lean-ctx-engine 3.12.2

//! Telemetry and metrics collection following OpenTelemetry GenAI conventions.
//!
//! Provides zero-allocation metrics collection with a short consistency lock
//! around tool-call counters so daily snapshots cannot lose partial updates:
//! - Token usage (input, output, saved, compression ratio)
//! - Tool call latency and success rates
//! - Search quality metrics (latency, result counts)
//! - Embedding inference performance
//! - Cache hit/miss rates
//!
//! Naming follows the OpenTelemetry GenAI Semantic Conventions:
//! <https://opentelemetry.io/docs/specs/semconv/gen-ai/>

use std::collections::BTreeMap;
use std::sync::OnceLock;
use std::sync::atomic::{AtomicU64, Ordering};
use std::time::Instant;

static METRICS: OnceLock<Metrics> = OnceLock::new();

pub(crate) const TOOL_LATENCY_BUCKET_UPPER_MS: [u64; 9] =
    [10, 50, 100, 250, 500, 1_000, 5_000, 60_000, i64::MAX as u64];

/// Distinct (tool, failure template) pairs one process keeps.
pub(crate) const MAX_FAILURE_TEMPLATES: usize = 256;

/// Calls, failures and summed latency of one tool since process start.
#[derive(Debug, Clone, Copy, Default, PartialEq, Eq)]
pub(crate) struct ToolCallCounter {
    pub calls: u64,
    pub failures: u64,
    pub latency_us: u64,
    /// Failures by [`crate::core::telemetry_failure::FAILURE_KINDS`] index.
    pub failure_kinds: [u64; crate::core::telemetry_failure::FAILURE_KINDS.len()],
    /// Class of the most recent call's failure; `None` after a success.
    pub last_failure: Option<crate::core::telemetry_failure::FailureKind>,
    /// Calls made right after a failed call of the same tool, and how many
    /// of those failed again.
    pub retries: u64,
    pub retry_failures: u64,
}

/// How the agent session served by this process went so far, from the
/// in-process counters only. Feeds the session-end tally in
/// `core::telemetry_features`; nothing here leaves the machine as is.
#[derive(Debug, Clone, Default, PartialEq, Eq)]
pub(crate) struct SessionOutcome {
    pub calls: u64,
    pub failures: u64,
    /// Failure classes of tools whose last call failed.
    pub unresolved: Vec<crate::core::telemetry_failure::FailureKind>,
    pub retries: u64,
    pub retry_failures: u64,
}

pub fn global_metrics() -> &'static Metrics {
    METRICS.get_or_init(Metrics::new)
}

#[derive(Debug)]
pub struct Metrics {
    /// Guards the tool-call counters so a daily snapshot never sees a
    /// half-applied call, and holds the per-tool counts. Keys are the static
    /// names of the built-in tool registry, never caller-supplied strings.
    tool_call_consistency: std::sync::Mutex<BTreeMap<&'static str, ToolCallCounter>>,
    /// Scrubbed failure templates per built-in tool since process start.
    failure_templates: std::sync::Mutex<BTreeMap<(&'static str, String), u64>>,
    // gen_ai.usage.input_tokens / gen_ai.usage.output_tokens
    pub tokens_input: AtomicU64,
    pub tokens_output: AtomicU64,
    pub tokens_saved: AtomicU64,

    pub tool_calls_total: AtomicU64,
    pub tool_calls_error: AtomicU64,
    pub tool_call_latency_sum_us: AtomicU64,
    tool_call_latency_buckets: [AtomicU64; TOOL_LATENCY_BUCKET_UPPER_MS.len()],

    pub search_queries_total: AtomicU64,
    pub search_latency_sum_us: AtomicU64,
    pub search_results_total: AtomicU64,

    pub embedding_inferences_total: AtomicU64,
    pub embedding_latency_sum_us: AtomicU64,
    pub embedding_tokens_total: AtomicU64,

    pub cache_hits: AtomicU64,
    pub cache_misses: AtomicU64,

    pub compression_calls: AtomicU64,
    pub compression_input_bytes: AtomicU64,
    pub compression_output_bytes: AtomicU64,

