//! Utility functions for interacting with any runtime.

use commonware_utils::sync::{Condvar, Mutex};
use futures::task::ArcWake;
use prometheus_client::{encoding::text::encode, registry::Registry as PrometheusRegistry};
use std::{
    any::Any,
    collections::BTreeMap,
    future::Future,
    pin::Pin,
    sync::Arc,
    task::{Context, Poll},
};

commonware_macros::stability_mod!(BETA, pub mod buffer);
pub mod signal;

mod handle;
pub use handle::Handle;
#[commonware_macros::stability(ALPHA)]
pub(crate) use handle::Panicked;
pub(crate) use handle::{Aborter, MetricHandle, Panicker};

mod cell;
pub use cell::Cell as ContextCell;

pub(crate) mod supervision;

/// The execution mode of a task.
#[derive(Copy, Clone, Debug)]
pub enum Execution {
    /// Task runs on a dedicated thread.
    Dedicated,
    /// Task runs on the shared executor. `true` marks short blocking work that should
    /// use the runtime's blocking-friendly pool.
    Shared(bool),
}

impl Default for Execution {
    fn default() -> Self {
        Self::Shared(false)
    }
}

/// Yield control back to the runtime.
pub async fn reschedule() {
    struct Reschedule {
        yielded: bool,
    }

    impl Future for Reschedule {
        type Output = ();

        fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<()> {
            if self.yielded {
                Poll::Ready(())
            } else {
                self.yielded = true;
                cx.waker().wake_by_ref();
                Poll::Pending
            }
        }
    }

    Reschedule { yielded: false }.await
}

fn extract_panic_message(err: &(dyn Any + Send)) -> String {
    err.downcast_ref::<&str>().map_or_else(
        || {
            err.downcast_ref::<String>()
                .map_or_else(|| format!("{err:?}"), |s| s.clone())
        },
        |s| s.to_string(),
    )
}

/// Synchronization primitive that enables a thread to block until a waker delivers a signal.
pub struct Blocker {
    /// Tracks whether a wake-up signal has been delivered (even if wait has not started yet).
    state: Mutex<bool>,
    /// Condvar used to park and resume the thread when the signal flips to true.
    cv: Condvar,
}

impl Blocker {
    /// Create a new [Blocker].
    pub fn new() -> Arc<Self> {
        Arc::new(Self {
            state: Mutex::new(false),
            cv: Condvar::new(),
        })
    }

    /// Block the current thread until a waker delivers a signal.
    pub fn wait(&self) {
        // Use a loop to tolerate spurious wake-ups and only proceed once a real signal arrives.
        let mut signaled = self.state.lock();
        while !*signaled {
            self.cv.wait(&mut signaled);
        }

        // Reset the flag so subsequent waits park again until the next wake signal.
        *signaled = false;
    }
}

impl ArcWake for Blocker {
    fn wake_by_ref(arc_self: &Arc<Self>) {
        // Mark as signaled (and release lock before notifying).
        {
            let mut signaled = arc_self.state.lock();
            *signaled = true;
        }

        // Notify a single waiter so the blocked thread re-checks the flag.
        arc_self.cv.notify_one();
    }
}

#[cfg(any(test, feature = "test-utils"))]
/// Count the number of running tasks whose name starts with the given prefix.
///
/// This function encodes metrics and counts tasks that are currently running
/// (have a value of 1) and whose name starts with the specified prefix.
///
/// This is useful for verifying that all child tasks under a given label hierarchy
/// have been properly shut down.
///
/// # Example
///
/// ```rust
/// use commonware_runtime::{Clock, Metrics, Runner, Spawner, deterministic};
/// use commonware_runtime::utils::count_running_tasks;
/// use std::time::Duration;
///
/// let executor = deterministic::Runner::default();
/// executor.start(|context| async move {
///     // Spawn a task under a labeled context
///     let handle = context.with_label("worker").spawn(|ctx| async move {
///         ctx.sleep(Duration::from_secs(100)).await;
///     });
///
///     // Allow the task to start
///     context.sleep(Duration::from_millis(10)).await;
///
///     // Count running tasks with "worker" prefix
///     let count = count_running_tasks(&context, "worker");
///     assert!(count > 0, "worker task should be running");
///
///     // Abort the task
///     handle.abort();
///     let _ = handle.await;
///     context.sleep(Duration::from_millis(10)).await;
///
///     // Verify task is stopped
///     let count = count_running_tasks(&context, "worker");
///     assert_eq!(count, 0, "worker task should be stopped");
/// });
/// ```
pub fn count_running_tasks(metrics: &impl crate::Metrics, prefix: &str) -> usize {
    let encoded = metrics.encode();
    encoded
        .lines()
        .filter(|line| {
            line.starts_with("runtime_tasks_running{")
                && line.contains("kind=\"Task\"")
                && line.trim_end().ends_with(" 1")
                && line
                    .split("name=\"")
                    .nth(1)
                    .is_some_and(|s| s.split('"').next().unwrap_or("").starts_with(prefix))
        })
        .count()
}

