import { syntaxHighlighting } from '@codemirror/language';
import type { LanguageSupport } from '@codemirror/language';
import type { Extension } from '@codemirror/state';

import { languageStyling } from '../../ui/syntaxHighlightingTheme';

import { mapLanguageToCodeMirror } from './languageMap';

/**
 * Manages loading the languages (for syntax highlighting, etc.)
 * from CodeMirror and updating the language in the CodeMirror view
 */
export class LanguageLoader {
	private languageName: string = '';

	constructor(
		private updateLanguageCompartment: (
			value: LanguageSupport | [LanguageSupport, Extension] | [],
		) => void,
	) {}

	async updateLanguage(languageName: string): Promise<void> {
		if (languageName === this.languageName) {
			return;
		}
		const language = mapLanguageToCodeMirror(languageName);

		const configureEmpty = () => {
			if (this.languageName) {
				this.updateLanguageCompartment([]);
			}
			this.languageName = '';
		};

		if (!language) {
			configureEmpty();
			return;
		}

		try {
			const lang = await language.load();

			if (lang) {
				const styling = languageStyling(lang.language);
				if (styling) {
					this.updateLanguageCompartment([lang, syntaxHighlighting(styling)]);
				} else {
					this.updateLanguageCompartment(lang);
				}
				this.languageName = languageName;
			} else {
				configureEmpty();
			}
		} catch (e) {
			configureEmpty();
		}
	}
}