import urllib.request
import urllib.parse
import json
import re
import asyncio
from typing import Any, Dict, Optional
from .utils import ToolError
import config

API_URL = "https://en.wikipedia.org/w/api.php"

def strip_html(text: str) -> str:
    """Removes HTML tags from a string using regex to provide clean text to the LLM."""
    return re.sub(r'<[^>]*>', '', text)

def _make_request(params: Dict[str, Any]) -> Dict[str, Any]:
    """
    Synchronous helper to make the API request using urllib.
    urllib is used instead of httpx to avoid TLS/HTTP fingerprinting 
    that triggers 403 Forbidden responses from Wikipedia.
    """
    query_string = urllib.parse.urlencode(params)
    url = f"{API_URL}?{query_string}"
    
    headers = {
        "User-Agent": config.USER_AGENT
    }
    
    req = urllib.request.Request(url, headers=headers)
    with urllib.request.urlopen(req) as response:
        return json.loads(response.read().decode('utf-8'))

async def _search(title: str, limit: int = 5, fallback: bool = False) -> str:
    """
    Searches Wikipedia for a title.
    fallback=True: Used when a direct page request fails, providing 'Article not found' header.
    """
    params = {
        "action": "query",
        "list": "search",
        "srsearch": title,
        "format": "json",
        "srlimit": limit
    }
    # Run synchronous urllib call in a thread to avoid blocking the event loop
    data = await asyncio.to_thread(_make_request, params)
    
    search_results = data.get("query", {}).get("search", [])
    if not search_results:
        return f"No Wikipedia results found for '{title}'."
    
    if fallback:
        header = f"Article not found. Here are some similar results for '{title}':"
    else:
        header = f"Search results for '{title}':"
        
    lines = [header]
    for i, res in enumerate(search_results, 1):
        title_res = res.get("title")
        snippet = strip_html(res.get("snippet", ""))
        # Brackets around title help the AI identify the exact string for subsequent calls
        lines.append(f"{i}. [{title_res}] - Snippet: {snippet}")
    
    return "\n".join(lines)

async def _fetch_content(title: str, section_index: int) -> Optional[str]:
    """
    Retrieves raw Wikitext for a specific section.
    section_index=0 returns the lead section.
    """
    params = {
        "action": "query",
        "prop": "revisions",
        "rvprop": "content",
        "rvsection": section_index,
        "titles": title,
        "redirects": 1,
        "format": "json"
    }
    data = await asyncio.to_thread(_make_request, params)
    
    pages = data.get("query", {}).get("pages", {})
    if not pages:
        return None
        
    page_id = next(iter(pages))
    page = pages[page_id]
    
    if "missing" in page:
        return None
        
    revisions = page.get("revisions", [])
    if not revisions:
        return None
        
    return revisions[0].get("*")

async def _fetch_toc(title: str) -> Optional[str]:
    """
    Retrieves the Table of Contents data and formats it hierarchically.
    """
    params = {
        "action": "parse",
        "page": title,
        "prop": "tocdata",
        "format": "json",
        "redirects": 1
    }
    data = await asyncio.to_thread(_make_request, params)
    
    parse_data = data.get("parse")
    if not parse_data:
        return None
        
    toc_data = parse_data.get("tocdata", {})
    sections = toc_data.get("sections", [])
    if not sections:
        return "No table of contents found for this page."
    
    lines = [f"Table of Contents for \"{parse_data.get('title', title)}\":"]
    for s in sections:
        level = s.get("tocLevel", 1)
        index = s.get("index")
        line = s.get("line")
        indent = "  " * (level - 1)
        lines.append(f"{indent}[{index}] {line}")
        
    return "\n".join(lines)

async def handle(args: Dict[str, Any]) -> Dict[str, Any]:
    """
    Main handler for the browse_wikipedia tool.
    Supports modes: summary, toc, section, and search.
    """
    title = args.get("title")
    if not title:
        raise ToolError("Missing required parameter: 'title'")
        
    mode = args.get("mode", "summary")
    section_index = args.get("section_index")
    search_limit = args.get("search_limit", 5)
    
    if mode == "search":
        result = await _search(title, search_limit, fallback=False)
    elif mode == "summary":
        # Lead section + ToC is the default 'summary' to guide the AI's next steps
        content = await _fetch_content(title, 0)
        if content is None:
            result = await _search(title, search_limit, fallback=True)
        else:
            toc = await _fetch_toc(title)
            result = f"{content}\n\n---\n\n{toc}"
    elif mode == "toc":
        toc = await _fetch_toc(title)
        if toc is None:
            result = await _search(title, search_limit, fallback=True)
        else:
            result = toc
    elif mode == "section":
        if section_index is None:
            raise ToolError("Missing required parameter 'section_index' for mode='section'")
        content = await _fetch_content(title, int(section_index))
        if content is None:
            result = await _search(title, search_limit, fallback=True)
        else:
            result = content
    else:
        raise ToolError(f"Invalid mode '{mode}'. Supported modes: summary, toc, section, search")
            
    return {"text": result}