/// Validates that a label matches Prometheus metric name format: `[a-zA-Z][a-zA-Z0-9_]*`.
///
/// # Panics
///
/// Panics if the label is empty, starts with a non-alphabetic character,
/// or contains characters other than `[a-zA-Z0-9_]`.
pub fn validate_label(label: &str) {
    let mut chars = label.chars();
    assert!(
        chars.next().is_some_and(|c| c.is_ascii_alphabetic()),
        "label must start with [a-zA-Z]: {label}"
    );
    assert!(
        chars.all(|c| c.is_ascii_alphanumeric() || c == '_'),
        "label must only contain [a-zA-Z0-9_]: {label}"
    );
}

/// Add an attribute to a sorted attribute list, maintaining sorted order via binary search.
///
/// Returns `true` if the key was new, `false` if it was a duplicate (value overwritten).
pub fn add_attribute(
    attributes: &mut Vec<(String, String)>,
    key: &str,
    value: impl std::fmt::Display,
) -> bool {
    let key_string = key.to_string();
    let value_string = value.to_string();

    match attributes.binary_search_by(|(k, _)| k.cmp(&key_string)) {
        Ok(pos) => {
            attributes[pos].1 = value_string;
            false
        }
        Err(pos) => {
            attributes.insert(pos, (key_string, value_string));
            true
        }
    }
}

/// A writer that groups metrics by family name and deduplicates HELP/TYPE metadata
/// during Prometheus encoding.
///
/// When the same metric is registered across scoped registries (via
/// `Registry::encode`), prometheus_client outputs each scope's metrics
/// separately, interleaving families. This writer collects all lines and
/// regroups them so that every sample for a given metric name appears
/// together with a single HELP/TYPE header.
///
/// Also strips `# EOF` lines so that `Registry::encode` can append exactly one at
/// the end of the combined output.
///
/// Uses "first wins" semantics: keeps the first HELP/TYPE description encountered
/// for each metric name and discards subsequent duplicates.
pub struct MetricEncoder {
    line_buffer: String,
    families: BTreeMap<String, MetricFamily>,
    active_family: Option<String>,
}

#[derive(Default)]
struct MetricFamily {
    help: Option<String>,
    type_line: Option<String>,
    unit: Option<String>,
    metric_type: Option<String>,
    data: Vec<String>,
}

/// OpenMetrics data lines use type-specific suffixes that differ from the
/// base name in HELP/TYPE headers (e.g., a counter named `foo` emits data
/// as `foo_total`). Each suffix is only valid for specific metric types.
///
/// See: <https://github.com/OpenObservability/OpenMetrics/blob/main/specification/OpenMetrics.md#suffixes>
const TYPED_SUFFIXES: &[(&str, &[&str])] = &[
    ("_total", &["counter"]),
    ("_bucket", &["histogram", "gaugehistogram"]),
    ("_count", &["histogram", "summary"]),
    ("_sum", &["histogram", "summary"]),
    ("_gcount", &["gaugehistogram"]),
    ("_gsum", &["gaugehistogram"]),
    ("_created", &["counter", "histogram", "summary"]),
    ("_info", &["info"]),
];

/// Returns true if `sample_name` can belong to `family_name` (either an
/// exact match or a valid type-specific suffix per the OpenMetrics spec).
///
/// See: <https://github.com/OpenObservability/OpenMetrics/blob/main/specification/OpenMetrics.md#suffixes>
fn family_accepts_sample(
    families: &BTreeMap<String, MetricFamily>,
    family_name: &str,
    sample_name: &str,
) -> bool {
    if sample_name == family_name {
        return true;
    }
    let Some(metric_type) = families
        .get(family_name)
        .and_then(|family| family.metric_type.as_deref())
    else {
        return false;
    };
    let Some(suffix) = sample_name.strip_prefix(family_name) else {
        return false;
    };
    TYPED_SUFFIXES.iter().any(|(known_suffix, valid_types)| {
        suffix == *known_suffix && valid_types.contains(&metric_type)
    })
}

