use std::collections::HashMap;
use std::sync::Arc;
use std::time::Duration;

use std::net::{IpAddr, SocketAddr};

use reqwest::dns::{Addrs, Name, Resolve, Resolving};
use reqwest::header::{HeaderMap, HeaderName, HeaderValue, USER_AGENT};
use reqwest::redirect::Policy;
use reqwest::{Client, Method};
use tokio::sync::RwLock;
use url::Url;

use crate::cookies::CookieJar;
use crate::interceptor::{InterceptAction, RequestInterceptor};

#[derive(Debug, Clone)]
pub struct Response {
    pub url: Url,
    pub status: u16,
    pub headers: HashMap<String, String>,
    pub body: Vec<u8>,
    pub redirected_from: Vec<Url>,
}

impl Response {
    /// Decode the body as text, honoring the response charset.
    ///
    /// Uses the HTTP `Content-Type` header's `charset=` parameter, then for
    /// HTML responses falls back to sniffing `<meta charset>` in the first
    /// 1KB, then UTF-8. Mirrors browser behaviour per the HTML5 spec.
    pub fn text(&self) -> String {
        if self.is_html() {
            crate::encoding::decode_response(&self.body, self.content_type())
        } else {
            crate::encoding::decode_non_html(&self.body, self.content_type())
        }
    }

    pub fn header(&self, name: &str) -> Option<&str> {
        self.headers.get(&name.to_lowercase()).map(|s| s.as_str())
    }

    pub fn content_type(&self) -> Option<&str> {
        self.header("content-type")
    }

    pub fn is_html(&self) -> bool {
        self.content_type()
            .map(|ct| ct.contains("text/html"))
            .unwrap_or(false)
    }
}

#[derive(Debug, Clone)]
pub struct RequestInfo {
    pub url: Url,
    pub method: String,
    pub headers: HashMap<String, String>,
    pub resource_type: ResourceType,
}

#[derive(Debug, Clone, PartialEq, Eq)]
pub enum ResourceType {
    Document,
    Script,
    Stylesheet,
    Image,
    Font,
    Xhr,
    Fetch,
    Other,
}

pub type RequestCallback = Arc<dyn Fn(&RequestInfo) + Send + Sync>;
pub type ResponseCallback = Arc<dyn Fn(&RequestInfo, &Response) + Send + Sync>;

/// Process-wide opt-in via env var. Older flow that issue #4 introduced. The
/// new `--allow-private-network` CLI flag (issue #33) sets a per-client field
/// that is OR'd with this so existing scripts and Docker setups that pin the
/// env var keep working unchanged.
pub fn env_allows_private_network() -> bool {
    matches!(
        std::env::var("OBSCURA_ALLOW_PRIVATE_NETWORK")
            .ok()
            .as_deref()
            .map(str::trim)
            .map(str::to_ascii_lowercase)
            .as_deref(),
        Some("1") | Some("true") | Some("yes") | Some("on")
    )
}

/// True when `ip` must never be the target of an outbound request from the
/// engine: loopback, RFC1918 private, link-local (incl. the 169.254.169.254
/// cloud-metadata endpoint), broadcast, documentation, the unspecified address
/// (0.0.0.0 / ::, which the OS routes to localhost), IPv6 unique-local
/// (fc00::/7), and any IPv4-mapped/compatible IPv6 form of the above.
/// Centralizes the SSRF deny-set so the literal-host check and the
/// DNS-resolution check (`SsrfGuardResolver`) can never disagree.
pub fn is_forbidden_ip(ip: IpAddr) -> bool {
    match ip {
        IpAddr::V4(v4) => {
            v4.is_loopback()
                || v4.is_private()
                || v4.is_link_local()
                || v4.is_broadcast()
                || v4.is_documentation()
                || v4.is_unspecified()
        }
        IpAddr::V6(v6) => {
            if v6.is_loopback()
                || v6.is_unspecified()
                || v6.is_unique_local()
                || v6.is_unicast_link_local()
            {
                return true;
            }
            // Unwrap IPv4-mapped (::ffff:a.b.c.d) and IPv4-compatible (::a.b.c.d)
            // forms and re-check the embedded v4 so e.g. [::ffff:127.0.0.1] or
            // [::ffff:169.254.169.254] cannot slip past the v6 arm.
            if let Some(v4) = v6.to_ipv4_mapped().or_else(|| v6.to_ipv4()) {
                return is_forbidden_ip(IpAddr::V4(v4));
            }
            false
        }
    }
}

