineering.

0. Summary

The Location Service is a module inside the existing Spring Boot backend (not a microservice). It owns everything about where things are:

Shipping (providers, quotes, tracking) is out of scope — it will be built later on top of this service.

0.1 Where the Location Service is used across NexGate

It is the shared foundation for every feature that cares about where. Build the two core calls — resolve(pin) → ward/district/region and areaMatch(areaSet, pin-or-area) → bool — as reusable functions, because all of these call them:

Everything above reuses the same ward data and the same two functions — no new map work per feature. Only the two core calls are in scope now; the rest are listed so the API is designed to serve them.

1. Principles (non-negotiable)

  1. The pin (lat/lng) is the truth. Every saved location has a pin confirmed by the user on a map. No location is ever saved without coordinates.
  2. We take location only for a reason. No location request on app open, no background tracking for buyers or shops, no movement trails. Store only the pin the user confirmed.
  3. Hierarchy comes from our own data, not Google. Region/district/ward are computed on the backend from NBS ward shapes. Google is used only on the client (map display, place search, live label while placing the pin). The backend never calls Google and never stores Google text.
  4. Orders keep their own frozen copy of addresses. Editing or deleting a saved address never changes past orders.
  5. Simple. One module, plain SQL for spatial work, no Flyway, no version tracking, no JPA entity for the ward table.

2. Architecture

┌──────────────────────── CLIENTS (Android · iOS · Web) ────────────────────────┐
│  Pin screen: Google Map + Places search + live Google label (display only)    │
│  Sends: confirmed lat/lng + user text (landmark/note/phone/label)             │
└───────────────────────────────────────┬───────────────────────────────────────┘
                                        │ REST
┌───────────────────────────────────────▼───────────────────────────────────────┐
│                     NexGate Spring Boot backend                                │
│                                                                                │
│  ┌──────────────────────── location module ───────────────────────────────┐  │
│  │  WardResolver        pin → ward/district/region (PostGIS query)         │  │
│  │  LocationValidator   coverage, nearest-ward snap, device-distance check │  │
│  │  UserAddressService  saved addresses, default, duplicates, limits       │  │
│  │  RecentLocationSvc   last unsaved pins (max 5, 60 days)                 │  │
│  │  ShopLocationService one mandatory location per shop                    │  │
│  │  SnapshotFactory     frozen AddressSnapshot for orders                  │  │
│  │  WardDataSeeder      creates tables/indexes + loads ward file once      │  │
│  └────────────────────────────────┬────────────────────────────────────────┘  │
│                                   │ (internal Java calls)                      │
│  ┌────────────── orders / checkout ─────────┐   ┌──── shipping (FUTURE) ────┐ │
│  │ stores AddressSnapshot on each order      │──►│ reads snapshots only      │ │
│  └───────────────────────────────────────────┘   └───────────────────────────┘ │
└───────────────────────────────────────┬───────────────────────────────────────┘
                                        │ JDBC
┌───────────────────────────────────────▼───────────────────────────────────────┐
│  PostgreSQL + PostGIS (Docker image postgis/postgis)                           │
│  tz_wards · shop_locations · user_addresses · recent_locations                 │
└────────────────────────────────────────────────────────────────────────────────┘

   Ward data file (NOT in Git):  tz_wards_2022.geojson.gz  → mounted read-only into app container

Who decides what

              📍 confirmed pin (lat, lng)
             /                          \
   NBS ward shapes (ours, backend)     Google (client only)
   region, district, ward, codes        "Mlimani City, Sinza Mori…"
        │                                    │
     STORED (truth)                    shown on pin screen only, never sent/stored

