# API Design Instructions

> **Parent Document**: `main-instructions.md` - Read that first!

## 🔌 API Design Principles

### Rule #1: API Endpoints Serve the UI

Every API endpoint must exist to support a specific UI feature or user action.

**The Process**:

1. Identify UI interaction (button click, form submit, page load)
2. Determine what data is needed
3. Create API endpoint that provides exactly that data
4. No more, no less

### API Architecture in Next.js

```
src/
  app/
    api/                    # REST API Routes (when needed)
      auth/
        route.ts
      work-orders/
        route.ts
        [id]/
          route.ts

    [feature]/
      actions.ts            # Server Actions (preferred for mutations)
```

## 🔒 Type Safety in Server Actions

### NEVER Use `any` Type

**ALWAYS validate inputs with Zod - no exceptions:**

```typescript
"use server";

import { z } from "zod";
import type { ActionResult } from "@/lib/types";

// ❌ BAD - using any
export async function createProject(data: any): Promise<ActionResult<Project>> {
  // FORBIDDEN! Never use 'any'
}

// ❌ BAD - unvalidated FormData
export async function createProject(
  formData: FormData,
): Promise<ActionResult<Project>> {
  const name = formData.get("name"); // Type is FormDataEntryValue | null - not safe!
  // No validation!
}

// ✅ GOOD - strict Zod schema
const createProjectSchema = z.object({
  name: z.string().min(1, "Name is required").max(255),
  description: z.string().optional(),
  clientId: z.string().uuid("Invalid client ID"),
  startDate: z.string().datetime(),
  budget: z.number().positive("Budget must be positive"),
});

type CreateProjectInput = z.infer<typeof createProjectSchema>;

export async function createProject(
  input: unknown, // Unknown until validated
): Promise<ActionResult<Project>> {
  // Validate at runtime + get full type safety
  const result = createProjectSchema.safeParse(input);
  if (!result.success) {
    return {
      success: false,
      error: result.error.errors
        .map((e) => `${e.path.join(".")}: ${e.message}`)
        .join(", "),
    };
  }

  // result.data is now fully typed as CreateProjectInput
  const validatedData = result.data;

  // ... rest of implementation with full type safety
}
```

### Avoid Type Casting with `as`

**Use Zod validation instead of unsafe casting:**

```typescript
// ❌ BAD - type casting (unsafe!)
const project = data as Project; // No validation!
const userId = (formData.get("userId") as string).toUpperCase(); // Can crash!

// ✅ GOOD - Zod validation
const projectSchema = z.object({
  id: z.string().uuid(),
  data: z.object({
    name: z.string(),
    status: z.enum(["active", "completed", "cancelled"]),
  }),
  createdAt: z.coerce.date(), // Converts + validates
  updatedAt: z.coerce.date(),
});

const project = projectSchema.parse(data); // Type-safe + runtime validation ✅

const userIdSchema = z.string().min(1);
const userId = userIdSchema.parse(formData.get("userId")); // Safe ✅
```

### FormData Validation Pattern

**Always validate FormData with Zod:**

```typescript
"use server";

export async function updateUser(
  formData: FormData,
): Promise<ActionResult<User>> {
  // Convert FormData to object
  const rawData = Object.fromEntries(formData);

  // Define schema
  const schema = z.object({
    userId: z.string().uuid(),
    name: z.string().min(1).max(255),
    email: z.string().email(),
    age: z.coerce.number().int().positive(), // Coerce string to number
  });

  // Validate
  const result = schema.safeParse(rawData);
  if (!result.success) {
    return { success: false, error: result.error.message };
  }

  // Now result.data is fully typed and validated
  const validatedData = result.data;

  // ... safe to use
}
```

