# Query API Surface

These are ALL available methods for Query. Do not use any method not listed here.

## Types

```typescript
type Query<T, E> = OkSome<T> | OkNone | ErrNone<E>
type QueryPromise<T, E> = Promise<Query<T, E>>
type OkSomePromise<T> = Promise<OkSome<T>>
type OkNonePromise = Promise<OkNone>
type ErrNonePromise<E> = Promise<ErrNone<E>>
type QueryPartitionResult<T, E> = { values: T[]; noneCount: number; errors: E[] }
type QueryFromType<T> = /* conditional: OkSome<NonNullable<T>> if T excludes null|undefined, else OkSome<NonNullable<T>> | OkNone */
```

## Factory Functions

```typescript
function okSome<T>(value: T): OkSome<T>
function okNone(): OkNone  // returns frozen singleton
function errNone<E>(error: E): ErrNone<E>
```

## OkSome<T> Instance Methods

```typescript
class OkSome<T> {
  readonly value: T

  isSome(): this is OkSome<T>
  isNone(): this is never
  isErr(): this is never

  map<U>(fn: (value: T) => U): OkSome<U>
  mapErr<F>(): OkSome<T>

  flatMap<R extends Query<any, any>>(fn: (value: T) => R): R
  flatMapErr(): this

  match<U>(onSome: (value: T) => U, onNone: () => U, onErr: (error: never) => U): U

  // Overload 1: type-narrowing predicate
  filter<U extends T>(predicate: (value: T) => value is U): OkSome<U> | OkNone
  // Overload 2: boolean predicate
  filter(predicate: (value: T) => boolean): OkSome<T> | OkNone

  toNullable(): T
  toUndefined(): T
  toString(): string
}
```

## OkNone Instance Methods

```typescript
class OkNone {
  // OkNone has no .value or .err property

  isSome(): this is never
  isNone(): this is OkNone
  isErr(): this is never

  map<U>(): OkNone
  mapErr<F>(): OkNone

  flatMap(): this
  flatMapErr(): this

  match<U>(onSome: (value: never) => U, onNone: () => U, onErr: (error: never) => U): U

  filter(): OkNone

  toNullable(): null
  toUndefined(): undefined
  toString(): string
}
```

## ErrNone<E> Instance Methods

```typescript
class ErrNone<E> {
  readonly err: E

  isSome(): this is never
  isNone(): this is never
  isErr(): this is ErrNone<E>

  map<U>(): ErrNone<E>
  mapErr<F>(fn: (error: E) => F): ErrNone<F>

  flatMap(): this
  flatMapErr<R extends Query<any, any>>(fn: (error: E) => R): R

  match<U>(onSome: (value: never) => U, onNone: () => U, onErr: (error: E) => U): U

  filter(): ErrNone<E>

  toNullable(): null
  toUndefined(): undefined
  toString(): string
}
```

## Query Namespace (Static Methods)

```typescript
Query.from<T>(value: T): QueryFromType<T>
Query.from<T, E = unknown>(fn: () => T, errorMap?: (error: unknown) => E): QueryFromType<T> | ErrNone<E>
Query.isQuery<T, E>(value: unknown): value is Query<T, E>
Query.all<T>(queries: OkSome<T>[]): OkSome<T[]>
Query.all<T, E>(queries: Query<T, E>[]): Query<T[], E>
Query.partition<T, E>(queries: Query<T, E>[]): QueryPartitionResult<T, E>
Query.compact<T, E>(queries: Query<T, E>[]): T[]
Query.some<T, E>(queries: Query<T, E>[]): boolean
Query.every<T, E>(queries: Query<T, E>[]): boolean
```

## QueryPromise Namespace (Async Methods)

```typescript
QueryPromise.from<T, E = unknown>(fn: () => Promise<T>, errorMap?: (error: unknown) => E): Promise<QueryFromType<T> | ErrNone<E>>
QueryPromise.all<T>(promises: Promise<OkSome<T>>[]): Promise<OkSome<T[]>>
QueryPromise.all<T, E>(promises: Promise<Query<T, E>>[]): Promise<Query<T[], E>>
QueryPromise.partition<T, E>(promises: Promise<Query<T, E>>[]): Promise<QueryPartitionResult<T, E>>
QueryPromise.compact<T, E>(promises: Promise<Query<T, E>>[]): Promise<T[]>
QueryPromise.some<T, E>(promises: Promise<Query<T, E>>[]): Promise<boolean>
QueryPromise.every<T, E>(promises: Promise<Query<T, E>>[]): Promise<boolean>
```