# Copyright (c) 2025 Bytedance Ltd. and/or its affiliates
# SPDX-License-Identifier: MIT

import re
import logging

from .article import Article
from .jina_client import JinaClient
from .readability_extractor import ReadabilityExtractor

logger = logging.getLogger(__name__)


def safe_truncate(text: str, max_length: int = 500) -> str:
    """
    Safely truncate text to a maximum length without breaking multi-byte characters.
    
    Args:
        text: The text to truncate
        max_length: Maximum number of characters to keep
        
    Returns:
        Truncated text that is safe to use without encoding issues
    """
    if text is None:
        return None
    
    if len(text) <= max_length:
        return text
    
    # Ensure max_length is at least 3 to accommodate the placeholder
    if max_length < 3:
        return "..."[:max_length]
    
    # Use Python's built-in textwrap.shorten which handles unicode safely
    try:
        import textwrap
        return textwrap.shorten(text, width=max_length, placeholder="...")
    except (ImportError, TypeError):
        # Fallback for older Python versions or if textwrap.shorten has issues
        # Truncate to max_length - 3 to make room for "..."
        truncated = text[:max_length - 3]
        # Remove any incomplete Unicode surrogate pair
        while truncated and ord(truncated[-1]) >= 0xD800 and ord(truncated[-1]) <= 0xDFFF:
            truncated = truncated[:-1]
        return truncated + "..."


def is_html_content(content: str) -> bool:
    """
    Check if the provided content is HTML.
    
    Uses a more robust detection method that checks for common HTML patterns
    including DOCTYPE declarations, HTML tags, and other HTML markers.
    """
    if not content or not content.strip():
        return False
    
    content = content.strip()
    
    # Check for HTML comments
    if content.startswith('<!--') and '-->' in content:
        return True
    
    # Check for DOCTYPE declarations (case insensitive)
    if re.match(r'^<!DOCTYPE\s+html', content, re.IGNORECASE):
        return True
    
    # Check for XML declarations followed by HTML
    if content.startswith('<?xml') and '<html' in content:
        return True
    
    # Check for common HTML tags at the beginning
    html_start_patterns = [
        r'^<html',
        r'^<head',
        r'^<body',
        r'^<title',
        r'^<meta',
        r'^<link',
        r'^<script',
        r'^<style',
        r'^<div',
        r'^<p>',
        r'^<p\s',
        r'^<span',
        r'^<h[1-6]',
        r'^<!DOCTYPE',
        r'^<\!DOCTYPE',  # Some variations
    ]
    
    for pattern in html_start_patterns:
        if re.match(pattern, content, re.IGNORECASE):
            return True
    
    # Check for any HTML-like tags in the content (more permissive)
    if re.search(r'<[^>]+>', content):
        # Additional check: ensure it's not just XML or other markup
        # Look for common HTML attributes or elements
        html_indicators = [
            r'href\s*=',
            r'src\s*=',
            r'class\s*=',
            r'id\s*=',
            r'<img\s',
            r'<a\s',
            r'<div',
            r'<p>',
            r'<p\s',
            r'<!DOCTYPE',
        ]
        
        for indicator in html_indicators:
            if re.search(indicator, content, re.IGNORECASE):
                return True
        
        # Also check for self-closing HTML tags
        self_closing_tags = [
            r'<img\s+[^>]*?/>',
            r'<br\s*/?>',
            r'<hr\s*/?>',
            r'<input\s+[^>]*?/>',
            r'<meta\s+[^>]*?/>',
            r'<link\s+[^>]*?/>',
        ]
        
        for tag in self_closing_tags:
            if re.search(tag, content, re.IGNORECASE):
                return True
    
    return False


class Crawler:
    def crawl(self, url: str) -> Article:
        # To help LLMs better understand content, we extract clean
        # articles from HTML, convert them to markdown, and split
        # them into text and image blocks for one single and unified
        # LLM message.
        #
        # Jina is not the best crawler on readability, however it's
        # much easier and free to use.
        #
        # Instead of using Jina's own markdown converter, we'll use
        # our own solution to get better readability results.
        try:
            jina_client = JinaClient()
            html = jina_client.crawl(url, return_format="html")
        except Exception as e:
            logger.error(f"Failed to fetch URL {url} from Jina: {repr(e)}")
            raise
        
        # Check if we got valid HTML content
        if not html or not html.strip():
            logger.warning(f"Empty content received from URL {url}")
            article = Article(
                title="Empty Content",
                html_content="<p>No content could be extracted from this page</p>"
            )
            article.url = url
            return article
        
        # Check if content is actually HTML using more robust detection
        if not is_html_content(html):
            logger.warning(f"Non-HTML content received from URL {url}, creating fallback article")
            # Return a simple article with the raw content (safely truncated)
            article = Article(
                title="Non-HTML Content",
                html_content=f"<p>This URL returned content that cannot be parsed as HTML. Raw content: {safe_truncate(html, 500)}</p>"
            )
            article.url = url
            return article
        
        try:
            extractor = ReadabilityExtractor()
            article = extractor.extract_article(html)
        except Exception as e:
            logger.error(f"Failed to extract article from {url}: {repr(e)}")
            # Fall back to a simple article with the raw HTML (safely truncated)
            article = Article(
                title="Content Extraction Failed",
                html_content=f"<p>Content extraction failed. Raw content: {safe_truncate(html, 500)}</p>"
            )
            article.url = url
            return article
        
        article.url = url
        return article