    pub session_start: Instant,
}

impl Default for Metrics {
    fn default() -> Self {
        Self {
            tool_call_consistency: std::sync::Mutex::new(BTreeMap::new()),
            failure_templates: std::sync::Mutex::new(BTreeMap::new()),
            tokens_input: AtomicU64::new(0),
            tokens_output: AtomicU64::new(0),
            tokens_saved: AtomicU64::new(0),
            tool_calls_total: AtomicU64::new(0),
            tool_calls_error: AtomicU64::new(0),
            tool_call_latency_sum_us: AtomicU64::new(0),
            tool_call_latency_buckets: std::array::from_fn(|_| AtomicU64::new(0)),
            search_queries_total: AtomicU64::new(0),
            search_latency_sum_us: AtomicU64::new(0),
            search_results_total: AtomicU64::new(0),
            embedding_inferences_total: AtomicU64::new(0),
            embedding_latency_sum_us: AtomicU64::new(0),
            embedding_tokens_total: AtomicU64::new(0),
            cache_hits: AtomicU64::new(0),
            cache_misses: AtomicU64::new(0),
            compression_calls: AtomicU64::new(0),
            compression_input_bytes: AtomicU64::new(0),
            compression_output_bytes: AtomicU64::new(0),
            session_start: Instant::now(),
        }
    }
}

impl Metrics {
    pub fn new() -> Self {
        Self::default()
    }

    pub fn record_tool_call(&self, latency_us: u64, success: bool) {
        let guard = self
            .tool_call_consistency
            .lock()
            .unwrap_or_else(std::sync::PoisonError::into_inner);
        self.record_tool_call_locked(latency_us, success);
        drop(guard);
    }

    /// Record a call of a built-in tool: the totals and the tool's own counter
    /// move together under one lock.
    pub fn record_named_tool_call(&self, tool: &'static str, latency_us: u64, success: bool) {
        self.record_named_tool_outcome(
            tool,
            latency_us,
            (!success).then_some(crate::core::telemetry_failure::FailureKind::Other),
        );
    }

    /// Like [`Self::record_named_tool_call`], with the class of a failure.
    pub fn record_named_tool_outcome(
        &self,
        tool: &'static str,
        latency_us: u64,
        failure: Option<crate::core::telemetry_failure::FailureKind>,
    ) {
        let mut per_tool = self
            .tool_call_consistency
            .lock()
            .unwrap_or_else(std::sync::PoisonError::into_inner);
        self.record_tool_call_locked(latency_us, failure.is_none());
        let counter = per_tool.entry(tool).or_default();
        counter.calls = counter.calls.saturating_add(1);
        counter.latency_us = counter.latency_us.saturating_add(latency_us);
        if counter.last_failure.is_some() {
            counter.retries = counter.retries.saturating_add(1);
            if failure.is_some() {
                counter.retry_failures = counter.retry_failures.saturating_add(1);
            }
        }
        counter.last_failure = failure;
        if let Some(kind) = failure {
            counter.failures = counter.failures.saturating_add(1);
            let slot = &mut counter.failure_kinds[kind.index()];
            *slot = slot.saturating_add(1);
        }
    }

    /// Like [`Self::record_named_tool_outcome`], also counting the failure's
    /// scrubbed template. Templates are bounded per process.
    pub fn record_named_tool_failure(
        &self,
        tool: &'static str,
        latency_us: u64,
        failure: Option<crate::core::telemetry_failure::Failure>,
    ) {
        let template = failure
            .as_ref()
            .and_then(|failure| failure.template.clone());
        self.record_named_tool_outcome(tool, latency_us, failure.map(|failure| failure.kind));
        let Some(template) = template else { return };
        let mut templates = self
            .failure_templates
            .lock()
            .unwrap_or_else(std::sync::PoisonError::into_inner);
        let key = (tool, template);
        if templates.len() < MAX_FAILURE_TEMPLATES || templates.contains_key(&key) {
            let count = templates.entry(key).or_default();
            *count = count.saturating_add(1);
        }
    }

