impl Settings {
    pub fn validate(&self) -> Result<()> {
        ensure!(
            self.max_bytes >= 65_536,
            "cache.max_bytes must be at least 64 KiB"
        );
        ensure!(
            self.max_object_bytes >= 1024 && self.max_object_bytes <= self.max_bytes,
            "cache.max_object_bytes must be at least 1 KiB and no larger than max_bytes"
        );
        ensure!(
            (1..=16_384).contains(&self.max_entries),
            "cache.max_entries must be 1..16384"
        );
        ensure!(
            self.transient_max_bytes >= 65_536,
            "cache.transient_max_bytes must be at least 64 KiB"
        );
        ensure!(
            self.cold_queue_max_bytes >= 65_536
                && self.cold_queue_max_bytes <= self.transient_max_bytes,
            "cache.cold_queue_max_bytes must be at least 64 KiB and no larger than transient_max_bytes"
        );
        ensure!(
            (1..=4096).contains(&self.hot_eviction_max_objects),
            "cache.hot_eviction_max_objects must be 1..4096"
        );
        ensure!(
            (5..=86_400).contains(&self.hot_auto_trim_after_seconds),
            "cache.hot_auto_trim_after_seconds must be 5..86400"
        );
        ensure!(
            (10..=95).contains(&self.hot_auto_trim_target_percent),
            "cache.hot_auto_trim_target_percent must be 10..95"
        );
        ensure!(
            (65_536..=1024_u64 * 1024 * 1024 * 1024).contains(&self.cold_max_bytes),
            "cache.cold_max_bytes must be 64 KiB..1 TiB"
        );
        ensure!(
            (1..=1_000_000).contains(&self.cold_max_entries),
            "cache.cold_max_entries must be 1..1000000"
        );
        ensure!(
            (5..=86_400).contains(&self.cold_gc_interval_seconds),
            "cache.cold_gc_interval_seconds must be 5..86400"
        );
        ensure!(
            (1..=10_000).contains(&self.cold_gc_max_delete),
            "cache.cold_gc_max_delete must be 1..10000"
        );
        ensure!(
            (5..=604_800).contains(&self.cold_after_seconds),
            "cache.cold_after_seconds must be 5..604800"
        );
        ensure!(
            (5..=2_592_000).contains(&self.cold_max_hot_seconds),
            "cache.cold_max_hot_seconds must be 5..2592000"
        );
        ensure!(
            valid_relative_cache_path(&self.cold_path),
            "cache.cold_path must be a simple relative path inside the data directory"
        );
        ensure!(
            (1..=604_800).contains(&self.max_ttl_seconds)
                && self.default_ttl_seconds <= self.max_ttl_seconds,
            "cache TTL must be at most seven days; default TTL cannot exceed maximum"
        );
        ensure!(
            self.bypass_prefixes.len() <= 64,
            "at most 64 cache bypass prefixes"
        );
        for prefix in &self.bypass_prefixes {
            ensure!(
                prefix.len() <= 512
                    && prefix.starts_with('/')
                    && crate::acl::routing_path(prefix)? == *prefix,
                "cache bypass prefixes must be normalized absolute paths"
            );
        }
        self.validate_http_invalidation_allowlist()?;
        ensure!(
            self.static_extensions.len() <= 64,
            "at most 64 static cache extensions"
        );
        let mut extensions = std::collections::HashSet::new();
        for extension in &self.static_extensions {
            ensure!(
                !extension.is_empty()
                    && extension.len() <= 16
                    && extension.bytes().all(|b| b.is_ascii_alphanumeric()),
                "static cache extensions must be 1..16 ASCII letters or numbers without a dot"
            );
            ensure!(
                extensions.insert(extension.to_ascii_lowercase()),
                "duplicate static cache extension"
            );
        }
        ensure!(
            (10..=60_000).contains(&self.collapse_wait_timeout_ms),
            "cache.collapse_wait_timeout_ms must be 10..60000"
        );
        ensure!(
            self.stale_if_error_statuses.len() <= 32,
            "cache.stale_if_error_statuses supports at most 32 statuses"
        );
        let mut statuses = std::collections::HashSet::new();
        for status in &self.stale_if_error_statuses {
            ensure!(
                (500..=599).contains(status),
                "cache.stale_if_error_statuses must contain HTTP 5xx status codes"
            );
            ensure!(
                statuses.insert(*status),
                "duplicate stale-if-error HTTP status"
            );
        }
        ensure!(
            (1..=604_800).contains(&self.proactive_refresh_before_expiry_seconds),
            "cache.proactive_refresh_before_expiry_seconds must be 1..604800"
        );
        ensure!(
