<?php
/**
 * Markdown to Gutenberg Blocks Parser
 *
 * Converts Markdown content to WordPress Gutenberg blocks.
 *
 * @package WP_Agentic_Writer
 */

if ( ! defined( 'ABSPATH' ) ) {
	exit;
}

/**
 * Class WP_Agentic_Writer_Markdown_Parser
 *
 * @since 0.1.0
 */
class WP_Agentic_Writer_Markdown_Parser {

	/**
	 * Parse Markdown content and convert to Gutenberg blocks.
	 *
	 * @since 0.1.0
	 * @param string $markdown Markdown content.
	 * @return array Array of Gutenberg blocks.
	 */
	public static function parse( $markdown ) {
		$markdown = self::normalize_markdown( $markdown );
		$blocks = array();
		$lines = explode( "\n", $markdown );
		$current_paragraph = '';
		$in_code_block = false;
		$in_list = false;
		$list_items = array();
		$list_type = 'ul'; // 'ul' or 'ol'
		$code_lines = array();
		$code_language = '';
		$in_auto_code_block = false;
		$auto_code_lines = array();
		$auto_code_language = 'text';
		$is_code_like_line = function( $trimmed ) {
			if ( '' === $trimmed ) {
				return false;
			}
			if ( preg_match( '/^(<\\?php|define\\s*\\(|\\$[A-Za-z_]|function\\s+\\w+|class\\s+\\w+|if\\s*\\(|elseif\\s*\\(|else\\b|foreach\\s*\\(|for\\s*\\(|while\\s*\\(|switch\\s*\\(|case\\s+|echo\\s+|return\\s+|const\\s+|public\\s+|private\\s+|protected\\s+)/i', $trimmed ) ) {
				return true;
			}
			if ( preg_match( '/[;{}]$/', $trimmed ) && preg_match( '/[()$=]|->|::/', $trimmed ) ) {
				return true;
			}
			return false;
		};

		$line_count = count( $lines );
		for ( $i = 0; $i < $line_count; $i++ ) {
			$line = $lines[ $i ];
			$trimmed = trim( $line );

			if ( $in_auto_code_block ) {
				if ( '' === $trimmed ) {
					$blocks[] = self::create_code_block( $auto_code_language, implode( "\n", $auto_code_lines ) );
					$auto_code_lines = array();
					$auto_code_language = 'text';
					$in_auto_code_block = false;
					continue;
				}

				if ( $is_code_like_line( $trimmed ) || preg_match( '/^\\s+/', $line ) ) {
					$auto_code_lines[] = $line;
					continue;
				}

				$blocks[] = self::create_code_block( $auto_code_language, implode( "\n", $auto_code_lines ) );
				$auto_code_lines = array();
				$auto_code_language = 'text';
				$in_auto_code_block = false;
				// Continue processing current line normally below.
			}

			// Handle image placeholders: [IMAGE: description]
			if ( preg_match( '/^\[IMAGE:\s*(.+)\]$/i', $trimmed, $matches ) ) {
				// Flush any pending paragraph.
				if ( ! empty( $current_paragraph ) ) {
					$blocks[] = self::create_paragraph_block( $current_paragraph );
					$current_paragraph = '';
				}
				// Flush any pending list.
				if ( $in_list ) {
					$blocks[] = self::create_list_block( $list_type, $list_items );
					$list_items = array();
					$in_list = false;
				}

				// Create image placeholder block.
				$blocks[] = self::create_image_placeholder_block( $matches[1] );
				continue;
			}

			// Handle CTA/Button placeholders: [CTA: text] or [CTA: text (url)]
			if ( preg_match( '/^\[CTA:\s*(.+)\]$/i', $trimmed, $matches ) ) {
				// Flush any pending paragraph.
				if ( ! empty( $current_paragraph ) ) {
					$blocks[] = self::create_paragraph_block( $current_paragraph );
					$current_paragraph = '';
				}
				// Flush any pending list.
				if ( $in_list ) {
					$blocks[] = self::create_list_block( $list_type, $list_items );
					$list_items = array();
					$in_list = false;
				}

				// Create button block.
				$blocks[] = self::create_button_block( $matches[1] );
				continue;
			}