/// Extract the metric name from a sample line: `sample = metricname [labels] SP number ...`
///
/// See: <https://github.com/OpenObservability/OpenMetrics/blob/main/specification/OpenMetrics.md#abnf>
fn extract_metric_name(line: &str) -> &str {
    let end = line.find(['{', ' ']).unwrap_or(line.len());
    &line[..end]
}

impl MetricEncoder {
    pub const fn new() -> Self {
        Self {
            line_buffer: String::new(),
            families: BTreeMap::new(),
            active_family: None,
        }
    }

    pub fn into_string(mut self) -> String {
        if !self.line_buffer.is_empty() {
            self.flush_line();
        }
        let total: usize = self
            .families
            .values()
            .map(|f| {
                f.help.as_ref().map_or(0, |h| h.len() + 1)
                    + f.type_line.as_ref().map_or(0, |t| t.len() + 1)
                    + f.unit.as_ref().map_or(0, |u| u.len() + 1)
                    + f.data.iter().map(|d| d.len() + 1).sum::<usize>()
            })
            .sum();
        let mut output = String::with_capacity(total);
        for family in self.families.values() {
            if let Some(help) = &family.help {
                output.push_str(help);
                output.push('\n');
            }
            if let Some(type_line) = &family.type_line {
                output.push_str(type_line);
                output.push('\n');
            }
            if let Some(unit) = &family.unit {
                output.push_str(unit);
                output.push('\n');
            }
            for data in &family.data {
                output.push_str(data);
                output.push('\n');
            }
        }
        output
    }

    /// Resolve a data line's metric name to its family key, inserting a new
    /// family if none exists, and return a mutable reference to it.
    ///
    /// OpenMetrics appends type-specific suffixes to data lines that differ
    /// from the base name in HELP/TYPE headers (e.g., a counter named "votes"
    /// emits data as "votes_total"). This method uses the TYPE declaration to
    /// correctly match suffixed data lines to their family, even when another
    /// family with the suffixed name exists (e.g., a gauge named "votes_total").
    fn resolve_data_family(&mut self, name: &str) -> &mut MetricFamily {
        let key = self.find_typed_family(name).unwrap_or(name);
        self.families.entry(key.to_string()).or_default()
    }

    /// Try to find an existing family whose TYPE declaration expects the
    /// suffix present in `name`.
    fn find_typed_family<'a>(&self, name: &'a str) -> Option<&'a str> {
        TYPED_SUFFIXES.iter().find_map(|(suffix, valid_types)| {
            let base = name.strip_suffix(suffix)?;
            let family = self.families.get(base)?;
            let t = family.metric_type.as_deref()?;
            valid_types.contains(&t).then_some(base)
        })
    }

    fn flush_line(&mut self) {
        let line = std::mem::take(&mut self.line_buffer);
        if line == "# EOF" {
            self.active_family = None;
            return;
        }
        if let Some(rest) = line.strip_prefix("# HELP ") {
            let name = rest.split_whitespace().next().unwrap_or("").to_string();
            let family = self.families.entry(name.clone()).or_default();
            if family.help.is_none() {
                family.help = Some(line);
            }
            self.active_family = Some(name);
        } else if let Some(rest) = line.strip_prefix("# TYPE ") {
            let mut parts = rest.split_whitespace();
            let name = parts.next().unwrap_or("").to_string();
            let metric_type = parts.next().map(|s| s.to_string());
            let family = self.families.entry(name.clone()).or_default();
            if family.type_line.is_none() {
                family.type_line = Some(line);
                family.metric_type = metric_type;
            }
            self.active_family = Some(name);
        } else if let Some(rest) = line.strip_prefix("# UNIT ") {
            let name = rest.split_whitespace().next().unwrap_or("").to_string();
            let family = self.families.entry(name.clone()).or_default();
            if family.unit.is_none() {
                family.unit = Some(line);
            }
            self.active_family = Some(name);
        } else {
            let name = extract_metric_name(&line);
            if let Some(family_name) = &self.active_family {
                if family_accepts_sample(&self.families, family_name, name) {
                    self.families
                        .get_mut(family_name.as_str())
                        .unwrap()
                        .data
                        .push(line);
                    return;
                }
            }
            let family = self.resolve_data_family(name);
            family.data.push(line);
        }
    }
}