    fn record_tool_call_locked(&self, latency_us: u64, success: bool) {
        self.tool_calls_total.fetch_add(1, Ordering::Relaxed);
        self.tool_call_latency_sum_us
            .fetch_add(latency_us, Ordering::Relaxed);
        let latency_ms = latency_us / 1_000;
        let bucket = TOOL_LATENCY_BUCKET_UPPER_MS
            .iter()
            .position(|upper| latency_ms <= *upper)
            .unwrap_or(TOOL_LATENCY_BUCKET_UPPER_MS.len() - 1);
        self.tool_call_latency_buckets[bucket].fetch_add(1, Ordering::Relaxed);
        if !success {
            self.tool_calls_error.fetch_add(1, Ordering::Relaxed);
        }
    }

    pub fn record_tokens(&self, input: u64, output: u64, saved: u64) {
        self.tokens_input.fetch_add(input, Ordering::Relaxed);
        self.tokens_output.fetch_add(output, Ordering::Relaxed);
        self.tokens_saved.fetch_add(saved, Ordering::Relaxed);
    }

    pub fn record_search(&self, latency_us: u64, result_count: u64) {
        self.search_queries_total.fetch_add(1, Ordering::Relaxed);
        self.search_latency_sum_us
            .fetch_add(latency_us, Ordering::Relaxed);
        self.search_results_total
            .fetch_add(result_count, Ordering::Relaxed);
    }

    pub fn record_embedding(&self, latency_us: u64, token_count: u64) {
        self.embedding_inferences_total
            .fetch_add(1, Ordering::Relaxed);
        self.embedding_latency_sum_us
            .fetch_add(latency_us, Ordering::Relaxed);
        self.embedding_tokens_total
            .fetch_add(token_count, Ordering::Relaxed);
    }

    pub fn record_cache(&self, hit: bool) {
        if hit {
            self.cache_hits.fetch_add(1, Ordering::Relaxed);
        } else {
            self.cache_misses.fetch_add(1, Ordering::Relaxed);
        }
    }

    pub fn record_compression(&self, input_bytes: u64, output_bytes: u64) {
        self.compression_calls.fetch_add(1, Ordering::Relaxed);
        self.compression_input_bytes
            .fetch_add(input_bytes, Ordering::Relaxed);
        self.compression_output_bytes
            .fetch_add(output_bytes, Ordering::Relaxed);
    }

    pub fn snapshot(&self) -> MetricsSnapshot {
        let tool_calls = self.tool_calls_total.load(Ordering::Relaxed);
        let tool_latency = self.tool_call_latency_sum_us.load(Ordering::Relaxed);
        let cache_hits = self.cache_hits.load(Ordering::Relaxed);
        let cache_misses = self.cache_misses.load(Ordering::Relaxed);
        let comp_in = self.compression_input_bytes.load(Ordering::Relaxed);
        let comp_out = self.compression_output_bytes.load(Ordering::Relaxed);

        MetricsSnapshot {
            tokens_input: self.tokens_input.load(Ordering::Relaxed),
            tokens_output: self.tokens_output.load(Ordering::Relaxed),
            tokens_saved: self.tokens_saved.load(Ordering::Relaxed),
            tool_calls_total: tool_calls,
            tool_calls_error: self.tool_calls_error.load(Ordering::Relaxed),
            tool_call_avg_latency_ms: if tool_calls > 0 {
                tool_latency as f64 / tool_calls as f64 / 1000.0
            } else {
                0.0
            },
            search_queries_total: self.search_queries_total.load(Ordering::Relaxed),
            search_avg_latency_ms: {
                let q = self.search_queries_total.load(Ordering::Relaxed);
                if q > 0 {
                    self.search_latency_sum_us.load(Ordering::Relaxed) as f64 / q as f64 / 1000.0
                } else {
                    0.0
                }
            },
            embedding_inferences: self.embedding_inferences_total.load(Ordering::Relaxed),
            embedding_avg_latency_ms: {
                let e = self.embedding_inferences_total.load(Ordering::Relaxed);
                if e > 0 {
                    self.embedding_latency_sum_us.load(Ordering::Relaxed) as f64 / e as f64 / 1000.0
                } else {
                    0.0
                }
            },
            cache_hit_rate: if cache_hits + cache_misses > 0 {
                cache_hits as f64 / (cache_hits + cache_misses) as f64
            } else {
                0.0
            },
            compression_ratio: if comp_in > 0 {
                1.0 - (comp_out as f64 / comp_in as f64)
            } else {
                0.0
            },
            session_uptime_secs: self.session_start.elapsed().as_secs(),
        }
    }