			// Detect unfenced code lines and create a code block automatically.
			if ( ! $in_code_block && $is_code_like_line( $trimmed ) ) {
				// Flush any pending paragraph.
				if ( ! empty( $current_paragraph ) ) {
					$blocks[] = self::create_paragraph_block( $current_paragraph );
					$current_paragraph = '';
				}
				// Flush any pending list.
				if ( $in_list ) {
					$blocks[] = self::create_list_block( $list_type, $list_items );
					$list_items = array();
					$in_list = false;
				}

				$auto_code_language = preg_match( '/^(<\\?php|define\\s*\\(|\\$[A-Za-z_])/', $trimmed ) ? 'php' : 'text';
				$in_auto_code_block = true;
				$auto_code_lines[] = $line;
				continue;
			}

			// Handle code blocks.
			if ( preg_match( '/^```(\w*)/', $trimmed, $matches ) ) {
				if ( $in_code_block ) {
					// End code block.
					$blocks[] = self::create_code_block( $code_language, implode( "\n", $code_lines ) );
					$code_lines = array();
					$code_language = '';
					$in_code_block = false;
				} else {
					// Start code block.
					// Flush any pending paragraph.
					if ( ! empty( $current_paragraph ) ) {
						$blocks[] = self::create_paragraph_block( $current_paragraph );
						$current_paragraph = '';
					}
					// Flush any pending list.
					if ( $in_list ) {
						$blocks[] = self::create_list_block( $list_type, $list_items );
						$list_items = array();
						$in_list = false;
					}
					$in_code_block = true;
					$code_language = $matches[1];
				}
				continue;
			}

			if ( $in_code_block ) {
				$code_lines[] = $line;
				continue;
			}

			// Handle headings.
			if ( preg_match( '/^(#{1,6})\s+(.+)$/', $trimmed, $matches ) ) {
				// Flush any pending paragraph.
				if ( ! empty( $current_paragraph ) ) {
					$blocks[] = self::create_paragraph_block( $current_paragraph );
					$current_paragraph = '';
				}
				// Flush any pending list.
				if ( $in_list ) {
					$blocks[] = self::create_list_block( $list_type, $list_items );
					$list_items = array();
					$in_list = false;
				}

				$level = strlen( $matches[1] );
				$content = $matches[2];
				$blocks[] = self::create_heading_block( $content, $level );
				continue;
			}

			// Handle markdown tables (header + separator + rows).
			if ( ! $in_list && self::is_table_row( $trimmed ) && $i + 1 < $line_count ) {
				$next_line = trim( $lines[ $i + 1 ] );
				if ( self::is_table_separator( $next_line ) ) {
					if ( ! empty( $current_paragraph ) ) {
						$blocks[] = self::create_paragraph_block( $current_paragraph );
						$current_paragraph = '';
					}
					if ( $in_list ) {
						$blocks[] = self::create_list_block( $list_type, $list_items );
						$list_items = array();
						$in_list = false;
					}

					$headers = self::split_table_row( $trimmed );
					$rows = array();
					$i += 2;
					for ( ; $i < $line_count; $i++ ) {
						$row_line = trim( $lines[ $i ] );
						if ( '' === $row_line || ! self::is_table_row( $row_line ) ) {
							$i -= 1;
							break;
						}
						$rows[] = self::split_table_row( $row_line );
					}

					$blocks[] = self::create_table_block( $headers, $rows );
					continue;
				}
			}

			// Handle horizontal rules.
			if ( preg_match( '/^[-*_]{3,}/', $trimmed ) ) {
				if ( ! empty( $current_paragraph ) ) {
					$blocks[] = self::create_paragraph_block( $current_paragraph );
					$current_paragraph = '';
				}
				if ( $in_list ) {
					$blocks[] = self::create_list_block( $list_type, $list_items );
					$list_items = array();
					$in_list = false;
				}
				// Gutenberg doesn't have a native separator block, use a spacer.
				$blocks[] = array(
					'blockName' => 'core/spacer',
					'attrs' => array(
						'height' => '20px',
					),
					'innerBlocks' => array(),
					'innerContent' => array(),
				);
				continue;
			}

