import { Fragment, useId, useRef, type KeyboardEvent } from "react";
import { panelId, tabId } from "./tabPanel";
import { type LucideIcon } from "lucide-react";
import CountBadge from "./CountBadge";

// Reusable pill tab-rail for in-page sub-navigation (Configuration, Users & roles, the Settings
// sections, the Stats overview/system split…). Horizontal by default; `orientation="vertical"` gives
// the Settings-style side rail (full-width, left-aligned, icon + label) — from the `sm` breakpoint up.
// Below it a side rail leaves a phone too little width for the content beside it (measured at 390 px:
// the rail clipped its own labels and Settings → Account pushed its buttons over their text), so there
// it is a horizontal row that scrolls. A page whose sub-tab is worth keeping persists it with
// lib/storage's useTabPersistedState (per browser tab: Admin Users, Config, Settings, Stats):
// a reload keeps the user where they were, and a fresh tab opens on the first sub-tab. Not every
// caller: the channel manager's view is account-wide (ChannelsProvider), and Downloads, a channel page
// and the player settings start on their first tab each time.
//
// An ARIA tab list, not a row of toggle buttons: `tablist` / `tab` / `aria-selected`,
// ONE Tab stop (the selected tab; roving tabindex), the arrows move and select (either axis, since the
// vertical rail is a row below `sm`), Home/End jump to the ends. The panel it controls is wired with
// `useTabPanel`: the tabs point at it (`aria-controls`) and it is labelled by the selected tab.
// `tone="media"` is the same list painted for the player's dark chrome (the Plex player's settings
// panel), which looks the same on every theme because the picture under it does.

export interface TabDef {
  id: string;
  label: string;
  badge?: number; // optional count pill (e.g. pending requests); hidden when 0/undefined
  icon?: LucideIcon; // optional leading icon (the vertical settings rail)
  testId?: string; // optional data-testid, to preserve existing e2e hooks
  /** The vertical rail's heading this tab sits under (Configuration's sixteen groups under four).
   *  Drawn above the first tab of each run; tabs of one heading stay together. */
  group?: string;
}

export default function Tabs({
  tabs,
  active,
  onChange,
  orientation = "horizontal",
  className,
  idBase,
  label,
  tone,
}: {
  tabs: TabDef[];
  active: string;
  onChange: (id: string) => void;
  // "vertical" gives the Settings-style side rail; "horizontal" (default) is the standard row.
  orientation?: "horizontal" | "vertical";
  // Override the row/rail wrapper — e.g. the channel manager embeds the rail in a justify-between
  // header, or the settings rail adds a width + right border. Omit for the orientation default.
  className?: string;
  /** `useTabPanel().idBase`: the tabs then name the panel they control. */
  idBase?: string;
  /** The tab list's accessible name, when the page heading beside it does not say what it switches. */
  label?: string;
  /** Painted for the media chrome instead of the page (equal-width, white on black). */
  tone?: "media";
}) {
  const ownBase = useId();
  const base = idBase ?? ownBase;
  const refs = useRef(new Map<string, HTMLButtonElement>());
  const vertical = orientation === "vertical";
  const wrapCls =
    className ??
    (vertical ? "flex gap-1 overflow-x-auto sm:flex-col" : "flex flex-wrap gap-1 mb-4");
  // Selection follows focus (automatic activation): every panel here renders at once, so the arrow
  // can show what it lands on. An unknown `active` (still loading) leaves the first tab the stop.
  const stop = tabs.some((tb) => tb.id === active) ? active : tabs[0]?.id;
  const onKeyDown = (e: KeyboardEvent) => {
    const at = tabs.findIndex((tb) => tb.id === stop);
    const to =
      e.key === "ArrowRight" || e.key === "ArrowDown"
        ? (at + 1) % tabs.length
        : e.key === "ArrowLeft" || e.key === "ArrowUp"
          ? (at - 1 + tabs.length) % tabs.length
          : e.key === "Home"
            ? 0
            : e.key === "End"
              ? tabs.length - 1
              : -1;
    const next = tabs[to];
    if (!next || e.altKey || e.ctrlKey || e.metaKey) return;
    e.preventDefault();
    refs.current.get(next.id)?.focus();
    if (next.id !== active) onChange(next.id);
  };
  return (
    <div
      role="tablist"
      aria-label={label}
      aria-orientation={vertical ? "vertical" : "horizontal"}
      onKeyDown={onKeyDown}
      className={wrapCls}
    >
      {tabs.map((tb, i) => {
        const on = tb.id === active;
        const Icon = tb.icon;
        const heading = vertical && tb.group && tb.group !== tabs[i - 1]?.group ? tb.group : null;
        return (
          <Fragment key={tb.id}>
            {/* A heading, not a tab: no role a tab list would have to own, its text still read. Only
                on the side rail; the phone's scrolling row has no room for it. */}
            {heading && (
              <div
                role="presentation"
                className="hidden px-3 pt-3 pb-1 text-2xs font-semibold tracking-wide text-muted uppercase first:pt-1 sm:block"
              >
                {heading}
              </div>
            )}
            <button
              ref={(node) => {
                if (node) refs.current.set(tb.id, node);
                else refs.current.delete(tb.id);
              }}
              type="button"
              role="tab"
              id={tabId(base, tb.id)}
              aria-selected={on}
              aria-controls={idBase ? panelId(idBase) : undefined}
              tabIndex={tb.id === stop ? 0 : -1}
              data-testid={tb.testId}
              onClick={() => onChange(tb.id)}
              className={
                tone === "media"
                  ? `touch-target flex-1 items-center justify-center whitespace-nowrap rounded px-2 py-1 text-2xs ${
                      on ? "bg-white/15 text-accent" : "text-white/70 hover:bg-white/10"
                    }`
                  : `pill touch-target items-center rounded-lg px-3 text-sm ${
                      vertical
                        ? "inline-flex shrink-0 gap-1.5 py-1.5 sm:flex sm:w-full sm:justify-start sm:gap-2 sm:py-2 sm:text-left"
                        : "inline-flex gap-1.5 py-1.5"
                    } ${on ? "font-medium shadow-md shadow-accent/20" : "state-layer"}`
              }
            >
              {Icon && <Icon className="h-4 w-4 shrink-0" />}
              {tb.label}
              {tb.badge != null && tb.badge > 0 && <CountBadge count={tb.badge} active={on} />}
            </button>
          </Fragment>
        );
      })}
    </div>
  );
}