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

impl std::fmt::Write for MetricEncoder {
    fn write_str(&mut self, s: &str) -> std::fmt::Result {
        let mut remaining = s;
        while let Some(pos) = remaining.find('\n') {
            self.line_buffer.push_str(&remaining[..pos]);
            self.flush_line();
            remaining = &remaining[pos + 1..];
        }
        self.line_buffer.push_str(remaining);
        Ok(())
    }
}

/// Internal handle that deregisters a metric scope when dropped.
///
/// Stored inside contexts via `Arc<ScopeGuard>`. When the last context clone
/// holding this handle is dropped, the scope's metrics are automatically removed.
pub(crate) struct ScopeGuard {
    scope_id: u64,
    cleanup: Option<Box<dyn FnOnce(u64) + Send + Sync>>,
}

impl ScopeGuard {
    pub(crate) fn new(scope_id: u64, cleanup: impl FnOnce(u64) + Send + Sync + 'static) -> Self {
        Self {
            scope_id,
            cleanup: Some(Box::new(cleanup)),
        }
    }

    pub(crate) const fn scope_id(&self) -> u64 {
        self.scope_id
    }
}

impl Drop for ScopeGuard {
    fn drop(&mut self) {
        if let Some(cleanup) = self.cleanup.take() {
            cleanup(self.scope_id);
        }
    }
}

/// Manages multiple prometheus registries with lifecycle-based scoping.
///
/// Holds a permanent root registry for long-lived metrics (runtime internals)
/// and a collection of scoped registries that can be removed when the associated
/// work (e.g., an epoch's consensus engine) is done.
pub(crate) struct Registry {
    root: PrometheusRegistry,
    scopes: BTreeMap<u64, PrometheusRegistry>,
    next_scope_id: u64,
}

impl Registry {
    pub fn new() -> Self {
        Self {
            root: PrometheusRegistry::default(),
            scopes: BTreeMap::new(),
            next_scope_id: 0,
        }
    }

    pub const fn root_mut(&mut self) -> &mut PrometheusRegistry {
        &mut self.root
    }

    pub fn create_scope(&mut self) -> u64 {
        let id = self.next_scope_id;
        self.next_scope_id = self.next_scope_id.checked_add(1).expect("scope overflow");
        self.scopes.insert(id, PrometheusRegistry::default());
        id
    }

    pub fn get_scope(&mut self, scope: Option<u64>) -> &mut PrometheusRegistry {
        match scope {
            None => &mut self.root,
            Some(id) => self
                .scopes
                .get_mut(&id)
                .unwrap_or_else(|| panic!("scope {id} not found (already deregistered?)")),
        }
    }

    pub fn remove_scope(&mut self, id: u64) {
        self.scopes.remove(&id);
    }

    pub fn encode(&self) -> String {
        let mut encoder = MetricEncoder::new();
        encode(&mut encoder, &self.root).expect("encoding root failed");
        for registry in self.scopes.values() {
            encode(&mut encoder, registry).expect("encoding scope failed");
        }
        let mut output = encoder.into_string();
        output.push_str("# EOF\n");
        output
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::{deterministic, Metrics, Runner};
    use commonware_macros::test_traced;
    use futures::task::waker;
    use prometheus_client::metrics::counter::Counter;
    use std::sync::atomic::{AtomicBool, AtomicUsize, Ordering};

    fn encode_dedup(input: &str) -> String {
        use std::fmt::Write;
        let mut encoder = MetricEncoder::new();
        encoder.write_str(input).unwrap();
        encoder.into_string()
    }

    #[test]
    fn test_metric_encoder_empty() {
        assert_eq!(encode_dedup(""), "");
        assert_eq!(encode_dedup("# EOF\n"), "");
    }

    #[test]
    fn test_metric_encoder_no_duplicates() {
        let input = r#"# HELP foo_total A counter.
# TYPE foo_total counter
foo_total 1
# HELP bar_gauge A gauge.
# TYPE bar_gauge gauge
bar_gauge 42
# EOF
"#;
        let expected = r#"# HELP bar_gauge A gauge.
# TYPE bar_gauge gauge
bar_gauge 42
# HELP foo_total A counter.
# TYPE foo_total counter
foo_total 1
"#;
        assert_eq!(encode_dedup(input), expected);
    }