			// Handle unordered lists (supports common dash/bullet variants).
			if ( preg_match( '/^[\*\-+\x{2022}\x{2023}\x{2013}\x{2014}]\s+(.+)$/u', $trimmed, $matches ) ) {
				if ( ! empty( $current_paragraph ) ) {
					$blocks[] = self::create_paragraph_block( $current_paragraph );
					$current_paragraph = '';
				}
				if ( $in_list && $list_type !== 'ul' ) {
					$blocks[] = self::create_list_block( $list_type, $list_items );
					$list_items = array();
				}
				$in_list = true;
				$list_type = 'ul';
				$list_items[] = self::parse_inline_markdown( $matches[1] );
				continue;
			}

			// Handle ordered lists.
			if ( preg_match( '/^\d+\.\s+(.+)$/', $trimmed, $matches ) ) {
				if ( ! empty( $current_paragraph ) ) {
					$blocks[] = self::create_paragraph_block( $current_paragraph );
					$current_paragraph = '';
				}
				if ( $in_list && $list_type !== 'ol' ) {
					$blocks[] = self::create_list_block( $list_type, $list_items );
					$list_items = array();
				}
				$in_list = true;
				$list_type = 'ol';
				$list_items[] = self::parse_inline_markdown( $matches[1] );
				continue;
			}

			// Handle blockquotes.
			if ( preg_match( '/^>\s+(.+)$/', $trimmed, $matches ) ) {
				if ( ! empty( $current_paragraph ) ) {
					$blocks[] = self::create_paragraph_block( $current_paragraph );
					$current_paragraph = '';
				}
				if ( $in_list ) {
					$blocks[] = self::create_list_block( $list_type, $list_items );
					$list_items = array();
					$in_list = false;
				}
				$blocks[] = self::create_quote_block( $matches[1] );
				continue;
			}

			// Handle empty lines.
			if ( empty( $trimmed ) ) {
				// Flush paragraph.
				if ( ! empty( $current_paragraph ) ) {
					$blocks[] = self::create_paragraph_block( $current_paragraph );
					$current_paragraph = '';
				}
				// Flush list.
				if ( $in_list ) {
					$blocks[] = self::create_list_block( $list_type, $list_items );
					$list_items = array();
					$in_list = false;
				}
				continue;
			}

			// Accumulate paragraph text.
			if ( ! empty( $current_paragraph ) ) {
				$current_paragraph .= ' ' . $trimmed;
			} else {
				$current_paragraph = $trimmed;
			}

			// Check if paragraph ends with punctuation suggesting end of sentence.
			if ( preg_match( '/[.!?]$/', $trimmed ) ) {
				$blocks[] = self::create_paragraph_block( $current_paragraph );
				$current_paragraph = '';
			}
		}

		if ( $in_auto_code_block && ! empty( $auto_code_lines ) ) {
			$blocks[] = self::create_code_block( $auto_code_language, implode( "\n", $auto_code_lines ) );
		}

		// Flush any remaining content.
		if ( ! empty( $current_paragraph ) ) {
			$blocks[] = self::create_paragraph_block( $current_paragraph );
		}
		if ( $in_list ) {
			$blocks[] = self::create_list_block( $list_type, $list_items );
		}

		// Merge consecutive ordered lists (fix 1. 1. 1. issue)
		$merged_blocks = self::merge_consecutive_ordered_lists( $blocks );

		// Remove duplicate adjacent headings before returning
		$cleaned_blocks = array();
		$last_heading_content = null;

		foreach ( $merged_blocks as $block ) {
			if ( isset( $block['blockName'] ) && 'core/heading' === $block['blockName'] ) {
				if ( preg_match( '/<h[1-6]>(.+?)<\/h[1-6]>/i', $block['innerHTML'], $matches ) ) {
					$current_heading = trim( $matches[1] );

					// Skip if duplicate of last heading (case-insensitive)
					if ( null !== $last_heading_content && strtolower( $current_heading ) === strtolower( $last_heading_content ) ) {
						continue;
					}

					$last_heading_content = $current_heading;
				}
			} else {
				$last_heading_content = null;
			}

			$cleaned_blocks[] = $block;
		}

		return $cleaned_blocks;
	}

	/**
	 * Parse inline Markdown elements (bold, italic, code, links).
	 *
	 * @since 0.1.0
	 * @param string $text Text with inline Markdown.
	 * @return array HTML content with inline formatting.
	 */
	private static function parse_inline_markdown( $text ) {
		// Convert inline code.
		$text = preg_replace( '/`([^`]+)`/', '<code>$1</code>', $text );