## 🎯 ActionResult Pattern

### Use Shared ActionResult Type

**ALWAYS use the shared ActionResult type with helper functions:**

```typescript
import { type ActionResult, success, failure, toFailure } from "@/lib/types";

// ❌ BAD - inline result objects
export async function createProject(input: unknown) {
  return { success: true as const, data: project };
  return { success: false as const, error: "Failed" };
}

// ✅ GOOD - use helpers
export async function createProject(
  input: unknown,
): Promise<ActionResult<{ id: string }>> {
  try {
    // ... validation and logic
    return success({ id: result.id });
  } catch (error) {
    return toFailure(error, "Failed to create project");
  }
}
```

### Error Handling with toFailure

**Use `toFailure()` for catch blocks - it handles unknown error types safely:**

```typescript
// ❌ BAD - manual error handling
catch (error) {
  return failure(error instanceof Error ? error.message : "Unknown error");
}

// ✅ GOOD - use toFailure helper
catch (error) {
  console.error("Action error:", error);
  return toFailure(error, "Failed to perform action");
}
```

## 🔑 Authentication Helper

### Use Shared getCurrentUser Helper

**ALWAYS use the shared helper instead of duplicating auth logic:**

```typescript
// ❌ BAD - duplicated auth logic in each action file
async function getCurrentUser() {
  if (skipAuth) return mockUser;
  const session = await auth.api.getSession({ headers: await headers() });
  return session?.user ?? null;
}

// ✅ GOOD - import shared helper
import { getCurrentUser } from "@/lib/utils/get-current-user";

export async function myAction(input: unknown): Promise<ActionResult<Data>> {
  const user = await getCurrentUser();
  if (!user) {
    return failure("Unauthorized. Please log in.");
  }
  // ...
}
```

## 📋 Zod Schema Patterns

### Use .partial() at Object Level

**Prefer `.partial()` on object level instead of `.optional()` on each field:**

```typescript
// ❌ BAD - verbose, repetitive
const schema = z.object({
  title: z.string().optional(),
  description: z.string().optional(),
  status: z.string().optional(),
  // ... 20 more fields with .optional()
});

// ✅ GOOD - concise, maintainable
const baseSchema = z.object({
  title: z.string(),
  description: z.string(),
  status: z.string(),
});

const updateSchema = baseSchema.partial(); // All fields optional
const createSchema = baseSchema.partial().required({ title: true }); // title required
```

### Shared Enums

**Put reusable enum values in `@/lib/schemas/shared-enums.ts`:**

```typescript
// ❌ BAD - duplicated in multiple files
// In file A:
const statusSchema = z.enum(["New", "In Progress", "Completed"]);
// In file B:
const STATUS_OPTIONS = ["New", "In Progress", "Completed"];

// ✅ GOOD - single source of truth
// shared-enums.ts
export const STATUS_VALUES = ["New", "In Progress", "Completed"] as const;
export const statusSchema = z.enum(STATUS_VALUES);
export type Status = z.infer<typeof statusSchema>;

// Other files import from shared-enums
import { STATUS_VALUES, statusSchema } from "@/lib/schemas/shared-enums";
```

## 🗃️ Drizzle Type Inference

### Use $inferSelect for Types

**Use Drizzle's `$inferSelect` to avoid manual type definitions and casting:**

```typescript
// ❌ BAD - manual type + casting
type Project = {
  id: string;
  data: ProjectData;
  createdAt: Date;
  updatedAt: Date;
};

const result = await db.select().from(projects);
return result as Project[]; // Unsafe!

// ✅ GOOD - inferred type from schema
export type Project = typeof projects.$inferSelect;

const result = await db.select().from(projects);
return result; // Already typed correctly!
```

## 🛡️ Security in Server Actions

### 1. Authentication Check (ALWAYS)

**EVERY Server Action MUST check authentication:**

```typescript
"use server";

import { getServerSession } from "@/lib/auth";

export async function deleteProject(
  projectId: string,
): Promise<ActionResult<void>> {
  // ❌ FORBIDDEN - no auth check
  // await db.delete(projects).where(eq(projects.id, projectId));

  // ✅ REQUIRED - check authentication first
  const session = await getServerSession();
  if (!session?.user) {
    return { success: false, error: "Unauthorized - please log in" };
  }

  // Now proceed with validated user
  // ... rest of implementation
}
```