    pub(crate) fn daily_telemetry_snapshot(&self) -> DailyTelemetrySnapshot {
        let per_tool = self
            .tool_call_consistency
            .lock()
            .unwrap_or_else(std::sync::PoisonError::into_inner);
        DailyTelemetrySnapshot {
            per_tool: per_tool.clone(),
            tool_calls: self.tool_calls_total.load(Ordering::Relaxed),
            tool_failures: self.tool_calls_error.load(Ordering::Relaxed),
            tool_latency_buckets: std::array::from_fn(|index| {
                self.tool_call_latency_buckets[index].load(Ordering::Relaxed)
            }),
            session_uptime_secs: self.session_start.elapsed().as_secs(),
            tokens_input: self.tokens_input.load(Ordering::Relaxed),
            tokens_output: self.tokens_output.load(Ordering::Relaxed),
            failure_templates: self
                .failure_templates
                .lock()
                .unwrap_or_else(std::sync::PoisonError::into_inner)
                .clone(),
        }
    }

    pub(crate) fn session_outcome(&self) -> SessionOutcome {
        let per_tool = self
            .tool_call_consistency
            .lock()
            .unwrap_or_else(std::sync::PoisonError::into_inner);
        SessionOutcome {
            calls: self.tool_calls_total.load(Ordering::Relaxed),
            failures: self.tool_calls_error.load(Ordering::Relaxed),
            unresolved: per_tool.values().filter_map(|c| c.last_failure).collect(),
            retries: per_tool.values().map(|c| c.retries).sum(),
            retry_failures: per_tool.values().map(|c| c.retry_failures).sum(),
        }
    }

    /// Format as OpenTelemetry-compatible attributes for logging.
    pub fn to_otel_attributes(&self) -> Vec<(&'static str, String)> {
        let snap = self.snapshot();
        vec![
            ("gen_ai.usage.input_tokens", snap.tokens_input.to_string()),
            ("gen_ai.usage.output_tokens", snap.tokens_output.to_string()),
            ("lean_ctx.tokens.saved", snap.tokens_saved.to_string()),
            (
                "lean_ctx.tool.calls.total",
                snap.tool_calls_total.to_string(),
            ),
            (
                "lean_ctx.tool.calls.error",
                snap.tool_calls_error.to_string(),
            ),
            (
                "lean_ctx.tool.latency_avg_ms",
                format!("{:.2}", snap.tool_call_avg_latency_ms),
            ),
            (
                "lean_ctx.search.queries",
                snap.search_queries_total.to_string(),
            ),
            (
                "lean_ctx.search.latency_avg_ms",
                format!("{:.2}", snap.search_avg_latency_ms),
            ),
            (
                "lean_ctx.embedding.inferences",
                snap.embedding_inferences.to_string(),
            ),
            (
                "lean_ctx.embedding.latency_avg_ms",
                format!("{:.2}", snap.embedding_avg_latency_ms),
            ),
            (
                "lean_ctx.cache.hit_rate",
                format!("{:.4}", snap.cache_hit_rate),
            ),
            (
                "lean_ctx.compression.ratio",
                format!("{:.4}", snap.compression_ratio),
            ),
            (
                "lean_ctx.session.uptime_secs",
                snap.session_uptime_secs.to_string(),
            ),
        ]
    }
}

#[derive(Debug, Clone)]
pub(crate) struct DailyTelemetrySnapshot {
    pub tool_calls: u64,
    pub tool_failures: u64,
    pub tool_latency_buckets: [u64; TOOL_LATENCY_BUCKET_UPPER_MS.len()],
    pub session_uptime_secs: u64,
    pub per_tool: BTreeMap<&'static str, ToolCallCounter>,
    /// Tokens tool output would have cost uncompressed vs. what was delivered.
    pub tokens_input: u64,
    pub tokens_output: u64,
    /// Scrubbed failure templates by (tool, template).
    pub failure_templates: BTreeMap<(&'static str, String), u64>,
}

