//! Ambient session context for telemetry — product events + Mixpanel via
//! [`log_event`]. `session_id` and `turn_number` are injected from the
//! task-local [`TelemetryCtx`] active for the duration of a session.
//!
//! Extracted from `xai-grok-shell::agent::telemetry`.

use std::sync::Arc;

use serde::Serialize;
use serde_json::json;

use crate::client::{self, Metadata, UserContext};
use crate::events::TelemetryEvent;

/// Ambient session context for telemetry. Snapshotted synchronously by
/// `log_event` at call time to avoid racing with turn increments.
#[derive(Clone)]
pub struct TelemetryCtx {
    pub session_id: String,
    pub prompt_index: Arc<tokio::sync::Mutex<usize>>,
    /// Per-prompt correlation UUID for the external OTEL stream (`prompt.id`,
    /// events only — never metrics). Set at turn start where `prompt_index`
    /// increments; `None` outside a prompt.
    pub prompt_id: Arc<parking_lot::Mutex<Option<String>>>,
}

impl TelemetryCtx {
    pub fn new(session_id: String, prompt_index: Arc<tokio::sync::Mutex<usize>>) -> Self {
        Self {
            session_id,
            prompt_index,
            prompt_id: Arc::new(parking_lot::Mutex::new(None)),
        }
    }
}

/// Snapshot of the ambient ctx for the external OTEL stream.
pub(crate) struct ExternalCtxSnapshot {
    pub session_id: String,
    pub turn_number: Option<u32>,
    pub prompt_id: Option<String>,
}

/// Rotate the per-prompt correlation UUID at turn start (where
/// `prompt_index` increments). No-op outside a session ctx scope. The id is
/// attached as `prompt.id` to external OTEL events only.
pub fn begin_prompt_id() {
    let _ = TELEMETRY_CTX.try_with(|c| {
        *c.prompt_id.lock() = Some(uuid::Uuid::new_v4().to_string());
    });
}

/// Snapshot the task-local ctx (if any) for external emission. Non-blocking:
/// a contended `prompt_index` lock yields `turn_number = None` rather than
/// stalling the emitting task.
pub(crate) fn external_ctx_snapshot() -> Option<ExternalCtxSnapshot> {
    TELEMETRY_CTX
        .try_with(|c| ExternalCtxSnapshot {
            session_id: c.session_id.clone(),
            turn_number: c.prompt_index.try_lock().map(|g| *g as u32).ok(),
            prompt_id: c.prompt_id.lock().clone(),
        })
        .ok()
}

tokio::task_local! {
    static TELEMETRY_CTX: Arc<TelemetryCtx>;
}

/// The `session_id` field name the debug-log firehose router keys on:
/// `debug_log::SessionIdVisitor` stashes a `SessionId` extension on any span
/// carrying this field — the span *name* is not load-bearing for routing. Shared
/// so the `info_span!` here and the router in `debug_log` can't silently drift; a
/// rename trips `session_span_exposes_router_field` below.
pub(crate) const SESSION_ID_FIELD: &str = "session_id";

/// Build the per-session tracing span the firehose router routes by. The field
/// name MUST be the literal `session_id` (tracing field names can't come from a
/// const); the test below pins it against [`SESSION_ID_FIELD`].
fn session_span(session_id: &str) -> tracing::Span {
    tracing::info_span!("session", session_id = %session_id)
}

/// Run `fut` with telemetry context active. Also sets a `tracing` span.
pub async fn with_session_ctx<F: std::future::Future>(ctx: TelemetryCtx, fut: F) -> F::Output {
    use tracing::Instrument;
    let span = session_span(&ctx.session_id);
    TELEMETRY_CTX
        .scope(Arc::new(ctx), fut.instrument(span))
        .await
}

/// Product surface that emitted a telemetry event. Selects the analytics
/// event-name prefix so shell and workspace events are distinguishable on the
/// wire while sharing this emitter (and the `event_value` derivation in
/// [`crate::client`]).
#[derive(Debug, Clone, Copy, PartialEq, Eq, strum::EnumCount)]
pub enum EmitterOrigin {
    /// `xai-grok-shell` (and the pager/TUI that emit through it).
    Shell,
    /// `xai-grok-workspace` (remote sampler / workspace server).
    Workspace,
}

impl EmitterOrigin {
    /// Every emitter origin. [`crate::client::event_value`] iterates this to
    /// strip whichever prefix an event name carries. Iteration *order* is
    /// irrelevant: the prefixes are mutually exclusive (no
    /// [`EmitterOrigin::event_prefix`] is a prefix of another — pinned by
    /// `client`'s `emitter_prefixes_are_mutually_exclusive` test), so at most
    /// one entry ever matches a given name. Completeness is compiler-enforced
    /// by the `EmitterOrigin::ALL` length assertion below, so a newly added
    /// variant that is omitted here fails to compile.
    pub const ALL: [EmitterOrigin; 2] = [EmitterOrigin::Shell, EmitterOrigin::Workspace];

