import	{
			Pipe,
			PipeTransform,
			ChangeDetectorRef
		}							from '@angular/core'

import	{
			RccTranslationService
		}							from './translations.service'

import	{
			extendTranslationKey,
			TranslationKey,
			Translator
		}							from '../nong'


/**
 * This pipe is just the pipe version of {@link RccTranslationService.translate()}.
 * You cannot specify a language. It will always translate to {@link RccTranslationService.activeLanguage}
 */
@Pipe({
	name: 	'translate',
	pure:	false
})
export class RccTranslatePipe implements PipeTransform {

	protected lastResult 		: string
	protected lastInput			: unknown
	protected lastParam			: Record<string, unknown>
	protected lastTranslator	: Translator
	protected lastHash			: string | null

	constructor(
		private rccTranslationService	: RccTranslationService,
		private changeDetectorRef		: ChangeDetectorRef
	){
		this.rccTranslationService.activeLanguageChange$
		.subscribe( () => this.reset() )
	}

	reset() : void {
		this.lastResult 	= null
		this.lastTranslator = null
		this.lastInput		= null
		this.lastParam		= null
		this.lastHash		= null
	}

	update(input: unknown, param?:Record<string,unknown>, language?: string): void {
		const [text, translator] 	= 	this.rccTranslationService.getTranslationData(input, param, language)
		const hash					= 	translator
										?	translator.hash(input, param)
										:	null	// translation failed

		this.lastTranslator 		= 	translator
		this.lastResult 			= 	text || String(input)
		this.lastInput				=	input
		this.lastHash				=	hash
	}

	transform(input: unknown, param?:Record<string,unknown>, language?: string): string {

		// Since this pipe is NOT pure, it is probably a good idea to cache results.
		// We could do the caching in the .translate() method of RccTranslationService,
		// but then all input values would be stored there forever, whereas values stored on the
		// pipe should be deleted when the pipe gets destroyed.

		if(this.lastInput != input) { this.update(input, param, language); return this.lastResult }

		// Translation failed last time, no reason to try again:
		if(!this.lastTranslator) 	return this.lastResult

		const hash = this.lastTranslator.hash(input,param)

		if(this.lastHash != hash)	{ this.update(input, param, language); return this.lastResult }

		return this.lastResult

	}
}


/**
 * This pipe is meant for basic replacements in translation strings.
 * Occurrences of %_n_ , with _n_ being some integer, will be replaced by the _n_-th parameter, starting at 1.
 * Occurrences of %_s_ with _s_ being a single lowercase letter, will be replaced by the parameters in the order of their appearance.
 * The replacement text will only include capital letters, digits and underscored, everything else will be stripped off:
 * ```
 * 	{{ 'SOME_SCOPE.%s' | fill: paused ? 'player_running':'player_paused' }} // yields 'SOME_SCOPE.PLAYER_PAUSED' if pause is truthy.
 *
 * 	{{ 'SOME_SCOPE.GROUP_%2.LABEL_%1' | fill :  'long', 1}} // yields 'SOME_SCOPE.GROUP_1.LABEL_LONG'.
 *
 * 	{{ 'SOME_SCOPE.GROUP_%s.LABEL_%t' | fill :  'long', 1}} // yields 'SOME_SCOPE.GROUP_LONG.LABEL_1'.
 *
 * ```
 **/
@Pipe({ name: 'fill' })
export class RccFillPipe implements PipeTransform {

	transform(translationKey : TranslationKey, ...content: string[]) : TranslationKey {
		return extendTranslationKey(translationKey, ...content)
	}
}