import { useEffect, useRef, useState } from "react";
import { api } from "./api";
import { HttpError } from "./api/core";
import { clearEntryUrl, entryHash } from "./entryUrl";

/** What confirming the emailed token produced. `ok_reset` means the address is confirmed but this
 * account's password had been revoked (SEC-10), so signing in would only meet the uniform credentials
 * error — the user has to set a new one. `unreachable` is a TRANSPORT failure, kept apart from
 * `invalid` on purpose (DX-16): the fragment is already cleared by the time we know, so telling
 * someone their link is spent when the server was merely restarting sends them to request a fresh one
 * on the strength of a false statement. The same rule is already written one file away, for the
 * reset-link probe: "a network blip must never be cached as 'this link is dead'". */
type VerifyOutcome = "ok" | "ok_reset" | "invalid" | "unreachable";

export type VerifyEntry = {
  outcome: VerifyOutcome | null;
  /** The address that was confirmed, when the server named it. */
  email: string | null;
  /** A `#reset=` link opened in a tab that already holds a session. Only the signed-OUT auth card
   * consumes a reset token, so nothing here can act on it — but silence is what made the verify half
   * a bug, so this says out loud that the link needs a signed-out window. The fragment is deliberately
   * left in the address bar, so signing out still recovers it. */
  resetPending: boolean;
  /** Dismiss the outcome — the banner is a one-time entry notice, not persistent state. */
  dismiss: () => void;
};

/**
 * Confirm a `#verify=` token from the entry URL, wherever the user opened it.
 *
 * App calls this ABOVE its signed-in/signed-out branch, which is the whole point: the token used to be
 * consumed inside Welcome.tsx, and `App.tsx` renders <Welcome /> only when there is no session. Open
 * the emailed link in a browser that already holds a Siftlode session and the token was never posted,
 * the fragment was then stripped, and the user got no signal at all — the link simply did nothing.
 * Incognito worked, which is why it survived so long.
 *
 * The link does not always arrive as a page LOAD. When the app is already open in the tab and the URL
 * differs only in the fragment, the browser performs a same-document navigation — no reload, so the
 * import-time snapshot never sees the new token. Pasting the emailed link into a running tab's address
 * bar does exactly that, and our verification mails were plain text until 0.78.8, which makes pasting
 * the normal way to use one. Without the `hashchange` listener below the token would sit unconsumed in
 * the address bar: the same silence signed-in users met before, in a second disguise.
 *
 * Each token is posted exactly once. It is single-use, so a repeat POST (a StrictMode remount, any
 * re-render) would 400 and wrongly flip a successful confirmation to "invalid".
 */
export function useVerifyEntry(): VerifyEntry {
  const [token, setToken] = useState<string | null>(() => entryHash.get("verify"));
  const [outcome, setOutcome] = useState<VerifyOutcome | null>(null);
  const [email, setEmail] = useState<string | null>(null);
  const [resetPending, setResetPending] = useState<boolean>(() => !!entryHash.get("reset"));
  const consumed = useRef(new Set<string>());

  useEffect(() => {
    const onHashChange = () => {
      const hash = new URLSearchParams(window.location.hash.replace(/^#/, ""));
      const next = hash.get("verify");
      if (next) setToken(next);
      // Both halves of the mailed pair arrive the same way — pasted into a running tab, which is a
      // same-document navigation the import-time snapshot never sees. The verify half got this
      // listener first; the reset half was left out, so it stayed silent (DX-17).
      //
      // Set from the live hash rather than one-way, because the flag must not outlive the token it
      // describes: navigating away from a `#reset=` (a pasted verify link, the back button) leaves
      // the banner promising that signing out will resume a reset whose token is gone — and, being
      // checked first, hiding whatever arrived in its place. `clearEntryUrl`'s own replaceState
      // fires no hashchange, so this cannot undo the deliberate keep-the-reset-fragment behaviour.
      setResetPending(!!hash.get("reset"));
    };
    // replaceState (how clearEntryUrl strips the fragment) does NOT fire hashchange, so this cannot
    // feed itself.
    window.addEventListener("hashchange", onHashChange);
    return () => window.removeEventListener("hashchange", onHashChange);
  }, []);

  useEffect(() => {
    // Clear the address bar even with no token to consume, so a spent one leaves no trace on a
    // reload. An unspent `#reset=` is the exception and `clearEntryUrl` says why: nothing in a
    // signed-in tree reads it, so erasing it there is a dead end rather than a cleanup.
    clearEntryUrl();
    if (!token || consumed.current.has(token)) return;
    consumed.current.add(token);
    // A second link arriving over an unread first outcome must not leave the OLD banner standing.
    setOutcome(null);
    setEmail(null);
    api
      .verifyEmail(token)
      .then((r) => {
        setOutcome(r.password_reset_required ? "ok_reset" : "ok");
        setEmail(r.email ?? null);
      })
      // Only the server's own verdict on the token means "invalid". `/auth/verify` refuses a spent
      // or expired token with a 400 carrying {code:"verify"}; a 502 during a deploy, or a dropped
      // connection (no HttpError at all), says nothing about the token and must not be reported as
      // if it did. The token itself is unspent in that case — but the fragment has already been
      // cleared, so the honest message is "we could not reach the server", not "request a new link".
      .catch((e: unknown) => {
        const spent =
          e instanceof HttpError &&
          e.status === 400 &&
          (e.detailData as { code?: string } | undefined)?.code === "verify";
        setOutcome(spent ? "invalid" : "unreachable");
      });
  }, [token]);

  return {
    outcome,
    email,
    resetPending,
    // Dismiss peels ONE layer. The two states are independent — a reset link can arrive over an
    // unread confirmation, and a slow /auth/verify can resolve after one did — so clearing both at
    // once silently discards whichever the user had not read yet. The banner shows the reset
    // guidance first (it is the one with something to do), and dismissing it reveals the outcome
    // underneath rather than taking it with it.
    dismiss: () => {
      if (resetPending) {
        setResetPending(false);
        return;
      }
      setOutcome(null);
      setEmail(null);
    },
  };
}