import { useEffect, useLayoutEffect, useRef, useState } from "react";
import { createPortal } from "react-dom";
import { Link, useLocation } from "react-router-dom";
import { CourseCover, SegmentedToggle } from "@stc/ui";
import { courseHref, toast, useLibrary, useLook, useMe, useSearch, useToast } from "../api";
import { DirI, Down, MenuI, SearchI } from "../icons";

export interface HeaderCourse { id: string; title: string; coverUrl: string | null; accent: string | null }

const useIsoLayoutEffect = typeof window === "undefined" ? useEffect : useLayoutEffect;

/**
 * Course switcher, search, Reading/Work and the account link, portalled into the Phase 0 header (`.stc-top`).
 * Rendered only after mount, so server-side rendering of a page skips it.
 */
export function HeaderExtras({ course, lookMode, outline }: {
  course: HeaderCourse | null;
  /** "toggle": show Reading/Work; "work": shown but fixed to Work (exercise pages); null: hidden. */
  lookMode: "toggle" | "work" | null;
  outline?: { open: boolean; toggle: () => void } | null;
}) {
  const [host, setHost] = useState<Element | null>(null);
  useIsoLayoutEffect(() => { setHost(document.querySelector(".stc-top")); }, []);
  const msg = useToast();
  if (!host) return null;
  return (
    <>
      {createPortal(
        <div className="lr lr-h">
          {outline ? (
            <button type="button" className="lr-icon" aria-label="Course outline" aria-expanded={outline.open} aria-controls="lr-side" onClick={outline.toggle}><MenuI /></button>
          ) : null}
          <CourseSwitcher course={course} />
          <SearchBox placeholder={course ? "Search this course" : "Search the library"} />
          {lookMode ? <LookToggle mode={lookMode} /> : null}
          <AccountLink />
        </div>,
        host,
      )}
      {msg ? <div className="lr lr-toast" role="status">{msg}</div> : null}
    </>
  );
}

function LookToggle({ mode }: { mode: "toggle" | "work" }) {
  const [look, setLook] = useLook();
  const value = mode === "work" ? "work" : look;
  return (
    <SegmentedToggle
      label="Look"
      value={value}
      options={[{ value: "reading", label: "Reading" }, { value: "work", label: "Work" }]}
      onChange={(v) => {
        setLook(v as "reading" | "work");
        if (mode === "work" && v === "reading") toast("Exercises always use Work. Reading applies to text lessons.");
      }}
    />
  );
}

function SearchBox({ placeholder }: { placeholder: string }) {
  const [q, setQ] = useSearch();
  const loc = useLocation();
  const path = useRef(loc.pathname.split("/").slice(0, 3).join("/"));
  // Clear the query when moving to another course or to the library.
  useEffect(() => {
    const p = loc.pathname.split("/").slice(0, 3).join("/");
    if (p !== path.current) { path.current = p; setQ(""); }
  }, [loc.pathname, setQ]);
  return (
    <label className="lr-search">
      <SearchI />
      <span className="sr">Search</span>
      <input
        type="search" value={q} placeholder={placeholder} autoComplete="off"
        onChange={(e) => setQ(e.target.value)}
        onKeyDown={(e) => { if (e.key === "Escape") { setQ(""); (e.target as HTMLInputElement).blur(); } }}
      />
    </label>
  );
}

function CourseSwitcher({ course }: { course: HeaderCourse | null }) {
  const [open, setOpen] = useState(false);
  const lib = useLibrary();
  const ref = useRef<HTMLDivElement>(null);
  const loc = useLocation();
  useEffect(() => { setOpen(false); }, [loc.pathname]);
  useEffect(() => {
    if (!open) return;
    const onDoc = (e: MouseEvent) => { if (!ref.current?.contains(e.target as Node)) setOpen(false); };
    const onKey = (e: KeyboardEvent) => {
      if (e.key === "Escape") { setOpen(false); ref.current?.querySelector<HTMLButtonElement>("button")?.focus(); }
    };
    document.addEventListener("mousedown", onDoc);
    document.addEventListener("keydown", onKey);
    ref.current?.querySelector<HTMLAnchorElement>(".lr-menu a")?.focus();
    return () => { document.removeEventListener("mousedown", onDoc); document.removeEventListener("keydown", onKey); };
  }, [open]);
  const n = lib?.courses.length ?? 0;
  return (
    <div className="lr-switch" ref={ref}>
      <button type="button" className="lr-switch-btn" aria-haspopup="true" aria-expanded={open} onClick={() => setOpen(!open)}>
        {course
          ? <span className="lr-cover-tiny"><CourseCover title={course.title} image={course.coverUrl ?? undefined} accent={course.accent ?? undefined} /></span>
          : <span className="lr-tile"><DirI /></span>}
        <span className="t">{course ? course.title : "All courses"}</span>
        <Down />
      </button>
      {open ? (
        <ul className="lr-menu">
          <li>
            <Link to="/" aria-current={course ? undefined : "page"}>
              <span className="lr-tile"><DirI /></span>
              <span><span className="mt">Library</span><span className="ms">{n === 1 ? "1 course" : `${n} courses`}</span></span>
            </Link>
          </li>
          {(lib?.courses ?? []).map((c) => (
            <li key={c.id}>
              <Link to={courseHref(c.id)} aria-current={course?.id === c.id ? "page" : undefined}>
                <span className="lr-cover-tiny"><CourseCover title={c.title} image={c.coverUrl ?? undefined} accent={c.accent ?? undefined} /></span>
                <span style={{ minWidth: 0 }}><span className="mt">{c.title}</span><span className="ms">{c.authors.join(", ") || (c.source === "authored" ? "Authored course" : c.source ? `Imported (${c.source})` : "")}</span></span>
              </Link>
            </li>
          ))}
        </ul>
      ) : null}
    </div>
  );
}

function AccountLink() {
  const { loaded, user } = useMe();
  if (!loaded) return null;
  return user
    ? <Link className="stc-pill stc-pill--ghost lr-acct" to="/account">{user.name || user.email}</Link>
    : <Link className="stc-pill lr-acct" to="/account">Sign in</Link>;
}