import "./types.ts";

const Fragment = Symbol("fragment");

declare namespace JSX {
  interface Element {}
  interface IntrinsicElements {
    div: any;
  }
}

export type Element = {
  component: Component | string | typeof Fragment;
  props: any;
  children: any[];
};
export type ComponentRetElm = Element | Element[];
export type Component = (
  props: any,
  children: any
) => ComponentRetElm | Promise<ComponentRetElm>;

export function h(
  component: string | Component,
  props: any,
  ...children: Element[]
): Element {
  return {
    component,
    props,
    children,
  };
}

const createElement = h;

export { Fragment, createElement };

export async function renderSSR(element: Element | string): Promise<string> {
  if (typeof element === "string") return element;
  else if (typeof element.component === "string")
    return await renderHTML(element as Element);
  else if (
    typeof element.component === "function" ||
    element.component === Fragment
  )
    return await renderCustom(element as Element);

  console.warn("renderSSR: invalid element", element);

  return "";
}

const selfClosing = new Set([
  "area",
  "base",
  "br",
  "col",
  "embed",
  "hr",
  "img",
  "input",
  "link",
  "meta",
  "param",
  "source",
  "track",
  "wbr",
]);

function flatDeep(arr: any, d = Infinity): any[] {
  if (Array.isArray(arr) && d >= 0) {
    let res = [];
    for (const val of arr) {
      const v = flatDeep(val, d - 1);
      res.push(...v);
    }
    return res;
  }
  return [arr];
}

function cleanChildren(children: any) {
  return flatDeep(children).filter((e) => !!e);
}

async function renderHTML(element: Element) {
  if (typeof element.component !== "string")
    throw new Error("Internal consistency error");

  let props = "";

  for (const key in element.props) {
    if (key == "innerHTML") continue;
    props += `${key}="${element.props[key] || ""}" `;
  }

  const tag = element.component;

  if (selfClosing.has(element.component)) {
    return `<${tag} ${props}/>`;
  } else {
    let inner = "";
    if (element.props && element.props["innerHTML"]) {
      inner = element.props["innerHTML"];
    } else {
      const children = cleanChildren(element.children);
      inner = (
        await Promise.all(children.map((child) => renderSSR(child)))
      ).join("");
    }
    return `<${tag} ${props}>${inner || ""}</${tag}>`;
  }
}

async function renderCustom(element: Element) {
  if (typeof element.component === "string")
    throw new Error("Internal consistency error");

  if (element.component === Fragment) {
    const ch = (
      await Promise.all(
        cleanChildren(element.children).map((child) => renderSSR(child))
      )
    ).join("");

    return ch;
  } else {
    const res = await Promise.resolve(
      element.component(
        {
          ...element.props,
          children: element.children,
        },
        element.children
      )
    );

    const ch = (
      await Promise.all(cleanChildren(res).map((child) => renderSSR(child)))
    ).join("");

    return ch;
  }
}