3. Ward data

3.1 Source

3.2 File format (what the seeder reads)

{
  "type": "FeatureCollection",
  "crs": { "type": "name", "properties": { "name": "urn:ogc:def:crs:OGC:1.3:CRS84" } },
  "features": [
    {
      "type": "Feature",
      "properties": {
        "ward_id": 1, "nbs_code": "010111011",
        "reg_code": "01", "reg_name": "Dodoma",
        "dist_code": "01", "dist_name": "Kondoa",
        "counc_code": "11", "counc_name": "Halmashauri ya Wilaya ya Kondoa",
        "ward_code": "011", "ward_name": "Changaa"
      },
      "geometry": { "type": "Polygon", "coordinates": [[[35.6782, -4.736511], ...]] }
    }
  ]
}

3.3 Data facts the code must respect

Fact Consequence
Coordinates are [longitude, latitude] (GeoJSON order) ST_MakePoint(lng, lat) — longitude first. Most common bug.
Geometry is a mix of Polygon and MultiPolygon Always store with ST_Multi(...) into a MultiPolygon column.
ward_code alone is NOT unique; even nbs_code repeats for 5 wards (NBS data issue) ward_id (1..4344) is the primary key. nbs_code is informational, not unique.
Shapes stop at shorelines (sea, Lake Victoria, etc.) Pins on beaches/jetties may fall outside every ward → nearest-ward fallback (§6).
31 regions, ~4,344 wards. Dar es Salaam has 5 councils (Ilala, Kinondoni, Temeke, Ubungo, Kigamboni) Expected counts for sanity tests.

3.4 District & region come from the ward rows — no separate files

There is no separate district or region boundary table. Every ward row already carries its council, district and region names and codes, so a single ST_Contains lookup returns all levels at once:

pin → ward (Kariakoo) → already has dist_name=Ilala, reg_name=Dar es Salaam, codes included

-- district outlines (view or materialized view, optional)
SELECT reg_code, reg_name, dist_code, dist_name, ST_Union(geom) AS geom
FROM tz_wards GROUP BY reg_code, reg_name, dist_code, dist_name;

-- region outlines
SELECT reg_code, reg_name, ST_Union(geom) AS geom
FROM tz_wards GROUP BY reg_code, reg_name;

Use counc_code as well if councils (halmashauri) matter for coverage; the ward rows carry it too.

4. Infrastructure

4.1 Docker

services:
  db:
    image: postgis/postgis:16-3.4        # match current PG major version
  app:
    volumes:
      - /opt/nexgate/geo:/app/geo:ro      # host folder holding tz_wards_2022.geojson.gz
    environment:
      GEO_WARDS_FILE: /app/geo/tz_wards_2022.geojson.gz

4.2 Config

# path to .geojson or .geojson.gz ; empty/missing → seeder logs WARN and skips
geo.wards-file=${GEO_WARDS_FILE:./data/geo/tz_wards_2022.geojson.gz}

4.3 No Flyway, no version tracking

Schema for this module is created by the WardDataSeeder at startup using idempotent SQL (IF NOT EXISTS). It runs after Hibernate initialises (use ApplicationRunner or ApplicationReadyEvent).

5. Database

5.1 Entity relationships

erDiagram
    TZ_WARDS ||--o{ SHOP_LOCATIONS : "resolved to"
    TZ_WARDS ||--o{ USER_ADDRESSES : "resolved to"
    TZ_WARDS ||--o{ RECENT_LOCATIONS : "resolved to"
    USERS ||--o{ USER_ADDRESSES : owns
    USERS ||--o{ RECENT_LOCATIONS : has
    SHOPS ||--|| SHOP_LOCATIONS : "has exactly one"
    ORDERS ||--|| ADDRESS_SNAPSHOT : "pickup (frozen copy)"
    ORDERS ||--|| ADDRESS_SNAPSHOT : "drop-off (frozen copy)"

Addresses store ward_id and copies of the names/codes (denormalised) so reads never need a join and display stays stable.

