# app.py
import re
from dataclasses import dataclass, asdict
from typing import Dict, List, Optional, Tuple
from urllib.parse import urlparse, urljoin

import requests
from bs4 import BeautifulSoup
from urllib.robotparser import RobotFileParser

import gradio as gr

# --- Known / common AI user agents (extend as needed) ---
DEFAULT_AI_AGENTS = [
    # Major AI-specific or AI-extended crawlers
    "GPTBot",                # OpenAI
    "Google-Extended",       # Google for AI training opt-out
    "Anthropic-ai",          # Anthropic
    "PerplexityBot",         # Perplexity
    "Claude-Web",            # Anthropic variant seen in the wild
    "CCBot",                 # Common Crawl (often used for model datasets)
    "DuckAssistBot",         # DuckDuckGo AI assistant
    "Bytespider",            # ByteDance (ML datasets)
    "Amazonbot",             # Amazon web crawler (AI datasets reported)
    "FacebookBot",           # Meta (generic)
    # Fallbacks that some sites target
    "ai-bot", "aibot"
]

# Tokens that imply AI-blocking (non-standard but widely used)
AI_BLOCK_TOKENS = {"noai", "noimageai"}

# Standard robots tokens that imply non-crawlability of content
ROBOTS_BLOCK_TOKENS = {"noindex", "nofollow", "none", "noarchive"}

# Allowed content types for HTML pages
ALLOWED_CONTENT_TYPES = {"text/html", "application/xhtml+xml"}


@dataclass
class RobotsCheck:
    fetched: bool
    url: Optional[str]
    allowed_map: Dict[str, bool]
    disallow_matches: Dict[str, List[str]]
    errors: List[str]


@dataclass
class MetaRobotsCheck:
    found: bool
    directives: List[str]
    ai_block_tokens: List[str]
    robots_block_tokens: List[str]
    source: str  # "html" or "header"
    raw: str


@dataclass
class HttpCheck:
    status: int
    final_url: str
    redirects: List[Tuple[int, str]]
    content_type: str


@dataclass
class CrawlabilityResult:
    url: str
    verdict: str              # "AI-crawlable", "AI-blocked", "Indeterminate"
    reasons: List[str]
    http: HttpCheck
    robots: RobotsCheck
    meta_html: Optional[MetaRobotsCheck]
    xrobots: Optional[MetaRobotsCheck]
    analyzed_agents: List[str]
    summary: str


def _get_robots_url(page_url: str) -> str:
    parsed = urlparse(page_url)
    base = f"{parsed.scheme}://{parsed.netloc}"
    return urljoin(base, "/robots.txt")


def _fetch_with_redirects(url: str, timeout: int = 15) -> HttpCheck:
    redirects = []
    try:
        resp = requests.get(url, timeout=timeout, allow_redirects=True,
                            headers={"User-Agent": "Mozilla/5.0 AI-Crawlability/1.0"})
        # Collect redirect chain
        for r in resp.history:
            redirects.append((r.status_code, r.headers.get("Location", r.url)))
        content_type = resp.headers.get("Content-Type", "").split(";")[0].strip().lower()
        return HttpCheck(status=resp.status_code, final_url=resp.url,
                         redirects=redirects, content_type=content_type)
    except requests.RequestException as e:
        return HttpCheck(status=0, final_url=url, redirects=redirects, content_type=str(e))


def _parse_meta_robots_from_html(html: str) -> MetaRobotsCheck:
    soup = BeautifulSoup(html, "html.parser")
    metas = soup.find_all("meta", attrs={"name": re.compile(
        r"^(robots|googlebot|gptbot|anthropic-ai|perplexitybot)$", re.I)})
    directives = []
    raw = []
    for m in metas:
        content = (m.get("content") or "").strip()
        if content:
            raw.append(content)
            directives.extend([d.strip().lower() for d in content.split(",")])

    ai_tokens = sorted(set(d for d in directives if d in AI_BLOCK_TOKENS))
    robots_tokens = sorted(set(d for d in directives if d in ROBOTS_BLOCK_TOKENS))

    return MetaRobotsCheck(
        found=bool(directives),
        directives=sorted(set(directives)),
        ai_block_tokens=ai_tokens,
        robots_block_tokens=robots_tokens,
        source="html",
        raw=" | ".join(raw)
    )


def _parse_xrobots_from_headers(headers: Dict[str, str]) -> Optional[MetaRobotsCheck]:
    # X-Robots-Tag can appear multiple times; normalize
    values = []
    for k, v in headers.items():
        if k.lower() == "x-robots-tag":
            values.append(v)
    if not values:
        return None

    directives = []
    for val in values:
        # Pattern: "<agent>: <rules>" OR "<rules>"
        parts = [p.strip() for p in val.split(",")]
        directives.extend([p.lower() for p in parts])