/// reqwest DNS resolver that performs the lookup and then rejects the whole
/// request if ANY resolved address is in the SSRF deny-set. This closes the
/// DNS-rebinding bypass a host-string check alone cannot: a public name that
/// resolves to 127.0.0.1 / 169.254.169.254 / an RFC1918 address is blocked at
/// connect time, using the very addresses reqwest will dial. When private
/// access is permitted (`--allow-private-network` or
/// `OBSCURA_ALLOW_PRIVATE_NETWORK`) the lookup passes through unfiltered.
pub struct SsrfGuardResolver {
    allow_private: bool,
}

impl SsrfGuardResolver {
    pub fn new(allow_private: bool) -> Self {
        Self { allow_private }
    }
}

impl Resolve for SsrfGuardResolver {
    fn resolve(&self, name: Name) -> Resolving {
        let allow = self.allow_private || env_allows_private_network();
        let host = name.as_str().to_string();
        Box::pin(async move {
            let addrs: Vec<SocketAddr> = tokio::net::lookup_host((host.as_str(), 0))
                .await
                .map_err(|e| -> Box<dyn std::error::Error + Send + Sync> { Box::new(e) })?
                .collect();
            if !allow {
                if let Some(bad) = addrs.iter().find(|sa| is_forbidden_ip(sa.ip())) {
                    return Err(format!(
                        "SSRF blocked: '{}' resolves to forbidden address {}",
                        host,
                        bad.ip()
                    )
                    .into());
                }
            }
            let iter: Addrs = Box::new(addrs.into_iter());
            Ok(iter)
        })
    }
}

fn validate_url(url: &Url, allow_private_network: bool) -> Result<(), ObscuraNetError> {
    let allow_private_network = allow_private_network || env_allows_private_network();
    let scheme = url.scheme();
    if scheme != "http" && scheme != "https" && scheme != "file" {
        return Err(ObscuraNetError::Network(format!(
            "Forbidden URL scheme '{}' - only http, https, and file are allowed",
            scheme
        )));
    }

    if scheme == "file" || allow_private_network {
        return Ok(());
    }

    if let Some(host) = url.host() {
        match host {
            url::Host::Ipv4(ip) => {
                if is_forbidden_ip(IpAddr::V4(ip)) {
                    return Err(ObscuraNetError::Network(format!(
                        "Access to private/internal IP address {} is not allowed",
                        ip
                    )));
                }
            }
            url::Host::Ipv6(ip) => {
                if is_forbidden_ip(IpAddr::V6(ip)) {
                    return Err(ObscuraNetError::Network(format!(
                        "Access to private/internal IPv6 address {} is not allowed",
                        ip
                    )));
                }
            }
            url::Host::Domain(domain) => {
                let lower_domain = domain.to_lowercase();
                if lower_domain == "localhost"
                    || lower_domain.ends_with(".localhost")
                    || lower_domain == "127.0.0.1"
                    || lower_domain == "::1"
                {
                    return Err(ObscuraNetError::Network(format!(
                        "Access to localhost domain '{}' is not allowed",
                        domain
                    )));
                }
            }
        }
    }

    Ok(())
}

async fn fetch_file_url(url: &Url) -> Result<Response, ObscuraNetError> {
    let path = url
        .to_file_path()
        .map_err(|_| ObscuraNetError::Network("Invalid file URL".to_string()))?;
    let body = tokio::fs::read(&path)
        .await
        .map_err(|e| ObscuraNetError::Network(format!("Failed to read file: {}", e)))?;

    let mut headers = HashMap::new();
    if let Some(ext) = path.extension().and_then(|e| e.to_str()) {
        let ct = match ext.to_lowercase().as_str() {
            "html" | "htm" => "text/html",
            "css" => "text/css",
            "js" | "mjs" => "application/javascript",
            "json" => "application/json",
            "png" => "image/png",
            "jpg" | "jpeg" => "image/jpeg",
            "gif" => "image/gif",
            "svg" => "image/svg+xml",
            "webp" => "image/webp",
            "ico" => "image/x-icon",
            _ => "application/octet-stream",
        };
        headers.insert("content-type".to_string(), ct.to_string());
    }