/// Point-in-time snapshot of all metrics.
#[derive(Debug, Clone)]
pub struct MetricsSnapshot {
    pub tokens_input: u64,
    pub tokens_output: u64,
    pub tokens_saved: u64,
    pub tool_calls_total: u64,
    pub tool_calls_error: u64,
    pub tool_call_avg_latency_ms: f64,
    pub search_queries_total: u64,
    pub search_avg_latency_ms: f64,
    pub embedding_inferences: u64,
    pub embedding_avg_latency_ms: f64,
    pub cache_hit_rate: f64,
    pub compression_ratio: f64,
    pub session_uptime_secs: u64,
}

impl MetricsSnapshot {
    pub fn to_compact_string(&self) -> String {
        format!(
            "tok={}/{}/{} calls={}/{} search={} embed={} cache={:.0}% comp={:.0}% up={}s",
            self.tokens_input,
            self.tokens_output,
            self.tokens_saved,
            self.tool_calls_total,
            self.tool_calls_error,
            self.search_queries_total,
            self.embedding_inferences,
            self.cache_hit_rate * 100.0,
            self.compression_ratio * 100.0,
            self.session_uptime_secs,
        )
    }

    pub fn to_json(&self) -> String {
        serde_json::json!({
            "gen_ai": {
                "usage": {
                    "input_tokens": self.tokens_input,
                    "output_tokens": self.tokens_output,
                }
            },
            "lean_ctx": {
                "tokens": { "saved": self.tokens_saved },
                "tool": {
                    "calls_total": self.tool_calls_total,
                    "calls_error": self.tool_calls_error,
                    "avg_latency_ms": self.tool_call_avg_latency_ms,
                },
                "search": {
                    "queries": self.search_queries_total,
                    "avg_latency_ms": self.search_avg_latency_ms,
                },
                "embedding": {
                    "inferences": self.embedding_inferences,
                    "avg_latency_ms": self.embedding_avg_latency_ms,
                },
                "cache": { "hit_rate": self.cache_hit_rate },
                "compression": { "ratio": self.compression_ratio },
                "session": { "uptime_secs": self.session_uptime_secs },
            }
        })
        .to_string()
    }
}

/// RAII guard that records tool call latency on drop.
pub struct ToolCallTimer {
    start: Instant,
    tool_name: &'static str,
}

impl ToolCallTimer {
    pub fn new(tool_name: &'static str) -> Self {
        Self {
            start: Instant::now(),
            tool_name,
        }
    }

    pub fn finish(self, success: bool) {
        let elapsed = self.start.elapsed();
        let us = elapsed.as_micros() as u64;
        global_metrics().record_tool_call(us, success);
        tracing::debug!(
            tool = self.tool_name,
            latency_ms = elapsed.as_millis() as u64,
            success,
            "tool_call"
        );
    }
}

// ---------------------------------------------------------------------------
// Prometheus text format export (Zero-PII)
// ---------------------------------------------------------------------------

impl Metrics {
    pub fn to_prometheus(&self) -> String {
        let snap = self.snapshot();

        let mut lines = Vec::with_capacity(32);

        lines.push("# HELP lean_ctx_tokens_saved_total Total tokens saved by compression".into());
        lines.push("# TYPE lean_ctx_tokens_saved_total counter".into());
        lines.push(format!("lean_ctx_tokens_saved_total {}", snap.tokens_saved));

        lines.push("# HELP lean_ctx_tokens_input_total Total input tokens processed".into());
        lines.push("# TYPE lean_ctx_tokens_input_total counter".into());
        lines.push(format!("lean_ctx_tokens_input_total {}", snap.tokens_input));

        lines.push("# HELP lean_ctx_tokens_output_total Total output tokens generated".into());
        lines.push("# TYPE lean_ctx_tokens_output_total counter".into());
        lines.push(format!(
            "lean_ctx_tokens_output_total {}",
            snap.tokens_output
        ));

        lines.push("# HELP lean_ctx_compression_ratio Current compression ratio".into());
        lines.push("# TYPE lean_ctx_compression_ratio gauge".into());
        lines.push(format!(
            "lean_ctx_compression_ratio {:.4}",
            snap.compression_ratio
        ));

        lines.push("# HELP lean_ctx_tool_calls_total Total tool calls".into());
        lines.push("# TYPE lean_ctx_tool_calls_total counter".into());
        lines.push(format!(
            "lean_ctx_tool_calls_total {}",
            snap.tool_calls_total
        ));