    ai_tokens = sorted(set(d for d in directives if d in AI_BLOCK_TOKENS))
    robots_tokens = sorted(set(d for d in directives if d in ROBOTS_BLOCK_TOKENS))

    return MetaRobotsCheck(
        found=True,
        directives=sorted(set(directives)),
        ai_block_tokens=ai_tokens,
        robots_block_tokens=robots_tokens,
        source="header",
        raw=" | ".join(values)
    )


def _fetch_text(url: str, timeout: int = 15) -> Tuple[Optional[str], Dict[str, str], int]:
    try:
        resp = requests.get(url, timeout=timeout,
                            headers={"User-Agent": "Mozilla/5.0 AI-Crawlability/1.0"})
        return (resp.text if resp.status_code == 200 else None, resp.headers, resp.status_code)
    except requests.RequestException:
        return (None, {}, 0)


def _check_robots(page_url: str, ai_agents: List[str]) -> RobotsCheck:
    robots_url = _get_robots_url(page_url)
    errors = []
    allowed_map = {}
    disallow_matches = {}

    rp = RobotFileParser()
    rp.set_url(robots_url)

    try:
        rp.read()
        fetched = True
    except Exception as e:
        fetched = False
        errors.append(f"robots.txt fetch error: {e}")

    # For better diagnostics, fetch raw robots.txt to inspect Disallow lines for each agent
    robots_txt, _, status = _fetch_text(robots_url)
    if status == 404:
        errors.append("robots.txt not found (404) — defaulting to allowed unless meta/header blocks apply.")
    elif status != 200 and status != 0:
        errors.append(f"robots.txt unexpected HTTP {status}")

    for agent in ai_agents:
        try:
            allowed_map[agent] = rp.can_fetch(agent, page_url) if fetched else True
        except Exception as e:
            allowed_map[agent] = True
            errors.append(f"robotparser error for agent '{agent}': {e}")

        # Collect Disallow matching lines (informational)
        disallow_list = []
        if robots_txt:
            section_regex = re.compile(rf"(?i)User-agent:\s*{re.escape(agent)}\s*(.*?)\n(?=User-agent:|$)", re.S)
            # Fallback: global section
            global_regex = re.compile(r"(?i)User-agent:\s*\*\s*(.*?)\n(?=User-agent:|$)", re.S)
            matches = section_regex.findall(robots_txt) or global_regex.findall(robots_txt)
            for block in matches:
                for line in block.splitlines():
                    if line.strip().lower().startswith("disallow:"):
                        disallow_list.append(line.strip())
        disallow_matches[agent] = disallow_list

    return RobotsCheck(
        fetched=fetched,
        url=robots_url,
        allowed_map=allowed_map,
        disallow_matches=disallow_matches,
        errors=errors
    )


def check_ai_crawlability(
    url: str,
    ai_agents: Optional[List[str]] = None,
    timeout: int = 15
) -> Dict:
    """
    Returns a dict with keys:
      - verdict: "AI-crawlable" | "AI-blocked" | "Indeterminate"
      - reasons: list of strings explaining decision
      - http, robots, meta_html, xrobots: detailed sub-objects
      - analyzed_agents: list of agents considered
      - summary: one-line summary
    """
    ai_agents = ai_agents or DEFAULT_AI_AGENTS

    # Step 1: HTTP fetch (final URL, status, content type)
    http_info = _fetch_with_redirects(url, timeout=timeout)
    reasons = []
    if http_info.status != 200:
        reasons.append(f"Non-200 status ({http_info.status}) for final URL: {http_info.final_url}")
    if http_info.content_type and http_info.content_type not in ALLOWED_CONTENT_TYPES:
        reasons.append(f"Non-HTML content-type '{http_info.content_type}'")

    # Step 2: robots.txt checks
    robots_info = _check_robots(http_info.final_url, ai_agents)

    # Step 3: fetch final page to read HTML meta + headers (for X-Robots-Tag)
    page_text, headers, _ = _fetch_text(http_info.final_url, timeout=timeout)

    meta_html = _parse_meta_robots_from_html(page_text) if page_text else None
    xrobots = _parse_xrobots_from_headers(headers) if headers else None

