Change Detection

Track store listing changes over time for both tracked and competitor apps.

Overview

AppStoreCat detects changes in app store listings on every sync cycle. When a field changes (title, description, screenshots, etc.), the old and new values are recorded, producing a timeline of how apps evolve their store presence.

Tracked Fields

Field	Description
title	App title changed
subtitle	App subtitle changed (iOS)
description	App description changed
whats_new	Release notes changed
screenshots	Screenshot set changed
promotional_text	Promotional text changed (iOS only; always null on Android)
locale_added	A new supported locale was added
locale_removed	A supported locale was removed

How It Works

1. On every sync, the listing content is hashed into a checksum
2. If the checksum matches the previous sync, nothing has changed — it is skipped
3. If the checksum differs, each field is compared individually
4. For each changed field, a StoreListingChange record is created with:
   • Field name (field_changed)
   • Old value
   • New value
   • Detection timestamp
   • Locale (locale column)

Locale Change Detection

Beyond individual field changes, AppStoreCat also tracks locale-level changes:

• locale_added: when an app starts supporting a new language
• locale_removed: when an app drops support for a language

These are detected by comparing the supported_locales array between syncs.

API

Tracked App Changes

GET /api/v1/changes/apps?field=title&app_id=123&page=2

Returns changes for all tracked apps. Optional query params: field (filter by field type), app_id (restrict to a single tracked app the caller owns), page (page cursor).

Competitor Changes

GET /api/v1/changes/competitors?field=description&app_id=123&page=2

Returns changes for all competitor apps. Same optional query params as /changes/apps.

Response Shape

Both endpoints return a paginated envelope (PaginatedChangeResponse) rather than a bare array:

{
  "data": [ /* ChangeResource[] */ ],
  "links": { "first": "…", "last": "…", "prev": null, "next": "…" },
  "meta":  { "current_page": 1, "last_page": 4, "per_page": 50, "total": 183, "…": "…" },
  "meta_ext": { "has_scope_apps": true }
}

meta_ext.has_scope_apps lets the UI distinguish “no changes yet — keep watching” from “you have not tracked any apps yet”.

UI

Go to Changes > Apps or Changes > Competitors to see the change timeline. Each change shows:

• App name and icon
• Changed field
• Old and new values with diff highlighting
• Locale and timestamp

Technical Details

• Model: StoreListingChange
• Table: app_store_listing_changes (the locale column holds a BCP-47 code)
• Indexes: (app_id, detected_at), (version_id), (app_id, locale), (field_changed)
• Sync step: AppSyncer::syncListing() (field changes), AppSyncer::detectLocaleChanges() (locale changes)
• Controller: ChangeMonitorController
• Detection method: Checksum-based (SHA-256 of the combined listing content)