"use client";

// Discord's OAuth redirect target for "Connect a Discord server"
// (server-26#225 S7). Registered as each radio bot app's redirect URI:
// https://drb.cusano.net/discord/connected
//
// middleware.ts lets this path through without the drb_session cookie, for
// two reasons: a signed-out visitor would otherwise be redirected to /login
// with the query (code + state) dropped; and drb_session is SameSite=Strict,
// so even a signed-in user's cookie is not sent on the cross-site redirect
// back from discord.com. This page does its own auth check instead.

import { useEffect, useRef, useState } from "react";
import { useRouter } from "next/navigation";
import { useAuth } from "@/components/AuthProvider";
import { Card } from "@/components/ui/Card";
import { LinkButton } from "@/components/ui/Button";
import { parseC2Error } from "@/lib/discord";
import {
  OAUTH_CALLBACK_PATH,
  type OAuthCallback,
  type OAuthCompleteResult,
  captureCallback,
  clearCallback,
  completeDiscordOAuth,
} from "@/lib/discordOAuth";

type View =
  | { kind: "working" }
  | { kind: "none" }
  | { kind: "denied" }
  | { kind: "error"; message: string }
  | { kind: "done"; result: OAuthCompleteResult };

const SETTINGS = "/settings/organization";

function nextStepLabel(path: string): string {
  if (path.startsWith("/nodes/")) return "Add a radio channel on this node";
  if (path.startsWith("/settings/discord")) return "Back to Discord settings";
  if (path.startsWith(SETTINGS)) return "Back to organization settings";
  return "Continue";
}

export default function DiscordConnectedPage() {
  const { user, loading } = useAuth();
  const router = useRouter();
  const [view, setView] = useState<View>({ kind: "working" });
  const cb = useRef<OAuthCallback | null | undefined>(undefined);
  const sent = useRef(false);

  useEffect(() => {
    // First run: stash code/state for this tab and strip them from the
    // address bar. Later runs (auth settling) read the stashed copy.
    if (cb.current === undefined) cb.current = captureCallback();
    const c = cb.current;
    if (!c) {
      setView({ kind: "none" });
      return;
    }
    if (c.error) {
      clearCallback();
      // Only a short code from the URL is ever echoed, never free text a crafted link could carry.
      const code = /^[a-z_]{1,40}$/.test(c.error) ? ` (${c.error})` : "";
      setView(c.error === "access_denied"
        ? { kind: "denied" }
        : { kind: "error", message: `Discord didn't finish adding the bot${code}. Nothing was changed.` });
      return;
    }
    if (!c.code || !c.state) {
      clearCallback();
      setView({ kind: "error", message: "Discord's reply was incomplete. Nothing was changed — start again from Connect a Discord server." });
      return;
    }
    if (loading) return;
    if (!user) {
      // Keep the stash; /login sends the user back here once signed in.
      router.replace(`/login?next=${encodeURIComponent(OAUTH_CALLBACK_PATH)}`);
      return;
    }
    if (sent.current) return; // the code is single use — never send it twice (StrictMode, re-renders)
    sent.current = true;
    clearCallback();
    completeDiscordOAuth(c.code, c.state)
      .then((result) => setView({ kind: "done", result }))
      .catch((err) => setView({ kind: "error", message: parseC2Error(err).message }));
  }, [loading, user, router]);

  return (
    <div className="max-w-lg mx-auto pt-10">
      <Card padding="lg" className="space-y-4">
        <h1 className="text-ink text-lg font-semibold">Connect a Discord server</h1>
        <Body view={view} />
      </Card>
    </div>
  );
}

function Body({ view }: { view: View }) {
  switch (view.kind) {
    case "working":
      return <p className="text-sm text-ink-muted">Linking the server and checking the radio bot&apos;s permissions…</p>;
    case "none":
      return (
        <>
          <p className="text-sm text-ink-2">There is nothing to finish here. Start from <b className="text-ink">Connect a Discord server</b> in your organization settings.</p>
          <LinkButton href={SETTINGS} size="sm">Organization settings</LinkButton>
        </>
      );
    case "denied":
      return (
        <>
          <p className="text-sm text-ink-2"><b className="text-ink">Nothing changed.</b> The bot was not added, and no server was linked.</p>
          <LinkButton href={SETTINGS} size="sm" variant="secondary">Back to organization settings</LinkButton>
        </>
      );
    case "error":
      return (
        <>
          <p className="text-sm text-sev-major">{view.message}</p>
          <p className="text-xs text-ink-muted">If the bot did join the server, it stays there but cannot carry radio until the server is linked. Try Connect again, or use a link code.</p>
          <LinkButton href={SETTINGS} size="sm" variant="secondary">Back to organization settings</LinkButton>
        </>
      );
    case "done":
      return <Done r={view.result} />;
  }
}

function Done({ r }: { r: OAuthCompleteResult }) {
  const name = r.guild_name || "the server";
  const next = r.return_to ?? SETTINGS;
  const checked = r.channels_ready !== null || r.channels_blocked !== null;
  const blocked = r.channels_blocked ?? 0;
  return (
    <>
      <p className="text-sm text-ink">
        Linked <b>{name}</b>{r.bot_name ? <> and added <b>{r.bot_name}</b></> : null}.
      </p>
      {checked ? (
        <p className="text-sm text-ink-2">
          {r.channels_ready ?? 0} voice channel{r.channels_ready === 1 ? "" : "s"} ready
          {blocked > 0 && <>, <span className="text-sev-moderate">{blocked} need{blocked === 1 ? "s" : ""} a permission fix</span></>}.
        </p>
      ) : (
        <p className="text-sm text-ink-muted">The bot&apos;s channel permissions couldn&apos;t be checked yet. The node&apos;s Discord picker shows them.</p>
      )}
      {blocked > 0 && (
        <p className="text-xs text-ink-muted">The node&apos;s Discord picker names the missing permission on each channel and how to allow it.</p>
      )}
      {r.stopped > 0 && (
        <p className="text-xs text-ink-muted">
          {r.stopped} radio channel{r.stopped === 1 ? " was" : "s were"} stopped: this server used to act for the default organization.
        </p>
      )}
      <LinkButton href={next} size="sm">{nextStepLabel(next)}</LinkButton>
    </>
  );
}