"use client";

import { useEffect, useId, useRef, useState, type CSSProperties, type InputHTMLAttributes } from "react";
import { motion, useReducedMotion } from "motion/react";

type PasswordRevealProps = Omit<InputHTMLAttributes<HTMLInputElement>, "type" | "className"> & {
  /** Field name shown above the box. */
  label: string;
  /** Small help text under the field. */
  hint?: string;
  /** Error text under the field. Turns the field red and sets aria-invalid. */
  error?: string;
  /** Colour of the focus border and eye button. */
  accent?: string;
  /** Wrapper look (width etc.). */
  className?: string;
};

const FLIP_MS = 420;

/* PasswordReveal: a password field whose eye button flips the dots into letters one by one, left to right. It stays a real password input the rest of the time, so password managers keep working. */
export function PasswordReveal({
  label,
  hint,
  error,
  accent = "#a78bfa",
  className = "w-full max-w-sm",
  id,
  autoComplete = "current-password",
  ...rest
}: PasswordRevealProps) {
  const reduce = useReducedMotion();
  const autoId = useId();
  const inputId = id ?? autoId;
  const noteId = `${inputId}-note`;
  const note = error ?? hint;
  const input = useRef<HTMLInputElement>(null);
  const timer = useRef(0);
  const [shown, setShown] = useState(false);
  const [flip, setFlip] = useState<{ chars: string[]; offset: number } | null>(null);

  useEffect(() => () => window.clearTimeout(timer.current), []);

  const toggle = () => {
    const el = input.current;
    setShown(!shown);
    if (reduce || !el?.value) return;
    setFlip({ chars: Array.from(el.value), offset: el.scrollLeft });
    window.clearTimeout(timer.current);
    timer.current = window.setTimeout(() => setFlip(null), FLIP_MS + 120);
  };

  const gap = flip ? Math.min(0.03, FLIP_MS / 1000 / flip.chars.length) : 0;

  return (
    <div className={className} style={{ "--pr": error ? "#f87171" : accent } as CSSProperties}>
      <label htmlFor={inputId} className="mb-2 block text-sm font-medium text-white/80">
        {label}
      </label>
      <div className="relative">
        <input
          ref={input}
          id={inputId}
          type={shown ? "text" : "password"}
          autoComplete={autoComplete}
          spellCheck={false}
          aria-invalid={error ? true : undefined}
          aria-describedby={note ? noteId : undefined}
          style={flip ? { color: "transparent" } : undefined}
          className="h-12 w-full rounded-xl border border-white/12 bg-white/[0.04] pr-12 pl-4 font-mono text-base text-white caret-[var(--pr)] outline-none transition-colors duration-200 hover:border-white/25 focus:border-[var(--pr)] aria-invalid:border-red-400/70 motion-reduce:transition-none"
          {...rest}
        />
        {flip && (
          <span aria-hidden className="pointer-events-none absolute inset-y-0 right-12 left-4 flex items-center overflow-hidden font-mono text-base text-white">
            <span className="whitespace-pre" style={{ transform: `translateX(${-flip.offset}px)` }}>
              {flip.chars.map((c, i) => (
                <span key={i} className="relative inline-block w-[1ch] text-center">
                  <motion.span
                    className="inline-block"
                    initial={{ opacity: shown ? 0 : 1, rotateX: shown ? 90 : 0 }}
                    animate={{ opacity: shown ? 1 : 0, rotateX: shown ? 0 : 90 }}
                    transition={{ duration: 0.2, delay: i * gap }}
                  >
                    {c}
                  </motion.span>
                  <motion.span
                    className="absolute inset-0"
                    initial={{ opacity: shown ? 1 : 0, scale: shown ? 1 : 0.4 }}
                    animate={{ opacity: shown ? 0 : 1, scale: shown ? 0.4 : 1 }}
                    transition={{ duration: 0.2, delay: i * gap }}
                  >
                    •
                  </motion.span>
                </span>
              ))}
            </span>
          </span>
        )}
        <button
          type="button"
          aria-label="Show password"
          aria-pressed={shown}
          aria-controls={inputId}
          onMouseDown={(e) => e.preventDefault()}
          onClick={toggle}
          className="absolute top-1/2 right-1.5 grid size-9 -translate-y-1/2 place-items-center rounded-lg text-white/55 outline-none transition-colors duration-150 hover:text-white focus-visible:text-[var(--pr)] focus-visible:ring-2 focus-visible:ring-[var(--pr)] motion-reduce:transition-none"
        >
          <svg aria-hidden viewBox="0 0 24 24" fill="none" stroke="currentColor" strokeWidth="2" strokeLinecap="round" strokeLinejoin="round" className="size-5">
            <path d="M2.5 12S6 5.5 12 5.5 21.5 12 21.5 12 18 18.5 12 18.5 2.5 12 2.5 12Z" />
            <motion.circle cx="12" cy="12" r="3" initial={false} animate={{ scale: shown ? 1 : 0.6 }} transition={{ duration: reduce ? 0 : 0.2 }} />
            <motion.path d="m4 4 16 16" initial={false} animate={{ pathLength: shown ? 0 : 1, opacity: shown ? 0 : 1 }} transition={{ duration: reduce ? 0 : 0.22 }} />
          </svg>
        </button>
      </div>
      {note && (
        <p id={noteId} className={`mt-1.5 px-1 text-xs ${error ? "text-red-300" : "text-white/45"}`}>
          {note}
        </p>
      )}
    </div>
  );
}