            self.proactive_refresh_percent <= 100,
            "cache.proactive_refresh_percent must be 0..100"
        );
        ensure!(
            (1..=64).contains(&self.proactive_refresh_max_inflight),
            "cache.proactive_refresh_max_inflight must be 1..64"
        );
        if let Some(value) = &self.via_header {
            ensure!(
                !value.is_empty()
                    && value.len() <= 256
                    && value.bytes().all(|byte| byte >= 0x20 && byte != 0x7f)
                    && value.parse::<HeaderValue>().is_ok(),
                "cache.via_header must be a valid 1..256 byte HTTP header value"
            );
        }
        Ok(())
    }
    pub fn active_for(&self, route: Option<bool>) -> bool {
        self.enabled && route != Some(false)
    }
    pub fn allows_stale_error_class(&self, class: StaleErrorClass) -> bool {
        match class {
            StaleErrorClass::Timeout => self.stale_if_error_timeout,
            StaleErrorClass::Connection => self.stale_if_error_connection,
            StaleErrorClass::Dns => self.stale_if_error_dns,
            StaleErrorClass::Tls => self.stale_if_error_tls,
        }
    }
    pub fn allows_stale_error_status(&self, status: StatusCode) -> bool {
        self.stale_if_error_statuses.contains(&status.as_u16())
    }
    pub fn ignore_cookie_for_path(&self, path: &str) -> bool {
        if !self.static_ignore_cookies {
            return false;
        }
        let segment = path.rsplit('/').next().unwrap_or(path);
        let Some((_, extension)) = segment.rsplit_once('.') else {
            return false;
        };
        !extension.is_empty()
            && self
                .static_extensions
                .iter()
                .any(|item| item.eq_ignore_ascii_case(extension))
    }
    pub fn annotate(&self, headers: &mut HeaderMap, outcome: &'static str, hits: u64, ttl: u64) {
        // Origin values must never masquerade as this proxy's diagnostics.
        for name in [
            "x-cache",
            "x-cache-hits",
            "x-cache-status",
            "cache-status",
            "x-cache-reason",
            "x-cache-resident-age",
        ] {
            headers.remove(name);
        }
        // A vhost that explicitly disables cache must look like a normal reverse proxy.
        // Keep counters internally, but never expose cache diagnostics for that response.
        if !self.enabled {
            return;
        }
        if let Some(value) = &self.via_header {
            headers.append(
                http::header::VIA,
                value.parse::<HeaderValue>().expect("validated cache Via header"),
            );
        }
        if self.expose_only_hits && outcome != "HIT" {
            return;
        }
        if self.expose_status {
            headers.insert("x-cache", HeaderValue::from_static(outcome));
        }
        if self.expose_hits {
            headers.insert(
                "x-cache-hits",
                HeaderValue::from_str(&hits.to_string()).expect("integer header"),
            );
        }
        if self.expose_cache_status {
            let value = match outcome {
                "HIT" => format!("RustProxy; hit; ttl={ttl}"),
                "MISS" => "RustProxy; fwd=uri-miss".into(),
                _ => "RustProxy; fwd=bypass".into(),
            };
            headers.insert(
                "cache-status",
                HeaderValue::from_str(&value).expect("generated cache status"),
            );
        }
    }
    pub fn annotate_resident_age(&self, headers: &mut HeaderMap, resident_age: u64) {
        headers.remove("x-cache-resident-age");
        if !self.enabled {
            return;
        }
        if self.expose_resident_age {
            headers.insert(
                "x-cache-resident-age",
                HeaderValue::from_str(&resident_age.to_string()).expect("integer header"),
            );
        }
    }
    pub fn annotate_transformed(&self, headers: &mut HeaderMap, transformed: bool) {
        if !self.enabled || !self.expose_cache_status || !transformed
            || (self.expose_only_hits && !headers.get("cache-status")
                .and_then(|value| value.to_str().ok())
                .is_some_and(|value| value.starts_with("RustProxy; hit"))) {
            return;
        }
        let base = headers
            .get("cache-status")
            .and_then(|value| value.to_str().ok())
            .unwrap_or("RustProxy");
        if base
            .split(';')
            .any(|part| part.trim().eq_ignore_ascii_case("transformed"))
        {
            return;
        }
        if let Ok(value) = format!("{base}; transformed").parse() {
            headers.insert("cache-status", value);
        }
    }
    /// Reasons are fixed internal tokens: never echo request values or secrets.
