"""Webpage content fetching with caching, PDF extraction, and summarization helpers."""

import copy
import io
import ipaddress
import json
import os
import re
import logging
import socket
from datetime import datetime, timedelta
from typing import List
from urllib.parse import urljoin, urlparse

import httpx
from bs4 import BeautifulSoup

from src.constants import WEB_FETCH_SOFT_MAX_BYTES, WEB_FETCH_HARD_MAX_BYTES, WEB_FETCH_USER_AGENT

from .analytics import RateLimitError, error_logger
from .cache import (
    CONTENT_CACHE_DIR,
    content_cache_index,
    generate_cache_key,
    cleanup_cache,
)

logger = logging.getLogger(__name__)

_PRIVATE_NETWORKS = (
    ipaddress.ip_network("0.0.0.0/8"),
    ipaddress.ip_network("10.0.0.0/8"),
    ipaddress.ip_network("127.0.0.0/8"),
    ipaddress.ip_network("169.254.0.0/16"),
    ipaddress.ip_network("172.16.0.0/12"),
    ipaddress.ip_network("192.168.0.0/16"),
    ipaddress.ip_network("::1/128"),
    ipaddress.ip_network("fc00::/7"),
    ipaddress.ip_network("fe80::/10"),
)


def _is_private_address(addr: ipaddress._BaseAddress) -> bool:
    if isinstance(addr, ipaddress.IPv6Address) and addr.ipv4_mapped is not None:
        addr = addr.ipv4_mapped
    return (
        addr.is_private
        or addr.is_loopback
        or addr.is_link_local
        or addr.is_reserved
        or addr.is_multicast
        or addr.is_unspecified
        or any(addr in net for net in _PRIVATE_NETWORKS)
    )


def _resolve_hostname_ips(hostname: str) -> list[ipaddress._BaseAddress]:
    try:
        infos = socket.getaddrinfo(hostname, None)
    except Exception:
        return []
    out = []
    for info in infos:
        try:
            out.append(ipaddress.ip_address(info[4][0]))
        except Exception:
            continue
    return out


def _public_http_url(url: str) -> bool:
    try:
        parsed = urlparse(url)
        if parsed.scheme not in ("http", "https"):
            return False
        host = (parsed.hostname or "").strip()
        if not host:
            return False
        lower = host.lower()
        if lower in ("localhost", "metadata", "metadata.google.internal"):
            return False
        if lower.endswith((".local", ".localhost", ".internal", ".lan", ".intranet")):
            return False
        try:
            return not _is_private_address(ipaddress.ip_address(host))
        except ValueError:
            pass
        addrs = _resolve_hostname_ips(host)
        return bool(addrs) and not any(_is_private_address(a) for a in addrs)
    except Exception:
        return False


class BodyTooLargeError(Exception):
    """The server declared a body larger than the hard fetch ceiling."""

    def __init__(self, url: str, declared_bytes: int):
        self.url = url
        self.declared_bytes = declared_bytes
        super().__init__(
            f"response body is {declared_bytes:,} bytes, over the "
            f"{WEB_FETCH_HARD_MAX_BYTES:,}-byte hard cap"
        )


class _CappedFetch:
    """Result of a size-capped streaming GET.

    Carries just what fetch_webpage_content needs from an httpx.Response,
    plus the cap bookkeeping: the (possibly truncated) body, whether the
    cap cut it short, and the size the server declared via Content-Length
    (wire bytes; None when absent).
    """

    __slots__ = ("status_code", "headers", "content", "truncated",
                 "declared_bytes", "encoding", "url")

    def __init__(self, status_code, headers, content, truncated,
                 declared_bytes, encoding, url):
        self.status_code = status_code
        self.headers = headers
        self.content = content
        self.truncated = truncated
        self.declared_bytes = declared_bytes
        self.encoding = encoding
        self.url = url

    @property
    def text(self) -> str:
        return self.content.decode(self.encoding or "utf-8", errors="replace")

    def raise_for_status(self):
        if self.status_code >= 400:
            request = httpx.Request("GET", self.url)
            raise httpx.HTTPStatusError(
                f"HTTP {self.status_code} for {self.url}",
                request=request,
                response=httpx.Response(self.status_code, request=request),
            )


def _get_public_url(url: str, headers: dict, timeout: int, max_redirects: int = 5,
                    max_bytes: int = None) -> "_CappedFetch":
    """Capped streaming GET with SSRF-guarded manual redirects.