    Ok(Response {
        url: url.clone(),
        status: 200,
        headers,
        body,
        redirected_from: Vec::new(),
    })
}

pub struct ObscuraHttpClient {
    client: tokio::sync::OnceCell<Client>,
    proxy_url: Option<String>,
    pub cookie_jar: Arc<CookieJar>,
    pub user_agent: RwLock<String>,
    pub extra_headers: RwLock<HashMap<String, String>>,
    pub interceptor: RwLock<Option<Box<dyn RequestInterceptor + Send + Sync>>>,
    pub on_request: RwLock<Vec<RequestCallback>>,
    pub on_response: RwLock<Vec<ResponseCallback>>,
    pub timeout: Duration,
    pub in_flight: Arc<std::sync::atomic::AtomicU32>,
    pub block_trackers: bool,
    /// When true, `validate_url` lets localhost / RFC1918 / link-local addresses
    /// through in addition to the `OBSCURA_ALLOW_PRIVATE_NETWORK` env var.
    /// Set via `--allow-private-network` on the CLI (issue #33).
    pub allow_private_network: bool,
}

/// Derive the sec-ch-ua and sec-ch-ua-platform client-hint header values from a
/// User-Agent string, using Chromium's per-major-version GREASE algorithm so
/// the non-stealth HTTP path agrees with navigator.userAgentData instead of
/// shipping a fixed Linux/Chrome-145 hint that contradicts a Windows profile.
fn chrome_client_hints(ua: &str) -> (String, String) {
    let major: usize = ua
        .split("Chrome/")
        .nth(1)
        .and_then(|s| s.split('.').next())
        .and_then(|s| s.parse::<usize>().ok())
        .unwrap_or(145);
    const GREASE_CHARS: [char; 11] = [' ', '(', ':', '-', '.', '/', ')', ';', '=', '?', '_'];
    const GREASE_VER: [&str; 3] = ["8", "99", "24"];
    const PERMS: [[usize; 3]; 6] = [[0, 1, 2], [0, 2, 1], [1, 0, 2], [1, 2, 0], [2, 0, 1], [2, 1, 0]];
    let grease_brand = format!(
        "Not{}A{}Brand",
        GREASE_CHARS[major % 11],
        GREASE_CHARS[(major + 1) % 11]
    );
    let brands = [
        (grease_brand, GREASE_VER[major % 3].to_string()),
        ("Chromium".to_string(), major.to_string()),
        ("Google Chrome".to_string(), major.to_string()),
    ];
    let p = PERMS[major % 6];
    let sec_ch_ua = p
        .iter()
        .map(|&i| format!("\"{}\";v=\"{}\"", brands[i].0, brands[i].1))
        .collect::<Vec<_>>()
        .join(", ");
    let platform = if ua.contains("Windows NT") {
        "\"Windows\""
    } else if ua.contains("Macintosh") {
        "\"macOS\""
    } else {
        "\"Linux\""
    };
    (sec_ch_ua, platform.to_string())
}

impl ObscuraHttpClient {
    pub fn new() -> Self {
        Self::with_cookie_jar(Arc::new(CookieJar::new()))
    }

    pub fn with_cookie_jar(cookie_jar: Arc<CookieJar>) -> Self {
        Self::with_options(cookie_jar, None)
    }

    pub fn with_options(cookie_jar: Arc<CookieJar>, proxy_url: Option<&str>) -> Self {
        Self::with_full_options(cookie_jar, proxy_url, false)
    }

    pub fn with_full_options(
        cookie_jar: Arc<CookieJar>,
        proxy_url: Option<&str>,
        allow_private_network: bool,
    ) -> Self {
        ObscuraHttpClient {
            client: tokio::sync::OnceCell::new(),
            proxy_url: proxy_url.map(|s| s.to_string()),
            cookie_jar,
            user_agent: RwLock::new(
                "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/145.0.0.0 Safari/537.36".to_string(),
            ),
            extra_headers: RwLock::new(HashMap::new()),
            interceptor: RwLock::new(None),
            on_request: RwLock::new(Vec::new()),
            on_response: RwLock::new(Vec::new()),
            in_flight: Arc::new(std::sync::atomic::AtomicU32::new(0)),
            timeout: Duration::from_secs(30),
            block_trackers: false,
            allow_private_network,
        }
    }

    async fn get_client(&self) -> &Client {
        self.client.get_or_init(|| async {
            let mut builder = Client::builder()
                .redirect(Policy::none())
                .timeout(Duration::from_secs(30))
                .danger_accept_invalid_certs(false)
                // SSRF guard: reject hostnames that resolve to a private/loopback IP.
                .dns_resolver(Arc::new(SsrfGuardResolver::new(self.allow_private_network)))
;

