from __future__ import annotations

import re
from typing import Annotated, Dict, List, Tuple
from urllib.parse import urlparse, urljoin

import gradio as gr
import requests
from bs4 import BeautifulSoup
from markdownify import markdownify as md
from readability import Document

from app import _fetch_rate_limiter, _log_call_end, _log_call_start, _truncate_for_log
from ._docstrings import autodoc


# Single source of truth for the LLM-facing tool description
TOOL_SUMMARY = (
    "Fetch a webpage and return clean Markdown or a list of links, with max length and pagination via offset; "
    "if truncated, the output includes a notice with next_cursor for exact continuation."
)


def _http_get_enhanced(url: str, timeout: int | float = 30, *, skip_rate_limit: bool = False) -> requests.Response:
    headers = {
        "User-Agent": "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/91.0.4472.124 Safari/537.36",
        "Accept-Language": "en-US,en;q=0.9",
        "Accept": "text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8",
        "Accept-Encoding": "gzip, deflate, br",
        "DNT": "1",
        "Connection": "keep-alive",
        "Upgrade-Insecure-Requests": "1",
    }
    if not skip_rate_limit:
        _fetch_rate_limiter.acquire()
    try:
        response = requests.get(
            url,
            headers=headers,
            timeout=timeout,
            allow_redirects=True,
            stream=False,
        )
        response.raise_for_status()
        return response
    except requests.exceptions.Timeout as exc:
        raise requests.exceptions.RequestException("Request timed out. The webpage took too long to respond.") from exc
    except requests.exceptions.ConnectionError as exc:
        raise requests.exceptions.RequestException("Connection error. Please check the URL and your internet connection.") from exc
    except requests.exceptions.HTTPError as exc:
        if response.status_code == 403:
            raise requests.exceptions.RequestException("Access forbidden. The website may be blocking automated requests.") from exc
        if response.status_code == 404:
            raise requests.exceptions.RequestException("Page not found. Please check the URL.") from exc
        if response.status_code == 429:
            raise requests.exceptions.RequestException("Rate limited. Please try again in a few minutes.") from exc
        raise requests.exceptions.RequestException(f"HTTP error {response.status_code}: {exc}") from exc


def _normalize_whitespace(text: str) -> str:
    text = re.sub(r"[ \t\u00A0]+", " ", text)
    text = re.sub(r"\n\s*\n\s*\n+", "\n\n", text.strip())
    return text.strip()


def _truncate(text: str, max_chars: int) -> Tuple[str, bool]:
    if max_chars is None or max_chars <= 0 or len(text) <= max_chars:
        return text, False
    return text[:max_chars].rstrip() + " …", True


def _shorten(text: str, limit: int) -> str:
    if limit <= 0 or len(text) <= limit:
        return text
    return text[: max(0, limit - 1)].rstrip() + "…"


def _domain_of(url: str) -> str:
    try:
        return urlparse(url).netloc or ""
    except Exception:
        return ""


def _extract_links_from_soup(soup: BeautifulSoup, base_url: str) -> str:
    links = []
    for link in soup.find_all("a", href=True):
        href = link.get("href")
        text = link.get_text(strip=True)
        if href.startswith("http"):
            full_url = href
        elif href.startswith("//"):
            full_url = "https:" + href
        elif href.startswith("/"):
            full_url = urljoin(base_url, href)
        else:
            full_url = urljoin(base_url, href)
        if text and href not in ["#", "javascript:void(0)"]:
            links.append(f"- [{text}]({full_url})")
    if not links:
        return "No links found on this page."
    title = soup.find("title")
    title_text = title.get_text(strip=True) if title else "Links from webpage"
    return f"# {title_text}\n\n" + "\n".join(links)


def _fullpage_markdown_from_soup(full_soup: BeautifulSoup, base_url: str, strip_selectors: str = "") -> str:
    if strip_selectors:
        selectors = [s.strip() for s in strip_selectors.split(",") if s.strip()]
        for selector in selectors:
            try:
                for element in full_soup.select(selector):
                    element.decompose()
            except Exception:
                continue
    for element in full_soup.select("script, style, nav, footer, header, aside"):
        element.decompose()
    main = (
        full_soup.find("main")
        or full_soup.find("article")
        or full_soup.find("div", class_=re.compile(r"content|main|post|article", re.I))
        or full_soup.find("body")
    )
    if not main:
        return "No main content found on the webpage."
    markdown_text = md(str(main), heading_style="ATX")
    markdown_text = re.sub(r"\n{3,}", "\n\n", markdown_text)
    markdown_text = re.sub(r"\[\s*\]\([^)]*\)", "", markdown_text)
    markdown_text = re.sub(r"[ \t]+", " ", markdown_text)
    markdown_text = markdown_text.strip()
    title = full_soup.find("title")
    if title and title.get_text(strip=True):
        markdown_text = f"# {title.get_text(strip=True)}\n\n{markdown_text}"
    return markdown_text or "No content could be extracted."


