import unified from 'unified';
import parse from 'rehype-parse';
import toH from 'hast-to-hyperscript';
import { ComponentRenderer } from '../../@types/renderer';
import moize from 'moize';

/** @internal */
function childrenToTree(children: string[]) {
    return children.map(child => (unified().use(parse, { fragment: true }).parse(child) as any).children.pop());
}

/**
 * Converts an HTML fragment string into vnodes for rendering via provided framework
 * @param h framework's `createElement` function
 * @param children the HTML string children
 */
export const childrenToVnodes = moize.deep(function childrenToVnodes(h: any, children: string[]) {
    const tree = childrenToTree(children);
    const vnodes = tree.map(subtree => toH(h, subtree));
    return vnodes;
})

/**
 * Converts an HTML fragment string into h function calls as a string
 * @param h framework's `createElement` function
 * @param children the HTML string children
 */
export const childrenToH = moize.deep(function childrenToH(renderer: ComponentRenderer<any>, children: string[]): any {
    if (!renderer.jsxPragma) return;
    const tree = childrenToTree(children);
    const innerH = (name: any, attrs: Record<string, any>|null = null, _children: string[]|null = null) => {
        const vnode = renderer.jsxPragma?.(name, attrs, _children);
        const childStr = _children ? `, [${_children.map(child => serializeChild(child)).join(',')}]` : '';
        /* fix(react): avoid hard-coding keys into the serialized tree */
        if (attrs && attrs.key) attrs.key = undefined;
        const __SERIALIZED = `${renderer.jsxPragmaName}("${name}", ${attrs ? JSON.stringify(attrs) : 'null'}${childStr})` as string;
        return { ...vnode, __SERIALIZED }
    }
    const serializeChild = (child: unknown) => {
        if (typeof child === 'string') return `\`${child}\``;
        if (typeof child === 'number' || typeof child === 'boolean') return `${child}`;
        if (child === null) return `null`;
        if ((child as any).__SERIALIZED) return (child as any).__SERIALIZED;
        return innerH(child).__SERIALIZED;
    }
    return tree.map(subtree => toH(innerH, subtree).__SERIALIZED);
})