/**
 * Toggles the activation of a given font or font variant within a list of custom fonts.
 *
 * - If only the font is provided (without face), the entire font family's activation is toggled.
 * - If both font and face are provided, the activation of the specific font variant is toggled.
 *
 * @param {Object} font            - The font to be toggled.
 * @param {string} font.slug       - The unique identifier for the font.
 * @param {Array}  [font.fontFace] - The list of font variants (faces) associated with the font.
 *
 * @param {Object} [face]          - The specific font variant to be toggled.
 * @param {string} face.fontWeight - The weight of the font variant.
 * @param {string} face.fontStyle  - The style of the font variant.
 *
 * @param {Array}  initialfonts    - The initial list of custom fonts.
 *
 * @return {Array} - The updated list of custom fonts with the font/font variant toggled.
 *
 * @example
 * const customFonts = [
 *     { slug: 'roboto', fontFace: [{ fontWeight: '400', fontStyle: 'normal' }] }
 * ];
 *
 * toggleFont({ slug: 'roboto' }, null, customFonts);
 * // This will remove 'roboto' from customFonts
 *
 * toggleFont({ slug: 'roboto' }, { fontWeight: '400', fontStyle: 'normal' }, customFonts);
 * // This will remove the specified face from 'roboto' in customFonts
 *
 * toggleFont({ slug: 'roboto' }, { fontWeight: '500', fontStyle: 'normal' }, customFonts);
 * // This will add the specified face to 'roboto' in customFonts
 */
/**
 * WordPress dependencies
 */
import type { FontFamily, FontFace } from '@wordpress/core-data';

export function toggleFont(
	font: FontFamily,
	face?: FontFace,
	initialfonts: FontFamily[] = []
): FontFamily[] {
	// Helper to check if a font is activated based on its slug
	const isFontActivated = ( f: FontFamily ): boolean => f.slug === font.slug;

	// Helper to get the activated font from a list of fonts
	const getActivatedFont = ( fonts: FontFamily[] ): FontFamily | undefined =>
		fonts.find( isFontActivated );

	// Toggle the activation status of an entire font family
	const toggleEntireFontFamily = (
		activatedFont: FontFamily | undefined
	): FontFamily[] => {
		if ( ! activatedFont ) {
			// If the font is not active, activate the entire font family
			return [ ...initialfonts, font ];
		}
		// If the font is already active, deactivate the entire font family
		return initialfonts.filter(
			( f: FontFamily ) => ! isFontActivated( f )
		);
	};

	// Toggle the activation status of a specific font variant
	const toggleFontVariant = (
		activatedFont: FontFamily | undefined
	): FontFamily[] => {
		const isFaceActivated = ( f: FontFace ): boolean =>
			f.fontWeight === face!.fontWeight &&
			f.fontStyle === face!.fontStyle;

		if ( ! activatedFont ) {
			// If the font family is not active, activate the font family with the font variant
			return [ ...initialfonts, { ...font, fontFace: [ face! ] } ];
		}

		let newFontFaces = activatedFont.fontFace || [];

		if ( newFontFaces.find( isFaceActivated ) ) {
			// If the font variant is active, deactivate it
			newFontFaces = newFontFaces.filter(
				( f: FontFace ) => ! isFaceActivated( f )
			);
		} else {
			// If the font variant is not active, activate it
			newFontFaces = [ ...newFontFaces, face! ];
		}

		// If there are no more font faces, deactivate the font family
		if ( newFontFaces.length === 0 ) {
			return initialfonts.filter(
				( f: FontFamily ) => ! isFontActivated( f )
			);
		}

		// Return updated fonts list with toggled font variant
		return initialfonts.map( ( f: FontFamily ) =>
			isFontActivated( f ) ? { ...f, fontFace: newFontFaces } : f
		);
	};

	const activatedFont = getActivatedFont( initialfonts );

	if ( ! face ) {
		return toggleEntireFontFamily( activatedFont );
	}

	return toggleFontVariant( activatedFont );
}