import clsx from 'clsx';
import { createBlock } from '@wordpress/blocks';
import { InnerBlocks, getColorClassName } from '@wordpress/block-editor';

/**
 * Given an HTML string for a deprecated columns inner block, returns the
 * column index to which the migrated inner block should be assigned. Returns
 * undefined if the inner block was not assigned to a column.
 *
 * @param {string} originalContent Deprecated Columns inner block HTML.
 *
 * @return {number | undefined} Column to which inner block is to be assigned.
 */
function getDeprecatedLayoutColumn( originalContent ) {
	let { doc } = getDeprecatedLayoutColumn;
	if ( ! doc ) {
		doc = document.implementation.createHTMLDocument( '' );
		getDeprecatedLayoutColumn.doc = doc;
	}

	let columnMatch;

	doc.body.innerHTML = originalContent;
	for ( const classListItem of doc.body.firstChild.classList ) {
		if (
			( columnMatch = classListItem.match( /^layout-column-(\d+)$/ ) )
		) {
			return Number( columnMatch[ 1 ] ) - 1;
		}
	}
}

const migrateCustomColors = ( attributes ) => {
	if ( ! attributes.customTextColor && ! attributes.customBackgroundColor ) {
		return attributes;
	}
	const style = { color: {} };
	if ( attributes.customTextColor ) {
		style.color.text = attributes.customTextColor;
	}
	if ( attributes.customBackgroundColor ) {
		style.color.background = attributes.customBackgroundColor;
	}

	const { customTextColor, customBackgroundColor, ...restAttributes } =
		attributes;

	return {
		...restAttributes,
		style,
		isStackedOnMobile: true,
	};
};

export default [
	{
		attributes: {
			verticalAlignment: {
				type: 'string',
			},
			backgroundColor: {
				type: 'string',
			},
			customBackgroundColor: {
				type: 'string',
			},
			customTextColor: {
				type: 'string',
			},
			textColor: {
				type: 'string',
			},
		},
		migrate: migrateCustomColors,
		save( { attributes } ) {
			const {
				verticalAlignment,
				backgroundColor,
				customBackgroundColor,
				textColor,
				customTextColor,
			} = attributes;

			const backgroundClass = getColorClassName(
				'background-color',
				backgroundColor
			);

			const textClass = getColorClassName( 'color', textColor );

			const className = clsx( {
				'has-background': backgroundColor || customBackgroundColor,
				'has-text-color': textColor || customTextColor,
				[ backgroundClass ]: backgroundClass,
				[ textClass ]: textClass,
				[ `are-vertically-aligned-${ verticalAlignment }` ]:
					verticalAlignment,
			} );

			const style = {
				backgroundColor: backgroundClass
					? undefined
					: customBackgroundColor,
				color: textClass ? undefined : customTextColor,
			};

			return (
				<div
					className={ className ? className : undefined }
					style={ style }
				>
					<InnerBlocks.Content />
				</div>
			);
		},
	},
	{
		attributes: {
			columns: {
				type: 'number',
				default: 2,
			},
		},
		isEligible( attributes, innerBlocks ) {
			// Since isEligible is called on every valid instance of the
			// Columns block and a deprecation is the unlikely case due to
			// its subsequent migration, optimize for the `false` condition
			// by performing a naive, inaccurate pass at inner blocks.
			const isFastPassEligible = innerBlocks.some( ( innerBlock ) =>
				/layout-column-\d+/.test( innerBlock.originalContent )
			);

			if ( ! isFastPassEligible ) {
				return false;
			}

			// Only if the fast pass is considered eligible is the more
			// accurate, durable, slower condition performed.
			return innerBlocks.some(
				( innerBlock ) =>
					getDeprecatedLayoutColumn( innerBlock.originalContent ) !==
					undefined
			);
		},
		migrate( attributes, innerBlocks ) {
			const columns = innerBlocks.reduce( ( accumulator, innerBlock ) => {
				const { originalContent } = innerBlock;

				let columnIndex = getDeprecatedLayoutColumn( originalContent );
				if ( columnIndex === undefined ) {
					columnIndex = 0;
				}

				if ( ! accumulator[ columnIndex ] ) {
					accumulator[ columnIndex ] = [];
				}

				accumulator[ columnIndex ].push( innerBlock );

				return accumulator;
			}, [] );

			const migratedInnerBlocks = columns.map( ( columnBlocks ) =>
				createBlock( 'core/column', {}, columnBlocks )
			);

			const { columns: ignoredColumns, ...restAttributes } = attributes;

			return [
				{
					...restAttributes,
					isStackedOnMobile: true,
				},
				migratedInnerBlocks,
			];
		},
		save( { attributes } ) {
			const { columns } = attributes;

			return (
				<div className={ `has-${ columns }-columns` }>
					<InnerBlocks.Content />
				</div>
			);
		},
	},
	{
		attributes: {
			columns: {
				type: 'number',
				default: 2,
			},
		},
		migrate( attributes, innerBlocks ) {
			const { columns, ...restAttributes } = attributes;
			attributes = {
				...restAttributes,
				isStackedOnMobile: true,
			};

			return [ attributes, innerBlocks ];
		},
		save( { attributes } ) {
			const { verticalAlignment, columns } = attributes;

			const wrapperClasses = clsx( `has-${ columns }-columns`, {
				[ `are-vertically-aligned-${ verticalAlignment }` ]:
					verticalAlignment,
			} );

			return (
				<div className={ wrapperClasses }>
					<InnerBlocks.Content />
				</div>
			);
		},
	},
];