import { z } from "zod";

// 1. VALIDATION HELPERS (Reusable Refinements)
export const SafePathSchema = z
  .string()
  .min(1)
  .refine((p) => !p.includes(".."), "No traversal allowed");

// 2. INPUT (The Command) - "Parse, don't validate"
export const MyTaskInputSchema = z.object({
  path: SafePathSchema,
  force: z.boolean().default(false),
});
export type MyTaskInput = z.infer<typeof MyTaskInputSchema>;

// 3. ERROR CODES (Exhaustive)
export const MyTaskErrorCode = z.enum([
  "FILE_NOT_FOUND",
  "PERMISSION_DENIED",
  "UNKNOWN_ERROR",
]);

// 4. RESULT (The Monad)
export const MyTaskSuccess = z.object({
  success: z.literal(true),
  data: z.string(), // The output payload
});

export const MyTaskFailure = z.object({
  success: z.literal(false),
  error: z.object({
    code: MyTaskErrorCode,
    message: z.string(),
    suggestion: z.string().optional(),
    recoverable: z.boolean(),
  }),
});

export type MyTaskResult =
  | z.infer<typeof MyTaskSuccess>
  | z.infer<typeof MyTaskFailure>;

// 5. INTERFACE (The Capability)
export interface MyTaskSpec {
  execute(input: MyTaskInput): Promise<MyTaskResult>;
}

import { MyTaskSpec, MyTaskInput, MyTaskResult } from "./spec.js";
import * as fs from "fs";

export class MyTaskHandler implements MyTaskSpec {
  async execute(input: MyTaskInput): Promise<MyTaskResult> {
    try {
      // 1. Business Logic
      if (!fs.existsSync(input.path)) {
        // 2. Explicit Error Return (No Throwing)
        return {
          success: false,
          error: {
            code: "FILE_NOT_FOUND",
            message: `Path does not exist: ${input.path}`,
            recoverable: true,
          },
        };
      }

      // 3. Success Return
      return {
        success: true,
        data: "Operation complete",
      };
    } catch (error) {
      // 4. Safety Net: Catch unknown runtime errors
      return {
        success: false,
        error: {
          code: "UNKNOWN_ERROR",
          message: error instanceof Error ? error.message : String(error),
          recoverable: false,
        },
      };
    }
  }
}

// spec.test.ts
import { MyTaskInputSchema } from "./spec";

const invalidCases = [
  { val: "../etc/passwd", err: "No traversal allowed" },
  { val: "", err: "min(1)" },
];

test.each(invalidCases)("validates paths", ({ val, err }) => {
  const result = MyTaskInputSchema.safeParse({ path: val });
  expect(result.success).toBe(false);
});

// handler.test.ts
import { MyTaskHandler } from "./handler";
import { vi } from "vitest"; // or jest

test("returns FILE_NOT_FOUND if path missing", async () => {
  // MOCK
  vi.mocked(fs.existsSync).mockReturnValue(false);

  // EXECUTE
  const handler = new MyTaskHandler();
  const result = await handler.execute({ path: "/fake" });

  // ASSERT (Check the Result Object)
  expect(result.success).toBe(false);
  if (!result.success) {
    expect(result.error.code).toBe("FILE_NOT_FOUND");
  }
});