    #[test]
    fn test_metric_encoder_with_duplicates() {
        let input = r#"# HELP votes_total vote count.
# TYPE votes_total counter
votes_total{epoch="e5"} 1
# HELP votes_total vote count.
# TYPE votes_total counter
votes_total{epoch="e6"} 2
# EOF
"#;
        let expected = r#"# HELP votes_total vote count.
# TYPE votes_total counter
votes_total{epoch="e5"} 1
votes_total{epoch="e6"} 2
"#;
        assert_eq!(encode_dedup(input), expected);
    }

    #[test]
    fn test_metric_encoder_multiple_metrics() {
        let input = r#"# HELP a_total First.
# TYPE a_total counter
a_total{tag="x"} 1
# HELP b_total Second.
# TYPE b_total counter
b_total 5
# HELP a_total First.
# TYPE a_total counter
a_total{tag="y"} 2
# EOF
"#;
        let expected = r#"# HELP a_total First.
# TYPE a_total counter
a_total{tag="x"} 1
a_total{tag="y"} 2
# HELP b_total Second.
# TYPE b_total counter
b_total 5
"#;
        assert_eq!(encode_dedup(input), expected);
    }

    #[test]
    fn test_metric_encoder_groups_by_name() {
        let input = r#"# HELP a_total First.
# TYPE a_total counter
a_total{tag="x"} 1
# HELP b_total Second.
# TYPE b_total counter
b_total 5
# HELP a_total First.
# TYPE a_total counter
a_total{tag="y"} 2
# EOF
"#;
        let expected = r#"# HELP a_total First.
# TYPE a_total counter
a_total{tag="x"} 1
a_total{tag="y"} 2
# HELP b_total Second.
# TYPE b_total counter
b_total 5
"#;
        assert_eq!(encode_dedup(input), expected);
    }

    #[test]
    fn test_metric_encoder_deterministic_order() {
        let input = r#"# HELP z First alphabetically last.
# TYPE z counter
z_total 1
# HELP a Last alphabetically first.
# TYPE a counter
a_total 2
# EOF
"#;
        let expected = r#"# HELP a Last alphabetically first.
# TYPE a counter
a_total 2
# HELP z First alphabetically last.
# TYPE z counter
z_total 1
"#;
        assert_eq!(encode_dedup(input), expected);
    }

    #[test]
    fn test_metric_encoder_counter_suffix_grouping() {
        // prometheus_client uses the base name for HELP/TYPE (e.g., "ab_votes")
        // but appends "_total" to the data line (e.g., "ab_votes_total").
        // A metric whose name sorts between these (e.g., "ab_votes_size")
        // must not split the family.
        let input = r#"# HELP ab_votes vote count.
# TYPE ab_votes counter
ab_votes_total{epoch="1"} 1
# HELP ab_votes_size size gauge.
# TYPE ab_votes_size gauge
ab_votes_size 99
# HELP ab_votes vote count.
# TYPE ab_votes counter
ab_votes_total{epoch="2"} 2
# EOF
"#;
        let expected = r#"# HELP ab_votes vote count.
# TYPE ab_votes counter
ab_votes_total{epoch="1"} 1
ab_votes_total{epoch="2"} 2
# HELP ab_votes_size size gauge.
# TYPE ab_votes_size gauge
ab_votes_size 99
"#;
        assert_eq!(encode_dedup(input), expected);
    }

    #[test]
    fn test_metric_encoder_type_aware_suffix() {
        // A gauge named "foo_total" and a counter named "foo" both produce
        // data lines called "foo_total". The encoder must use the TYPE info
        // to route each data line to the correct family.
        let input = r#"# HELP foo_total A gauge.
# TYPE foo_total gauge
foo_total 42
# HELP foo A counter.
# TYPE foo counter
foo_total 1
# EOF
"#;
        let expected = r#"# HELP foo A counter.
# TYPE foo counter
foo_total 1
# HELP foo_total A gauge.
# TYPE foo_total gauge
foo_total 42
"#;
        assert_eq!(encode_dedup(input), expected);
    }