5.2 tz_wards (created + filled by seeder)

CREATE EXTENSION IF NOT EXISTS postgis;

CREATE TABLE IF NOT EXISTS tz_wards (
    ward_id     INTEGER PRIMARY KEY,
    nbs_code    VARCHAR(16)  NOT NULL,
    reg_code    VARCHAR(4)   NOT NULL,
    reg_name    VARCHAR(100) NOT NULL,
    dist_code   VARCHAR(4)   NOT NULL,
    dist_name   VARCHAR(100) NOT NULL,
    counc_code  VARCHAR(4)   NOT NULL,
    counc_name  VARCHAR(200) NOT NULL,
    ward_code   VARCHAR(8)   NOT NULL,
    ward_name   VARCHAR(100) NOT NULL,
    geom        geometry(MultiPolygon, 4326) NOT NULL
);
CREATE INDEX IF NOT EXISTS idx_tz_wards_geom ON tz_wards USING GIST (geom);
CREATE INDEX IF NOT EXISTS idx_tz_wards_names ON tz_wards (reg_name, dist_name, ward_name);

5.3 Location tables (logical schema — use project ID type & audit conventions)

shop_locations — exactly one per shop

column type rule
id project ID type PK
shop_id FK → shops unique
lat, lng double required, rounded to 6 decimals
ward_id int resolved by backend
reg_name, dist_name, ward_name, nbs_code text copied from ward
match_type enum CONTAINED / NEAREST from resolver
landmark text (≤ 300) required ("Near Shekilango stop, above Vodashop, 1st floor")
building text (≤ 100) optional ("Shop 12")
pickup_phone text required, E.164 (+255…)
official_address text (≤ 100) optional (Anwani za Makazi)
photo_url text optional (shop front photo, uses existing media upload)
created_at, updated_at timestamp

user_addresses — buyer's saved addresses (0..10 per user)

column type rule
id project ID type PK
user_id FK → users
label_type enum HOME / WORK / OTHER HOME and WORK max one each per user
custom_label text (≤ 40) required when OTHER ("Mama's place")
lat, lng double required, 6 decimals
ward_id, reg_name, dist_name, ward_name, nbs_code, match_type resolved by backend
note text (≤ 300) optional note for rider ("Black gate, call on arrival")
receiver_name text defaults to user's name
receiver_phone text defaults to user's phone, E.164
is_default boolean at most one true per user
last_used_at timestamp updated when used in an order
created_at, updated_at timestamp

recent_locations — unsaved delivery pins (max 5 per user, expire after 60 days)

column type rule
id project ID type PK
user_id FK → users
lat, lng, ward_id, reg_name, dist_name, ward_name, match_type as above
note, receiver_name, receiver_phone as used in that order
last_used_at timestamp

Indexes created by seeder after Hibernate (idempotent):

CREATE UNIQUE INDEX IF NOT EXISTS ux_shop_locations_shop ON shop_locations (shop_id);
CREATE INDEX IF NOT EXISTS idx_shop_locations_geog ON shop_locations
    USING GIST ((ST_SetSRID(ST_MakePoint(lng, lat), 4326)::geography));   -- for future "near me"
CREATE INDEX IF NOT EXISTS idx_user_addresses_user ON user_addresses (user_id);
CREATE UNIQUE INDEX IF NOT EXISTS ux_user_addresses_default ON user_addresses (user_id) WHERE is_default;
CREATE UNIQUE INDEX IF NOT EXISTS ux_user_addresses_home ON user_addresses (user_id) WHERE label_type = 'HOME';
CREATE UNIQUE INDEX IF NOT EXISTS ux_user_addresses_work ON user_addresses (user_id) WHERE label_type = 'WORK';
CREATE INDEX IF NOT EXISTS idx_recent_locations_user ON recent_locations (user_id, last_used_at DESC);

(If the project creates these tables itself via its own mechanism, keep the indexes in the seeder anyway.)

5.4 AddressSnapshot (frozen copy stored on orders)

Not a table owned by this module. The orders module stores it (e.g. a jsonb column pickup_snapshot / dropoff_snapshot, or embedded columns — follow project convention). Immutable once stored.