    The body is streamed and buffering stops at ``max_bytes`` (default: the
    soft cap), so an oversized resource cannot be pulled into memory or the
    content cache in full. When Content-Length already declares a body over
    the hard ceiling, the fetch is refused before any body bytes are read.
    """
    cap = min(max_bytes or WEB_FETCH_SOFT_MAX_BYTES, WEB_FETCH_HARD_MAX_BYTES)
    current = url
    for _ in range(max_redirects + 1):
        if not _public_http_url(current):
            raise httpx.RequestError("Blocked private/internal URL", request=httpx.Request("GET", current))
        # Force identity transfer-encoding. With gzip/deflate the wire bytes
        # (and Content-Length) can be a small fraction of the decoded body, so
        # a tiny compressed response could pass the hard-cap preflight and then
        # expand past the ceiling in a single decoded chunk before the streamed
        # cap below can slice it. Identity makes Content-Length the true body
        # size and keeps each streamed chunk bounded by the network read.
        req_headers = dict(headers or {})
        req_headers["Accept-Encoding"] = "identity"
        with httpx.stream("GET", current, headers=req_headers, timeout=timeout,
                          follow_redirects=False) as response:
            if response.status_code in (301, 302, 303, 307, 308):
                location = response.headers.get("location")
                if not location:
                    return _CappedFetch(response.status_code, response.headers, b"",
                                        False, None, response.encoding, str(response.url))
                current = urljoin(str(response.url), location)
                continue

            # A server can ignore the identity request and still return a
            # compressed body; httpx.iter_bytes would then decode it, and a tiny
            # gzip can balloon into one decoded chunk far past the cap before we
            # slice. Refuse a compressed Content-Encoding so the streamed cap
            # stays a real memory bound (Content-Length is the compressed wire
            # length here, so the preflight and size metadata are unreliable too).
            enc = (response.headers.get("content-encoding") or "").strip().lower()
            if enc and enc != "identity":
                raise httpx.RequestError(
                    f"Refusing compressed response (Content-Encoding: {enc}) after "
                    "requesting identity: cannot bound decoded body size",
                    request=httpx.Request("GET", current),
                )

            declared = None
            raw_len = response.headers.get("content-length")
            if raw_len and raw_len.isdigit():
                declared = int(raw_len)
            # Refuse before buffering anything when the server already tells
            # us the body exceeds the absolute ceiling (Content-Length is wire
            # bytes; the decompressed body can only be larger).
            if declared is not None and declared > WEB_FETCH_HARD_MAX_BYTES:
                raise BodyTooLargeError(current, declared)

            chunks = []
            read = 0
            truncated = False
            # We requested identity above, so iter_bytes yields the raw body in
            # network-read-sized chunks (no decompression expansion); the cap
            # therefore bounds what we actually buffer.
            for chunk in response.iter_bytes():
                read += len(chunk)
                if read > cap:
                    keep = cap - (read - len(chunk))
                    if keep > 0:
                        chunks.append(chunk[:keep])
                    truncated = True
                    break
                chunks.append(chunk)
            return _CappedFetch(response.status_code, response.headers,
                                b"".join(chunks), truncated, declared,
                                response.encoding, str(response.url))
    raise httpx.RequestError("Too many redirects", request=httpx.Request("GET", current))

# PDF extraction (optional dependency)
try:
    from pdfminer.high_level import extract_text as pdf_extract_text
except ImportError:
    pdf_extract_text = None  # type: ignore


# ----------------------------------------------------------------------
# HTML extraction helpers
# ----------------------------------------------------------------------
def _extract_meta(soup: BeautifulSoup) -> dict:
    """Pull meta description and keywords if present."""
    description = ""
    keywords = ""
    desc_tag = soup.find("meta", attrs={"name": re.compile("description", re.I)})
    if desc_tag and desc_tag.get("content"):
        description = desc_tag["content"].strip()
    kw_tag = soup.find("meta", attrs={"name": re.compile("keywords", re.I)})
    if kw_tag and kw_tag.get("content"):
        keywords = kw_tag["content"].strip()
    return {"description": description, "keywords": keywords}


def _extract_og_image(soup: BeautifulSoup) -> str:
    """Extract the best representative image URL from meta tags.