    #[test]
    fn test_metric_encoder_literal_suffix_family_not_hijacked() {
        // A family may legitimately end with a reserved OpenMetrics suffix.
        // The encoder must not always remap "foo_created" to base family "foo".
        let input = r#"# HELP foo A counter.
# TYPE foo counter
foo_total 1
# HELP foo_created A gauge.
# TYPE foo_created gauge
foo_created 42
# EOF
"#;
        let expected = r#"# HELP foo A counter.
# TYPE foo counter
foo_total 1
# HELP foo_created A gauge.
# TYPE foo_created gauge
foo_created 42
"#;
        assert_eq!(encode_dedup(input), expected);
    }

    #[test]
    fn test_metric_encoder_type_aware_suffix_interleaved_segments() {
        // Two families may emit lines with the same sample name (`foo_total`):
        // a counter named `foo` and a gauge named `foo_total`.
        //
        // Repeated counter descriptors (as emitted by separate scoped registries)
        // must keep all counter samples in family `foo` and not leak them into
        // family `foo_total`.
        let input = r#"# HELP foo Counter.
# TYPE foo counter
foo_total{scope="a"} 1
# HELP foo_total Gauge.
# TYPE foo_total gauge
foo_total 42
# HELP foo Counter.
# TYPE foo counter
foo_total{scope="b"} 2
# EOF
"#;
        let expected = r#"# HELP foo Counter.
# TYPE foo counter
foo_total{scope="a"} 1
foo_total{scope="b"} 2
# HELP foo_total Gauge.
# TYPE foo_total gauge
foo_total 42
"#;
        assert_eq!(encode_dedup(input), expected);
    }

    #[test]
    fn test_metric_encoder_unit_metadata_is_grouped() {
        let input = r#"# HELP latency Latency histogram.
# TYPE latency histogram
# UNIT latency seconds
latency_sum 1.2
latency_count 3
# HELP requests Requests.
# TYPE requests counter
requests_total 9
# EOF
"#;
        let expected = r#"# HELP latency Latency histogram.
# TYPE latency histogram
# UNIT latency seconds
latency_sum 1.2
latency_count 3
# HELP requests Requests.
# TYPE requests counter
requests_total 9
"#;
        assert_eq!(encode_dedup(input), expected);
    }

    #[test]
    fn test_metric_encoder_unit_metadata_deduped_across_segments() {
        let input = r#"# HELP req Requests.
# TYPE req counter
# UNIT req requests
req_total{scope="a"} 1
# HELP req Requests.
# TYPE req counter
# UNIT req requests
req_total{scope="b"} 2
# EOF
"#;
        let expected = r#"# HELP req Requests.
# TYPE req counter
# UNIT req requests
req_total{scope="a"} 1
req_total{scope="b"} 2
"#;
        assert_eq!(encode_dedup(input), expected);
    }

    #[test]
    fn test_metric_encoder_fallback_uses_typed_suffix_even_if_literal_exists() {
        // Regression test for a buggy fallback that preferred `contains_key(name)`
        // before typed-suffix mapping.
        //
        // Here `foo_total` exists as its own counter family, but a sample named
        // `foo_total` can only come from counter family `foo` (because
        // `foo_total` counter samples are `foo_total_total`).
        //
        // We force fallback mode by ending descriptor groups with `# EOF`, which
        // clears `active_family`.
        let input = r#"# HELP foo_total Counter with literal suffix.
# TYPE foo_total counter
foo_total_total 9
# EOF
# HELP foo Base counter.
# TYPE foo counter
# EOF
foo_total{scope="x"} 1
# EOF
"#;
        let expected = r#"# HELP foo Base counter.
# TYPE foo counter
foo_total{scope="x"} 1
# HELP foo_total Counter with literal suffix.
# TYPE foo_total counter
foo_total_total 9
"#;
        assert_eq!(encode_dedup(input), expected);
    }

    #[test]
    fn test_metric_encoder_strips_intermediate_eof() {
        let input = r#"# HELP a_total Root.
# TYPE a_total counter
a_total 1
# EOF
# HELP b_total Scoped.
# TYPE b_total counter
b_total 2
# EOF
"#;
        let expected = r#"# HELP a_total Root.
# TYPE a_total counter
a_total 1
# HELP b_total Scoped.
# TYPE b_total counter
b_total 2
"#;
        assert_eq!(encode_dedup(input), expected);
    }