### 2. Authorization Check (ALWAYS)

**Check if user has permission to perform the action:**

```typescript
"use server";

export async function updateProject(
  projectId: string,
  updates: unknown,
): Promise<ActionResult<Project>> {
  // 1. Validate input
  const idSchema = z.string().uuid();
  const projectIdResult = idSchema.safeParse(projectId);
  if (!projectIdResult.success) {
    return { success: false, error: "Invalid project ID" };
  }

  const updateSchema = z.object({
    name: z.string().min(1).max(255).optional(),
    status: z.enum(["active", "completed", "cancelled"]).optional(),
  });
  const updatesResult = updateSchema.safeParse(updates);
  if (!updatesResult.success) {
    return { success: false, error: updatesResult.error.message };
  }

  // 2. Check authentication
  const session = await getServerSession();
  if (!session?.user) {
    return { success: false, error: "Unauthorized" };
  }

  // 3. Check authorization - user must own the project or be admin
  const db = await getDatabase();
  const [project] = await db
    .select()
    .from(projects)
    .where(eq(projects.id, projectIdResult.data));

  if (!project) {
    return { success: false, error: "Project not found" };
  }

  // Check ownership or admin role
  const isOwner = project.data.ownerId === session.user.id;
  const isAdmin = session.user.role === "admin";

  if (!isOwner && !isAdmin) {
    return { success: false, error: "Forbidden - you do not have permission" };
  }

  // 4. Now safe to perform action
  const [updated] = await db
    .update(projects)
    .set({
      data: { ...project.data, ...updatesResult.data },
      updatedAt: new Date(),
    })
    .where(eq(projects.id, projectIdResult.data))
    .returning();

  return { success: true, data: updated };
}
```

### 3. Input Sanitization (ALWAYS)

**Validate ALL inputs, even from trusted sources:**

```typescript
"use server";

export async function searchProjects(
  query: unknown,
  filters: unknown,
): Promise<ActionResult<Project[]>> {
  // Validate search query
  const querySchema = z.string().min(1).max(255);
  const queryResult = querySchema.safeParse(query);
  if (!queryResult.success) {
    return { success: false, error: "Invalid search query" };
  }

  // Validate filters
  const filtersSchema = z.object({
    status: z.enum(["active", "completed", "cancelled"]).optional(),
    clientId: z.string().uuid().optional(),
    dateFrom: z.string().datetime().optional(),
    dateTo: z.string().datetime().optional(),
  });

  const filtersResult = filtersSchema.safeParse(filters);
  if (!filtersResult.success) {
    return { success: false, error: "Invalid filters" };
  }

  // Now both are fully typed and validated
  const safeQuery = queryResult.data;
  const safeFilters = filtersResult.data;

  // Safe to use in query (Drizzle prevents SQL injection)
  const db = await getDatabase();
  let dbQuery = db.select().from(projects);

  if (safeFilters.status) {
    dbQuery = dbQuery.where(sql`data->>'status' = ${safeFilters.status}`);
  }

  const results = await dbQuery;
  return { success: true, data: results };
}
```

### 4. Rate Limiting (Optional - Add When Needed)

**For now: simple validation is enough. Add rate limiting later if abuse occurs.**

```typescript
// ✅ NOW - simple validation prevents most abuse
export async function sendEmail(input: unknown): Promise<ActionResult<void>> {
  // Validate + authenticate
  const schema = z.object({ to: z.string().email() });
  const result = schema.safeParse(input);
  if (!result.success) {
    return { success: false, error: "Invalid email" };
  }

  const session = await getServerSession();
  if (!session?.user) {
    return { success: false, error: "Unauthorized" };
  }

  // ... send email
}

// 🔮 FUTURE - add rate limiting if users abuse the feature
// import { ratelimit } from '@/lib/ratelimit'; // Will use Redis when scaling
// const { success } = await ratelimit.limit(`email:${session.user.id}`, 5, '1h');
```