{
  "lat": -6.774512, "lng": 39.241871,
  "wardId": 1131, "nbsCode": "070113062",
  "regionName": "Dar es Salaam", "districtName": "Kinondoni", "wardName": "Kijitonyama",
  "matchType": "CONTAINED",
  "label": "Home",                         // null if unsaved
  "landmarkOrNote": "Black gate, call on arrival",
  "building": null,
  "contactName": "Kibuti", "contactPhone": "+2557XXXXXXXX",
  "sourceType": "USER_ADDRESS",            // USER_ADDRESS | NEW_PIN | SHOP_LOCATION
  "sourceId": "…",                         // id of saved address/shop location, null for NEW_PIN
  "capturedAt": "2026-10-08T12:30:00Z"
}

6. Pin resolution (core algorithm)

 input: lat, lng
   │
   ├─ basic checks: lat ∈ [-90,90], lng ∈ [-180,180], not (0,0) ── fail → 400 INVALID_COORDINATES
   │
   ├─ round to 6 decimals
   │
   ├─ Query A: ward whose shape CONTAINS the point
   │     found → matchType = CONTAINED, distanceM = 0  ───────────────────────► return ward
   │
   ├─ Query B: nearest ward within 500 m (shoreline, beach, jetty, border gaps)
   │     found → matchType = NEAREST, distanceM = n  ─────────────────────────► return ward
   │
   └─ nothing → OUTSIDE_COVERAGE (sea, lake, outside Tanzania)

-- Query A (uses GIST index)
SELECT ward_id, nbs_code, reg_name, dist_name, counc_name, ward_name
FROM tz_wards
WHERE ST_Contains(geom, ST_SetSRID(ST_MakePoint(:lng, :lat), 4326))
LIMIT 1;

-- Query B (only if A returns nothing)
SELECT ward_id, nbs_code, reg_name, dist_name, counc_name, ward_name,
       ST_Distance(geom::geography, ST_SetSRID(ST_MakePoint(:lng, :lat), 4326)::geography) AS distance_m
FROM tz_wards
WHERE ST_DWithin(geom::geography, ST_SetSRID(ST_MakePoint(:lng, :lat), 4326)::geography, 500)
ORDER BY distance_m
LIMIT 1;

Point exactly on a border → whichever ward Query A returns is fine. Constant: NEAREST_WARD_MAX_METERS = 500.

6.1 Validation rules

Check Applies to Result
Invalid coordinates all block INVALID_COORDINATES
No ward within 500 m all block OUTSIDE_COVERAGE ("We don't deliver here yet")
Matched by NEAREST all allow, matchType=NEAREST (info only)
Pin > 1 km from device position (client sends optional deviceLat/deviceLng) shop only allow, return warning FAR_FROM_DEVICE with distance; client asks "Your pin is 3.2 km from where you are. Is this your shop?"
Saved address within 50 m of another saved address of same user buyer save 409 NEAR_DUPLICATE with the existing address; client asks "This looks like 🏠 Home. Use it?"; client may resend with allowNearDuplicate=true
More than 10 saved addresses buyer save block ADDRESS_LIMIT_REACHED
Second HOME or WORK buyer save/edit block LABEL_ALREADY_USED

Client-only checks (not backend): GPS accuracy circle, minimum zoom before confirm, satellite toggle.

7. Business rules

7.1 Shop location

7.2 Buyer addresses

7.3 Recent locations

7.4 Orders / snapshots

7.5 Account deletion

Deletes all user_addresses and recent_locations of that user. Order snapshots remain (order records).

8. Privacy & visibility

Data Buyer Seller Rider / delivery provider Third parties
Buyer saved addresses / recents own only ❌ ❌ ❌
Order drop-off area (ward, district, region) ✅ ✅ ✅ ❌
Order drop-off exact pin + note + phone ✅ only if seller delivers itself (sellerDelivers=true) ✅ for that shipment only ❌
Shop location (pin, landmark, ward) ✅ public ✅ ✅ ❌
Shop pickup phone after order ✅ ✅ ❌

Implement as two snapshot views: AddressSnapshotPublicView (area only) and AddressSnapshotFullView. Analytics/reports aggregate by ward/district only — never per person. Never log full coordinates together with user identifiers at INFO level.

