AI Wrapper

The problem

The dominant AI text-tool apps charge $8 to $30 per month, lock you into one provider, cap usage per tier, and process every request through their server — which means they hold a copy of every prompt and every output. The technically savvy user already has an OpenAI / Anthropic / Gemini API key and would happily pay a one-time fee for an app that just talks to those APIs directly from their phone, without inserting an intermediate server. The non-savvy user wants the same convenience as the cloud apps. We wanted one app that serves both, with the user's API key never leaving the device.

How we built it

1. 01Built every API client (`openai_client.dart`, `anthropic_client.dart`, `gemini_client.dart`) behind a single pure-Dart `AiClient` interface and let the user runtime-switch providers. The high-level `ai_tools_service.dart` calls one tool method, which dispatches to whichever client the user picked.
2. 02Stored API keys in `flutter_secure_storage` (encrypted, on-device only) and validated each one against its provider on save. No key ever crosses the network except in the user's own request to OpenAI / Anthropic / Google. There is no server to trust because there is no server.
3. 03Shipped four tools — Summarizer, Rewriter (6 tones), Translator (15 languages), Grammar Checker — over the same UI shell. Each tool screen has per-tool loading state (no cross-tab interference), text stats (chars / words / tokens) on the input, and a cost estimator that shows the per-request cost for the chosen provider before the user submits.
4. 04Wrote a `history_service.dart` that persists every result with corrupt-entry resilience (one bad JSON row does not blow up the history), a `usage_service.dart` for per-tool counts, and a paywall that gates BYOK ($4.99 one-time, user's own key, no ads) vs. Pro ($5.99 / mo, API provided by us, premium models). Free tier subsidises 5 uses / day so the curious user can try every tool before deciding.
5. 05Wired the full release surface — RevenueCat entitlement service, AdMob banner ads (test IDs), Material 3 light + dark with `SafeArea` on every screen, store listing copy, privacy policy, release notes, splash + icon configs — so swapping the placeholder credentials for production keys is the entire remaining task.

Outcome

All work packages complete: 102 of 102 tests passing, zero analyzer issues, four tools live across three providers, secure key storage, per-tool loading, history with resilience, cost estimator, paywall with BYOK + Pro tiers, AdMob banner integration, full Material 3 theming, store-submission docs ready. Namespace `com.ninetyninersstudio.ai_wrapper`. The remaining work is human-only: app icon assets, Firebase + `google-services.json`, RevenueCat production keys, AdMob production ad-unit IDs, signing keystore, Play Console upload.

Next up

Asset creation (icon set + screenshots), Firebase project provisioning, RevenueCat + AdMob production credential swap, signing keystore generation, then submission. Future: Phase 5 expansion with code-explainer, email-tone matcher, and meeting-summary tools — each one is an additional `AiTool` enum + a screen + a prompt template.