    # Decision logic
    any_disallowed = any(not allowed for allowed in robots_info.allowed_map.values())
    any_allowed = any(robots_info.allowed_map.values())

    if any_disallowed:
        denied_agents = [a for a, ok in robots_info.allowed_map.items() if not ok]
        reasons.append(f"robots.txt disallows for agents: {', '.join(denied_agents)}")

    if meta_html and (meta_html.ai_block_tokens or meta_html.robots_block_tokens):
        reasons.append(f"HTML meta robots contains: {', '.join(meta_html.ai_block_tokens + meta_html.robots_block_tokens)}")

    if xrobots and (xrobots.ai_block_tokens or xrobots.robots_block_tokens):
        reasons.append(f"X-Robots-Tag contains: {', '.join(xrobots.ai_block_tokens + xrobots.robots_block_tokens)}")

    if (meta_html and any(t in AI_BLOCK_TOKENS for t in meta_html.ai_block_tokens)) or \
       (xrobots and any(t in AI_BLOCK_TOKENS for t in xrobots.ai_block_tokens)) or \
       any_disallowed:
        verdict = "AI-blocked"
    elif http_info.status == 200 and (any_allowed or robots_info.fetched is False):
        verdict = "AI-crawlable"
    else:
        verdict = "Indeterminate"

    if verdict == "AI-blocked":
        summary = "Page is NOT AI-crawlable due to robots/meta/header restrictions."
    elif verdict == "AI-crawlable":
        summary = "Page appears AI-crawlable."
    else:
        summary = "AI crawlability is indeterminate; manual review recommended."

    return {
        "url": url,
        "verdict": verdict,
        "reasons": reasons or ["No explicit blocks found."],
        "http": asdict(http_info),
        "robots": asdict(robots_info),
        "meta_html": asdict(meta_html) if meta_html else None,
        "xrobots": asdict(xrobots) if xrobots else None,
        "analyzed_agents": ai_agents,
        "summary": summary,
    }


# -------- Gradio UI --------
def run_check(url: str, agents_csv: str, timeout: int):
    url = (url or "").strip()
    if not url:
        return "Please enter a URL.", {}
    agents = None
    if agents_csv:
        agents = [a.strip() for a in agents_csv.split(",") if a.strip()]
    try:
        result = check_ai_crawlability(url, ai_agents=agents, timeout=timeout)
        # Human-readable summary
        readable = []
        readable.append(f"Verdict: {result['verdict']}")
        readable.append(f"Summary: {result['summary']}")
        readable.append("—")
        http = result.get("http", {})
        readable.append(f"HTTP: status={http.get('status')} final_url={http.get('final_url')} content_type={http.get('content_type')}")
        redirects = http.get("redirects") or []
        if redirects:
            readable.append("Redirect chain:")
            for code, loc in redirects:
                readable.append(f"  {code} -> {loc}")
        robots = result.get("robots", {})
        readable.append(f"robots.txt: fetched={robots.get('fetched')} url={robots.get('url')}")
        allowed_map = robots.get("allowed_map") or {}
        if allowed_map:
            readable.append("Agent allowances:")
            for agent, allowed in allowed_map.items():
                readable.append(f"  {agent}: {'allowed' if allowed else 'DISALLOWED'}")
        errors = robots.get("errors") or []
        if errors:
            readable.append("robots.txt errors:")
            for e in errors:
                readable.append(f"  - {e}")
        reasons = result.get("reasons") or []
        if reasons:
            readable.append("Decision reasons:")
            for r in reasons:
                readable.append(f"  - {r}")

        return "\n".join(readable), result
    except Exception as e:
        return f"Error: {e}", {}


CSS = """
.wrap { max-width: 1200px; margin: 0 auto; }
.small { font-size: 0.9em; color: #555; }
"""

with gr.Blocks(css=CSS, title="Generative Engine Optimization Checker") as demo:
    gr.Markdown(
        """
        # 🔍 Generative Engine Optimization Checker
        Enter a page URL to inspect its AI crawlability for common AI user agents.  
        The app checks redirects, `robots.txt`, HTML meta robots, and `X-Robots-Tag` headers.

        **Note:** Some sites block crawlers; network errors may occur.
        """
    )
    with gr.Row():
        url = gr.Textbox(label="Page URL", placeholder="https://example.com/article", scale=3)
    with gr.Row():
        agents = gr.Textbox(
            label="AI agents (comma-separated, optional)",
            placeholder="GPTBot,Anthropic-ai,PerplexityBot",
            value="",
            scale=2
        )
        timeout = gr.Slider(5, 30, value=15, step=1, label="Timeout (seconds)", scale=1)
    with gr.Row():
        run_btn = gr.Button("Run Check ✅", variant="primary")
    with gr.Row():
        summary = gr.Textbox(label="Summary", lines=12)
    with gr.Row():
        json_out = gr.JSON(label="Raw JSON Result")

    examples = gr.Examples(
        examples=[
            ["https://openai.com/", "GPTBot,Google-Extended", 15],
            ["https://example.com/", "", 15],
            ["https://www.anthropic.com/", "Anthropic-ai", 15],
        ],
        inputs=[url, agents, timeout],
        label="Examples"
    )

    run_btn.click(run_check, inputs=[url, agents, timeout], outputs=[summary, json_out])

if __name__ == "__main__":
    demo.launch()