        lines.push("# HELP lean_ctx_tool_calls_error_total Total failed tool calls".into());
        lines.push("# TYPE lean_ctx_tool_calls_error_total counter".into());
        lines.push(format!(
            "lean_ctx_tool_calls_error_total {}",
            snap.tool_calls_error
        ));

        lines.push("# HELP lean_ctx_cache_hit_rate Cache hit rate (0-1)".into());
        lines.push("# TYPE lean_ctx_cache_hit_rate gauge".into());
        lines.push(format!(
            "lean_ctx_cache_hit_rate {:.4}",
            snap.cache_hit_rate
        ));

        let verify_snap = crate::core::output_verification::stats_snapshot();
        lines.push("# HELP lean_ctx_verification_pass_total Total verification passes".into());
        lines.push("# TYPE lean_ctx_verification_pass_total counter".into());
        lines.push(format!(
            "lean_ctx_verification_pass_total {}",
            verify_snap.pass
        ));

        lines.push("# HELP lean_ctx_verification_warn_total Total verification warnings".into());
        lines.push("# TYPE lean_ctx_verification_warn_total counter".into());
        lines.push(format!(
            "lean_ctx_verification_warn_total {}",
            verify_snap.warn_items
        ));

        lines.push(
            "# HELP lean_ctx_verification_warn_runs_total Total runs with verification warnings"
                .into(),
        );
        lines.push("# TYPE lean_ctx_verification_warn_runs_total counter".into());
        lines.push(format!(
            "lean_ctx_verification_warn_runs_total {}",
            verify_snap.warn_runs
        ));

        lines.push("# HELP lean_ctx_verification_pass_rate Verification pass rate".into());
        lines.push("# TYPE lean_ctx_verification_pass_rate gauge".into());
        lines.push(format!(
            "lean_ctx_verification_pass_rate {:.4}",
            verify_snap.pass_rate
        ));

        lines.push("# HELP lean_ctx_info_loss_score Average info loss score (0..1)".into());
        lines.push("# TYPE lean_ctx_info_loss_score gauge".into());
        lines.push(format!(
            "lean_ctx_info_loss_score {:.6}",
            verify_snap.avg_info_loss_score
        ));

        lines.push("# HELP lean_ctx_session_uptime_seconds Session uptime in seconds".into());
        lines.push("# TYPE lean_ctx_session_uptime_seconds gauge".into());
        lines.push(format!(
            "lean_ctx_session_uptime_seconds {}",
            snap.session_uptime_secs
        ));

        // Verified savings from the hash-chained ledger (GL #401): the honest
        // FinOps numbers — measured baselines only, no counterfactual factors.
        let (ledger_tokens, ledger_usd) = ledger_totals_cached();
        lines.push(
            "# HELP lean_ctx_ledger_tokens_saved_total Verified tokens saved (signed ledger)"
                .into(),
        );
        lines.push("# TYPE lean_ctx_ledger_tokens_saved_total counter".into());
        lines.push(format!(
            "lean_ctx_ledger_tokens_saved_total {ledger_tokens}"
        ));

        lines.push(
            "# HELP lean_ctx_cost_saved_usd_total Verified cost saved in USD (signed ledger)"
                .into(),
        );
        lines.push("# TYPE lean_ctx_cost_saved_usd_total counter".into());
        lines.push(format!("lean_ctx_cost_saved_usd_total {ledger_usd:.4}"));

        // Resource info metric (GL #401): one constant series carrying the
        // drill-down tags (project, profile, role, model, version) in the
        // kube-state-metrics `_info` idiom. Deliberately a single series per
        // process — per-metric label combinations would explode Datadog
        // custom-metric cardinality (and the customer's bill).
        lines.push("# HELP lean_ctx_info Deployment metadata for tag joins".into());
        lines.push("# TYPE lean_ctx_info gauge".into());
        lines.push(format!("lean_ctx_info{{{}}} 1", info_labels()));

        lines.join("\n") + "\n"
    }
}

/// Escape a Prometheus label value (backslash, double quote, newline).
fn escape_label(v: &str) -> String {
    v.replace('\\', "\\\\")
        .replace('"', "\\\"")
        .replace('\n', "\\n")
}