9. REST API

Paths shown as examples — adapt prefix/style/auth to the existing project. All endpoints require authentication except GET /shops/{id}/location (public view).

9.1 Resolve (used live by pin screen after the map stops moving — debounce ~400 ms client side)

GET /api/v1/locations/resolve?lat=-6.8190&lng=39.2768

200 { "covered": true, "matchType": "CONTAINED", "distanceM": 0,
      "ward": { "wardId": 1146, "nbsCode": "070214112", "wardName": "Kariakoo",
                "districtName": "Ilala", "councilName": "Halmashauri ya Jiji la Dar es Salaam",
                "regionName": "Dar es Salaam" },
      "areaLabel": "Kariakoo, Ilala, Dar es Salaam" }
200 { "covered": false, "reason": "OUTSIDE_COVERAGE" }

Nothing is stored by this call.

9.2 Buyer addresses

Method Path Notes
GET /api/v1/me/addresses list, default first, then last_used_at desc
POST /api/v1/me/addresses create (body below)
PUT /api/v1/me/addresses/{id} update (same body)
DELETE /api/v1/me/addresses/{id} hard delete
POST /api/v1/me/addresses/{id}/default make default
GET /api/v1/me/recent-locations max 5, ≤ 60 days
DELETE /api/v1/me/recent-locations/{id} remove one
DELETE /api/v1/me/recent-locations clear all 
POST /api/v1/me/addresses
{ "lat": -6.774512, "lng": 39.241871,
  "labelType": "OTHER", "customLabel": "Mama's place",
  "note": "Black gate, call on arrival",
  "receiverName": null, "receiverPhone": null,      // null → use profile
  "makeDefault": false, "allowNearDuplicate": false }

9.3 Shop location

Method Path Notes
GET /api/v1/shops/{shopId}/location public view (no phone unless authorised)
PUT /api/v1/shops/{shopId}/location create or replace; owner only 
PUT /api/v1/shops/{shopId}/location
{ "lat": -6.770901, "lng": 39.229410,
  "landmark": "Near Shekilango stop, above Vodashop, 1st floor",
  "building": "Shop 12", "pickupPhone": "+2557XXXXXXXX",
  "officialAddress": null, "photoUrl": null,
  "deviceLat": -6.7712, "deviceLng": 39.2291 }       // optional, for FAR_FROM_DEVICE warning
→ 200 { ...location..., "warnings": [ { "code": "FAR_FROM_DEVICE", "distanceM": 3200 } ] }

9.4 Internal Java API (for orders/shop modules — not REST)

ResolveResult resolve(double lat, double lng);
boolean hasShopLocation(ShopId shopId);
AddressSnapshot snapshotFromShop(ShopId shopId);
AddressSnapshot snapshotFromAddress(UserId userId, AddressId addressId);   // also bumps last_used_at
AddressSnapshot snapshotFromRecent(UserId userId, RecentId recentId);
AddressSnapshot snapshotFromNewPin(UserId userId, NewPinRequest req);      // req.saveForLater → creates address, else records recent

9.5 Error codes

INVALID_COORDINATES, OUTSIDE_COVERAGE, NEAR_DUPLICATE (409, includes existing address), ADDRESS_LIMIT_REACHED, LABEL_ALREADY_USED, SHOP_LOCATION_REQUIRED (thrown by shop publish), NOT_FOUND, FORBIDDEN. Use the project's existing error response format.

