Google Play Billing integration — subscription (playstore flavor)

[Pivii]

Context

For the playstore flavor (Google Play Store distribution), Pro features are unlocked via a monthly subscription through Google Play Billing Library. This targets the mainstream Android audience.

Architecture

User taps "Upgrade to Pro"
  → App launches Google Play purchase flow (native UI)
  → User pays via Play Store (card, Google Pay, etc.)
  → BillingClient confirms purchase
  → App verifies purchase locally
  → isPro = true, stored in DataStore
  → Subscription auto-renews monthly

Key properties

• No server required: Google handles billing, receipt validation can be local
• Subscription model: Monthly (pricing TBD, likely ~2-3€/month)
• Yearly option: Optional discounted annual plan
• Restore: BillingClient.queryPurchasesAsync() on app start

What to implement

1. PlayStoreUnlocker in app/src/playstore/

class PlayStoreUnlocker(
    private val context: Context,
    private val dataStore: DataStore<Preferences>
) : ProUnlocker {

    private val billingClient = BillingClient.newBuilder(context)
        .setListener(purchasesUpdatedListener)
        .enablePendingPurchases()
        .build()

    override val isPro: StateFlow<Boolean>

    override fun launchPurchase(activity: Activity) {
        // Query product details → launch billing flow
    }

    override suspend fun restorePurchase(): Boolean {
        // queryPurchasesAsync → check for active subscription
    }
}

2. Play Console setup

• Create Google Play Developer account (25$ one-time)
• Create app listing for Dictus
• Configure subscription product ("dictus_pro_monthly", "dictus_pro_yearly")
• Upload playstore-release APK (or AAB)
• Set up internal testing track first

3. Subscription products

Product ID	Type	Price	Notes
dictus_pro_monthly	Subscription	~2-3€/mo	Main offer
dictus_pro_yearly	Subscription	~20-25€/yr	Optional discount

Pricing TBD — can be adjusted in Play Console without app update.

4. Paywall screen

• Show Pro features with descriptions
• Monthly / Yearly toggle
• "Subscribe" button → native Play purchase flow
• "Restore purchase" link
• Terms of service / privacy policy links (required by Google)

Acceptance criteria

• PlayStoreUnlocker implements ProUnlocker in playstore flavor
• BillingClient connects and queries products
• Purchase flow launches and completes
• Subscription status persisted in DataStore
• Restore purchase works on fresh install
• Paywall screen with feature list and pricing

Prerequisites

• Google Play Developer account created
• App listing created on Play Console
• At least one subscription product configured
• Depends on: #1 (playstore flavor), Gradle product flavors: libre + playstore #2 (ProUnlocker interface)

Notes

• Google takes 30% commission (15% for first $1M/year under Small Business program)
• Play Billing Library v6+ required
• Must handle edge cases: pending purchases, subscription paused, account hold