/// Deployment tags shared by the Prometheus `lean_ctx_info` series and the
/// Datadog push exporter. Values are bounded: project is the cwd basename
/// (never the full path), model/profile/role come from bounded registries —
/// cardinality stays at one series per running process.
pub fn info_tags() -> Vec<(&'static str, String)> {
    let project = std::env::current_dir()
        .ok()
        .and_then(|p| p.file_name().map(|n| n.to_string_lossy().into_owned()))
        .unwrap_or_else(|| "unknown".to_string());
    let model = crate::core::host_state::load_detected_model()
        .map_or_else(|| "unknown".to_string(), |(name, _)| name);
    vec![
        ("project", project),
        ("profile", crate::core::profiles::active_profile_name()),
        ("agent_role", crate::core::roles::active_role_name()),
        ("model", model),
        ("version", env!("CARGO_PKG_VERSION").to_string()),
    ]
}

/// The `lean_ctx_info` label set in Prometheus exposition syntax.
fn info_labels() -> String {
    info_tags()
        .iter()
        .map(|(k, v)| format!("{k}=\"{}\"", escape_label(v)))
        .collect::<Vec<_>>()
        .join(",")
}

/// Ledger totals with a 30 s cache: `summarize()` streams the whole JSONL —
/// fine once, wasteful for per-minute scrapes hitting `/metrics`.
pub(crate) fn ledger_totals_cached() -> (u64, f64) {
    use std::sync::Mutex;
    use std::time::{Duration, Instant};
    static CACHE: Mutex<Option<(Instant, (u64, f64))>> = Mutex::new(None);

    let Ok(mut guard) = CACHE.lock() else {
        return (0, 0.0);
    };
    if let Some((at, totals)) = *guard
        && at.elapsed() < Duration::from_secs(30)
    {
        return totals;
    }
    let summary = crate::core::savings_ledger::summary();
    let totals = (summary.net_saved_tokens(), summary.saved_usd);
    *guard = Some((Instant::now(), totals));
    totals
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn record_tool_call() {
        let m = Metrics::new();
        m.record_tool_call(5000, true);
        m.record_tool_call(3000, false);

        let snap = m.snapshot();
        assert_eq!(snap.tool_calls_total, 2);
        assert_eq!(snap.tool_calls_error, 1);
        assert!(snap.tool_call_avg_latency_ms > 0.0);
    }

    #[test]
    fn named_tool_call_moves_totals_and_per_tool_counter_together() {
        let m = Metrics::new();
        m.record_named_tool_call("ctx_read", 1_000, true);
        m.record_named_tool_call("ctx_read", 2_000, false);
        m.record_named_tool_call("ctx_shell", 3_000, true);

        let snap = m.daily_telemetry_snapshot();
        assert_eq!(snap.tool_calls, 3);
        assert_eq!(snap.tool_failures, 1);
        assert_eq!(
            snap.per_tool.get("ctx_read"),
            Some(&ToolCallCounter {
                calls: 2,
                failures: 1,
                latency_us: 3_000,
                failure_kinds: {
                    let mut kinds = [0; crate::core::telemetry_failure::FAILURE_KINDS.len()];
                    kinds[crate::core::telemetry_failure::FailureKind::Other.index()] = 1;
                    kinds
                },
                last_failure: Some(crate::core::telemetry_failure::FailureKind::Other),
                retries: 0,
                retry_failures: 0,
            })
        );
        assert_eq!(
            snap.per_tool.get("ctx_shell"),
            Some(&ToolCallCounter {
                calls: 1,
                failures: 0,
                latency_us: 3_000,
                ..ToolCallCounter::default()
            })
        );
    }

    #[test]
    fn session_outcome_tracks_retries_and_unresolved_tools() {
        use crate::core::telemetry_failure::FailureKind;
        let m = Metrics::new();
        m.record_named_tool_outcome("ctx_read", 1, Some(FailureKind::NotFound));
        m.record_named_tool_outcome("ctx_read", 1, Some(FailureKind::NotFound));
        m.record_named_tool_outcome("ctx_read", 1, None);
        m.record_named_tool_outcome("ctx_shell", 1, None);
        m.record_named_tool_outcome("ctx_shell", 1, Some(FailureKind::Timeout));

        assert_eq!(
            m.session_outcome(),
            SessionOutcome {
                calls: 5,
                failures: 3,
                unresolved: vec![FailureKind::Timeout],
                retries: 2,
                retry_failures: 1,
            }
        );
    }

