cohost/html/html.ts

export type Prop = string | number | boolean;
export type Attributes = Record<string, Prop>;
export type Html = string | NonText;
export type NonText = {
  tag: string;
  attributes: Attributes;
  children: Html[];
};

export const Fragment = "Fragment";

function is_string(elem: Html): elem is string {
  return typeof elem == "string";
}

export function fr(...children: Html[]): Html {
  return { tag: Fragment, attributes: {}, children };
}

function div(...children: Html[]): Html {
  return { tag: "div", attributes: {}, children };
}

function expand_fragments_in_list(children: Html[]): Html[] {
  let out = [];

  for (const child of children) {
    if (is_string(child)) {
      out.push(child);
    } else if (child.tag == Fragment) {
      out.push(...child.children.map(expand_fragments));
    } else {
      out.push(child);
    }
  }

  return out;
}

// NOTE: if you pass a fragment to this, it won't be expanded (which makes sense if you think about it)
function expand_fragments(elem: Html): Html {
  if (is_string(elem)) {
    return elem;
  } else {
    const children = expand_fragments_in_list(elem.children);
    return { ...elem, children };
  }
}

const attr = (attrs: Attributes) => (elem: Html): Html => {
  if (is_string(elem)) {
    return elem;
  } else {
    const { tag, attributes, children } = elem;
    return { tag, attributes: { ...attributes, ...attrs }, children };
  }
};

const escape = (unsafe: string): string => {
  return unsafe
    .replaceAll("&", "&amp;")
    .replaceAll("<", "&lt;")
    .replaceAll(">", "&gt;")
    .replaceAll('"', "&quot;")
    .replaceAll("'", "&#039;");
};

function render_attributes(attrs: Attributes): string {
  return (
    (Object.keys(attrs).length > 0 ? " " : "") +
    Object.entries(attrs)
      .filter(([_attr, val]) => typeof val != "undefined")
      .map(([attr, val]) => `${attr}="${escape((val ?? "").toString())}"`)
      .join(" ")
  );
}

function indent(str: string, amount = 4, char = " "): string {
  const ind = char.repeat(4);
  return str
    .split("\n")
    .map((l) => ind + l)
    .join("\n");
}

function render_elem(
  { tag, attributes, children }: NonText,
  mini = false,
): string {
  if (children.length == 0) {
    return (
      `<${tag}${render_attributes(attributes)}` + (mini ? "/>" : " />")
    );
  } else {
    let inner = "";
    let string_last = false;
    for (let i = 0; i < children.length; i++) {
      let child = children[i];
      const rendered = render(child, mini);

      if (is_string(child)) {
        mini && string_last && (inner += " ");
        inner += rendered;

        string_last = true;
      } else {
        inner += rendered;
        string_last = false;
      }

      if (!mini && i + 1 < children.length) inner += "\n";
    }

    return [
      `<${tag}${render_attributes(attributes)}>`,
      mini ? inner : indent(inner),
      `</${tag}>`,
    ].join(mini ? "" : "\n");
  }
}
// old:
// joining with " " is inefficient, but necessary for correct string behavior
// i've decided that joining with "" is worth the size savings
// THIS MEANS MINIFICATION IS SEMANTICALLY DIFFERENT
// JK I DID IT THE HARD WAY :]

export function render(elem: Html, mini = true): string {
  if (is_string(elem)) {
    return escape(elem);
  } else if (elem.tag == Fragment) {
    // mimics react's behavior with fragments, ehhh nvm different aims
    return elem.children.map((elem) => render(elem, mini)).join("\n");
  } else {
    const { tag, attributes } = elem;
    const expanded = expand_fragments(elem);

    if (is_string(expanded)) {
      throw "impossible";
    }

    return render_elem(
      { tag, attributes, children: expanded.children },
      mini,
    );
  }
}