# API Type Improvements Summary

This document summarizes the type safety improvements made to the API based on [Hono's best practices](https://hono.dev/docs/guides/rpc).

## Changes Made

### 1. Created Centralized Type System

**New File: `src/app.types.ts`**

Introduced shared environment types that all routers can use:

- `BaseEnv` - Base environment with Supabase client
- `AuthEnv` - Environment with authenticated user
- `MaybeAuthEnv` - Environment with optional authentication  
- `AppEnv` - Full environment with all services
- `ExtractEnv<T>` - Helper type to extract environment from Hono instances

**Benefits:**
- ✅ Eliminates duplicate type definitions across routers
- ✅ Ensures consistency in environment variable types
- ✅ Makes it easy to add new global services

### 2. Added RPC Client Type Exports

**New File: `src/client.ts`**

Exports type-safe client types for frontend and testing:

```typescript
import { hc } from 'hono/client'
import type { AppType } from './client'

const client = hc<AppType>('http://localhost:8080')
// Full type safety and autocomplete!
```

**Benefits:**
- ✅ Type-safe API calls from frontend
- ✅ Autocomplete for all endpoints
- ✅ Compile-time error checking
- ✅ No need to manually sync types

### 3. Enhanced Router Type Safety

**Updated Files:**
- `src/routers.ts` - Main router now exports `ApiRoutes` type
- `src/notes.ts` - Uses `AuthEnv` instead of custom type
- `src/public.ts` - Uses `BaseEnv` instead of custom type

**Benefits:**
- ✅ Better type inference in handlers
- ✅ Typed route parameters
- ✅ Typed context variables

### 4. Created Comprehensive Documentation

**New File: `docs/TYPE_SAFETY.md`**

Complete guide covering:
- How to use environment types
- RPC client usage examples
- Best practices for type-safe routers
- Migration guide for existing code
- Testing with type safety

**Benefits:**
- ✅ Team members can easily understand the type system
- ✅ Examples for common patterns
- ✅ Clear migration path for existing code

### 5. Updated Test Examples

**Updated File: `src/__tests__/notes/notes.test.ts`**

Added documentation showing type-safe testing patterns.

**Benefits:**
- ✅ Tests serve as examples for developers
- ✅ Demonstrates type inference in action

## Type Safety Improvements

### Before
```typescript
// Each router defined its own types
type NotesEnv = {
  Variables: {
    user: User;
    supabase: SupabaseClient;
  };
};

// No RPC type exports
// Manual type definitions needed in frontend
```

### After
```typescript
// Shared types across all routers
import type { AuthEnv } from "./app.types.js";

// Exported RPC types for frontend
export type ApiRoutes = ReturnType<typeof getMainRouter>;

// Full type inference everywhere!
```

## Example Usage

### In Backend Router
```typescript
import { createFactory } from "hono/factory";
import type { AuthEnv } from "./app.types.js";

const factory = createFactory<AuthEnv>();

const getUser = factory.createHandlers(async (c) => {
  const user = c.get("user"); // ✅ Typed as User
  const id = c.req.param("id"); // ✅ Typed as string
  return c.json({ user });
});
```

### In Frontend
```typescript
import { hc } from "hono/client";
import type { ApiRoutes } from "@api/client";

const client = hc<ApiRoutes>("https://api.example.com/api/v1");

const res = await client.users[":id"].$get({
  param: { id: "123" } // ✅ Type-checked
});

if (res.ok) {
  const data = await res.json(); // ✅ Fully typed response
}
```

### In Tests
```typescript
import { testClient } from "hono/testing";

const app = getNotesRouter();
const client = testClient(app);

const res = await client[":tabloId"].$get({
  param: { tabloId: "123" } // ✅ Type-checked parameter
});
```

## Test Results

All 67 tests pass successfully with the new type system:

```
✓ Notes Endpoint (4.953917ms)
✓ generateTimeSlots (28.547792ms)
✓ encodeURIComponent with slashes (3.631208ms)
ℹ tests 67
ℹ pass 67
ℹ fail 0
```

## Next Steps

### Recommended Actions

1. **Update remaining routers** to use shared types from `app.types.ts`:
   - `user.ts`
   - `stripe.ts`
   - `tablo.ts`
   - `tablo_data.ts`
   - `tasks.ts`
   - `invite.ts`

2. **Create frontend client** using the exported types:
   ```typescript
   import { hc } from "hono/client";
   import type { ApiRoutes } from "@api/client";
   ```

3. **Add more type-safe tests** following the pattern in `notes.test.ts`

4. **Consider adding Zod validation** for request/response schemas with full type inference

## Resources

- 📚 [Hono RPC Documentation](https://hono.dev/docs/guides/rpc)
- 📚 [Hono Factory Pattern](https://hono.dev/docs/api/factory)  
- 📚 [Hono TypeScript Best Practices](https://hono.dev/docs/guides/best-practices#typescript)
- 📄 [Local Documentation](./docs/TYPE_SAFETY.md)

## Performance Impact

✅ **Zero runtime impact** - All type improvements are compile-time only

## Breaking Changes

✅ **None** - All changes are backward compatible. Existing code continues to work while gaining better type safety.

## Conclusion

These improvements bring world-class type safety to the API, leveraging Hono's powerful RPC pattern for end-to-end type inference from server to client. The codebase is now more maintainable, self-documenting, and less prone to runtime errors.


