Inventory Sync & Anti-Fraud

Copy codedata class StockInfo(
    val productId: String,
    val status: StockStatus,    // IN_STOCK, LOW_STOCK, OUT_OF_STOCK
    val quantity: Int?,         // show actual count only if < 10 (urgency cue)
    val updatedAt: Long         // freshness timestamp
)

enum class StockStatus { IN_STOCK, LOW_STOCK, OUT_OF_STOCK }

// Refresh stock for visible products as user scrolls
class InventoryManager(private val api: InventoryApi, private val cache: InventoryCache) {

    suspend fun getStock(productId: String): StockInfo {
        val cached = cache.get(productId)

        // Use cache if fresh (< 5 minutes)
        if (cached != null && System.currentTimeMillis() - cached.updatedAt < 5 * 60 * 1000) {
            return cached
        }

        // Refresh in background, return stale cache immediately
        scope.launch { refreshStock(productId) }
        return cached ?: StockInfo(productId, StockStatus.IN_STOCK, null, 0)
    }

    private suspend fun refreshStock(productId: String) {
        try {
            val fresh = api.getStock(productId)
            cache.put(productId, fresh.copy(updatedAt = System.currentTimeMillis()))
        } catch (e: IOException) {
            // Keep stale cache; don't crash product listing
        }
    }

    // Batch refresh for product list (single API call)
    suspend fun refreshBatch(productIds: List<String>) {
        val fresh = api.getBatchStock(productIds)
        fresh.forEach { cache.put(it.productId, it.copy(updatedAt = System.currentTimeMillis())) }
    }
}

Copy code@Composable
fun StockBadge(stock: StockInfo) {
    when (stock.status) {
        StockStatus.OUT_OF_STOCK ->
            Text("Out of Stock", color = MaterialTheme.colorScheme.error, style = MaterialTheme.typography.labelSmall)
        StockStatus.LOW_STOCK ->
            Text(
                if (stock.quantity != null) "Only ${stock.quantity} left!" else "Low stock",
                color = Color(0xFFE65100),  // deep orange — urgency
                style = MaterialTheme.typography.labelSmall
            )
        StockStatus.IN_STOCK -> {}  // don't show "In Stock" — it's assumed
    }
}

Copy codeclass DeviceRiskProfiler(private val context: Context) {
    fun getRiskSignals(): DeviceRiskSignals {
        return DeviceRiskSignals(
            // Emulator indicators
            isEmulator = isEmulator(),
            // Rooted device
            isRooted = isRooted(),
            // Screen interaction patterns (real users scroll; bots don't)
            userAgent = buildUserAgent(),
            // Play Integrity token (strongest device attestation)
            // Fetched separately via Play Integrity API
        )
    }

    private fun isEmulator(): Boolean {
        return (Build.FINGERPRINT.startsWith("generic") ||
                Build.FINGERPRINT.startsWith("unknown") ||
                Build.MODEL.contains("Emulator") ||
                Build.MODEL.contains("Android SDK built for x86"))
    }

    private fun isRooted(): Boolean {
        return arrayOf("/su", "/system/bin/su", "/system/xbin/su").any { File(it).exists() }
    }

    private fun buildUserAgent(): String =
        "Android/${Build.VERSION.RELEASE} ${Build.MANUFACTURER}/${Build.MODEL}"
}

data class DeviceRiskSignals(
    val isEmulator: Boolean,
    val isRooted: Boolean,
    val userAgent: String
)

Copy codeclass CheckoutRiskManager {
    fun requiresAdditionalVerification(order: Order, riskSignals: DeviceRiskSignals): Boolean {
        return order.totalCents > 100_00 ||  // > $100
               riskSignals.isRooted ||
               riskSignals.isEmulator ||
               order.isFirstOrder ||
               order.shippingAddressDiffersFromBilling
    }
}

Copy codeclass AddToCartThrottler {
    private val clickTimes = LinkedList<Long>()
    private val maxClicksPerMinute = 10

    fun canAddToCart(): Boolean {
        val now = System.currentTimeMillis()
        // Remove clicks older than 1 minute
        while (clickTimes.isNotEmpty() && now - clickTimes.first() > 60_000) {
            clickTimes.removeFirst()
        }
        if (clickTimes.size >= maxClicksPerMinute) return false
        clickTimes.addLast(now)
        return true
    }
}