    #[test]
    fn test_blocker_waits_until_wake() {
        let blocker = Blocker::new();
        let started = Arc::new(AtomicBool::new(false));
        let completed = Arc::new(AtomicBool::new(false));

        let thread_blocker = blocker.clone();
        let thread_started = started.clone();
        let thread_completed = completed.clone();
        let handle = std::thread::spawn(move || {
            thread_started.store(true, Ordering::SeqCst);
            thread_blocker.wait();
            thread_completed.store(true, Ordering::SeqCst);
        });

        while !started.load(Ordering::SeqCst) {
            std::thread::yield_now();
        }

        assert!(!completed.load(Ordering::SeqCst));
        waker(blocker).wake();
        handle.join().unwrap();
        assert!(completed.load(Ordering::SeqCst));
    }

    #[test]
    fn test_blocker_handles_pre_wake() {
        let blocker = Blocker::new();
        waker(blocker.clone()).wake();

        let completed = Arc::new(AtomicBool::new(false));
        let thread_blocker = blocker;
        let thread_completed = completed.clone();
        std::thread::spawn(move || {
            thread_blocker.wait();
            thread_completed.store(true, Ordering::SeqCst);
        })
        .join()
        .unwrap();

        assert!(completed.load(Ordering::SeqCst));
    }

    #[test]
    fn test_blocker_reusable_across_signals() {
        let blocker = Blocker::new();
        let completed = Arc::new(AtomicUsize::new(0));

        let thread_blocker = blocker.clone();
        let thread_completed = completed.clone();
        let handle = std::thread::spawn(move || {
            for _ in 0..2 {
                thread_blocker.wait();
                thread_completed.fetch_add(1, Ordering::SeqCst);
            }
        });

        for expected in 1..=2 {
            waker(blocker.clone()).wake();
            while completed.load(Ordering::SeqCst) < expected {
                std::thread::yield_now();
            }
        }

        handle.join().unwrap();
        assert_eq!(completed.load(Ordering::SeqCst), 2);
    }

    #[test_traced]
    fn test_count_running_tasks() {
        use crate::{Metrics, Runner, Spawner};
        use futures::future;

        let executor = deterministic::Runner::default();
        executor.start(|context| async move {
            // Initially no tasks with "worker" prefix
            assert_eq!(
                count_running_tasks(&context, "worker"),
                0,
                "no worker tasks initially"
            );

            // Spawn a task under a labeled context that stays running
            let worker_ctx = context.with_label("worker");
            let handle1 = worker_ctx.clone().spawn(|_| async move {
                future::pending::<()>().await;
            });

            // Count running tasks with "worker" prefix
            let count = count_running_tasks(&context, "worker");
            assert_eq!(count, 1, "worker task should be running");

            // Non-matching prefix should return 0
            assert_eq!(
                count_running_tasks(&context, "other"),
                0,
                "no tasks with 'other' prefix"
            );

            // Spawn a nested task (worker_child)
            let handle2 = worker_ctx.with_label("child").spawn(|_| async move {
                future::pending::<()>().await;
            });

            // Count should include both parent and nested tasks
            let count = count_running_tasks(&context, "worker");
            assert_eq!(count, 2, "both worker and worker_child should be counted");

            // Abort parent task
            handle1.abort();
            let _ = handle1.await;

            // Only nested task remains
            let count = count_running_tasks(&context, "worker");
            assert_eq!(count, 1, "only worker_child should remain");

            // Abort nested task
            handle2.abort();
            let _ = handle2.await;

            // All tasks stopped
            assert_eq!(
                count_running_tasks(&context, "worker"),
                0,
                "all worker tasks should be stopped"
            );
        });
    }

    #[test_traced]
    fn test_no_duplicate_metrics() {
        let executor = deterministic::Runner::default();
        executor.start(|context| async move {
            // Register metrics under different labels (no duplicates)
            let c1 = Counter::<u64>::default();
            context.with_label("a").register("test", "help", c1);
            let c2 = Counter::<u64>::default();
            context.with_label("b").register("test", "help", c2);
        });
        // Test passes if runtime doesn't panic on shutdown
    }

    #[test]
    #[should_panic(expected = "duplicate metric:")]
    fn test_duplicate_metrics_panics() {
        let executor = deterministic::Runner::default();
        executor.start(|context| async move {
            // Register metrics with the same label, causing duplicates
            let c1 = Counter::<u64>::default();
            context.with_label("a").register("test", "help", c1);
            let c2 = Counter::<u64>::default();
            context.with_label("a").register("test", "help", c2);
        });
    }
}