import { apiFetch } from "@/lib/next-zero-rpc/apiClient";
import { assertNever } from "@/lib/next-zero-rpc/responses";

// 1. Happy Path — response is fully typed from your route handler
const [ data
{ id: string; name: string; role: string } | null
, err
const err:
  ApiErrorPayload<"system:unknown-error"> |
  ApiErrorPayload<"system:database-error"> |
  null
 ] = await apiFetch("/api/users/123", { method: "GET" });

if (err) {
  console.error(err.message);
} else {
  // data.name, data.id, data.role — inferred directly from the route!
  console.log(data.name, data.role);
}

// 2. Exhaustive Error Narrowing
// TypeScript narrows err.code to exactly the codes this route can return.
// assertNever() is a compile-time guard — remove any case and TS errors.
const [ data2
{ id: string; name: string; role: string } | null
, err2
const err2:
  ApiErrorPayload<"system:unknown-error"> |
  ApiErrorPayload<"system:database-error"> |
  null
 ] = await apiFetch("/api/users/123", { method: "GET" });

if (err2) {
  const code = err2.code;
  switch (code) {
    case "system:database-error":
      console.error("User not found!");
      break;
    // Intentionally missing 'system:unknown-error' to show TS error
    default:
      assertNever(code
Argument of type '"system:unknown-error"' is not assignable to parameter of type 'never'.
); // TS Error if you miss a case!
  }
}

// 3. TypeScript Catches Typos — compile error on an invalid route path
await apiFetch("/api/uwsers/34"
Argument of type '"/api/uwsers/34"' is not assignable to parameter of type 'keyof KnownRoutes'.
, { method: "DELETE" });

// 4. TypeScript Catches Wrong Methods — POST is not exported from /api/status
await apiFetch("/api/status", { method
Type '"POST"' is not assignable to type '"GET"'.
: "POST" });

// 5a. IDE IntelliSense: Available Routes
// Place cursor inside the string — your IDE lists every registered route.
await apiFetch(""
/api/auth/login
↵/api/auth/login
/api/extreme/[orgId]/projects/[projectId]/tasks/[...catchall]
/api/extreme/complex-types
/api/extreme/methods
/api/status
/api/users/[userId]
/api/users/active);

// 5b. IDE IntelliSense: Allowed Methods
// Place cursor inside method — your IDE narrows to only what this route exports.
await apiFetch("/api/users/34", { method: ""
DELETE
↵DELETE
GET
PUT });

// 6. Static vs Dynamic Route Precedence
// /api/users/active matches the static route exactly — not the [userId] segment.
const [ activeUsers
const activeUsers: {
  activeUsers: {
    id: string;
    name: string;
    role: string;
  }[];
  count: number;
} | null
, errActive
const errActive: ApiErrorPayload<"system:unknown-error"> | null
 ] = await apiFetch("/api/users/active", { method: "GET" });

// /api/users/123 correctly resolves to the dynamic [userId] route.
const [ singleUser
const singleUser: {
  id: string;
  name: string;
  role: string;
} | null
, errSingle
const errSingle:
  ApiErrorPayload<"system:unknown-error"> |
  ApiErrorPayload<"system:database-error"> |
  null
 ] = await apiFetch("/api/users/123", { method: "GET" });

// 7. Multi-Variable Template Literals
// All three runtime variables resolve independently — TypeScript still correctly
// matches the route /api/extreme/[orgId]/projects/[projectId]/tasks/[...catchall]
const orgId = "acme";
const projectId = "proj-99";
const catchall = "step1/step2/step3";
const [ task
const task: {
  resolvedOrgId: string;
  resolvedProjectId: string;
  dynamicSegments: string[];
  deeplyNestedMatrix: {
    layer1: {
      layer2: {
        layer3: readonly [readonly [{
          readonly x: 1;
          readonly y: 2;
        }, {
          readonly x: 3;
          readonly y: 4;
        }], readonly [{
          readonly x: 5;
          readonly y: 6;
        }, {
          readonly x: 7;
          readonly y: 8;
        }]];
      };
    };
  };
} | null
, taskErr
const taskErr: ApiErrorPayload<"system:unknown-error"> | null
 ] = await apiFetch(
  `/api/extreme/${orgId}/projects/${projectId}/tasks/${catchall}` ,
  { method: "GET" }
);

// 8. Deeply Nested Catch-All Routes
const [ res3
const res3: {
  resolvedOrgId: string;
  resolvedProjectId: string;
  dynamicSegments: string[];
  deeplyNestedMatrix: {
    layer1: {
      layer2: {
        layer3: readonly [readonly [{
          readonly x: 1;
          readonly y: 2;
        }, {
          readonly x: 3;
          readonly y: 4;
        }], readonly [{
          readonly x: 5;
          readonly y: 6;
        }, {
          readonly x: 7;
          readonly y: 8;
        }]];
      };
    };
  };
} | null
, err3
const err3: ApiErrorPayload<"system:unknown-error"> | null
 ] = await apiFetch(
  "/api/extreme/acme/projects/xyz/tasks/a/b/c",
  { method: "GET" }
);

// 9. Strict Method Matching — each method has its own unique response type
const [ resGet
const resGet: {
  method: "GET";
  data: number[];
} | null
, errGet
const errGet: ApiErrorPayload<"system:unknown-error"> | null
 ] = await apiFetch("/api/extreme/methods", { method: "GET" });

// 10. Extreme Recursive Type Inference
// Discriminated unions, recursive trees, intersections — all preserved end-to-end.
const [ res2
const res2: {
  union: {
    type: "success";
    payload: {
      id: string;
      metrics: Record<string, number[]>;
    };
  };
  tree: RecursiveTree<DiscriminatedUnion>;
  intersection: {
    base: string;
  } & {
    variantB: boolean;
  };
  matrixStringTuple: readonly ["a", "b", "c"];
  nullableField: null;
  optionalField: string | undefined;
  bigIntSimulate: string;
} | null
, err2b
const err2b:
  ApiErrorPayload<"system:unknown-error"> |
  ApiErrorPayload<"system:internal-server-error"> |
  ApiErrorPayload<"validation:invalid-payload"> |
  null
 ] = await apiFetch("/api/extreme/complex-types", { method: "POST" });

// 11. Query Strings — safely stripped before validating the route path
const [ withQuery
const withQuery: {
  id: string;
  name: string;
  role: string;
} | null
, errQuery
const errQuery:
  ApiErrorPayload<"system:unknown-error"> |
  ApiErrorPayload<"system:database-error"> |
  null
 ] = await apiFetch("/api/users/123?include=profile", { method: "GET" });