## 🎯 Server Actions (Preferred)

### When to Use Server Actions

- ✅ Form submissions
- ✅ Data mutations (create, update, delete)
- ✅ Actions triggered by user interactions
- ✅ When you need to revalidate data
- ✅ **Data fetching from Client Components** (when you can't use Server Component)

**Best Practice**: Prefer Server Components for data fetching. Only fetch from Client Components when:

- You need client-side interactivity (filters, search, pagination) that triggers refetch
- Data depends on client state
- You're polling/refreshing data on interval

### Server Action Template

```typescript
// app/projects/actions.ts
"use server";

import { revalidatePath } from "next/cache";
import { redirect } from "next/navigation";
import { db } from "@/lib/getDatabase";
import { projects } from "@/schema/schema";
import { getCurrentUser } from "@/lib/auth-helpers-server";
import { eq } from "drizzle-orm";

// Define return type for consistency
type ActionResult<T = void> =
  | { success: true; data: T }
  | { success: false; error: string };

/**
 * Creates a new project
 */
export async function createProject(
  formData: FormData,
): Promise<ActionResult<{ id: string }>> {
  try {
    // 1. Authentication check
    const user = await getCurrentUser();
    if (!user) {
      return { success: false, error: "Not authenticated" };
    }

    // 2. Validate input
    const title = formData.get("title") as string;
    const description = formData.get("description") as string;

    if (!title || title.trim().length === 0) {
      return { success: false, error: "Title is required" };
    }

    // 3. Database operation
    const [newProject] = await db
      .insert(projects)
      .values({
        title: title.trim(),
        description: description?.trim() || "",
        userId: user.id,
        status: "draft",
      })
      .returning();

    // 4. Revalidate affected paths
    revalidatePath("/projects");
    revalidatePath("/");

    // 5. Return success
    return {
      success: true,
      data: { id: newProject.id },
    };
  } catch (error) {
    console.error("Error creating project:", error);
    return {
      success: false,
      error: "Failed to create project",
    };
  }
}

/**
 * Updates an existing project
 */
export async function updateProject(
  projectId: string,
  formData: FormData,
): Promise<ActionResult> {
  try {
    const user = await getCurrentUser();
    if (!user) {
      return { success: false, error: "Not authenticated" };
    }

    // Check ownership
    const project = await db.query.projects.findFirst({
      where: eq(projects.id, projectId),
    });

    if (!project) {
      return { success: false, error: "Project not found" };
    }

    if (project.userId !== user.id) {
      return { success: false, error: "Not authorized" };
    }

    // Update
    const title = formData.get("title") as string;
    const description = formData.get("description") as string;

    await db
      .update(projects)
      .set({
        title: title.trim(),
        description: description?.trim() || "",
        updatedAt: new Date(),
      })
      .where(eq(projects.id, projectId));

    revalidatePath("/projects");
    revalidatePath(`/projects/${projectId}`);

    return { success: true, data: undefined };
  } catch (error) {
    console.error("Error updating project:", error);
    return { success: false, error: "Failed to update project" };
  }
}

/**
 * Deletes a project (soft delete)
 */
export async function deleteProject(projectId: string): Promise<ActionResult> {
  try {
    const user = await getCurrentUser();
    if (!user) {
      return { success: false, error: "Not authenticated" };
    }

    // Check ownership
    const project = await db.query.projects.findFirst({
      where: eq(projects.id, projectId),
    });

    if (!project) {
      return { success: false, error: "Project not found" };
    }

    if (project.userId !== user.id) {
      return { success: false, error: "Not authorized" };
    }

    // Soft delete
    await db
      .update(projects)
      .set({ deletedAt: new Date() })
      .where(eq(projects.id, projectId));

    revalidatePath("/projects");

    return { success: true, data: undefined };
  } catch (error) {
    console.error("Error deleting project:", error);
    return { success: false, error: "Failed to delete project" };
  }
}
```