10. WardDataSeeder (startup)

App starts (after Hibernate)
  │
  ├─ 1. CREATE EXTENSION IF NOT EXISTS postgis          (log clear error if not permitted)
  ├─ 2. CREATE TABLE IF NOT EXISTS tz_wards …  + indexes
  ├─ 3. CREATE INDEX IF NOT EXISTS … on location tables (§5.3)
  │
  ├─ 4. BEGIN; SELECT pg_advisory_xact_lock(<constant>)   ← only one container seeds
  │      SELECT count(*) FROM tz_wards
  │        ├─ > 0  → COMMIT, done (normal startup, instant)
  │        └─ = 0  → file exists?
  │                    ├─ no  → WARN "ward file not found at …; ward lookup disabled", COMMIT, continue startup
  │                    └─ yes → stream features (Jackson streaming parser, gzip if *.gz)
  │                             batch insert 200 rows:
  │                             INSERT INTO tz_wards (…, geom)
  │                             VALUES (…, ST_Multi(ST_SetSRID(ST_GeomFromGeoJSON(?), 4326)))
  │                             ON CONFLICT (ward_id) DO NOTHING
  │                             COMMIT; ANALYZE tz_wards
  │                             log "Loaded N wards in X s" (expect 4344)
  │
  └─ 5. If wards were just loaded AND user_addresses/shop_locations/recent_locations already have rows
         → re-resolve all of them (update ward_id + name copies + match_type). Order snapshots untouched.

Rules:

11. Client behaviour (Android · iOS · Web)

11.1 Location permission

┌ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┐
┆           📍                  ┆
   Use your location?
┆ We use it once to place your  ┆
   pin faster. You can also
┆ search or move the map.       ┆
  ┌ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┐
┆ ┆   Use my location         ┆ ┆   → OS permission prompt
  └ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┘
┆        Not now              ┆     → stay on map, no prompt
└ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┘

11.2 Pin screen (shared component — shop, buyer, add-address)

Behaviour:

  1. Fixed centre pin, the map moves (Bolt/Uber pattern). Pin lifts while dragging, drops when the map stops.
  2. Start position: accurate GPS → last used location → centre of user's city. Never whole-country view.
  3. Map / Satellite toggle (satellite matters — many streets unnamed).
  4. GPS accuracy circle; if accuracy > 100 m show "Location is approximate — move the map to your exact spot".
  5. Confirm disabled until zoom ≥ 17 (street level). Hint: "Zoom in to place exactly".
  6. Search (Google Places) only moves the map: "Now move the map to the exact entrance".
  7. When map stops (debounce ~400 ms): show Google label + call /locations/resolve. If covered=false → disable Confirm, show "We don't deliver here yet".
┌ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┐
  ←  Shop location     Step 3/4
┆ ┌ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┐ ┆
  ┆ 🔍 Search place or area   ┆
┆ └ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┘ ┆
  ┌ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┐
┆ ┆ [Map|Satellite]           ┆ ┆
  ┆                           ┆
┆ ┆        ( ◌ )  ← accuracy  ┆ ┆
  ┆          📍  fixed centre ┆
┆ ┆        move the map       ┆ ┆
  ┆                    [◎]    ┆   [◎] = use my location
┆ └ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┘ ┆
  ⚠ Zoom in to place exactly
┆   (shown until zoom ≥ 17)     ┆
  📍 Sinza, Ubungo, Dar es Salaam      ← Google label (display only)
┆ ┌ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┐ ┆
  ┆   Confirm location   →    ┆
┆ └ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┘ ┆
└ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┘

11.3 Shop flow (mandatory, step in shop creation)

┌ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┐
  ←  Shop location     Step 3/4
┆ ┌ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┐ ┆
  ┆ [mini map 📍]   Change    ┆
┆ ┆ Makurumla, Ubungo, Dar    ┆ ┆   ← from /resolve (NBS)
  └ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┘
┆ Directions / landmark *       ┆
  ┌ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┐
┆ ┆ Near Shekilango stop,     ┆ ┆
  ┆ above Vodashop, 1st floor ┆
┆ └ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┘ ┆
  Building / shop no. (optional)
┆ ┌ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┐ ┆
  ┆ Shop 12                   ┆
┆ └ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┘ ┆
  Pickup contact phone *
┆ ┌ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┐ ┆
  ┆ +255 7XX XXX XXX          ┆
┆ └ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┘ ┆
  Official address (optional)
┆ ┌ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┐ ┆
  ┆ Anwani za Makazi          ┆
┆ └ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┘ ┆
  📷 Add shop front photo (optional)
┆ ┌ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┐ ┆
  ┆   Save & continue    →    ┆
┆ └ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┘ ┆
└ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┘

If response has FAR_FROM_DEVICE → dialog "Your pin is 3.2 km from where you are. Is this your shop?" [Yes, it's correct] [Adjust pin].