		// Convert bold.
		$text = preg_replace( '/\*\*(.+?)\*\*/', '<strong>$1</strong>', $text );
		$text = preg_replace( '/__(.+?)__/', '<strong>$1</strong>', $text );

		// Convert italic.
		$text = preg_replace( '/\*(.+?)\*/', '<em>$1</em>', $text );
		$text = preg_replace( '/_(.+?)_/', '<em>$1</em>', $text );

		// Convert links.
		$text = preg_replace( '/\[(.+?)\]\((.+?)\)/', '<a href="$2">$1</a>', $text );

		return $text;
	}

	/**
	 * Normalize markdown input to improve block parsing.
	 *
	 * @since 0.1.0
	 * @param string $markdown Raw markdown or HTML-ish content.
	 * @return string
	 */
	private static function normalize_markdown( $markdown ) {
		if ( null === $markdown ) {
			return '';
		}

		$markdown = (string) $markdown;
		$markdown = str_replace(
			array( '&#8211;', '&#8212;', '&ndash;', '&mdash;', '&bull;' ),
			'-',
			$markdown
		);
		$markdown = preg_replace( '/<br\\s*\\/?>/i', "\n", $markdown );
		$markdown = preg_replace( '/<\\/p>\\s*<p>/i', "\n\n", $markdown );
		$markdown = preg_replace( '/<\\/?p>/i', '', $markdown );
		$markdown = preg_replace( '/!\\[([^\\]]*)\\]\\([^\\)]*\\)/', '[IMAGE: $1]', $markdown );
		$markdown = preg_replace( '/\\[IMAGE:\\s*([^\\]]+)\\]/i', "\n[IMAGE: $1]\n", $markdown );

		return $markdown;
	}

	/**
	 * Check if a line looks like a markdown table row.
	 *
	 * @since 0.1.0
	 * @param string $line Line content.
	 * @return bool
	 */
	private static function is_table_row( $line ) {
		if ( '' === $line ) {
			return false;
		}
		return false !== strpos( $line, '|' );
	}

	/**
	 * Check if a line is a markdown table separator.
	 *
	 * @since 0.1.0
	 * @param string $line Line content.
	 * @return bool
	 */
	private static function is_table_separator( $line ) {
		return (bool) preg_match( '/^\|?\s*:?-{3,}:?\s*(\|\s*:?-{3,}:?\s*)+\|?$/', $line );
	}

	/**
	 * Split a markdown table row into cells.
	 *
	 * @since 0.1.0
	 * @param string $line Row line.
	 * @return array
	 */
	private static function split_table_row( $line ) {
		$trimmed = trim( $line );
		$trimmed = trim( $trimmed, " \t|" );
		if ( '' === $trimmed ) {
			return array();
		}
		return array_map( 'trim', explode( '|', $trimmed ) );
	}

	/**
	 * Create a heading block.
	 *
	 * @since 0.1.0
	 * @param string $content Heading content.
	 * @param int    $level Heading level (1-6).
	 * @return array Gutenberg block.
	 */
	private static function create_heading_block( $content, $level ) {
		$level = min( max( $level, 1 ), 6 ); // Ensure level is between 1-6.
		$parsed_content = self::parse_inline_markdown( $content );
		$html = '<h' . $level . '>' . $parsed_content . '</h' . $level . '>';

		return array(
			'blockName' => 'core/heading',
			'attrs' => array(
				'level' => $level,
				'content' => $parsed_content,
			),
			'innerBlocks' => array(),
			'innerContent' => array( $html ),
			'innerHTML' => $html,
		);
	}

	/**
	 * Create a paragraph block.
	 *
	 * @since 0.1.0
	 * @param string $content Paragraph content.
	 * @return array Gutenberg block.
	 */
	private static function create_paragraph_block( $content ) {
		$parsed_content = self::parse_inline_markdown( $content );
		$html = '<p>' . $parsed_content . '</p>';

		return array(
			'blockName' => 'core/paragraph',
			'attrs' => array(
				'content' => $parsed_content,
			),
			'innerBlocks' => array(),
			'innerContent' => array( $html ),
			'innerHTML' => $html,
		);
	}