def _truncate_markdown(markdown: str, max_chars: int) -> Tuple[str, Dict[str, object]]:
    total_chars = len(markdown)
    if total_chars <= max_chars:
        return markdown, {
            "truncated": False,
            "returned_chars": total_chars,
            "total_chars_estimate": total_chars,
            "next_cursor": None,
        }
    truncated = markdown[:max_chars]
    last_paragraph = truncated.rfind("\n\n")
    if last_paragraph > max_chars * 0.7:
        truncated = truncated[:last_paragraph]
        cursor_pos = last_paragraph
    elif "." in truncated[-100:]:
        last_period = truncated.rfind(".")
        if last_period > max_chars * 0.8:
            truncated = truncated[: last_period + 1]
            cursor_pos = last_period + 1
        else:
            cursor_pos = len(truncated)
    else:
        cursor_pos = len(truncated)
    metadata = {
        "truncated": True,
        "returned_chars": len(truncated),
        "total_chars_estimate": total_chars,
        "next_cursor": cursor_pos,
    }
    truncated = truncated.rstrip()
    truncation_notice = (
        "\n\n---\n"
        f"**Content Truncated:** Showing {metadata['returned_chars']:,} of {metadata['total_chars_estimate']:,} characters "
        f"({(metadata['returned_chars']/metadata['total_chars_estimate']*100):.1f}%)\n"
        f"**Next cursor:** {metadata['next_cursor']} (use this value with offset parameter for continuation)\n"
        "---"
    )
    return truncated + truncation_notice, metadata


@autodoc(summary=TOOL_SUMMARY)
def Web_Fetch(
    url: Annotated[str, "The absolute URL to fetch (must return HTML)."],
    max_chars: Annotated[int, "Maximum characters to return (0 = no limit, full page content)."] = 3000,
    strip_selectors: Annotated[str, "CSS selectors to remove (comma-separated, e.g., '.header, .footer, nav')."] = "",
    url_scraper: Annotated[bool, "Extract only links from the page instead of content."] = False,
    offset: Annotated[int, "Character offset to start from (for pagination, use next_cursor from previous call)."] = 0,
) -> str:
    _log_call_start(
        "Web_Fetch",
        url=url,
        max_chars=max_chars,
        strip_selectors=strip_selectors,
        url_scraper=url_scraper,
        offset=offset,
    )
    if not url or not url.strip():
        result = "Please enter a valid URL."
        _log_call_end("Web_Fetch", _truncate_for_log(result))
        return result
    try:
        resp = _http_get_enhanced(url)
        resp.raise_for_status()
    except requests.exceptions.RequestException as exc:
        result = f"An error occurred: {exc}"
        _log_call_end("Web_Fetch", _truncate_for_log(result))
        return result
    final_url = str(resp.url)
    ctype = resp.headers.get("Content-Type", "")
    if "html" not in ctype.lower():
        result = f"Unsupported content type for extraction: {ctype or 'unknown'}"
        _log_call_end("Web_Fetch", _truncate_for_log(result))
        return result
    resp.encoding = resp.encoding or resp.apparent_encoding
    html = resp.text
    full_soup = BeautifulSoup(html, "lxml")
    if url_scraper:
        result = _extract_links_from_soup(full_soup, final_url)
        if offset > 0:
            result = result[offset:]
        if max_chars > 0 and len(result) > max_chars:
            result, _ = _truncate_markdown(result, max_chars)
    else:
        full_result = _fullpage_markdown_from_soup(full_soup, final_url, strip_selectors)
        if offset > 0:
            if offset >= len(full_result):
                result = (
                    f"Offset {offset} exceeds content length ({len(full_result)} characters). "
                    f"Content ends at position {len(full_result)}."
                )
                _log_call_end("Web_Fetch", _truncate_for_log(result))
                return result
            result = full_result[offset:]
        else:
            result = full_result
        if max_chars > 0 and len(result) > max_chars:
            result, metadata = _truncate_markdown(result, max_chars)
            if offset > 0:
                metadata["total_chars_estimate"] = len(full_result)
                metadata["next_cursor"] = offset + metadata["next_cursor"] if metadata["next_cursor"] else None
    _log_call_end("Web_Fetch", f"chars={len(result)}, url_scraper={url_scraper}, offset={offset}")
    return result


def build_interface() -> gr.Interface:
    return gr.Interface(
        fn=Web_Fetch,
        inputs=[
            gr.Textbox(label="URL", placeholder="https://example.com/article", max_lines=1),
            gr.Slider(minimum=0, maximum=20000, value=3000, step=100, label="Max Characters", info="0 = no limit (full page), default 3000"),
            gr.Textbox(
                label="Strip Selectors",
                placeholder=".header, .footer, nav, .sidebar",
                value="",
                max_lines=1,
                info="CSS selectors to remove (comma-separated)",
            ),
            gr.Checkbox(label="URL Scraper", value=False, info="Extract only links instead of content"),
            gr.Slider(
                minimum=0,
                maximum=100000,
                value=0,
                step=100,
                label="Offset",
                info="Character offset to start from (use next_cursor from previous call for pagination)",
            ),
        ],
        outputs=gr.Markdown(label="Extracted Content"),
        title="Web Fetch",
        description=(
            "<div style=\"text-align:center\">Convert any webpage to clean Markdown format with precision controls, "
            "or extract all links. Supports custom element removal, length limits, and pagination with offset.</div>"
        ),
        api_description=TOOL_SUMMARY,
        flagging_mode="never",
    )


__all__ = [
    "Web_Fetch",
    "build_interface",
    "_http_get_enhanced",
    "_fullpage_markdown_from_soup",
]