### Using Server Actions in Components

```typescript
'use client'

import { useTransition } from 'react'
import { useRouter } from 'next/navigation'
import { createProject } from './actions'
import { Button } from '@/components/ui/button'
import { Input } from '@/components/ui/input'
import { useToast } from '@/hooks/use-toast'

export function ProjectForm() {
  const router = useRouter()
  const { toast } = useToast()
  const [isPending, startTransition] = useTransition()

  const handleSubmit = async (formData: FormData) => {
    startTransition(async () => {
      const result = await createProject(formData)

      if (result.success) {
        toast({
          title: 'Success',
          description: 'Project created successfully',
        })
        router.push(`/projects/${result.data.id}`)
      } else {
        toast({
          title: 'Error',
          description: result.error,
          variant: 'destructive',
        })
      }
    })
  }

  return (
    <form action={handleSubmit} className="space-y-4">
      <Input name="title" placeholder="Project title" required />
      <Input name="description" placeholder="Description" />
      <Button type="submit" disabled={isPending}>
        {isPending ? 'Creating...' : 'Create Project'}
      </Button>
    </form>
  )
}
```

## 🌐 REST API Routes (When Needed)

### When to Use API Routes

- ✅ Webhooks from third-party services (external systems calling your app)
- ✅ Public APIs that need to be consumed by non-Next.js clients

**Note**: Even these cases are RARE in this project. Default to Server Actions.

### API Route Template

```typescript
// app/api/work-orders/route.ts
import { NextRequest, NextResponse } from "next/server";
import { db } from "@/lib/getDatabase";
import { workOrders } from "@/schema/schema";
import { getCurrentUser } from "@/lib/auth-helpers-server";
import { eq, and, desc } from "drizzle-orm";

/**
 * GET /api/work-orders
 * Fetch work orders with optional filters
 */
export async function GET(request: NextRequest) {
  try {
    // 1. Authentication
    const user = await getCurrentUser();
    if (!user) {
      return NextResponse.json({ error: "Not authenticated" }, { status: 401 });
    }

    // 2. Parse query parameters
    const { searchParams } = new URL(request.url);
    const status = searchParams.get("status");
    const assignedTo = searchParams.get("assignedTo");

    // 3. Build query
    const conditions = [];
    if (status) {
      conditions.push(eq(workOrders.status, status));
    }
    if (assignedTo) {
      conditions.push(eq(workOrders.assignedTo, assignedTo));
    }

    // 4. Fetch data (RLS will filter based on user)
    const results = await db.query.workOrders.findMany({
      where: conditions.length > 0 ? and(...conditions) : undefined,
      orderBy: [desc(workOrders.createdAt)],
      with: {
        user: {
          columns: {
            id: true,
            name: true,
            email: true,
          },
        },
      },
    });

    // 5. Return response
    return NextResponse.json({
      success: true,
      data: results,
    });
  } catch (error) {
    console.error("Error fetching work orders:", error);
    return NextResponse.json(
      { error: "Internal server error" },
      { status: 500 },
    );
  }
}

/**
 * POST /api/work-orders
 * Create a new work order
 */
export async function POST(request: NextRequest) {
  try {
    const user = await getCurrentUser();
    if (!user) {
      return NextResponse.json({ error: "Not authenticated" }, { status: 401 });
    }

    // Parse body
    const body = await request.json();
    const { title, description, dueDate, assignedTo } = body;

    // Validate
    if (!title || title.trim().length === 0) {
      return NextResponse.json({ error: "Title is required" }, { status: 400 });
    }

    // Create work order
    const [newWorkOrder] = await db
      .insert(workOrders)
      .values({
        title: title.trim(),
        description: description?.trim() || "",
        dueDate: dueDate ? new Date(dueDate) : null,
        assignedTo: assignedTo || null,
        userId: user.id,
        status: "draft",
      })
      .returning();

    return NextResponse.json(
      {
        success: true,
        data: newWorkOrder,
      },
      { status: 201 },
    );
  } catch (error) {
    console.error("Error creating work order:", error);
    return NextResponse.json(
      { error: "Internal server error" },
      { status: 500 },
    );
  }
}
```