	/**
	 * Create a table block.
	 *
	 * @since 0.1.0
	 * @param array $headers Table headers.
	 * @param array $rows Table rows.
	 * @return array Gutenberg block.
	 */
	private static function create_table_block( $headers, $rows ) {
		$header_cells = array();
		foreach ( $headers as $header ) {
			$header_cells[] = '<th>' . self::parse_inline_markdown( $header ) . '</th>';
		}

		$tbody_rows = array();
		foreach ( $rows as $row ) {
			$cells = array();
			foreach ( $row as $cell ) {
				$cells[] = '<td>' . self::parse_inline_markdown( $cell ) . '</td>';
			}
			if ( empty( $cells ) ) {
				continue;
			}
			$tbody_rows[] = '<tr>' . implode( '', $cells ) . '</tr>';
		}

		$thead_html = '<thead><tr>' . implode( '', $header_cells ) . '</tr></thead>';
		$tbody_html = '<tbody>' . implode( '', $tbody_rows ) . '</tbody>';
		$table_html = '<figure class="wp-block-table"><table>' . $thead_html . $tbody_html . '</table></figure>';

		return array(
			'blockName' => 'core/table',
			'attrs' => array(
				'hasFixedLayout' => true,
			),
			'innerBlocks' => array(),
			'innerContent' => array( $table_html ),
			'innerHTML' => $table_html,
		);
	}

	/**
	 * Create a code block.
	 *
	 * @since 0.1.0
	 * @param string $language Programming language.
	 * @param string $code Code content.
	 * @return array Gutenberg block.
	 */
	private static function create_code_block( $language, $code ) {
		// Escape HTML entities in code.
		$escaped_code = htmlspecialchars( $code, ENT_NOQUOTES, 'UTF-8' );

		return array(
			'blockName' => 'core/code',
			'attrs' => array(
				'content' => $code,
				'language' => $language ?: 'text',
			),
			'innerBlocks' => array(),
			'innerContent' => array(),
			'innerHTML' => '<pre class="wp-block-code"><code>' . $escaped_code . '</code></pre>',
		);
	}

	/**
	 * Create a list block.
	 *
	 * @since 0.1.0
	 * @param string $type List type ('ul' or 'ol').
	 * @param array  $items List items.
	 * @return array Gutenberg block.
	 */
	private static function create_list_block( $type, $items ) {
		$tag = $type === 'ol' ? 'ol' : 'ul';
		$html = '<' . $tag . '>';

		// Create inner blocks for each list item
		$inner_blocks = array();
		$inner_content = array();

		foreach ( $items as $item ) {
			$item_content = self::parse_inline_markdown( $item );
			$li_html = '<li>' . $item_content . '</li>';
			$html .= $li_html;
			$inner_content[] = $li_html;

			// Create list item with content in attrs
			$inner_blocks[] = array(
				'blockName' => 'core/list-item',
				'attrs' => array(
					'content' => $item_content,
				),
				'innerBlocks' => array(),
				'innerContent' => array( $li_html ),
				'innerHTML' => $li_html,
			);
		}

		$html .= '</' . $tag . '>';

		return array(
			'blockName' => 'core/list',
			'attrs' => array(
				'ordered' => $type === 'ol',
			),
			'innerBlocks' => $inner_blocks,
			'innerContent' => $inner_content,
			'innerHTML' => $html,
		);
	}

	/**
	 * Create a quote block.
	 *
	 * @since 0.1.0
	 * @param string $content Quote content.
	 * @return array Gutenberg block.
	 */
	private static function create_quote_block( $content ) {
		$parsed_content = self::parse_inline_markdown( $content );
		$html = '<blockquote class="wp-block-quote"><p>' . $parsed_content . '</p></blockquote>';

		return array(
			'blockName' => 'core/quote',
			'attrs' => array(
				'value' => $parsed_content,
			),
			'innerBlocks' => array(),
			'innerContent' => array( $html ),
			'innerHTML' => $html,
		);
	}

	/**
	 * Create an image placeholder block.
	 *
	 * @since 0.1.0
	 * @param string $description Image description/alt text.
	 * @return array Gutenberg block.
	 */
	private static function create_image_placeholder_block( $description ) {
		$alt = trim( $description );
		$attrs = array(
			'id' => 0,
			'url' => '',
			'alt' => $alt,
			'caption' => '',
			'sizeSlug' => 'large',
			'linkDestination' => 'none',
		);

