import React, { useState, useRef } from 'react';

interface CurrencyInputProps {
  value: number; // Value in cents (integer)
  onChange: (cents: number) => void;
  disabled?: boolean;
  required?: boolean;
  placeholder?: string;
  className?: string;
  min?: number;
  max?: number;
}

/**
 * ATM-style currency input where digits are entered as cents.
 * As more digits are entered, they shift from cents to dollars.
 * Only accepts integer values (digits 0-9).
 *
 * Example: typing "1234" displays "$12.34"
 * - Type "1" → $0.01
 * - Type "2" → $0.12
 * - Type "3" → $1.23
 * - Type "4" → $12.34
 */
const CurrencyInput: React.FC<CurrencyInputProps> = ({
  value,
  onChange,
  disabled = false,
  required = false,
  placeholder = '$0.00',
  className = '',
  min,
  max,
}) => {
  const inputRef = useRef<HTMLInputElement>(null);
  const [isFocused, setIsFocused] = useState(false);

  // Ensure value is always an integer
  const safeValue = Math.floor(Math.abs(value)) || 0;

  // Format cents as dollars string (e.g., 1234 → "$12.34")
  const formatCentsAsDollars = (cents: number): string => {
    if (cents === 0 && !isFocused) return '';
    const dollars = cents / 100;
    return `$${dollars.toFixed(2)}`;
  };

  const displayValue = safeValue > 0 || isFocused ? formatCentsAsDollars(safeValue) : '';

  // Process a new digit being added
  const addDigit = (digit: number) => {
    let newValue = safeValue * 10 + digit;

    // Enforce max if specified
    if (max !== undefined && newValue > max) {
      newValue = max;
    }

    onChange(newValue);
  };

  // Remove the last digit
  const removeDigit = () => {
    const newValue = Math.floor(safeValue / 10);
    onChange(newValue);
  };

  const handleKeyDown = (e: React.KeyboardEvent<HTMLInputElement>) => {
    // Allow navigation keys without preventing default
    if (
      e.key === 'Tab' ||
      e.key === 'Escape' ||
      e.key === 'Enter' ||
      e.key === 'ArrowLeft' ||
      e.key === 'ArrowRight' ||
      e.key === 'Home' ||
      e.key === 'End'
    ) {
      return;
    }

    // Handle backspace/delete
    if (e.key === 'Backspace' || e.key === 'Delete') {
      e.preventDefault();
      removeDigit();
      return;
    }

    // Only allow digits 0-9
    if (/^[0-9]$/.test(e.key)) {
      e.preventDefault();
      addDigit(parseInt(e.key, 10));
      return;
    }

    // Block everything else
    e.preventDefault();
  };

  // Catch input from mobile keyboards, IME, voice input, etc.
  const handleBeforeInput = (e: React.FormEvent<HTMLInputElement>) => {
    const inputEvent = e.nativeEvent as InputEvent;
    const data = inputEvent.data;

    // Always prevent default - we handle all input ourselves
    e.preventDefault();

    if (!data) return;

    // Extract only digits from the input
    const digits = data.replace(/\D/g, '');

    // Add each digit one at a time
    for (const char of digits) {
      addDigit(parseInt(char, 10));
    }
  };

  const handleFocus = () => {
    setIsFocused(true);
  };

  const handleBlur = () => {
    setIsFocused(false);
    // Enforce min on blur if specified
    if (min !== undefined && safeValue < min && safeValue > 0) {
      onChange(min);
    }
  };

  // Handle paste - extract digits only
  const handlePaste = (e: React.ClipboardEvent<HTMLInputElement>) => {
    e.preventDefault();
    const pastedText = e.clipboardData.getData('text');
    const digits = pastedText.replace(/\D/g, '');

    if (digits) {
      let newValue = parseInt(digits, 10);
      if (max !== undefined && newValue > max) {
        newValue = max;
      }
      onChange(newValue);
    }
  };

  // Handle drop - extract digits only
  const handleDrop = (e: React.DragEvent<HTMLInputElement>) => {
    e.preventDefault();
    const droppedText = e.dataTransfer.getData('text');
    const digits = droppedText.replace(/\D/g, '');

    if (digits) {
      let newValue = parseInt(digits, 10);
      if (max !== undefined && newValue > max) {
        newValue = max;
      }
      onChange(newValue);
    }
  };

  return (
    <input
      ref={inputRef}
      type="text"
      inputMode="numeric"
      pattern="[0-9]*"
      value={displayValue}
      onKeyDown={handleKeyDown}
      onBeforeInput={handleBeforeInput}
      onFocus={handleFocus}
      onBlur={handleBlur}
      onPaste={handlePaste}
      onDrop={handleDrop}
      onChange={() => {}} // Controlled via onKeyDown/onBeforeInput
      disabled={disabled}
      required={required}
      placeholder={placeholder}
      className={className}
      autoComplete="off"
      autoCorrect="off"
      autoCapitalize="off"
      spellCheck={false}
    />
  );
};

export default CurrencyInput;