    Only returns absolute http(s) URLs -- skips relative paths and data URIs.
    """
    candidates = []
    for prop in ("og:image", "og:image:url", "og:image:secure_url"):
        tag = soup.find("meta", attrs={"property": prop})
        if tag and tag.get("content", "").strip():
            candidates.append(tag["content"].strip())
    tag = soup.find("meta", attrs={"name": "twitter:image"})
    if tag and tag.get("content", "").strip():
        candidates.append(tag["content"].strip())
    tag = soup.find("meta", attrs={"name": "thumbnail"})
    if tag and tag.get("content", "").strip():
        candidates.append(tag["content"].strip())
    for url in candidates:
        if url.startswith(("https://", "http://")) and not url.endswith((".svg", ".ico")):
            return url
    return ""


def _extract_lists(soup: BeautifulSoup) -> List[List[str]]:
    """Return a list of lists, each inner list representing a <ul>/<ol>."""
    all_lists = []
    for lst in soup.find_all(["ul", "ol"]):
        items = [li.get_text(separator=" ", strip=True) for li in lst.find_all("li")]
        if items:
            all_lists.append(items)
    return all_lists


def _extract_tables(soup: BeautifulSoup) -> List[List[List[str]]]:
    """Return a list of tables, each table is a list of rows, each row a list of cell texts."""
    tables_data = []
    for table in soup.find_all("table"):
        rows = []
        for tr in table.find_all("tr"):
            cells = [td.get_text(separator=" ", strip=True) for td in tr.find_all(["td", "th"])]
            if cells:
                rows.append(cells)
        if rows:
            tables_data.append(rows)
    return tables_data


def _extract_code_blocks(soup: BeautifulSoup) -> List[str]:
    """Collect text from <pre> and <code> blocks."""
    blocks = []
    for tag in soup.find_all(["pre", "code"]):
        txt = tag.get_text(separator=" ", strip=True)
        if txt:
            blocks.append(txt)
    return blocks


def _detect_js_frameworks(soup: BeautifulSoup) -> bool:
    """Very naive detection of common JS frameworks."""
    js_indicators = [
        "react", "angular", "vue", "svelte", "next", "nuxt",
        "ember", "backbone", "jquery", "polymer", "mithril",
    ]
    for script in soup.find_all("script"):
        src = script.get("src", "").lower()
        if any(fr in src for fr in js_indicators):
            return True
        if script.string:
            content = script.string.lower()
            if any(fr in content for fr in js_indicators):
                return True
    if soup.find(attrs={"data-reactroot": True}) or soup.find(attrs={"ng-app": True}):
        return True
    return False


def _empty_result(url: str, error: str = "") -> dict:
    """Build a standard failure result dict."""
    return {
        "url": url,
        "title": "",
        "content": "",
        "lists": [],
        "tables": [],
        "code_blocks": [],
        "meta_description": "",
        "meta_keywords": "",
        "js_rendered": False,
        "js_message": "",
        "success": False,
        "error": error,
    }


# ----------------------------------------------------------------------
# Main content fetcher
# ----------------------------------------------------------------------
def fetch_webpage_content(url: str, timeout: int = 5, retry_attempt: int = 0,
                          max_bytes: int = None) -> dict:
    """Fetch and extract meaningful content from a webpage with caching.

    ``max_bytes`` raises the download budget per call (clamped to the hard
    cap); the default is the soft cap. When the body is cut short the result
    carries ``truncated``/``fetched_bytes``/``total_bytes`` so callers can
    tell the model the content is partial (#3812).
    """
    effective_cap = min(max_bytes or WEB_FETCH_SOFT_MAX_BYTES, WEB_FETCH_HARD_MAX_BYTES)
    # The cap is part of the cache identity: a truncated soft-cap fetch must
    # not be served to a later full-budget request for the same URL.
    cache_key = generate_cache_key(f"{url}#cap={effective_cap}")
    cache_file = CONTENT_CACHE_DIR / f"{cache_key}.cache"

    # Check cache
    if cache_file.exists():
        try:
            with open(cache_file, "r", encoding="utf-8") as f:
                cached_data = json.load(f)
            timestamp = datetime.fromisoformat(cached_data["timestamp"])
            if datetime.now() - timestamp < timedelta(hours=2):
                logger.debug(f"Content cache hit for URL: {url}")
                return cached_data["data"]
            else:
                cache_file.unlink(missing_ok=True)
                content_cache_index.pop(cache_key, None)
        except Exception as e:
            logger.warning(f"Failed to read content cache for {url}: {e}")
            cache_file.unlink(missing_ok=True)
            content_cache_index.pop(cache_key, None)

