/**
 * External dependencies
 */
import { renderFrontend } from '@woocommerce/base-utils';
import {
	Fragment,
	Suspense,
	isValidElement,
	cloneElement,
} from '@wordpress/element';
import parse from 'html-react-parser';
import {
	getRegisteredBlocks,
	hasInnerBlocks,
} from '@woocommerce/blocks-checkout';

/**
 * This file contains logic used on the frontend to convert DOM elements (saved by the block editor) to React
 * Components. These components are registered using registerBlockComponent() and registerCheckoutBlock() and map 1:1
 * to a block by name.
 *
 * Blocks using this system will have their blockName stored as a data attribute, for example:
 * 		<div data-block-name="woocommerce/product-title"></div>
 *
 * This block name is then read, and using the map, dynamically converted to a real React Component.
 *
 * @see registerBlockComponent
 * @see registerCheckoutBlock
 */

/**
 * Gets a component from the block map for a given block name, or returns null if a component is not registered.
 */
const getBlockComponentFromMap = (
	block: string,
	blockMap: Record< string, React.ReactNode >
): React.ElementType | null => {
	return block && blockMap[ block ]
		? ( blockMap[ block ] as React.ElementType )
		: null;
};

/**
 * Render forced blocks which are missing from the template.
 *
 * Forced blocks are registered in registerCheckoutBlock. If a block is forced, it will be inserted in the editor
 * automatically, however, until that happens they may be missing from the frontend. To fix this, we look up what blocks
 * are registered as forced, and then append them here if they are missing.
 *
 * @see registerCheckoutBlock
 */
const renderForcedBlocks = (
	block: string,
	blockMap: Record< string, React.ReactNode >,
	// Current children from the parent (siblings of the forced block)
	blockChildren: HTMLCollection | null
) => {
	if ( ! hasInnerBlocks( block ) ) {
		return null;
	}

	const currentBlocks = blockChildren
		? ( Array.from( blockChildren )
				.map( ( element: Element ) =>
					element instanceof HTMLElement
						? element?.dataset.blockName || null
						: null
				)
				.filter( Boolean ) as string[] )
		: [];

	const forcedBlocks = getRegisteredBlocks( block ).filter(
		( { blockName, force } ) =>
			force === true && ! currentBlocks.includes( blockName )
	);

	return forcedBlocks.map(
		( { blockName, component }, index: number ): JSX.Element | null => {
			const ForcedComponent = component
				? component
				: getBlockComponentFromMap( blockName, blockMap );
			return ForcedComponent ? (
				<ForcedComponent key={ `${ blockName }_forced_${ index }` } />
			) : null;
		}
	);
};

/**
 * Recursively replace block markup in the DOM with React Components.
 */
const renderInnerBlocks = ( {
	// This is the parent block we're working within (see renderParentBlock)
	block,
	// This is the map of blockNames->components
	blockMap,
	// Component which inner blocks are wrapped with.
	blockWrapper,
	// The children from the DOM we're currently iterating over.
	children,
	// Current depth of the children. Used to ensure keys are unique.
	depth = 1,
}: {
	// Block (parent) being rendered. Used for inner block component mapping.
	block: string;
	// Map of block names to block components for children.
	blockMap: Record< string, React.ReactNode >;
	// Wrapper for inner components.
	blockWrapper?: React.ElementType;
	// Elements from the DOM being converted to components.
	children: HTMLCollection;
	// Depth within the DOM hierarchy.
	depth?: number;
} ): ( JSX.Element | null )[] | null => {
	if ( ! children || children.length === 0 ) {
		return null;
	}
	return Array.from( children ).map( ( element: Element, index: number ) => {
		/**
		 * This will grab the blockName from the data- attributes stored in block markup. Without a blockName, we cannot
		 * convert the HTMLElement to a React component.
		 */
		const { blockName = '', ...componentProps } = {
			key: `${ block }_${ depth }_${ index }`,
			...( element instanceof HTMLElement ? element.dataset : {} ),
		};

		const InnerBlockComponent = getBlockComponentFromMap(
			blockName,
			blockMap
		);

		/**
		 * If the component cannot be found, or blockName is missing, return the original element. This also ensures
		 * that children within the element are processed also, since it may be an element containing block markup.
		 */
		if ( ! InnerBlockComponent ) {
			const parsedElement = parse( element.outerHTML );

			if ( isValidElement( parsedElement ) ) {
				const elementChildren = renderInnerBlocks( {
					block,
					blockMap,
					children: element.children || [],
					depth: depth + 1,
					blockWrapper,
				} );
				return elementChildren
					? cloneElement(
							parsedElement,
							componentProps,
							elementChildren
					  )
					: cloneElement( parsedElement, componentProps );
			}
			return null;
		}

		// This will wrap inner blocks with the provided wrapper. If no wrapper is provided, we default to Fragment.
		const InnerBlockComponentWrapper = blockWrapper
			? blockWrapper
			: Fragment;

		return (
			<Suspense
				key={ `${ block }_${ depth }_${ index }_suspense` }
				fallback={ <div className="wc-block-placeholder" /> }
			>
				<InnerBlockComponentWrapper>
					<InnerBlockComponent { ...componentProps }>
						{
							/**
							 * Within this Inner Block Component we also need to recursively render it's children. This
							 * is done here with a depth+1. The same block map and parent is used, but we pass new
							 * children from this element.
							 */
							renderInnerBlocks( {
								block,
								blockMap,
								children: element.children,
								depth: depth + 1,
								blockWrapper,
							} )
						}
						{
							/**
							 * In addition to the inner blocks, we may also need to render FORCED blocks which have not
							 * yet been added to the inner block template. We do this by comparing the current children
							 * to the list of registered forced blocks.
							 *
							 * @see registerCheckoutBlock
							 */
							renderForcedBlocks(
								blockName,
								blockMap,
								element.children
							)
						}
					</InnerBlockComponent>
				</InnerBlockComponentWrapper>
			</Suspense>
		);
	} );
};

/**
 * Render a parent block on the frontend.
 *
 * This is the main entry point used on the frontend to convert Block Markup (with inner blocks) in the DOM to React
 * Components.
 *
 * This uses renderFrontend(). The difference is, renderFrontend renders a single block, but renderParentBlock() also
 * handles inner blocks by recursively running over children from the DOM.
 *
 * @see renderInnerBlocks
 * @see renderFrontend
 */
export const renderParentBlock = ( {
	Block,
	selector,
	blockName,
	getProps = () => ( {} ),
	blockMap,
	blockWrapper,
}: {
	// Parent Block Name. Used for inner block component mapping.
	blockName: string;
	// Map of block names to block components for children.
	blockMap: Record< string, React.ReactNode >;
	// Wrapper for inner components.
	blockWrapper?: React.ElementType;
	// React component to use as a replacement.
	Block: React.FunctionComponent;
	// CSS selector to match the elements to replace.
	selector: string;
	// Function to generate the props object for the block.
	getProps: ( el: Element, i: number ) => Record< string, unknown >;
} ): void => {
	/**
	 * In addition to getProps, we need to render and return the children. This adds children to props.
	 */
	const getPropsWithChildren = ( element: Element, i: number ) => {
		const children = renderInnerBlocks( {
			block: blockName,
			blockMap,
			children: element.children || [],
			blockWrapper,
		} );
		return { ...getProps( element, i ), children };
	};
	/**
	 * The only difference between using renderParentBlock and renderFrontend is that here we provide children.
	 */
	renderFrontend( {
		Block,
		selector,
		getProps: getPropsWithChildren,
	} );
};