11.4 Buyer delivery flow (pin only, Bolt style)

Checkout — choose where

┌ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┐
  Deliver to
┆ ┌ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┐ ┆
  ┆ ● 🏠 Home      (default)   ┆
┆ ┆   Mbezi Juu, Ubungo       ┆ ┆
  ┆ ○ 💼 Work                  ┆
┆ ┆   Kivukoni, Ilala         ┆ ┆
  ┆ ○ ⭐ Mama's place          ┆
┆ ┆   Tabata, Ilala           ┆ ┆
  ├ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┤
┆ ┆ Recent                    ┆ ┆
  ┆ ○ 🕘 Kijitonyama   [Save]  ┆
┆ ├ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┤ ┆
  ┆ ＋ New location (pin)      ┆
┆ └ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┘ ┆
         Manage addresses
└ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┘

First-time buyer with nothing saved → goes straight to the pin screen.

New location — full map + bottom sheet

┌ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┐
  ←  Deliver to       [Sat]
┆                               ┆
          FULL MAP
┆           📍                  ┆
                         [◎]
┆ ┌ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┐ ┆
  ┆ 🔍 Search                 ┆
┆ ┆ 🏠 Home     Mbezi Juu      ┆ ┆   ← tap jumps the pin there
  ┆ 💼 Work     Kivukoni       ┆
┆ ┆ 🕘 Recent   Kijitonyama    ┆ ┆
  ├ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┤
┆ ┆ 📍 Mikocheni, Kinondoni    ┆ ┆
  ┆ [ Deliver here → ]        ┆
┆ └ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┘ ┆
└ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┘

Quick confirm sheet

┌ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┐
  📍 Mikocheni, Kinondoni
┆                               ┆
  Note for rider (optional)
┆ ┌ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┐ ┆
  ┆ Black gate, call on arrival┆
┆ └ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┘ ┆
  Receiver: Me (+255 7XX…)  ✎        ← "Someone else" → name + phone
┆                               ┆
  [ ] Save as  🏠  💼  ✎             ← labels shown only when ticked
┆ ┌ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┐ ┆
  ┆      Continue  →          ┆
┆ └ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┘ ┆
└ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┘

Profile — manage addresses

┌ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┐
  ←  My addresses
┆ ┌ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┐ ┆
  ┆ 🏠 Home  ✓default     ⋮   ┆
┆ ┆ Mbezi Juu, Ubungo         ┆ ┆
  ├ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┤
┆ ┆ 💼 Work               ⋮   ┆ ┆
  ┆ Kivukoni, Ilala           ┆
┆ ├ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┤ ┆
  ┆ ⭐ Mama's place        ⋮   ┆
┆ ┆ Tabata, Ilala             ┆ ┆
  └ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┘
┆   ⋮ = Edit pin · Rename ·     ┆
    Set default · Delete
┆ ┌ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┐ ┆
  ┆   ＋ Add address           ┆
┆ └ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┘ ┆
  🕘 Clear recent locations
└ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┘

Optional secondary onboarding (buyer)

┌ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┐
┆           📦                  ┆
   Faster checkout?
┆  Add your home address now    ┆
   and skip it at checkout.
┆ ┌ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┐ ┆
  ┆      Add address          ┆      → pin screen → quick confirm (Save always on)
┆ └ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┘ ┆
           Maybe later
└ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ─ ┘

Area lines shown after saving (lists, checkout) are built from NBS names (ward, district) plus the user's label — never from Google text.

