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import { Observable } from '../Observable';
import { identity } from '../util/identity';
import { ObservableInput, SchedulerLike } from '../types';
import { isScheduler } from '../util/isScheduler';
import { defer } from './defer';
import { scheduleIterable } from '../scheduled/scheduleIterable';
type ConditionFunc<S> = (state: S) => boolean;
type IterateFunc<S> = (state: S) => S;
type ResultFunc<S, T> = (state: S) => T;
export interface GenerateBaseOptions<S> {
/**
* Initial state.
*/
initialState: S;
/**
* Condition function that accepts state and returns boolean.
* When it returns false, the generator stops.
* If not specified, a generator never stops.
*/
condition?: ConditionFunc<S>;
/**
* Iterate function that accepts state and returns new state.
*/
iterate: IterateFunc<S>;
/**
* SchedulerLike to use for generation process.
* By default, a generator starts immediately.
*/
scheduler?: SchedulerLike;
}
export interface GenerateOptions<T, S> extends GenerateBaseOptions<S> {
/**
* Result selection function that accepts state and returns a value to emit.
*/
resultSelector: ResultFunc<S, T>;
}
/**
* Generates an observable sequence by running a state-driven loop
* producing the sequence's elements, using the specified scheduler
* to send out observer messages.
*
* 
*
* ## Examples
*
* Produces sequence of numbers
*
* ```ts
* import { generate } from 'rxjs';
*
* const result = generate(0, x => x < 3, x => x + 1, x => x);
*
* result.subscribe(x => console.log(x));
*
* // Logs:
* // 0
* // 1
* // 2
* ```
*
* Use `asapScheduler`
*
* ```ts
* import { generate, asapScheduler } from 'rxjs';
*
* const result = generate(1, x => x < 5, x => x * 2, x => x + 1, asapScheduler);
*
* result.subscribe(x => console.log(x));
*
* // Logs:
* // 2
* // 3
* // 5
* ```
*
* @see {@link from}
* @see {@link Observable}
*
* @param {S} initialState Initial state.
* @param {function (state: S): boolean} condition Condition to terminate generation (upon returning false).
* @param {function (state: S): S} iterate Iteration step function.
* @param {function (state: S): T} resultSelector Selector function for results produced in the sequence. (deprecated)
* @param {SchedulerLike} [scheduler] A {@link SchedulerLike} on which to run the generator loop. If not provided, defaults to emit immediately.
* @returns {Observable<T>} The generated sequence.
* @deprecated Instead of passing separate arguments, use the options argument. Signatures taking separate arguments will be removed in v8.
*/
export function generate<T, S>(
initialState: S,
condition: ConditionFunc<S>,
iterate: IterateFunc<S>,
resultSelector: ResultFunc<S, T>,
scheduler?: SchedulerLike
): Observable<T>;
/**
* Generates an Observable by running a state-driven loop
* that emits an element on each iteration.
*
* <span class="informal">Use it instead of nexting values in a for loop.</span>
*
* 
*
* `generate` allows you to create a stream of values generated with a loop very similar to
* a traditional for loop. The first argument of `generate` is a beginning value. The second argument
* is a function that accepts this value and tests if some condition still holds. If it does,
* then the loop continues, if not, it stops. The third value is a function which takes the
* previously defined value and modifies it in some way on each iteration. Note how these three parameters
* are direct equivalents of three expressions in a traditional for loop: the first expression
* initializes some state (for example, a numeric index), the second tests if the loop can perform the next
* iteration (for example, if the index is lower than 10) and the third states how the defined value
* will be modified on every step (for example, the index will be incremented by one).
*
* Return value of a `generate` operator is an Observable that on each loop iteration
* emits a value. First of all, the condition function is ran. If it returns true, then the Observable
* emits the currently stored value (initial value at the first iteration) and finally updates
* that value with iterate function. If at some point the condition returns false, then the Observable
* completes at that moment.
*
* Optionally you can pass a fourth parameter to `generate` - a result selector function which allows you
* to immediately map the value that would normally be emitted by an Observable.
*
* If you find three anonymous functions in `generate` call hard to read, you can provide
* a single object to the operator instead where the object has the properties: `initialState`,
* `condition`, `iterate` and `resultSelector`, which should have respective values that you
* would normally pass to `generate`. `resultSelector` is still optional, but that form
* of calling `generate` allows you to omit `condition` as well. If you omit it, that means
* condition always holds, or in other words the resulting Observable will never complete.
*
* Both forms of `generate` can optionally accept a scheduler. In case of a multi-parameter call,
* scheduler simply comes as a last argument (no matter if there is a `resultSelector`
* function or not). In case of a single-parameter call, you can provide it as a
* `scheduler` property on the object passed to the operator. In both cases, a scheduler decides when
* the next iteration of the loop will happen and therefore when the next value will be emitted
* by the Observable. For example, to ensure that each value is pushed to the Observer
* on a separate task in the event loop, you could use the `async` scheduler. Note that
* by default (when no scheduler is passed) values are simply emitted synchronously.
*
*
* ## Examples
*
* Use with condition and iterate functions
*
* ```ts
* import { generate } from 'rxjs';
*
* const result = generate(0, x => x < 3, x => x + 1);
*
* result.subscribe({
* next: value => console.log(value),
* complete: () => console.log('Complete!')
* });
*
* // Logs:
* // 0
* // 1
* // 2
* // 'Complete!'
* ```
*
* Use with condition, iterate and resultSelector functions
*
* ```ts
* import { generate } from 'rxjs';
*
* const result = generate(0, x => x < 3, x => x + 1, x => x * 1000);
*
* result.subscribe({
* next: value => console.log(value),
* complete: () => console.log('Complete!')