### Dynamic Route Template

```typescript
// app/api/work-orders/[id]/route.ts
import { NextRequest, NextResponse } from "next/server";
import { db } from "@/lib/getDatabase";
import { workOrders } from "@/schema/schema";
import { getCurrentUser } from "@/lib/auth-helpers-server";
import { eq } from "drizzle-orm";

type Params = {
  params: {
    id: string;
  };
};

/**
 * GET /api/work-orders/[id]
 */
export async function GET(request: NextRequest, { params }: Params) {
  try {
    const user = await getCurrentUser();
    if (!user) {
      return NextResponse.json({ error: "Not authenticated" }, { status: 401 });
    }

    const workOrder = await db.query.workOrders.findFirst({
      where: eq(workOrders.id, params.id),
      with: {
        user: true,
      },
    });

    if (!workOrder) {
      return NextResponse.json({ error: "Not found" }, { status: 404 });
    }

    return NextResponse.json({ success: true, data: workOrder });
  } catch (error) {
    console.error("Error fetching work order:", error);
    return NextResponse.json(
      { error: "Internal server error" },
      { status: 500 },
    );
  }
}

/**
 * PUT /api/work-orders/[id]
 */
export async function PUT(request: NextRequest, { params }: Params) {
  try {
    const user = await getCurrentUser();
    if (!user) {
      return NextResponse.json({ error: "Not authenticated" }, { status: 401 });
    }

    // Check existence and ownership
    const existing = await db.query.workOrders.findFirst({
      where: eq(workOrders.id, params.id),
    });

    if (!existing) {
      return NextResponse.json({ error: "Not found" }, { status: 404 });
    }

    if (existing.userId !== user.id) {
      return NextResponse.json({ error: "Forbidden" }, { status: 403 });
    }

    // Update
    const body = await request.json();
    const [updated] = await db
      .update(workOrders)
      .set({
        ...body,
        updatedAt: new Date(),
      })
      .where(eq(workOrders.id, params.id))
      .returning();

    return NextResponse.json({ success: true, data: updated });
  } catch (error) {
    console.error("Error updating work order:", error);
    return NextResponse.json(
      { error: "Internal server error" },
      { status: 500 },
    );
  }
}

/**
 * DELETE /api/work-orders/[id]
 */
export async function DELETE(request: NextRequest, { params }: Params) {
  try {
    const user = await getCurrentUser();
    if (!user) {
      return NextResponse.json({ error: "Not authenticated" }, { status: 401 });
    }

    const existing = await db.query.workOrders.findFirst({
      where: eq(workOrders.id, params.id),
    });

    if (!existing) {
      return NextResponse.json({ error: "Not found" }, { status: 404 });
    }

    if (existing.userId !== user.id) {
      return NextResponse.json({ error: "Forbidden" }, { status: 403 });
    }

    // Soft delete
    await db
      .update(workOrders)
      .set({ deletedAt: new Date() })
      .where(eq(workOrders.id, params.id));

    return NextResponse.json({ success: true });
  } catch (error) {
    console.error("Error deleting work order:", error);
    return NextResponse.json(
      { error: "Internal server error" },
      { status: 500 },
    );
  }
}
```

## 📋 API Response Standards

### Consistent Response Format

```typescript
// Success Response
{
  "success": true,
  "data": { /* result data */ }
}

// Error Response
{
  "success": false,
  "error": "Human-readable error message"
}

// List Response (with pagination)
{
  "success": true,
  "data": [ /* items */ ],
  "pagination": {
    "total": 100,
    "page": 1,
    "limit": 10,
    "pages": 10
  }
}
```