    pub fn annotate_reason(
        &self,
        headers: &mut HeaderMap,
        outcome: &'static str,
        hits: u64,
        ttl: u64,
        reason: &'static str,
    ) {
        self.annotate(headers, outcome, hits, ttl);
        if !self.enabled || (self.expose_only_hits && outcome != "HIT") {
            return;
        }
        if self.expose_status {
            headers.insert("x-cache-reason", HeaderValue::from_static(reason));
        }
        if self.expose_cache_status {
            let base = headers
                .get("cache-status")
                .and_then(|v| v.to_str().ok())
                .unwrap_or("RustProxy");
            if let Ok(value) = format!("{base}; detail=\"{reason}\"").parse() {
                headers.insert("cache-status", value);
            }
        }
    }
}
fn valid_relative_cache_path(value: &str) -> bool {
    if value.is_empty() || value.len() > 256 {
        return false;
    }
    let path = Path::new(value);
    !path.is_absolute()
        && path
            .components()
            .all(|part| matches!(part, Component::Normal(_)))
}

/// Explicit, per-vhost-only request-side cache override. It never weakens the
/// response-side privacy guards (Set-Cookie/private/no-store/Vary rules).
#[derive(Debug, Clone, Default, Serialize, Deserialize)]
#[serde(default, deny_unknown_fields)]
pub struct UnsafeForce {
    pub enabled: bool,
    pub targets: Vec<String>,
}
impl UnsafeForce {
    pub fn validate(&self) -> Result<()> {
        ensure!(self.targets.len() <= 32, "forced cache supports at most 32 target prefixes");
        for target in &self.targets {
            ensure!(
                !target.is_empty()
                    && target.len() <= 2048
                    && target.starts_with('/')
                    && !target.contains('#')
                    && !target.chars().any(char::is_control),
                "forced cache targets must be 1..2048 byte origin-form path/query prefixes"
            );
            let path = target.split('?').next().unwrap_or(target);
            ensure!(crate::acl::routing_path(path)? == path, "forced cache target path must be normalized");
        }
        Ok(())
    }
    pub fn matches(&self, path: &str, target: &str) -> bool {
        if !self.enabled {
            return false;
        }
        self.targets.iter().any(|configured| {
            if configured.contains('?') {
                target.starts_with(configured)
            } else {
                crate::config::prefix_matches(configured, path)
            }
        })
    }
}

/// Per-vhost behavior, not independent memory pools. None inherits the global
/// default; the global resident-byte/entry/object ceilings remain hard limits.
#[derive(Debug, Clone, Default, Serialize, Deserialize)]
#[serde(default, deny_unknown_fields)]
pub struct Overrides {
    pub enabled: Option<bool>,
    pub default_ttl_seconds: Option<u64>,
    pub max_ttl_seconds: Option<u64>,
    pub max_object_bytes: Option<usize>,
    pub bypass_query: Option<bool>,
    pub bypass_prefixes: Option<Vec<String>>,
    pub static_ignore_cookies: Option<bool>,
    pub static_extensions: Option<Vec<String>>,
    pub expose_status: Option<bool>,
    pub expose_hits: Option<bool>,
    pub expose_cache_status: Option<bool>,
    pub expose_resident_age: Option<bool>,
    pub expose_only_hits: Option<bool>,
    /// Deliberately unavailable in the global cache configuration.
    pub unsafe_force: UnsafeForce,
}
impl Overrides {
    pub fn resolve(&self, global: &Settings) -> Result<Settings> {
        self.unsafe_force.validate()?;
        let mut result = global.clone();
        // A vhost may narrow the global policy, but can never re-enable a cache
        // that the administrator disabled globally.