* });
*
* // Logs:
* // 0
* // 1000
* // 2000
* // 'Complete!'
* ```
*
* Use with options object
*
* ```ts
* import { generate } from 'rxjs';
*
* const result = generate({
* initialState: 0,
* condition(value) { return value < 3; },
* iterate(value) { return value + 1; },
* resultSelector(value) { return value * 1000; }
* });
*
* result.subscribe({
* next: value => console.log(value),
* complete: () => console.log('Complete!')
* });
*
* // Logs:
* // 0
* // 1000
* // 2000
* // 'Complete!'
* ```
*
* Use options object without condition function
*
* ```ts
* import { generate } from 'rxjs';
*
* const result = generate({
* initialState: 0,
* iterate(value) { return value + 1; },
* resultSelector(value) { return value * 1000; }
* });
*
* result.subscribe({
* next: value => console.log(value),
* complete: () => console.log('Complete!') // This will never run
* });
*
* // Logs:
* // 0
* // 1000
* // 2000
* // 3000
* // ...and never stops.
* ```
*
* @see {@link from}
*
* @param {S} initialState Initial state.
* @param {function (state: S): boolean} condition Condition to terminate generation (upon returning false).
* @param {function (state: S): S} iterate Iteration step function.
* @param {function (state: S): T} [resultSelector] Selector function for results produced in the sequence.
* @param {Scheduler} [scheduler] A {@link Scheduler} on which to run the generator loop. If not provided, defaults to emitting immediately.
* @return {Observable<T>} The generated sequence.
* @deprecated Instead of passing separate arguments, use the options argument. Signatures taking separate arguments will be removed in v8.
*/
export function generate<S>(
initialState: S,
condition: ConditionFunc<S>,
iterate: IterateFunc<S>,
scheduler?: SchedulerLike
): Observable<S>;
/**
* Generates an observable sequence by running a state-driven loop
* producing the sequence's elements, using the specified scheduler
* to send out observer messages.
* The overload accepts options object that might contain initial state, iterate,
* condition and scheduler.
*
* 
*
* ## Examples
*
* Use options object with condition function
*
* ```ts
* import { generate } from 'rxjs';
*
* const result = generate({
* initialState: 0,
* condition: x => x < 3,
* iterate: x => x + 1
* });
*
* result.subscribe({
* next: value => console.log(value),
* complete: () => console.log('Complete!')
* });
*
* // Logs:
* // 0
* // 1
* // 2
* // 'Complete!'
* ```
*
* @see {@link from}
* @see {@link Observable}
*
* @param {GenerateBaseOptions<S>} options Object that must contain initialState, iterate and might contain condition and scheduler.
* @returns {Observable<S>} The generated sequence.
*/
export function generate<S>(options: GenerateBaseOptions<S>): Observable<S>;
/**
* Generates an observable sequence by running a state-driven loop
* producing the sequence's elements, using the specified scheduler
* to send out observer messages.
* The overload accepts options object that might contain initial state, iterate,
* condition, result selector and scheduler.
*
* 
*
* ## Examples
*
* Use options object with condition and iterate function
*
* ```ts
* import { generate } from 'rxjs';
*
* const result = generate({
* initialState: 0,
* condition: x => x < 3,
* iterate: x => x + 1,
* resultSelector: x => x
* });
*
* result.subscribe({
* next: value => console.log(value),
* complete: () => console.log('Complete!')
* });
*
* // Logs:
* // 0
* // 1
* // 2
* // 'Complete!'
* ```
*
* @see {@link from}
* @see {@link Observable}
*
* @param {GenerateOptions<T, S>} options Object that must contain initialState, iterate, resultSelector and might contain condition and scheduler.
* @returns {Observable<T>} The generated sequence.
*/
export function generate<T, S>(options: GenerateOptions<T, S>): Observable<T>;
export function generate<T, S>(
initialStateOrOptions: S | GenerateOptions<T, S>,
condition?: ConditionFunc<S>,
iterate?: IterateFunc<S>,
resultSelectorOrScheduler?: ResultFunc<S, T> | SchedulerLike,
scheduler?: SchedulerLike
): Observable<T> {
let resultSelector: ResultFunc<S, T>;
let initialState: S;
// TODO: Remove this as we move away from deprecated signatures
// and move towards a configuration object argument.
if (arguments.length === 1) {
// If we only have one argument, we can assume it is a configuration object.
// Note that folks not using TypeScript may trip over this.
({
initialState,
condition,
iterate,
resultSelector = identity as ResultFunc<S, T>,
scheduler,
} = initialStateOrOptions as GenerateOptions<T, S>);
} else {
// Deprecated arguments path. Figure out what the user
// passed and set it here.
initialState = initialStateOrOptions as S;
if (!resultSelectorOrScheduler || isScheduler(resultSelectorOrScheduler)) {
resultSelector = identity as ResultFunc<S, T>;
scheduler = resultSelectorOrScheduler as SchedulerLike;
} else {
resultSelector = resultSelectorOrScheduler as ResultFunc<S, T>;
}
}
// The actual generator used to "generate" values.
function* gen() {
for (let state = initialState; !condition || condition(state); state = iterate!(state)) {
yield resultSelector(state);
}
}
// We use `defer` because we want to defer the creation of the iterator from the iterable.
return defer(
(scheduler
? // If a scheduler was provided, use `scheduleIterable` to ensure that iteration/generation
// happens on the scheduler.
() => scheduleIterable(gen(), scheduler!)
: // Otherwise, if there's no scheduler, we can just use the generator function directly in
// `defer` and executing it will return the generator (which is iterable).
gen) as () => ObservableInput<T>
);
}