            if let Some(ref proxy) = self.proxy_url {
                if let Ok(p) = reqwest::Proxy::all(proxy.as_str()) {
                    builder = builder.proxy(p);
                }
            }

            builder.build().expect("failed to build HTTP client")
        }).await
    }

    /// Read-only accessor for the proxy URL the client was configured with
    /// (if any). Exposed so callers outside the `obscura-net` crate — notably
    /// `op_fetch_url` in `obscura-js` (#139) — can route their own reqwest
    /// requests through the same upstream proxy.
    pub fn proxy_url(&self) -> Option<&str> {
        self.proxy_url.as_deref()
    }

    pub async fn fetch(&self, url: &Url) -> Result<Response, ObscuraNetError> {
        self.fetch_with_method(Method::GET, url, None).await
    }

    pub async fn post_form(&self, url: &Url, body: &str) -> Result<Response, ObscuraNetError> {
        self.fetch_with_method(Method::POST, url, Some(body.as_bytes().to_vec())).await
    }

    pub async fn fetch_with_method(
        &self,
        initial_method: Method,
        url: &Url,
        initial_body: Option<Vec<u8>>,
    ) -> Result<Response, ObscuraNetError> {
        validate_url(url, self.allow_private_network)?;

        if url.scheme() == "file" {
            return fetch_file_url(url).await;
        }

        let mut method = initial_method;
        let mut body = initial_body;
        if self.block_trackers {
            if let Some(host) = url.host_str() {
                if crate::blocklist::is_blocked(host) {
                    tracing::debug!("Blocked tracker: {}", url);
                    return Ok(Response {
                        status: 0,
                        url: url.clone(),
                        headers: HashMap::new(),
                        body: Vec::new(),
                        redirected_from: Vec::new(),
                    });
                }
            }
        }

        let mut current_url = url.clone();
        let mut redirects = Vec::new();
        let max_redirects = 20;

        for _redirect_count in 0..max_redirects {
            let request_info = RequestInfo {
                url: current_url.clone(),
                method: method.to_string(),
                headers: self.extra_headers.read().await.clone(),
                resource_type: ResourceType::Document,
            };

            if let Some(interceptor) = self.interceptor.read().await.as_ref() {
                match interceptor.intercept(&request_info).await {
                    InterceptAction::Continue => {}
                    InterceptAction::Block => {
                        return Err(ObscuraNetError::Blocked(current_url.to_string()));
                    }
                    InterceptAction::Fulfill(response) => {
                        return Ok(response);
                    }
                    InterceptAction::ModifyHeaders(headers) => {
                        let mut extra = self.extra_headers.write().await;
                        extra.extend(headers);
                    }
                }
            }

            for cb in self.on_request.read().await.iter() {
                cb(&request_info);
            }

            let ua = self.user_agent.read().await.clone();
            let (sec_ch_ua, sec_ch_ua_platform) = chrome_client_hints(&ua);
            let mut headers = HeaderMap::new();
            // Chrome's top-level navigation header order. (reqwest appends
            // accept-encoding/host after these, so accept-encoding lands after
            // accept-language rather than before it; the rest matches Chrome.)
            headers.insert(
                HeaderName::from_static("sec-ch-ua"),
                HeaderValue::from_str(&sec_ch_ua)
                    .unwrap_or_else(|_| HeaderValue::from_static("\"Not:A-Brand\";v=\"99\", \"Google Chrome\";v=\"145\", \"Chromium\";v=\"145\"")),
            );
            headers.insert(HeaderName::from_static("sec-ch-ua-mobile"), HeaderValue::from_static("?0"));
            headers.insert(
                HeaderName::from_static("sec-ch-ua-platform"),
                HeaderValue::from_str(&sec_ch_ua_platform)
                    .unwrap_or_else(|_| HeaderValue::from_static("\"Windows\"")),
            );
            headers.insert(HeaderName::from_static("upgrade-insecure-requests"), HeaderValue::from_static("1"));
            headers.insert(USER_AGENT, HeaderValue::from_str(&ua).unwrap_or_else(|_| {
                HeaderValue::from_static("Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/145.0.0.0 Safari/537.36")
            }));
            headers.insert(
                reqwest::header::ACCEPT,
                HeaderValue::from_static("text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.7"),
            );
            headers.insert(HeaderName::from_static("sec-fetch-site"), HeaderValue::from_static("none"));
            headers.insert(HeaderName::from_static("sec-fetch-mode"), HeaderValue::from_static("navigate"));
            headers.insert(HeaderName::from_static("sec-fetch-user"), HeaderValue::from_static("?1"));
            headers.insert(HeaderName::from_static("sec-fetch-dest"), HeaderValue::from_static("document"));
            headers.insert(
                reqwest::header::ACCEPT_LANGUAGE,
                HeaderValue::from_static("en-US,en;q=0.9"),
            );