        result.enabled = global.enabled && self.enabled.unwrap_or(true);
        if let Some(value) = self.default_ttl_seconds {
            result.default_ttl_seconds = value;
        }
        if let Some(value) = self.max_ttl_seconds {
            result.max_ttl_seconds = value;
        }
        if let Some(value) = self.max_object_bytes {
            ensure!(
                value <= global.max_object_bytes,
                "vhost object limit cannot exceed the global ceiling"
            );
            result.max_object_bytes = value;
        }
        if let Some(value) = self.bypass_query {
            result.bypass_query = value;
        }
        if let Some(value) = &self.bypass_prefixes {
            result.bypass_prefixes = value.clone();
        }
        if let Some(value) = self.static_ignore_cookies {
            result.static_ignore_cookies = value;
        }
        if let Some(value) = &self.static_extensions {
            result.static_extensions = value.clone();
        }
        if let Some(value) = self.expose_status {
            result.expose_status = value;
        }
        if let Some(value) = self.expose_hits {
            result.expose_hits = value;
        }
        if let Some(value) = self.expose_cache_status {
            result.expose_cache_status = value;
        }
        if let Some(value) = self.expose_resident_age {
            result.expose_resident_age = value;
        }
        if let Some(value) = self.expose_only_hits {
            result.expose_only_hits = value;
        }
        result.validate()?;
        Ok(result)
    }
}
#[derive(Debug, Clone, Serialize)]
pub struct ScopeView {
    pub entries: usize,
    pub resident_bytes: usize,
    pub cold_entries: usize,
    pub cold_bytes: u64,
}

#[derive(Default)]
struct Counters {
    hits: AtomicU64,
    misses: AtomicU64,
    bypasses: AtomicU64,
    stored: AtomicU64,
    evictions: AtomicU64,
    expired: AtomicU64,
    rejected_fills: AtomicU64,
    memory_pressure_rejections: AtomicU64,
    hot_eviction_limited: AtomicU64,
    purges: AtomicU64,
    cold_hits: AtomicU64,
    cold_promotions: AtomicU64,
    hot_demotions: AtomicU64,
    cold_evictions: AtomicU64,
    cold_errors: AtomicU64,
    cold_queue_dropped: AtomicU64,
    collapsed_fills: AtomicU64,
    collapse_timeouts: AtomicU64,
    purge_entries: AtomicU64,
    bans_created: AtomicU64,
    bans_removed: AtomicU64,
    ban_matches: AtomicU64,
    proactive_scheduled: AtomicU64,
    proactive_started: AtomicU64,
    proactive_skipped: AtomicU64,
}
#[derive(Debug, Clone, Serialize)]
pub struct View {
    pub hits: u64,
    pub misses: u64,
    pub bypasses: u64,
    pub stored: u64,
    pub evictions: u64,
    pub expired: u64,
    pub rejected_fills: u64,
    pub memory_pressure_rejections: u64,
    pub hot_eviction_limited: u64,
    pub purges: u64,
    pub entries: usize,
    /// Compatibility alias for HOT allocated/charged bytes.
    pub resident_bytes: usize,
    pub hot_logical_bytes: usize,
    pub hot_allocated_bytes: usize,
    pub hot_limit_bytes: usize,
    pub transient_limit_bytes: usize,
    pub cold_queue_limit_bytes: usize,
    pub cold_entries: usize,
    pub cold_bytes: u64,
    pub cold_limit_bytes: u64,
    pub cold_limit_entries: usize,
    pub cold_hits: u64,
    pub cold_promotions: u64,
    pub hot_demotions: u64,
    pub cold_evictions: u64,
    pub cold_errors: u64,
    pub cold_queue_dropped: u64,
    pub collapsed_fills: u64,
    pub collapse_timeouts: u64,
    pub collapse_waiters: u64,
    pub purge_entries: u64,
    pub bans_created: u64,
    pub bans_removed: u64,
    pub ban_matches: u64,
    pub active_bans: usize,
    pub proactive_scheduled: u64,
    pub proactive_started: u64,
    pub proactive_skipped: u64,
    pub proactive_inflight: u64,
    pub fills_active: usize,
    /// Bytes currently allocated by in-progress response cache fills.
    pub fill_bytes_active: u64,
    /// Demoted objects accepted by the bounded cold-writer queue.
    pub cold_queue_items: u64,
    pub cold_queue_bytes: u64,
    /// Body bytes currently owned by the cold writer after leaving the queue.
    pub cold_write_bytes_active: u64,
    /// Full cold bodies currently read into RAM for promotion.
    pub cold_read_bytes_active: u64,
    /// RustProxy-accounted cache RAM outside the published hot store.
    pub transient_bytes: u64,
    pub hit_ratio: f64,
}
#[derive(Debug, Clone, Default, Serialize)]
pub struct DomainCounters {
    pub hits: u64,
    pub misses: u64,
    pub bypasses: u64,
    pub stored: u64,
    pub saved_body_bytes: u64,
    pub reasons: BTreeMap<String, u64>,
}