### HTTP Status Codes

| Code | Meaning               | When to Use                                         |
| ---- | --------------------- | --------------------------------------------------- |
| 200  | OK                    | Successful GET, PUT, DELETE                         |
| 201  | Created               | Successful POST (resource created)                  |
| 204  | No Content            | Successful DELETE with no response body             |
| 400  | Bad Request           | Invalid input, validation error                     |
| 401  | Unauthorized          | Not authenticated                                   |
| 403  | Forbidden             | Authenticated but not authorized                    |
| 404  | Not Found             | Resource doesn't exist                              |
| 409  | Conflict              | Resource conflict (duplicate, constraint violation) |
| 500  | Internal Server Error | Unexpected server error                             |

## 🔐 Authentication & Authorization

### Authentication Check

```typescript
import { getCurrentUser } from "@/lib/auth-helpers-server";

export async function GET(request: NextRequest) {
  const user = await getCurrentUser();

  if (!user) {
    return NextResponse.json({ error: "Not authenticated" }, { status: 401 });
  }

  // Continue with authenticated request
}
```

### Authorization Check

```typescript
// Check ownership
const resource = await db.query.projects.findFirst({
  where: eq(projects.id, projectId),
});

if (!resource) {
  return NextResponse.json({ error: "Not found" }, { status: 404 });
}

if (resource.userId !== user.id) {
  return NextResponse.json({ error: "Forbidden" }, { status: 403 });
}

// Check role
const hasPermission = user.role === "admin" || user.role === "manager";
if (!hasPermission) {
  return NextResponse.json({ error: "Forbidden" }, { status: 403 });
}
```

## ✅ Input Validation

### Using Zod for Validation

```typescript
import { z } from "zod";

const createWorkOrderSchema = z.object({
  title: z.string().min(1, "Title is required").max(200),
  description: z.string().max(2000).optional(),
  status: z.enum(["draft", "pending", "approved", "in_progress", "completed"]),
  dueDate: z.string().datetime().optional(),
  assignedTo: z.string().uuid().optional(),
});

export async function POST(request: NextRequest) {
  try {
    const body = await request.json();

    // Validate
    const validationResult = createWorkOrderSchema.safeParse(body);

    if (!validationResult.success) {
      return NextResponse.json(
        {
          error: "Validation failed",
          details: validationResult.error.issues,
        },
        { status: 400 },
      );
    }

    const data = validationResult.data;

    // Proceed with validated data
    // ...
  } catch (error) {
    // Handle error
  }
}
```

## 🔄 Data Revalidation

### When to Revalidate

```typescript
import { revalidatePath, revalidateTag } from "next/cache";

// After creating/updating/deleting
export async function createProject(formData: FormData) {
  // ... create project

  // Revalidate specific path
  revalidatePath("/projects");
  revalidatePath("/");

  // Or revalidate by tag (if using fetch with tags)
  revalidateTag("projects");
}
```

---

## 💡 Custom API Guidelines

### ⚠️ CRITICAL: NO REST API Routes

<!-- Zaktualizowano: 2026-02-13 -->

**MANDATORY RULE**:

- ❌ **DO NOT create REST API routes** (`app/api/*/route.ts`)
- ✅ **USE Server Actions ONLY** for all data operations

**ONLY Exception**: Webhooks from external services (e.g., payment providers) or integrations with external service providers

**Why?**

- Server Actions are more efficient
- Better type safety
- Automatic revalidation
- No API route overhead

