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!(
            self.varnish_grace_seconds <= 604_800,
            "cache.varnish_grace_seconds must be 0..604800"
        );
        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) {
        self.annotate_internal(headers, outcome, hits, ttl as i64, None, false, None);
    }

    pub fn annotate_reason(
        &self,
        headers: &mut HeaderMap,
        outcome: &'static str,
        hits: u64,
        ttl: u64,
        reason: &'static str,
    ) {
        self.annotate_internal(
            headers,
            outcome,
            hits,
            ttl as i64,
            Some(reason),
            false,
            None,
        );
    }

    pub fn annotate_reason_transformed(
        &self,
        headers: &mut HeaderMap,
        outcome: &'static str,
        hits: u64,
        ttl: u64,
        reason: &'static str,
        transformed: bool,
    ) {
        self.annotate_internal(
            headers,
            outcome,
            hits,
            ttl as i64,
            Some(reason),
            transformed,
            None,
        );
    }

    pub fn annotate_reason_transformed_freshness(
        &self,
        headers: &mut HeaderMap,
        outcome: &'static str,
        hits: u64,
        freshness_ttl: i64,
        reason: &'static str,
        transformed: bool,
    ) {
        self.annotate_internal(
            headers,
            outcome,
            hits,
            freshness_ttl,
            Some(reason),
            transformed,
            None,
        );
    }

    pub fn annotate_reason_transformed_forwarded(
        &self,
        headers: &mut HeaderMap,
        outcome: &'static str,
        hits: u64,
        ttl: u64,
        reason: &'static str,
        transformed: bool,
        forward: &'static str,
        forward_status: Option<StatusCode>,
    ) {
        self.annotate_internal(
            headers,
            outcome,
            hits,
            ttl as i64,
            Some(reason),
            transformed,
            Some((forward, forward_status)),
        );
    }

    fn annotate_internal(
        &self,
        headers: &mut HeaderMap,
        outcome: &'static str,
        hits: u64,
        ttl: i64,
        reason: Option<&'static str>,
        transformed: bool,
        forwarded: Option<(&'static str, Option<StatusCode>)>,
    ) {
        if !self.enabled {
            return;
        }
        if let Some(value) = self
            .via_header
            .as_deref()
            .and_then(crate::settings::cached_header_value)
        {
            headers.append(http::header::VIA, value);
        }
        if self.expose_only_hits && outcome != "HIT" {
            return;
        }
        if self.expose_status {
            insert_cache_diagnostic(
                headers,
                "x-cache",
                "x-upstream-cache",
                HeaderValue::from_static(outcome),
            );
            if let Some(reason) = reason {
                insert_cache_diagnostic(
                    headers,
                    "x-cache-reason",
                    "x-upstream-cache-reason",
                    HeaderValue::from_static(reason),
                );
            }
        }
        if self.expose_hits {
            insert_cache_diagnostic(
                headers,
                "x-cache-hits",
                "x-upstream-cache-hits",
                HeaderValue::from(hits),
            );
        }
        if self.expose_cache_status {
            let forwarded = forwarded.or_else(|| {
                matches!(
                    reason,
                    Some("cache_revalidated" | "cache_revalidated_uncached")
                )
                .then_some(("stale", Some(StatusCode::NOT_MODIFIED)))
            });
            use std::fmt::Write as _;
            let mut value = String::with_capacity(96);
            value.push_str("RustProxy; ");
            if let Some((why, status)) = forwarded {
                let _ = write!(value, "fwd={why}");
                if let Some(status) = status {
                    let _ = write!(value, "; fwd-status={}", status.as_u16());
                }
            } else {
                match outcome {
                    "HIT" => {
                        let _ = write!(value, "hit; ttl={ttl}");
                    }
                    "MISS" => value.push_str("fwd=miss"),
                    "BYPASS" if reason == Some("request_method") => value.push_str("fwd=method"),
                    _ => value.push_str("fwd=bypass"),
                }
            }
            if let Some(reason) = reason {
                let _ = write!(value, "; detail=\"{reason}\"");
            }
            if transformed {
                value.push_str("; transformed");
            }
            headers.append(
                ::http::header::CACHE_STATUS,
                HeaderValue::from_maybe_shared(bytes::Bytes::from(value))
                    .expect("generated Cache-Status member"),
            );
        }
    }

    pub fn annotate_resident_age(&self, headers: &mut HeaderMap, resident_age: u64) {
        if self.enabled && self.expose_resident_age {
            insert_cache_diagnostic(
                headers,
                "x-cache-resident-age",
                "x-upstream-cache-resident-age",
                HeaderValue::from(resident_age),
            );
        }
    }
}

fn insert_cache_diagnostic(
    headers: &mut HeaderMap,
    name: &'static str,
    upstream_name: &'static str,
    value: HeaderValue,
) {
    let name = http::HeaderName::from_static(name);
    if headers.contains_key(&name) {
        let upstream_values: Vec<HeaderValue> = headers.get_all(&name).iter().cloned().collect();
        let upstream_name = http::HeaderName::from_static(upstream_name);
        for upstream_value in upstream_values {
            headers.append(&upstream_name, upstream_value);
        }
    }
    headers.insert(name, 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(_)))
}

#[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)
            }
        })
    }
}

#[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>,
    pub unsafe_force: UnsafeForce,
}
impl Overrides {
    pub fn resolve(&self, global: &Settings) -> Result<Settings> {
        self.unsafe_force.validate()?;
        let mut result = global.clone();
        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,
    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,
    pub fill_bytes_active: u64,
    pub cold_queue_items: u64,
    pub cold_queue_bytes: u64,
    pub cold_write_bytes_active: u64,
    pub cold_read_bytes_active: u64,
    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>,
}