import { Result } from "better-result";

// Wrap throwing functions
const parsed = Result.try(() => JSON.parse(input));

// Check and use
if (Result.isOk(parsed)) {
  console.log(parsed.value);
} else {
  console.error(parsed.error);
}

// Or use pattern matching
const message = parsed.match({
  ok: (data) => `Got: ${data.name}`,
  err: (e) => `Failed: ${e.message}`,
});

// Success
const ok = Result.ok(42);

// Error
const err = Result.err(new Error("failed"));

// From throwing function
const result = Result.try(() => riskyOperation());

// From promise
const result = await Result.tryPromise(() => fetch(url));

// With custom error handling
const result = Result.try({
  try: () => JSON.parse(input),
  catch: (e) => new ParseError(e),
});

const result = Result.ok(2)
  .map((x) => x * 2) // Ok(4)
  .andThen(
    (
      x, // Chain Result-returning functions
    ) => (x > 0 ? Result.ok(x) : Result.err("negative")),
  );

// Standalone functions (data-first or data-last)
Result.map(result, (x) => x + 1);
Result.map((x) => x + 1)(result); // Pipeable

// Transform error type
const result = fetchUser(id).mapError((e) => new AppError(`Failed to fetch user: ${e.message}`));

// Recover from specific errors
const result = fetchUser(id).match({
  ok: (user) => Result.ok(user),
  err: (e) => (e._tag === "NotFoundError" ? Result.ok(defaultUser) : Result.err(e)),
});

// Unwrap (throws on Err)
const value = result.unwrap();
const value = result.unwrap("custom error message");

// With fallback
const value = result.unwrapOr(defaultValue);

// Pattern match
const value = result.match({
  ok: (v) => v,
  err: (e) => fallback,
});

const result = Result.gen(function* () {
  const a = yield* parseNumber(inputA); // Unwraps or short-circuits
  const b = yield* parseNumber(inputB);
  const c = yield* divide(a, b);
  return Result.ok(c);
});
// Result<number, ParseError | DivisionError>

const result = await Result.gen(async function* () {
  const user = yield* Result.await(fetchUser(id));
  const posts = yield* Result.await(fetchPosts(user.id));
  return Result.ok({ user, posts });
});

class ParseError extends TaggedError("ParseError")<{ message: string }>() {}
class ValidationError extends TaggedError("ValidationError")<{ message: string }>() {}
class AppError extends TaggedError("AppError")<{ source: string; message: string }>() {}

const result = Result.gen(function* () {
  const parsed = yield* parseInput(input); // Err: ParseError
  const valid = yield* validate(parsed); // Err: ValidationError
  return Result.ok(valid);
}).mapError((e): AppError => new AppError({ source: e._tag, message: e.message }));
// Result<ValidatedData, AppError> - error union normalized to single type

const result = await Result.tryPromise(() => fetch(url), {
  retry: {
    times: 3,
    delayMs: 100,
    backoff: "exponential", // or "linear" | "constant"
  },
});

class NetworkError extends TaggedError("NetworkError")<{ message: string }>() {}
class ValidationError extends TaggedError("ValidationError")<{ message: string }>() {}

const result = await Result.tryPromise(
  {
    try: () => fetchData(url),
    catch: (e) =>
      e instanceof TypeError // Network failures often throw TypeError
        ? new NetworkError({ message: (e as Error).message })
        : new ValidationError({ message: String(e) }),
  },
  {
    retry: {
      times: 3,
      delayMs: 100,
      backoff: "exponential",
      shouldRetry: (e) => e._tag === "NetworkError", // Only retry network errors
    },
  },
);

class ApiError extends TaggedError("ApiError")<{
  message: string;
  rateLimited: boolean;
}>() {}

const result = await Result.tryPromise(
  {
    try: () => callApi(url),
    catch: async (e) => {
      // Fetch async state in catch handler
      const retryAfter = await redis.get(`ratelimit:${userId}`);
      return new ApiError({
        message: (e as Error).message,
        rateLimited: retryAfter !== null,
      });
    },
  },
  {
    retry: {
      times: 3,
      delayMs: 100,
      backoff: "exponential",
      shouldRetry: (e) => !e.rateLimited, // Sync predicate uses enriched error
    },
  },
);

import { Result, UnhandledException } from "better-result";

