API Handler

API Handler Skill

Overview

Use withApiHandler for all API routes. It eliminates boilerplate and ensures consistent auth, validation, and error handling.

Basic Usage

import { withApiHandler } from "@/lib/api/handler";
import { z } from "zod";

const mySchema = z.object({
  name: z.string(),
  count: z.number().optional(),
});

export const POST = withApiHandler({
  auth: 'required',
  schema: mySchema,
}, async ({ user, body, adminClient }) => {
  const { data } = await adminClient
    .from("table")
    .insert({ ...body, user_id: user.id })
    .select()
    .single();
  
  return { success: true, data };
});

Auth Levels

League Auth Examples

// Any league member can access
export const GET = withApiHandler({
  auth: 'league_member',
}, async ({ user, membership }) => {
  // membership.role is 'owner', 'admin', or 'member'
  return { role: membership?.role };
});

// Only admins and owners
export const PUT = withApiHandler({
  auth: 'league_admin',
  schema: updateSchema,
}, async ({ user, body, adminClient, membership }) => {
  // membership.role is guaranteed 'admin' or 'owner'
  return { updated: true };
});

League ID Resolution

For league auth, the handler looks for league_id in this order:

1. Request body ({ league_id: "..." })
2. URL params (/api/leagues/[id])
3. Query params (?league_id=...)

Handler Context

The handler function receives:

interface HandlerContext<T> {
  user: User | null;           // Authenticated user
  body: T;                     // Parsed & validated request body
  adminClient: SupabaseClient; // Admin client (bypasses RLS)
  request: Request;            // Original request
  params: Record<string, string>; // URL params (e.g., { id: 'xxx' })
  membership: Membership | null;  // For league_* auth levels
}

Schema Validation

Use Zod for request validation:

const createSchema = z.object({
  name: z.string().min(1).max(100),
  description: z.string().optional(),
  is_active: z.boolean().default(true),
  league_id: z.string().uuid(),
});

export const POST = withApiHandler({
  auth: 'required',
  schema: createSchema,
}, async ({ body }) => {
  // body is fully typed and validated
  console.log(body.name); // string
  console.log(body.is_active); // boolean (defaulted to true if not provided)
});

Validation Errors

If validation fails, the handler automatically returns:

{
  "error": "Validation failed: name: Required, league_id: Invalid uuid"
}

Returning Responses

Return Object (Auto-wrapped)

return { success: true, data };
// Becomes: Response with JSON { success: true, data }

Return Response Directly

import { json, badRequest, forbidden } from "@/lib/api";

// Custom status or headers
return json({ data }, { status: 201 });

// Error responses
return badRequest("Invalid input");
return forbidden("Not allowed");

Error Handling

Errors thrown in the handler are caught and logged:

export const POST = withApiHandler({
  auth: 'required',
}, async ({ adminClient }) => {
  const { data, error } = await adminClient.from("table").insert({});
  
  if (error) {
    // Use AppError for typed errors
    throw new AppError({
      code: ErrorCode.DB_INSERT_FAILED,
      message: error.message,
      context: { table: 'table' },
    });
  }
  
  return { success: true };
});

Reference the error-handling skill for more on AppError.

Complete Example

// src/app/api/leagues/[id]/members/route.ts

import { withApiHandler } from "@/lib/api/handler";
import { z } from "zod";
import { AppError, ErrorCode } from "@/lib/errors";

const addMemberSchema = z.object({
  user_id: z.string().uuid(),
  role: z.enum(['member', 'admin']).default('member'),
});

// GET - List members (any league member can view)
export const GET = withApiHandler({
  auth: 'league_member',
}, async ({ params, adminClient }) => {
  const { data } = await adminClient
    .from("memberships")
    .select("*, users(*)")
    .eq("league_id", params.id);
  
  return { members: data };
});

// POST - Add member (only admins/owners)
export const POST = withApiHandler({
  auth: 'league_admin',
  schema: addMemberSchema,
}, async ({ params, body, adminClient }) => {
  const { data, error } = await adminClient
    .from("memberships")
    .insert({
      league_id: params.id,
      user_id: body.user_id,
      role: body.role,
    })
    .select()
    .single();
  
  if (error) {
    throw new AppError({
      code: ErrorCode.DB_INSERT_FAILED,
      message: "Failed to add member",
      context: { error: error.message },
    });
  }
  
  return { success: true, member: data };
});

Legacy Pattern

For existing routes not yet migrated:

import { createServerSupabaseClient, createAdminClient } from "@/lib/supabase/server";
import { json, badRequest, unauthorized } from "@/lib/api";

export async function GET(request: Request) {
  const supabase = await createServerSupabaseClient();
  const { data: { user } } = await supabase.auth.getUser();
  if (!user) return unauthorized();

  const adminClient = createAdminClient();
  const { data } = await adminClient.from("table").select("*");
  return json({ data });
}

Rule: Use withApiHandler for all NEW routes. Migrate legacy routes only when modifying them for other reasons.

Reference Files

Related Skills

• supabase-patterns - Database operations with adminClient
• error-handling - Error codes and AppError usage
• architecture-philosophy - Why we use this pattern