    # Fetch
    try:
        headers = {
            "User-Agent": WEB_FETCH_USER_AGENT,
            "Accept": "text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8",
            "Accept-Language": "en-US,en;q=0.5",
            # identity so the streamed size cap in _get_public_url stays honest
            # (a compressed body can decode to far more than Content-Length).
            "Accept-Encoding": "identity",
            "Connection": "keep-alive",
        }
        response = _get_public_url(url, headers=headers, timeout=timeout,
                                   max_bytes=effective_cap)

        if response.status_code == 429:
            raise RateLimitError(f"Rate limit hit for {url} (attempt {retry_attempt})")

        response.raise_for_status()
    except BodyTooLargeError as e:
        error_logger.warning(f"Refused oversized body for {url}: {e}")
        return _empty_result(url, f"TooLarge: {e}")
    except httpx.HTTPStatusError as e:
        error_logger.warning(f"HTTP {e.response.status_code} fetching {url}: {e}")
        return _empty_result(url, f"HTTP {e.response.status_code}: {e}")
    except httpx.RequestError as e:
        error_logger.error(f"NetworkError fetching {url} (attempt {retry_attempt}): {e}")
        return _empty_result(url, f"NetworkError: {e}")
    except RateLimitError as e:
        error_logger.error(str(e))
        return _empty_result(url, str(e))

    # Size bookkeeping shared by every content branch below. getattr keeps
    # plain httpx.Response stand-ins (tests) working without the cap fields.
    _size_fields = {
        "truncated": getattr(response, "truncated", False),
        "fetched_bytes": len(response.content),
        "total_bytes": getattr(response, "declared_bytes", None),
    }

    # PDF handling
    content_type = response.headers.get("Content-Type", "").lower()
    if "application/pdf" in content_type or url.lower().endswith(".pdf"):
        if _size_fields["truncated"]:
            # A PDF cut mid-stream is not parseable; unlike text there is no
            # useful partial result, so report the budget problem instead.
            _declared = _size_fields["total_bytes"]
            return _empty_result(
                url,
                f"TooLarge: PDF exceeds the {effective_cap:,}-byte fetch budget"
                + (f" (size {_declared:,} bytes)" if _declared else "")
                + "; retry with a larger budget if it fits under the hard cap",
            )
        if pdf_extract_text is None:
            logger.error("pdfminer.six is not installed; cannot extract PDF text.")
            pdf_text = ""
        else:
            try:
                pdf_bytes = io.BytesIO(response.content)
                pdf_text = pdf_extract_text(pdf_bytes)
            except Exception as e:
                logger.warning(f"PDF extraction failed for {url}: {e}")
                pdf_text = ""
        result = {
            "url": url,
            "title": os.path.basename(url),
            "content": pdf_text,
            "lists": [],
            "tables": [],
            "code_blocks": [],
            "meta_description": "",
            "meta_keywords": "",
            "js_rendered": False,
            "js_message": "",
            "success": bool(pdf_text),
            "error": "" if pdf_text else "Failed to extract PDF text",
            **_size_fields,
        }
        _cache_result(cache_file, cache_key, result, url)
        return result

    # Plain-text / Markdown / JSON handling. Sources like
    # raw.githubusercontent.com serve Markdown as `text/plain`, JSON APIs and
    # raw config files serve `application/json`, and a lot of code and tool
    # docs live in `.md` / `.txt`. These have no HTML structure, so the HTML
    # branch below would extract nothing and report "no readable text content".
    # Return the body verbatim instead. The `is_html` guard keeps real HTML
    # (including `application/xhtml+xml`) on the parsing path; the `json` check
    # covers `application/json` and `+json` suffixes; the URL-suffix fallback
    # catches servers that mislabel text files as `application/octet-stream`.
    is_html = "html" in content_type
    is_json = "json" in content_type
    url_path = url.lower().split("?", 1)[0].split("#", 1)[0]
    looks_like_text_file = url_path.endswith(
        (".md", ".markdown", ".txt", ".text", ".json", ".jsonl")
    )
    if not is_html and (content_type.startswith("text/") or is_json or looks_like_text_file):
        text_body = (response.text or "").strip()
        result = {
            "url": url,
            "title": os.path.basename(url_path) or url,
            "content": text_body,
            "lists": [],
            "tables": [],
            "code_blocks": [],
            "meta_description": "",
            "meta_keywords": "",
            "js_rendered": False,
            "js_message": "",
            "success": bool(text_body),
            "error": "" if text_body else "Empty response body",
            **_size_fields,
        }
        _cache_result(cache_file, cache_key, result, url)
        return result