// Automatic — error type is UnhandledException
const result = Result.try(() => JSON.parse(input));
//    ^? Result<unknown, UnhandledException>

// Custom handler — you control the error type
const result = Result.try({
  try: () => JSON.parse(input),
  catch: (e) => new ParseError(e),
});
//    ^? Result<unknown, ParseError>

// Same for async
await Result.tryPromise(() => fetch(url));
//    ^? Promise<Result<Response, UnhandledException>>

if (Result.isError(result)) {
  const original = result.error.cause;
  if (original instanceof SyntaxError) {
    // Handle JSON parse error
  }
}

import { Panic, isPanic } from "better-result";

// Callback throws → Panic
Result.ok(1).map(() => {
  throw new Error("bug");
}); // throws Panic

// Generator cleanup throws → Panic
Result.gen(function* () {
  try {
    yield* Result.err("expected failure");
  } finally {
    throw new Error("cleanup bug");
  }
}); // throws Panic

// Catch handler throws → Panic
Result.try({
  try: () => riskyOp(),
  catch: () => {
    throw new Error("bug in handler");
  },
}); // throws Panic

// Catching Panic (for error reporting)
try {
  result.map(() => { throw new Error("bug"); });
} catch (error) {
  if (isPanic(error)) {
    // isPanic() is a type guard function
    console.error("Defect:", error.message, error.cause);
  }

  if (Panic.is(error)) {
    // Panic.is() is a static method (same behavior)
  }

  if (error instanceof Panic) {
    // instanceof works too
  }
}

import { TaggedError, matchError, matchErrorPartial } from "better-result";

// Factory API: TaggedError("Tag")<Props>()
class NotFoundError extends TaggedError("NotFoundError")<{
  id: string;
  message: string;
}>() {}

class ValidationError extends TaggedError("ValidationError")<{
  field: string;
  message: string;
}>() {}

type AppError = NotFoundError | ValidationError;

// Create errors with object args
const err = new NotFoundError({ id: "123", message: "User not found" });

// Exhaustive matching
matchError(error, {
  NotFoundError: (e) => `Missing: ${e.id}`,
  ValidationError: (e) => `Bad field: ${e.field}`,
});

// Partial matching with fallback
matchErrorPartial(
  error,
  { NotFoundError: (e) => `Missing: ${e.id}` },
  (e) => `Unknown: ${e.message}`,
);

// Type guards
TaggedError.is(value); // any tagged error
NotFoundError.is(value); // specific class

class NetworkError extends TaggedError("NetworkError")<{
  url: string;
  status: number;
  message: string;
}>() {
  constructor(args: { url: string; status: number }) {
    super({ ...args, message: `Request to ${args.url} failed: ${args.status}` });
  }
}

new NetworkError({ url: "/api", status: 404 });

import { Result, SerializedResult, ResultDeserializationError } from "better-result";

// Serialize to plain object
const result = Result.ok(42);
const serialized = Result.serialize(result);
// { status: "ok", value: 42 }

// Deserialize back to Result instance
const deserialized = Result.deserialize<number, never>(serialized);
// Ok(42) - can use .map(), .andThen(), etc.

// Invalid input returns ResultDeserializationError
const invalid = Result.deserialize({ foo: "bar" });
if (Result.isError(invalid) && ResultDeserializationError.is(invalid.error)) {
  console.log("Bad input:", invalid.error.value);
}

// Typed boundary for Next.js server actions
async function createUser(data: FormData): Promise<SerializedResult<User, ValidationError>> {
  const result = await validateAndCreate(data);
  return Result.serialize(result);
}

// Client-side
const serialized = await createUser(formData);
const result = Result.deserialize<User, ValidationError>(serialized);