import { Token } from '@rimbu/base';
import { CollectFun, OptLazy, TraverseState } from '@rimbu/common';
import { type Reducer, type FastIterator, type Stream, type StreamSource } from '@rimbu/stream';
import { type StreamSourceHelpers } from '@rimbu/stream/custom';
/**
 * A frozen `IteratorResult` instance representing the completed iterator state.
 * This value is reused by several fast iterator implementations to avoid allocations.
 */
export declare const fixedDoneIteratorResult: IteratorResult<any>;
/**
 * A `FastIterator` that is already exhausted and never yields values.
 * Its `fastNext` method always returns the provided fallback value.
 */
export declare const emptyFastIterator: FastIterator<any>;
/**
 * Returns true if the given `iterator` implements the `FastIterator` interface.
 * @param iterator - the iterator instance to test
 */
export declare function isFastIterator<T>(iterator: Iterator<T>): iterator is FastIterator<T>;
/**
 * A base class for `FastIterator` instances that implements the standard `next`
 * method in terms of the abstract `fastNext` method.
 */
export declare abstract class FastIteratorBase<T> implements FastIterator<T> {
    abstract fastNext<O>(otherwise?: OptLazy<O>): T | O;
    next(): IteratorResult<T>;
}
export declare class ReducerFastIterator<T, R> extends FastIteratorBase<R> {
    readonly sourceIterator: FastIterator<T>;
    readonly reducerInstance: Reducer.Instance<T, R>;
    constructor(sourceIterator: FastIterator<T>, reducerInstance: Reducer.Instance<T, R>);
    fastNext<O>(otherwise?: OptLazy<O>): R | O;
}
export declare class TransformerFastIterator<T, R> extends FastIteratorBase<R> {
    readonly sourceIterator: FastIterator<T>;
    readonly transformerInstance: Reducer.Instance<T, StreamSource<R>>;
    constructor(sourceIterator: FastIterator<T>, transformerInstance: Reducer.Instance<T, StreamSource<R>>);
    ___done: boolean;
    ___currentValues: FastIterator<R> | undefined;
    fastNext<O>(otherwise?: OptLazy<O>): R | O;
}
export declare class ConcatIterator<T> extends FastIteratorBase<T> {
    readonly source: Stream<T>;
    readonly otherSources: StreamSource<T>[];
    readonly streamSourceHelpers: StreamSourceHelpers;
    iterator: FastIterator<T>;
    constructor(source: Stream<T>, otherSources: StreamSource<T>[], streamSourceHelpers: StreamSourceHelpers);
    sourceIndex: number;
    fastNext<O>(otherwise?: OptLazy<O>): T | O;
}
export declare class IndexedIterator<T> extends FastIteratorBase<[number, T]> {
    readonly source: FastIterator<T>;
    readonly startIndex: number;
    constructor(source: FastIterator<T>, startIndex: number);
    index: number;
    fastNext<O>(otherwise?: OptLazy<O> | undefined): [number, T] | O;
}
export declare class FilterIterator<T> extends FastIteratorBase<T> {
    readonly source: FastIterator<T>;
    readonly pred: (value: T, index: number, halt: () => void) => boolean;
    readonly negate: boolean;
    constructor(source: FastIterator<T>, pred: (value: T, index: number, halt: () => void) => boolean, negate: boolean);
    readonly state: TraverseState;
    fastNext<O>(otherwise?: OptLazy<O>): T | O;
}
export declare class FilterPureIterator<T, A extends readonly unknown[]> extends FastIteratorBase<T> {
    readonly source: FastIterator<T>;
    readonly pred: (value: T, ...args: A) => boolean;
    readonly args: A;
    readonly negate: boolean;
    constructor(source: FastIterator<T>, pred: (value: T, ...args: A) => boolean, args: A, negate: boolean);
    fastNext<O>(otherwise?: OptLazy<O>): T | O;
}
export declare class CollectIterator<T, R> extends FastIteratorBase<R> {
    readonly source: FastIterator<T>;
    readonly collectFun: CollectFun<T, R>;
    constructor(source: FastIterator<T>, collectFun: CollectFun<T, R>);
    readonly state: TraverseState;
    fastNext<O>(otherwise?: OptLazy<O>): R | O;
}
export declare class DropWhileIterator<T> extends FastIteratorBase<T> {
    readonly source: FastIterator<T>;
    readonly pred: (value: T, index: number) => boolean;
    readonly negate: boolean;
    constructor(source: FastIterator<T>, pred: (value: T, index: number) => boolean, negate: boolean);
    pass: boolean;
    index: number;
    fastNext<O>(otherwise?: OptLazy<O>): T | O;
}
export declare class TakeIterator<T> extends FastIteratorBase<T> {
    readonly source: FastIterator<T>;
    readonly amount: number;
    constructor(source: FastIterator<T>, amount: number);
    i: number;
    fastNext<O>(otherwise?: OptLazy<O>): T | O;
}
export declare class DropIterator<T> extends FastIteratorBase<T> {
    readonly source: FastIterator<T>;
    readonly amount: number;
    remain: number;
    constructor(source: FastIterator<T>, amount: number);
    fastNext<O>(otherwise?: OptLazy<O>): T | O;
}
export declare class RepeatIterator<T> extends FastIteratorBase<T> {
    readonly source: Stream<T>;
    readonly amount?: number | undefined;
    iterator: FastIterator<T>;
    remain: number | undefined;
    constructor(source: Stream<T>, amount?: number | undefined);
    isEmpty: boolean;
    fastNext<O>(otherwise?: OptLazy<O>): T | O;
}
export declare class ArrayIterator<T> extends FastIteratorBase<T> {