            let cookie_header = self.cookie_jar.get_cookie_header(&current_url);
            tracing::debug!(
                "Cookie header for {}: {} cookies ({} bytes)",
                current_url.host_str().unwrap_or("?"),
                cookie_header.split("; ").filter(|s| !s.is_empty()).count(),
                cookie_header.len(),
            );
            if !cookie_header.is_empty() {
                match HeaderValue::from_str(&cookie_header) {
                    Ok(val) => {
                        headers.insert(reqwest::header::COOKIE, val);
                    }
                    Err(_) => {
                        let filtered: String = cookie_header
                            .split("; ")
                            .filter(|pair| HeaderValue::from_str(pair).is_ok())
                            .collect::<Vec<_>>()
                            .join("; ");
                        if !filtered.is_empty() {
                            if let Ok(val) = HeaderValue::from_str(&filtered) {
                                headers.insert(reqwest::header::COOKIE, val);
                            }
                        }
                        tracing::debug!(
                            "Cookie header invalid chars, filtered {} -> {} bytes",
                            cookie_header.len(), filtered.len(),
                        );
                    }
                }
            }

            for (k, v) in self.extra_headers.read().await.iter() {
                if let (Ok(name), Ok(val)) = (
                    HeaderName::from_bytes(k.as_bytes()),
                    HeaderValue::from_str(v),
                ) {
                    headers.insert(name, val);
                }
            }

            let mut req_builder = self.get_client().await.request(method.clone(), current_url.as_str())
                .headers(headers);

            if let Some(ref b) = body {
                if method == Method::POST {
                    req_builder = req_builder.header(
                        reqwest::header::CONTENT_TYPE,
                        "application/x-www-form-urlencoded",
                    );
                }
                req_builder = req_builder.body(b.clone());
            }

            self.in_flight.fetch_add(1, std::sync::atomic::Ordering::Relaxed);
            let resp = req_builder.send().await.map_err(|e| {
                self.in_flight.fetch_sub(1, std::sync::atomic::Ordering::Relaxed);
                ObscuraNetError::Network(format!("{}: {}", current_url, e))
            })?;
            self.in_flight.fetch_sub(1, std::sync::atomic::Ordering::Relaxed);

            let status = resp.status();

            for val in resp.headers().get_all(reqwest::header::SET_COOKIE) {
                if let Ok(s) = val.to_str() {
                    self.cookie_jar.set_cookie(s, &current_url);
                }
            }

            let response_headers: HashMap<String, String> = resp
                .headers()
                .iter()
                .map(|(k, v)| (k.as_str().to_lowercase(), v.to_str().unwrap_or("").to_string()))
                .collect();

            if status.is_redirection() {
                if let Some(location) = resp.headers().get(reqwest::header::LOCATION) {
                    let location_str = location.to_str().map_err(|_| {
                        ObscuraNetError::Network("Invalid redirect Location header".into())
                    })?;
                    let next_url = current_url.join(location_str).map_err(|e| {
                        ObscuraNetError::Network(format!("Invalid redirect URL: {}", e))
                    })?;
                    validate_url(&next_url, self.allow_private_network)?;
                    redirects.push(current_url.clone());
                    current_url = next_url;
                    if status == reqwest::StatusCode::MOVED_PERMANENTLY
                        || status == reqwest::StatusCode::FOUND
                        || status == reqwest::StatusCode::SEE_OTHER
                    {
                        method = Method::GET;
                        body = None;
                    }
                    continue;
                }
            }

            let body_bytes = resp.bytes().await.map_err(|e| {
                ObscuraNetError::Network(format!("Failed to read body: {}", e))
            })?.to_vec();

            let response = Response {
                url: current_url,
                status: status.as_u16(),
                headers: response_headers,
                body: body_bytes,
                redirected_from: redirects,
            };

            for cb in self.on_response.read().await.iter() {
                cb(&request_info, &response);
            }

            return Ok(response);
        }

        Err(ObscuraNetError::TooManyRedirects(current_url.to_string()))
    }

    pub async fn set_user_agent(&self, ua: &str) {
        *self.user_agent.write().await = ua.to_string();
    }

    pub async fn set_extra_headers(&self, headers: HashMap<String, String>) {
        *self.extra_headers.write().await = headers;
    }

    pub fn active_requests(&self) -> u32 {
        self.in_flight.load(std::sync::atomic::Ordering::Relaxed)
    }

    pub fn is_network_idle(&self) -> bool {
        self.active_requests() == 0
    }
}

impl Default for ObscuraHttpClient {
    fn default() -> Self {
        Self::new()
    }
}