		$html = '<figure class="wp-block-image size-large"><img alt="' . esc_attr( $alt ) . '" /></figure>';

		return array(
			'blockName' => 'core/image',
			'attrs' => $attrs,
			'innerBlocks' => array(),
			'innerContent' => array(),
			'innerHTML' => $html,
		);
	}

	/**
	 * Merge consecutive ordered lists into one continuous list.
	 * Fixes the "1. 1. 1." issue when numbered items are separated by other content.
	 *
	 * @since 0.1.0
	 * @param array $blocks Array of blocks.
	 * @return array Merged blocks.
	 */
	private static function merge_consecutive_ordered_lists( $blocks ) {
		$result = array();
		$pending_ol = null;
		$pending_ol_items = array();

		foreach ( $blocks as $block ) {
			$is_ordered_list = isset( $block['blockName'] ) 
				&& 'core/list' === $block['blockName'] 
				&& ! empty( $block['attrs']['ordered'] );

			if ( $is_ordered_list ) {
				// Accumulate ordered list items
				if ( ! empty( $block['innerBlocks'] ) ) {
					foreach ( $block['innerBlocks'] as $item ) {
						$pending_ol_items[] = $item;
					}
				}
				if ( null === $pending_ol ) {
					$pending_ol = $block;
				}
			} else {
				// Flush pending ordered list if we have one
				if ( null !== $pending_ol && ! empty( $pending_ol_items ) ) {
					$result[] = self::rebuild_ordered_list( $pending_ol_items );
					$pending_ol = null;
					$pending_ol_items = array();
				}
				$result[] = $block;
			}
		}

		// Flush any remaining ordered list
		if ( null !== $pending_ol && ! empty( $pending_ol_items ) ) {
			$result[] = self::rebuild_ordered_list( $pending_ol_items );
		}

		return $result;
	}

	/**
	 * Rebuild an ordered list from accumulated items.
	 *
	 * @since 0.1.0
	 * @param array $items List item blocks.
	 * @return array Ordered list block.
	 */
	private static function rebuild_ordered_list( $items ) {
		$html = '<ol>';
		$inner_content = array();

		foreach ( $items as $item ) {
			$li_html = isset( $item['innerHTML'] ) ? $item['innerHTML'] : '<li></li>';
			$html .= $li_html;
			$inner_content[] = $li_html;
		}

		$html .= '</ol>';

		return array(
			'blockName' => 'core/list',
			'attrs' => array(
				'ordered' => true,
			),
			'innerBlocks' => $items,
			'innerContent' => $inner_content,
			'innerHTML' => $html,
		);
	}

	/**
	 * Create a button block from CTA syntax.
	 *
	 * @since 0.1.0
	 * @param string $content CTA content (may include URL in parentheses).
	 * @return array Gutenberg block.
	 */
	private static function create_button_block( $content ) {
		$text = trim( $content );
		$url = '#';

		// Check for URL in parentheses: "Button Text (https://example.com)"
		if ( preg_match( '/^(.+?)\s*\(([^)]+)\)\s*$/', $content, $matches ) ) {
			$text = trim( $matches[1] );
			$url = trim( $matches[2] );
		}

		// Clean up common patterns like "Link ke..." or "(Link..."
		$text = preg_replace( '/\s*\(Link\s+ke\s+.*$/i', '', $text );
		$text = preg_replace( '/\s*\(Link\s+.*$/i', '', $text );

		$button_html = '<div class="wp-block-button"><a class="wp-block-button__link wp-element-button" href="' . esc_attr( $url ) . '">' . esc_html( $text ) . '</a></div>';

		$button_block = array(
			'blockName' => 'core/button',
			'attrs' => array(
				'text' => $text,
				'url' => $url,
			),
			'innerBlocks' => array(),
			'innerContent' => array( $button_html ),
			'innerHTML' => $button_html,
		);

		// Wrap in buttons container
		$wrapper_html = '<div class="wp-block-buttons">' . $button_html . '</div>';

		return array(
			'blockName' => 'core/buttons',
			'attrs' => array(),
			'innerBlocks' => array( $button_block ),
			'innerContent' => array( $wrapper_html ),
			'innerHTML' => $wrapper_html,
		);
	}
}