12. Flows

12.1 Shop sets location

sequenceDiagram
    actor Owner
    participant App
    participant Google as Google Maps/Places (client)
    participant API as Location module
    participant DB as PostGIS
    Owner->>App: Step 3 "Shop location"
    App->>Owner: Explainer → tap "Use my location"
    App->>App: OS permission (while in use), one GPS reading
    Owner->>App: Move map under fixed pin, zoom ≥ 17
    App->>Google: label for map centre (display only)
    App->>API: GET /locations/resolve?lat&lng
    API->>DB: ST_Contains / nearest ≤ 500 m
    DB-->>API: ward, district, region
    API-->>App: covered=true, areaLabel
    Owner->>App: Confirm → landmark, phone, (building, photo)
    App->>API: PUT /shops/{id}/location (+deviceLat/Lng)
    API->>DB: resolve again, upsert shop_locations
    API-->>App: saved (+ FAR_FROM_DEVICE warning if > 1 km)

12.2 Buyer checkout with a new pin

sequenceDiagram
    actor Buyer
    participant App
    participant Orders as Orders/Checkout
    participant Loc as Location module
    participant DB as PostGIS
    Buyer->>App: Checkout → "＋ New location"
    Buyer->>App: Place pin, note, receiver, [Save?]
    App->>Loc: GET /locations/resolve (live while moving)
    Buyer->>App: Continue / Pay
    App->>Orders: place order { newPin, saveForLater }
    Orders->>Loc: snapshotFromNewPin(user, req)
    Loc->>DB: resolve ward
    alt saveForLater = true
        Loc->>DB: insert user_addresses (rules §7.2)
    else
        Loc->>DB: upsert recent_locations (max 5, 60 days)
    end
    Loc-->>Orders: AddressSnapshot (frozen)
    Orders->>DB: store order + pickup & drop-off snapshots

12.3 Shop publish guard

Shop "Publish" → shopModule calls location.hasShopLocation(shopId)
   ├─ true  → publish
   └─ false → 400 SHOP_LOCATION_REQUIRED → app opens Shop location step

13. Out of scope (do NOT build now)

14. Acceptance tests

14.1 Ward resolution (integration test against loaded data — these were verified against the file)

Place lat lng Expected ward District Region
Kariakoo market -6.8190 39.2768 Kariakoo Ilala Dar es Salaam
Ubungo bus terminal -6.7889 39.2083 Ubungo Ubungo Dar es Salaam
JNIA airport -6.8781 39.2026 Kipawa Ilala Dar es Salaam
Posta / city centre -6.8160 39.2900 Kivukoni Ilala Dar es Salaam
Stone Town -6.1622 39.1887 Shangani Mjini Mjini Magharibi
Arusha clock tower -3.3700 36.6940 Sekei Arusha Arusha
Mwanza centre -2.5164 32.9006 Nyamagana Nyamagana Mwanza
Mbeya town -8.9094 33.4608 Ruanda Mbeya Mbeya
Dodoma centre -6.1722 35.7395 Majengo Dodoma Dodoma
Indian Ocean off Dar -6.80 39.40 — OUTSIDE_COVERAGE
Nairobi -1.2864 36.8172 — OUTSIDE_COVERAGE

Also: SELECT count(*) FROM tz_wards = 4344; SELECT count(DISTINCT reg_name) = 31. Use Testcontainers with postgis/postgis image if the project already uses Testcontainers; otherwise follow project test setup.

14.2 Rules

15. Build order

  1. Docker: switch DB to postgis/postgis (same PG major), mount /opt/nexgate/geo, add config, .gitignore data/geo/.
  2. WardDataSeeder + WardResolver + GET /locations/resolve + tests §14.1. ← foundation
  3. Shop location (entity, PUT/GET, hasShopLocation, publish guard).
  4. Buyer addresses + recents (+ rules tests).
  5. AddressSnapshot + checkout integration + privacy views.
  6. Clients: shared pin-screen component, shop step, checkout picker, manage addresses, optional onboarding.
Revision #2
Created 11 October 2026 14:39:15 by Admin Qbit
Updated 11 October 2026 14:42:51 by Admin Qbit