### Server Actions with Typed Schema

<!-- Zaktualizowano: 2026-02-13 -->

**Working with Properly Typed Database Schema:**

```typescript
"use server";

import { revalidatePath } from "next/cache";
import { db } from "@/lib/getDatabase";
import { workOrders } from "@/schema/schema";
import { getCurrentUser } from "@/lib/auth-helpers-server";
import { z } from "zod";
import { eq } from "drizzle-orm";

// Define input schemas with Zod
const createWorkOrderSchema = z.object({
  title: z.string().min(1, "Title is required").max(200),
  description: z.string().max(2000).optional(),
  status: z
    .enum(["draft", "pending", "approved", "completed"])
    .default("draft"),
  assignedTo: z.string().uuid().nullable().optional(),
  dueDate: z.coerce.date().nullable().optional(),
  budget: z.number().positive().nullable().optional(),
  priority: z.number().int().min(0).max(5).default(0),
});

const updateWorkOrderSchema = createWorkOrderSchema.partial();

type ActionResult<T = void> =
  | { success: true; data: T }
  | { success: false; error: string };

/**
 * Create work order - stores data in typed columns
 */
export async function createWorkOrder(
  formData: FormData,
): Promise<ActionResult<{ id: string }>> {
  try {
    const user = await getCurrentUser();
    if (!user) {
      return { success: false, error: "Not authenticated" };
    }

    // Parse and validate data
    const rawData = {
      title: formData.get("title"),
      description: formData.get("description") || undefined,
      status: formData.get("status") || "draft",
      assignedTo: formData.get("assignedTo") || null,
      dueDate: formData.get("dueDate") || null,
      budget: formData.get("budget") ? Number(formData.get("budget")) : null,
      priority: formData.get("priority") ? Number(formData.get("priority")) : 0,
    };

    const validationResult = createWorkOrderSchema.safeParse(rawData);
    if (!validationResult.success) {
      return {
        success: false,
        error: validationResult.error.issues[0].message,
      };
    }

    // Insert with typed columns
    const [newWorkOrder] = await db
      .insert(workOrders)
      .values({
        ...validationResult.data,
        createdBy: user.id,
      })
      .returning();

    revalidatePath("/work-orders");

    return {
      success: true,
      data: { id: newWorkOrder.id },
    };
  } catch (error) {
    console.error("Error creating work order:", error);
    return { success: false, error: "Failed to create work order" };
  }
}

/**
 * Update work order - update specific columns
 */
export async function updateWorkOrder(
  id: string,
  formData: FormData,
): Promise<ActionResult> {
  try {
    const user = await getCurrentUser();
    if (!user) {
      return { success: false, error: "Not authenticated" };
    }

    // Get existing work order
    const [existing] = await db
      .select()
      .from(workOrders)
      .where(eq(workOrders.id, id));

    if (!existing) {
      return { success: false, error: "Not found" };
    }

    // Parse updates
    const updates: Record<string, unknown> = {};
    const title = formData.get("title");
    const status = formData.get("status");
    const description = formData.get("description");

    if (title) updates.title = title;
    if (status) updates.status = status;
    if (description !== null) updates.description = description;

    // Validate updates
    const validationResult = updateWorkOrderSchema.safeParse(updates);
    if (!validationResult.success) {
      return { success: false, error: "Invalid data" };
    }

    // Update typed columns
    await db
      .update(workOrders)
      .set({
        ...validationResult.data,
        updatedAt: new Date(),
      })
      .where(eq(workOrders.id, id));

    revalidatePath("/work-orders");
    revalidatePath(`/work-orders/${id}`);

    return { success: true, data: undefined };
  } catch (error) {
    console.error("Error updating work order:", error);
    return { success: false, error: "Failed to update" };
  }
}

/**
 * Fetch work orders - query typed columns
 */
export async function getWorkOrders() {
  const user = await getCurrentUser();
  if (!user) {
    throw new Error("Not authenticated");
  }

  return await db
    .select()
    .from(workOrders)
    .where(eq(workOrders.deletedAt, null))
    .orderBy(workOrders.createdAt);
}

/**
 * Filter by status - simple column query
 */
export async function getWorkOrdersByStatus(status: string) {
  const user = await getCurrentUser();
  if (!user) {
    throw new Error("Not authenticated");
  }

  return await db
    .select()
    .from(workOrders)
    .where(eq(workOrders.status, status))
    .orderBy(workOrders.createdAt);
}
```

### Rate Limiting

<!-- Dodaj tutaj zasady rate limiting -->

### Webhooks

<!-- Dodaj tutaj zasady obsługi webhooks -->

### Third-Party Integrations

<!-- Dodaj tutaj zasady integracji z zewnętrznymi API -->

### Error Logging

<!-- Dodaj tutaj zasady logowania błędów -->

---

**Last Updated**: 2026-02-13
**Version**: 1.1.0