    #[test]
    fn concurrent_daily_snapshot_never_observes_partial_tool_call() {
        let metrics = std::sync::Arc::new(Metrics::new());
        let writers = (0..4)
            .map(|worker| {
                let metrics = std::sync::Arc::clone(&metrics);
                std::thread::spawn(move || {
                    for call in 0..1_000 {
                        metrics.record_tool_call((call + 1) * 1_000, (call + worker) % 3 != 0);
                    }
                })
            })
            .collect::<Vec<_>>();
        while writers.iter().any(|writer| !writer.is_finished()) {
            let snapshot = metrics.daily_telemetry_snapshot();
            assert_eq!(
                snapshot.tool_latency_buckets.iter().sum::<u64>(),
                snapshot.tool_calls
            );
            assert!(snapshot.tool_failures <= snapshot.tool_calls);
        }
        for writer in writers {
            writer.join().expect("writer");
        }
        let snapshot = metrics.daily_telemetry_snapshot();
        assert_eq!(snapshot.tool_calls, 4_000);
        assert_eq!(
            snapshot.tool_latency_buckets.iter().sum::<u64>(),
            snapshot.tool_calls
        );
        assert!(snapshot.tool_failures <= snapshot.tool_calls);
    }

    #[test]
    fn record_tokens() {
        let m = Metrics::new();
        m.record_tokens(100, 50, 200);
        m.record_tokens(150, 75, 300);

        let snap = m.snapshot();
        assert_eq!(snap.tokens_input, 250);
        assert_eq!(snap.tokens_output, 125);
        assert_eq!(snap.tokens_saved, 500);
    }

    #[test]
    fn record_search() {
        let m = Metrics::new();
        m.record_search(2000, 5);
        m.record_search(4000, 3);

        let snap = m.snapshot();
        assert_eq!(snap.search_queries_total, 2);
        assert!((snap.search_avg_latency_ms - 3.0).abs() < 0.01);
    }

    #[test]
    fn cache_hit_rate() {
        let m = Metrics::new();
        m.record_cache(true);
        m.record_cache(true);
        m.record_cache(false);

        let snap = m.snapshot();
        assert!((snap.cache_hit_rate - 0.6667).abs() < 0.01);
    }

    #[test]
    fn compression_ratio() {
        let m = Metrics::new();
        m.record_compression(1000, 200);

        let snap = m.snapshot();
        assert!((snap.compression_ratio - 0.8).abs() < 0.01);
    }

    #[test]
    fn snapshot_compact_string() {
        let m = Metrics::new();
        m.record_tokens(100, 50, 200);
        m.record_tool_call(5000, true);
        let compact = m.snapshot().to_compact_string();
        assert!(compact.contains("tok=100/50/200"));
        assert!(compact.contains("calls=1/0"));
    }

    #[test]
    fn snapshot_json() {
        let m = Metrics::new();
        m.record_tokens(100, 50, 200);
        let json = m.snapshot().to_json();
        let parsed: serde_json::Value = serde_json::from_str(&json).unwrap();
        assert_eq!(parsed["gen_ai"]["usage"]["input_tokens"], 100);
        assert_eq!(parsed["lean_ctx"]["tokens"]["saved"], 200);
    }

    #[test]
    fn otel_attributes() {
        let m = Metrics::new();
        m.record_tokens(100, 50, 200);
        let attrs = m.to_otel_attributes();
        assert!(
            attrs
                .iter()
                .any(|(k, v)| *k == "gen_ai.usage.input_tokens" && v == "100")
        );
    }

    #[test]
    fn global_metrics_singleton() {
        let m1 = global_metrics();
        let m2 = global_metrics();
        assert!(std::ptr::eq(m1, m2));
    }

    #[test]
    fn tool_call_timer() {
        let timer = ToolCallTimer::new("test_tool");
        std::thread::sleep(std::time::Duration::from_millis(5));
        timer.finish(true);
    }
}