"use client";

import React, { useRef, useEffect } from "react";
import { toEnglishDigits } from "../lib/utils";

interface OtpInput5Props {
  value: string;
  onChange: (val: string) => void;
  disabled?: boolean;
  autoFocus?: boolean;
  onComplete?: (code: string) => void;
}

export default function OtpInput5({
  value,
  onChange,
  disabled = false,
  autoFocus = true,
  onComplete,
}: OtpInput5Props) {
  const inputRefs = useRef<(HTMLInputElement | null)[]>([]);

  // Array of 5 characters
  const digits = Array.from({ length: 5 }, (_, i) => value[i] || "");

  useEffect(() => {
    if (autoFocus && inputRefs.current[0]) {
      const timer = setTimeout(() => {
        inputRefs.current[0]?.focus({ preventScroll: true });
      }, 80);
      return () => clearTimeout(timer);
    }
  }, [autoFocus]);

  const handleDigitChange = (index: number, char: string) => {
    const cleanChars = toEnglishDigits(char).replace(/[^0-9]/g, "");
    if (!cleanChars) {
      // Empty / Backspace in controlled input
      const newDigits = [...digits];
      newDigits[index] = "";
      const newVal = newDigits.join("");
      onChange(newVal);
      return;
    }

    // If multiple chars pasted or typed
    if (cleanChars.length > 1) {
      const slice5 = cleanChars.slice(0, 5);
      onChange(slice5);
      const nextIndex = Math.min(slice5.length, 4);
      inputRefs.current[nextIndex]?.focus();
      if (slice5.length === 5 && onComplete) {
        onComplete(slice5);
      }
      return;
    }

    const single = cleanChars[0];
    const newDigits = [...digits];
    newDigits[index] = single;
    const newVal = newDigits.join("");
    onChange(newVal);

    if (index < 4) {
      inputRefs.current[index + 1]?.focus();
    }

    if (newVal.length === 5 && onComplete) {
      onComplete(newVal);
    }
  };

  const handleKeyDown = (index: number, e: React.KeyboardEvent<HTMLInputElement>) => {
    if (e.key === "Backspace") {
      if (!digits[index] && index > 0) {
        // Move to previous and clear
        inputRefs.current[index - 1]?.focus();
        const newDigits = [...digits];
        newDigits[index - 1] = "";
        onChange(newDigits.join(""));
      }
    } else if (e.key === "ArrowLeft") {
      // In LTR inputs, Left goes to previous
      if (index > 0) {
        inputRefs.current[index - 1]?.focus();
      }
    } else if (e.key === "ArrowRight") {
      // In LTR inputs, Right goes to next
      if (index < 4) {
        inputRefs.current[index + 1]?.focus();
      }
    }
  };

  const handlePaste = (e: React.ClipboardEvent) => {
    e.preventDefault();
    const pasted = e.clipboardData.getData("text");
    const clean = toEnglishDigits(pasted).replace(/[^0-9]/g, "").slice(0, 5);
    if (clean) {
      onChange(clean);
      const targetIndex = Math.min(clean.length, 4);
      inputRefs.current[targetIndex]?.focus();
      if (clean.length === 5 && onComplete) {
        onComplete(clean);
      }
    }
  };

  return (
    <div className="flex items-center justify-center gap-2.5 sm:gap-3.5 my-2" dir="ltr">
      {[0, 1, 2, 3, 4].map((idx) => {
        const val = digits[idx] || "";
        const isFilled = Boolean(val);

        return (
          <input
            key={idx}
            ref={(el) => {
              inputRefs.current[idx] = el;
            }}
            type="tel"
            inputMode="numeric"
            pattern="[0-9]*"
            // idx === 0: no maxLength so browser OTP autofill can inject the full code.
            // The handleDigitChange handler distributes multi-char input across all boxes.
            maxLength={idx === 0 ? undefined : 1}
            autoComplete={idx === 0 ? "one-time-code" : "off"}
            value={val}
            disabled={disabled}
            onChange={(e) => handleDigitChange(idx, e.target.value)}
            onKeyDown={(e) => handleKeyDown(idx, e)}
            onPaste={handlePaste}
            onFocus={(e) => e.target.select()}
            className={`w-12 h-14 sm:w-14 sm:h-16 text-center text-xl sm:text-2xl font-black font-mono rounded-2xl border-2 transition-all outline-none shadow-xs ${
              isFilled
                ? "border-canina-blue bg-canina-blue/5 text-canina-blue ring-2 ring-canina-blue/20"
                : "border-medical-gray-200 bg-medical-gray-50/80 text-medical-gray-900 focus:border-canina-blue focus:bg-white focus:ring-4 focus:ring-canina-blue/15"
            } ${disabled ? "opacity-50 cursor-not-allowed" : "cursor-text"}`}
          />
        );
      })}
    </div>
  );
}