import React, { useState, useCallback } from 'react';
import clsx from 'clsx';
import { Button } from '../Button';
import { XrplArrowInternalLinkIcon } from '../Icons';

export interface CardImageProps {
  /** Image source URL */
  image: string;
  /** Alt text for the image */
  imageAlt: string;
  /** Card title (1 line only) */
  title: string;
  /** Card subtitle (max 3 lines). `\n` renders as a line break; an all-bullet subtitle renders as a list. */
  subtitle: string;
  /** Button label text */
  buttonLabel: string;
  /** Link destination (renders card as clickable link) */
  href?: string;
  /** Click handler for the button */
  onClick?: () => void;
  /** Disabled state */
  disabled?: boolean;
  /** Optional className for custom styling */
  className?: string;
  /** When true, image fills entire container with object-fit: cover (no visible background) */
  fullBleed?: boolean;
  /** Custom background color for image container (defaults to gray-100) */
  backgroundColor?: string;
}

// Matches a leading bullet marker on a subtitle line, e.g. "\u2022 ", "- ", "* ".
const BULLET_MARKER = /^\s*[\u2022\u2023\u25E6\u2043\-*]\s+/;

/**
 * Renders the subtitle.
 *
 * When every line of the subtitle is a bullet (`\n`-separated), it renders as a
 * real `<ul>` so wrapped text hangs-indents under the first character instead of
 * running back to the left edge — and so screen readers announce it as a list.
 * Any other subtitle renders as a paragraph, where `white-space: pre-line` still
 * turns `\n` into a plain line break.
 */
const renderSubtitle = (subtitle: string): React.ReactNode => {
  const lines = subtitle.split('\n').filter((line) => line.trim() !== '');
  const isBulletList = lines.length > 0 && lines.every((line) => BULLET_MARKER.test(line));

  if (!isBulletList) {
    return <p className="bds-card-image__subtitle body-l">{subtitle}</p>;
  }

  return (
    <ul className="bds-card-image__subtitle bds-card-image__subtitle--list body-l">
      {lines.map((line, index) => (
        <li key={index} className="bds-card-image__subtitle-item">
          {line.replace(BULLET_MARKER, '')}
        </li>
      ))}
    </ul>
  );
};

/**
 * BDS CardImage Component
 *
 * A responsive card component displaying an image, title, subtitle, and CTA button.
 * Features three responsive size variants (LG/MD/SM) that adapt to viewport width.
 *
 * Key behaviors:
 * - Hovering the card triggers the button's hover animation
 * - Card can link to a URL or trigger a click handler
 * - Supports disabled state
 *
 * @example
 * // Basic card with link
 * <CardImage
 *   image="/images/docs-hero.png"
 *   imageAlt="Documentation illustration"
 *   title="Documentation"
 *   subtitle="Access everything you need to get started working with the XRPL."
 *   buttonLabel="Get Started"
 *   href="/docs"
 * />
 *
 * @example
 * // Card with click handler
 * <CardImage
 *   image="/images/feature.png"
 *   imageAlt="Feature illustration"
 *   title="New Feature"
 *   subtitle="Learn about our latest feature."
 *   buttonLabel="Learn More"
 *   onClick={() => console.log('clicked')}
 * />
 */
export const CardImage: React.FC<CardImageProps> = ({
  image,
  imageAlt,
  title,
  subtitle,
  buttonLabel,
  href,
  onClick,
  disabled = false,
  className = '',
  fullBleed = false,
  backgroundColor,
}) => {
  // Track hover state for button animation
  const [isHovered, setIsHovered] = useState(false);

  const handleMouseEnter = useCallback(() => {
    if (!disabled) {
      setIsHovered(true);
    }
  }, [disabled]);

  const handleMouseLeave = useCallback(() => {
    if (!disabled) {
      setIsHovered(false);
    }
  }, [disabled]);

  // Build class names using BEM with bds namespace
  const classNames = clsx(
    'bds-card-image',
    disabled && 'bds-card-image--disabled',
    isHovered && 'bds-card-image--hovered',
    fullBleed && 'bds-card-image--full-bleed',
    className
  );

  // Handle button click
  const handleButtonClick = useCallback(() => {
    onClick?.();
  }, [onClick]);

  // Build inline style for image container background color
  const imageContainerStyle = backgroundColor
    ? { '--bds-card-image-bg': backgroundColor } as React.CSSProperties
    : undefined;

  // A link card is one link end to end, so the CTA is painted rather than built:
  // a <Button href> here would nest an <a> inside the card's own <a>, which the
  // HTML parser rewrites on the way back in from SSR. The class list and the
  // label/icon slots mirror Button's own output — see Button.tsx — so the icon
  // meets the motion contract in Icons/shared.scss and engages with the card.
  const cta = href && !disabled ? (
    <span className="bds-btn bds-btn--brand bds-btn--strong bds-btn--on-theme">
      <span className="bds-btn__label">{buttonLabel}</span>
      <span className="bds-btn__icon" aria-hidden="true">
        <XrplArrowInternalLinkIcon />
      </span>
    </span>
  ) : (
    <Button
      emphasis="strong"
      intention="brand"
      disabled={disabled}
      onClick={handleButtonClick}
      iconEnd={<XrplArrowInternalLinkIcon />}
    >
      {buttonLabel}
    </Button>
  );

  // Common content structure
  const content = (
    <>
      {/* Image container with customizable background */}
      <div className="bds-card-image__image-container" style={imageContainerStyle}>
        <img
          src={image}
          alt={imageAlt}
          className="bds-card-image__image"
          loading="lazy"
          decoding="async"
        />
      </div>

      {/* Content area: title, subtitle, and button */}
      <div className="bds-card-image__content">
        <div className="bds-card-image__text">
          <h3 className="bds-card-image__title sh-md-l">{title}</h3>
          {renderSubtitle(subtitle)}
        </div>

        {cta}
      </div>
    </>
  );

  if (href && !disabled) {
    return (
      <a
        href={href}
        className={classNames}
        onMouseEnter={handleMouseEnter}
        onMouseLeave={handleMouseLeave}
        onClick={onClick ? () => onClick() : undefined}
      >
        {content}
      </a>
    );
  }

  return (
    <div
      className={classNames}
      onMouseEnter={handleMouseEnter}
      onMouseLeave={handleMouseLeave}
      aria-disabled={disabled}
    >
      {content}
    </div>
  );
};

export default CardImage;