#[derive(Debug, thiserror::Error)]
pub enum ObscuraNetError {
    #[error("Network error: {0}")]
    Network(String),

    #[error("Too many redirects: {0}")]
    TooManyRedirects(String),

    #[error("Request blocked: {0}")]
    Blocked(String),
}

#[cfg(test)]
mod ssrf_tests {
    use super::{is_forbidden_ip, validate_url, SsrfGuardResolver};
    use reqwest::dns::{Name, Resolve};
    use std::net::IpAddr;
    use std::str::FromStr;
    use url::Url;

    fn ip(s: &str) -> IpAddr {
        IpAddr::from_str(s).unwrap()
    }

    #[test]
    fn ipv4_private_and_special_ranges_are_forbidden() {
        for s in [
            "127.0.0.1",
            "127.5.6.7",
            "10.0.0.1",
            "172.16.0.1",
            "192.168.1.1",
            "169.254.169.254", // cloud-metadata endpoint
            "0.0.0.0",         // unspecified -> localhost (was a bypass)
            "255.255.255.255", // broadcast
            "192.0.2.1",       // documentation
        ] {
            assert!(is_forbidden_ip(ip(s)), "{s} should be forbidden");
        }
    }

    #[test]
    fn public_ipv4_is_allowed() {
        for s in ["1.1.1.1", "8.8.8.8", "93.184.216.34"] {
            assert!(!is_forbidden_ip(ip(s)), "{s} should be allowed");
        }
    }

    #[test]
    fn ipv6_loopback_ula_linklocal_and_mapped_are_forbidden() {
        for s in [
            "::1",                    // loopback
            "::",                     // unspecified
            "fc00::1",                // unique-local (was a bypass)
            "fd12:3456:789a::1",      // unique-local
            "fe80::1",                // link-local
            "::ffff:127.0.0.1",       // v4-mapped loopback (was a bypass)
            "::ffff:169.254.169.254", // v4-mapped metadata
        ] {
            assert!(is_forbidden_ip(ip(s)), "{s} should be forbidden");
        }
    }

    #[test]
    fn public_ipv6_is_allowed() {
        assert!(!is_forbidden_ip(ip("2606:4700:4700::1111"))); // cloudflare dns
    }

    #[test]
    fn validate_url_blocks_unspecified_and_allows_public() {
        // 0.0.0.0 previously slipped through validate_url's literal-host check.
        assert!(validate_url(&Url::parse("http://0.0.0.0:8080/").unwrap(), false).is_err());
        assert!(validate_url(&Url::parse("http://127.0.0.1/").unwrap(), false).is_err());
        assert!(validate_url(&Url::parse("http://example.com/").unwrap(), false).is_ok());
        // The allow flag bypasses the guard (local-dev escape hatch).
        assert!(validate_url(&Url::parse("http://127.0.0.1/").unwrap(), true).is_ok());
    }

    #[tokio::test]
    async fn resolver_blocks_hostname_that_resolves_to_loopback() {
        // localtest.me is a public DNS name that resolves to 127.0.0.1 — the
        // canonical DNS-rebinding test. The guard must reject it. If DNS is
        // unavailable the lookup itself errors (also Err), so the assertion
        // holds either way.
        let r = SsrfGuardResolver::new(false);
        let res = r.resolve(Name::from_str("localtest.me").unwrap()).await;
        assert!(res.is_err(), "localtest.me -> 127.0.0.1 must be blocked");
    }

    #[tokio::test]
    async fn resolver_does_not_ssrf_block_public_host() {
        // A public host must not be SSRF-blocked. Tolerate a no-network sandbox
        // by only failing on an actual SSRF rejection, not a lookup failure.
        let r = SsrfGuardResolver::new(false);
        match r.resolve(Name::from_str("example.com").unwrap()).await {
            Ok(_) => {}
            Err(e) => assert!(
                !e.to_string().contains("SSRF blocked"),
                "example.com wrongly SSRF-blocked: {e}"
            ),
        }
    }
}