    # HTML handling
    try:
        soup = BeautifulSoup(response.text, "html.parser")
    except Exception as e:
        error_logger.error(f"ParseError parsing HTML from {url} (attempt {retry_attempt}): {e}")
        result = _empty_result(url, f"ParseError: {e}")
        _cache_result(cache_file, cache_key, result, url)
        return result

    title_tag = soup.find("title")
    title_text = title_tag.get_text(strip=True) if title_tag else ""
    meta_info = _extract_meta(soup)
    og_image = _extract_og_image(soup)
    js_rendered = _detect_js_frameworks(soup)
    js_message = "Page appears to be rendered by a JavaScript framework; content may be incomplete." if js_rendered else ""

    # Main textual content (heuristic): prefer semantic / "content"-classed
    # containers to skip nav/footer/boilerplate; tuned for article pages.
    main_content = ""
    content_areas = soup.find_all(
        ["main", "article", "section", "div"],
        class_=re.compile("content|main|body|article|post|entry|text", re.I),
    )
    if content_areas:
        for area in content_areas[:3]:
            main_content += area.get_text(separator=" ", strip=True) + " "
    main_content = re.sub(r"\s+", " ", main_content).strip()

    # If the heuristic finds only a tiny wrapper, fall back to body text with
    # obvious boilerplate stripped so UI/deep-research search results do not
    # look empty for app/landing pages.
    THIN_CONTENT_CHARS = 600
    if len(main_content) < THIN_CONTENT_CHARS:
        body = soup.find("body")
        if body:
            body_copy = copy.copy(body)
            for noise in body_copy.find_all(
                ["script", "style", "noscript", "template", "nav", "header", "footer", "aside"]
            ):
                noise.extract()
            body_text = re.sub(r"\s+", " ", body_copy.get_text(separator=" ", strip=True)).strip()
            if len(body_text) > len(main_content):
                main_content = body_text

    result = {
        "url": url,
        "title": title_text,
        "content": main_content,
        "lists": _extract_lists(soup),
        "tables": _extract_tables(soup),
        "code_blocks": _extract_code_blocks(soup),
        "meta_description": meta_info.get("description", ""),
        "meta_keywords": meta_info.get("keywords", ""),
        "og_image": og_image,
        "js_rendered": js_rendered,
        "js_message": js_message,
        "success": True,
        "error": "",
        **_size_fields,
    }
    _cache_result(cache_file, cache_key, result, url)
    return result


def _cache_result(cache_file, cache_key: str, result: dict, url: str):
    """Write a result to the content cache."""
    try:
        cache_data = {"timestamp": datetime.now().isoformat(), "data": result}
        with open(cache_file, "w", encoding="utf-8") as f:
            json.dump(cache_data, f)
        content_cache_index[cache_key] = datetime.now()
        cleanup_cache(CONTENT_CACHE_DIR, content_cache_index, timedelta(hours=2))
    except Exception as e:
        logger.warning(f"Failed to write content cache for {url}: {e}")


# ----------------------------------------------------------------------
# Content summarization helpers
# ----------------------------------------------------------------------
def extract_key_points(text: str) -> List[str]:
    """Pull out bullet-style key points from a block of text."""
    points: List[str] = []
    bullet_pat = re.compile(r"^\s*[-*•]\s+(.*)")
    numbered_pat = re.compile(r"^\s*\d+[\.\)]\s+(.*)")
    for line in text.splitlines():
        m = bullet_pat.match(line) or numbered_pat.match(line)
        if m:
            points.append(m.group(1).strip())
    return points


def get_tldr(text: str, max_sentences: int = 3) -> str:
    """Produce a very short TL;DR by taking the first few sentences."""
    sentences = re.split(r"(?<=[.!?])\s+", text)
    selected = [s.strip() for s in sentences if s][:max_sentences]
    return " ".join(selected)


def extract_quotes(text: str) -> List[str]:
    """Return quoted excerpts that are at least 15 characters long."""
    # Backreference the opening quote so the closing quote must match it —
    # otherwise `"text'` (open double, close single) is treated as a quote.
    return [m.group(2).strip() for m in re.finditer(r'(["\'])([^"\']{15,}?)\1', text)]


def extract_statistics(text: str) -> List[str]:
    """Find numbers, percentages, dates and simple measurements."""
    # Match a comma-grouped number (1,000,000) OR a plain digit run (50000) —
    # the old `\d{1,3}(?:,\d{3})*` matched only the first 3 digits of a
    # comma-less number, and the trailing `\b` dropped a closing `%`.
    pattern = re.compile(
        r"\b(?:\d{1,3}(?:,\d{3})+|\d+)(?:\.\d+)?\s*(%|percent|‰|per cent|[a-zA-Z]+)?",
        re.IGNORECASE,
    )
    return [m.group(0).strip() for m in pattern.finditer(text)]