    readonly array: readonly T[];
    readonly startIndex: number;
    readonly endIndex: number;
    i: number;
    constructor(array: readonly T[], startIndex: number, endIndex: number);
    fastNext<O>(otherwise?: OptLazy<O>): T | O;
}
export declare class ArrayReverseIterator<T> extends FastIteratorBase<T> {
    readonly array: readonly T[];
    readonly startIndex: number;
    i: number;
    constructor(array: readonly T[], startIndex: number, endIndex: number);
    fastNext<O>(otherwise?: OptLazy<O>): T | O;
}
export declare class AlwaysIterator<T> extends FastIteratorBase<T> {
    readonly value: T;
    constructor(value: T);
    fastNext(): T;
}
export declare class MapApplyIterator<T extends readonly unknown[], A extends readonly unknown[], R> extends FastIteratorBase<R> {
    readonly f: (...args: [...T, ...A]) => R;
    readonly args: A;
    constructor(source: StreamSource<T>, f: (...args: [...T, ...A]) => R, args: A, streamSourceHelpers: StreamSourceHelpers);
    iter: FastIterator<T>;
    fastNext<O>(otherwise?: OptLazy<O>): R | O;
}
export declare class FilterApplyIterator<T extends readonly unknown[], A extends readonly unknown[]> extends FastIteratorBase<T> {
    readonly pred: (...args: [...T, ...A]) => boolean;
    readonly args: A;
    readonly negate: boolean;
    constructor(source: StreamSource<T>, pred: (...args: [...T, ...A]) => boolean, args: A, negate: boolean, streamSourceHelpers: StreamSourceHelpers);
    iter: FastIterator<T>;
    fastNext<O>(otherwise?: OptLazy<O>): T | O;
}
export declare class RangeUpIterator extends FastIteratorBase<number> {
    readonly start: number;
    readonly end: number | undefined;
    readonly delta: number;
    state: number;
    constructor(start: number | undefined, end: number | undefined, delta: number);
    fastNext<O>(otherwise?: OptLazy<O>): number | O;
}
export declare class RangeDownIterator extends FastIteratorBase<number> {
    readonly start: number;
    readonly end: number | undefined;
    readonly delta: number;
    state: number;
    constructor(start: number | undefined, end: number | undefined, delta: number);
    fastNext<O>(otherwise?: OptLazy<O>): number | O;
}
export declare class RandomIterator extends FastIteratorBase<number> {
    fastNext(): number;
}
export declare class RandomIntIterator extends FastIteratorBase<number> {
    readonly min: number;
    readonly max: number;
    readonly width: number;
    constructor(min: number, max: number);
    fastNext(): number;
}
export declare class UnfoldIterator<T> extends FastIteratorBase<T> {
    readonly getNext: (current: T, index: number, stop: Token) => T | Token;
    constructor(init: T, getNext: (current: T, index: number, stop: Token) => T | Token);
    current: T | Token;
    index: number;
    fastNext<O>(otherwise?: OptLazy<O>): T | O;
}
export declare class ZipWithIterator<I extends readonly unknown[], R> extends FastIteratorBase<R> {
    readonly iterables: {
        [K in keyof I]: StreamSource<I[K]>;
    };
    readonly zipFun: (...values: I) => R;
    constructor(iterables: {
        [K in keyof I]: StreamSource<I[K]>;
    }, zipFun: (...values: I) => R, streamSourceHelpers: StreamSourceHelpers);
    readonly sources: FastIterator<any>[];
    fastNext<O>(otherwise?: OptLazy<O>): R | O;
}
export declare class ZipAllWithItererator<I extends readonly unknown[], F, R> extends FastIteratorBase<R> {
    readonly fillValue: OptLazy<F>;
    readonly iters: {
        [K in keyof I]: StreamSource<I[K]>;
    };
    readonly zipFun: (...values: {
        [K in keyof I]: I[K] | F;
    }) => R;
    constructor(fillValue: OptLazy<F>, iters: {
        [K in keyof I]: StreamSource<I[K]>;
    }, zipFun: (...values: {
        [K in keyof I]: I[K] | F;
    }) => R, streamSourceHelpers: StreamSourceHelpers);
    readonly sources: FastIterator<any>[];
    allDone: boolean;
    fastNext<O>(otherwise?: OptLazy<O>): R | O;
}
export declare class PrependIterator<T> extends FastIteratorBase<T> {
    readonly source: FastIterator<T>;
    readonly item: OptLazy<T>;
    constructor(source: FastIterator<T>, item: OptLazy<T>);
    prependDone: boolean;
    fastNext<O>(otherwise?: OptLazy<O>): T | O;
}
export declare class AppendIterator<T> extends FastIteratorBase<T> {
    readonly source: FastIterator<T>;
    readonly item: OptLazy<T>;
    constructor(source: FastIterator<T>, item: OptLazy<T>);
    appendDone: boolean;
    fastNext<O>(otherwise?: OptLazy<O>): T | O;
}
export declare class MapIterator<T, T2> extends FastIteratorBase<T2> {
    readonly source: FastIterator<T>;
    readonly mapFun: (value: T, index: number) => T2;
    constructor(source: FastIterator<T>, mapFun: (value: T, index: number) => T2);
    readonly state: TraverseState;
    fastNext<O>(otherwise?: OptLazy<O>): T2 | O;
}
export declare class MapPureIterator<T, A extends readonly unknown[], T2> extends FastIteratorBase<T2> {
    readonly source: FastIterator<T>;
    readonly mapFun: (value: T, ...args: A) => T2;
    readonly args: A;
    constructor(source: FastIterator<T>, mapFun: (value: T, ...args: A) => T2, args: A);
    fastNext<O>(otherwise?: OptLazy<O>): T2 | O;
}