import { useEffect, useRef, useState, type FormEvent } from "react";
import { ApiError, errorCode } from "../api/client";
import type { SignBody } from "../api/types";
import type { Factor } from "../auth/types";
import { useAuth } from "../auth/useAuth";
import { errorText } from "../lib/format";
import { applyKey, type KeypadKey } from "../lib/keypad";
import { Keypad } from "./Keypad";
import { Sheet } from "./Sheet";

const PIN_MAX = 12;

interface SignatureSheetProps {
  /** What the signature means, from the rule. */
  meaning: string;
  sub?: string | undefined;
  /** Sends the step with the signature. A wrong secret keeps the sheet open. */
  onSign: (sign: SignBody) => Promise<void>;
  /** Any other failure. The caller closes the sheet. */
  onFail: (err: unknown) => void;
  onCancel: () => void;
}

function attemptsLeft(err: unknown): number | null {
  if (err instanceof ApiError && err.body && typeof err.body === "object" && "attempts_left" in err.body) {
    const n = Number((err.body as { attempts_left: unknown }).attempts_left);
    return Number.isFinite(n) ? n : null;
  }
  return null;
}

/** Signs a step with the user's PIN or password. */
export function SignatureSheet({ meaning, sub, onSign, onFail, onCancel }: SignatureSheetProps) {
  const auth = useAuth();
  const me = auth.me;
  const hasPin = me ? me.pin.set && !me.pin.disabled : false;
  const [factor, setFactor] = useState<Factor>(hasPin ? "pin" : "password");
  const [secret, setSecret] = useState("");
  const [busy, setBusy] = useState(false);
  const [error, setError] = useState<string | null>(null);
  const [left, setLeft] = useState<number | null>(null);
  const [missed, setMissed] = useState(false);
  const inputRef = useRef<HTMLInputElement>(null);

  useEffect(() => {
    inputRef.current?.focus();
  }, [factor]);

  const switchTo = (f: Factor) => {
    setFactor(f);
    setSecret("");
    setError(null);
  };

  const submit = async (e: FormEvent) => {
    e.preventDefault();
    if (!secret || busy) return;
    setBusy(true);
    setError(null);
    try {
      await onSign({ factor, secret });
    } catch (err) {
      const code = errorCode(err);
      if (code === "session_ended") {
        // The auth layer signs out on this 401 too. Make sure, with the server's words.
        auth.endSession(errorText(err));
        return;
      }
      if (code === "wrong_secret" || code === "bad_secret") {
        setError(errorText(err));
        setLeft(attemptsLeft(err));
        setMissed(true);
        setSecret("");
        setBusy(false);
        inputRef.current?.focus();
        return;
      }
      onFail(err);
    }
  };

  const onKey = (k: KeypadKey) => setSecret((v) => applyKey(v, k, PIN_MAX));

  return (
    <Sheet title="Sign" sub={sub} onClose={onCancel}>
      <div className="sigmean">
        <div className="eyebrow">This signature means</div>
        <div className="tt">{meaning}</div>
      </div>
      <div className="small">
        You are signing as <b>{me?.user.display_name ?? "yourself"}</b>.
      </div>
      {error ? (
        <div className="callout warn flush" role="alert">
          {error}
          {left !== null ? <div className="small">{left === 1 ? "1 attempt left." : `${left} attempts left.`}</div> : null}
          {missed ? <div className="small">Three wrong attempts end the session.</div> : null}
        </div>
      ) : null}
      <form className="auth-form" onSubmit={submit} noValidate autoComplete="off">
        {factor === "pin" ? (
          <>
            <label className="f">
              PIN
              <input
                ref={inputRef}
                className="in big"
                name="sign-pin"
                type="password"
                inputMode="numeric"
                autoComplete="off"
                maxLength={PIN_MAX}
                value={secret}
                onChange={(e) => setSecret(e.target.value.replace(/\D/g, "").slice(0, PIN_MAX))}
              />
            </label>
            <Keypad onKey={onKey} disabled={busy} label="Keypad, signature PIN" />
          </>
        ) : (
          <label className="f">
            Password
            <input
              ref={inputRef}
              className="in"
              name="sign-password"
              type="password"
              autoComplete="current-password"
              value={secret}
              onChange={(e) => setSecret(e.target.value)}
            />
          </label>
        )}
        <div className="sheet-acts">
          {factor === "pin" ? (
            <button className="lnk small" type="button" onClick={() => switchTo("password")}>
              Use your password instead
            </button>
          ) : hasPin ? (
            <button className="lnk small" type="button" onClick={() => switchTo("pin")}>
              Use your PIN instead
            </button>
          ) : null}
          <span className="grow" />
          <button className="btn ghost" type="button" onClick={onCancel}>
            Cancel
          </button>
          <button className="btn pri" type="submit" disabled={busy || !secret}>
            {busy ? "Signing" : "Sign"}
          </button>
        </div>
      </form>
    </Sheet>
  );
}