    /// Analytics event-name prefix for this origin. [`crate::client::event_value`]
    /// strips the same prefix to derive the wire `event_value`, so the two must
    /// stay in lockstep.
    pub fn event_prefix(self) -> &'static str {
        match self {
            EmitterOrigin::Shell => "grok-shell-",
            EmitterOrigin::Workspace => "grok-workspace-",
        }
    }
}

/// Compile-time completeness guard for [`EmitterOrigin::ALL`]: adding a variant
/// without listing it in `ALL` makes `ALL.len()` diverge from the
/// `strum::EnumCount`-derived variant count and fails this assertion, so
/// `client::event_value` can never silently stop stripping an origin's prefix.
const _: () = assert!(EmitterOrigin::ALL.len() == <EmitterOrigin as strum::EnumCount>::COUNT);

/// Product analytics event (type-safe). Only fires in `Enabled` mode.
/// Unconditionally fans out to the external OTEL stream first ("one call
/// site, two sinks, independent gates"): the external gate is
/// `external::is_active()`, independent of `TelemetryMode`.
pub fn log_event<T: TelemetryEvent>(data: T) {
    crate::external::emit(&data);
    if !client::is_enabled() {
        return;
    }
    emit_event(T::NAME, data);
}

/// Emit one event to the external stream always (no-op unless the stream is
/// active) and to the product events/Mixpanel funnel only when `internal_enabled`.
///
/// Used by call sites whose internal sink is gated by a *stricter* predicate
/// than [`log_event`]'s own `TelemetryMode::Enabled` check (the shell's
/// `telemetry_enabled` = `Enabled && !ZDR`, or `!is_data_collection_disabled()`).
/// Because [`log_event`] already fans out to the external sink before its
/// internal gate, the two branches are **mutually exclusive**: routing through
/// `log_event` when internal is enabled reaches both sinks, and calling
/// [`crate::external::emit`] directly otherwise keeps `session.count` /
/// `turn.count` exactly-once on every path while never sending an internal
/// record under ZDR.
pub fn log_event_dual<T: TelemetryEvent>(internal_enabled: bool, data: T) {
    if internal_enabled {
        log_event(data);
    } else {
        crate::external::emit(&data);
    }
}

/// Session lifecycle event (type-safe). Fires in both `Enabled` and
/// `SessionMetrics` modes. Emits with the [`EmitterOrigin::Shell`] prefix;
/// workspace-side callers use [`log_session_event_with_origin`].
/// Unconditionally fans out to the external OTEL stream first (independent
/// gate; see [`log_event`]).
pub fn log_session_event<T: TelemetryEvent>(data: T) {
    crate::external::emit(&data);
    if !client::is_session_metrics_enabled() {
        return;
    }
    emit_event_with_origin(EmitterOrigin::Shell, T::NAME, data);
}

/// Session lifecycle event tagged with the emitting [`EmitterOrigin`]. Fires in
/// both `Enabled` and `SessionMetrics` modes; the origin selects the analytics
/// event-name prefix (`grok-shell-*` vs `grok-workspace-*`).
///
/// Deliberately **no external fan-out** here: workspace-side callers
/// (`EmitterOrigin::Workspace` — remote sampler / workspace server, a
/// different process and monitoring audience) invoke this directly, and the
/// external stream is Shell-origin only. An `external = …` macro arm on a
/// workspace-only event therefore has no effect (pinned by test in
/// `external::tests`). If the external stream ever needs workspace events,
/// the hook moves here behind an explicit `origin == Shell` filter.
pub fn log_session_event_with_origin<T: TelemetryEvent>(origin: EmitterOrigin, data: T) {
    if !client::is_session_metrics_enabled() {
        return;
    }
    emit_event_with_origin(origin, T::NAME, data);
}

/// Emit an event with the default [`EmitterOrigin::Shell`] prefix.
pub fn emit_event<T: Serialize + Send + 'static>(event_suffix: impl Into<String>, data: T) {
    emit_event_with_origin(EmitterOrigin::Shell, event_suffix, data);
}

/// Emit an event whose analytics name is `{origin prefix}{event_suffix}`.
pub fn emit_event_with_origin<T: Serialize + Send + 'static>(
    origin: EmitterOrigin,
    event_suffix: impl Into<String>,
    data: T,
) {
    let event_name = format!("{}{}", origin.event_prefix(), event_suffix.into());
    let ctx_snapshot = TELEMETRY_CTX
        .try_with(|c| {
            (
                c.session_id.clone(),
                c.prompt_index.try_lock().map(|g| *g as u32).ok(),
            )
        })
        .ok();

    tokio::spawn(async move {
        let user_ctx = UserContext::collect();
        let request_id = format!("{}-{}", event_name, uuid::Uuid::new_v4());

        let mut metadata = match serde_json::to_value(data) {
            Ok(serde_json::Value::Object(map)) => map,
            Ok(other) => {
                let mut m = Metadata::new();
                m.insert("value".into(), other);
                m
            }
            Err(_) => Metadata::new(),
        };

        if let Some((session_id, turn_number)) = ctx_snapshot {
            metadata.insert("session_id".into(), json!(session_id));
            if let Some(turn) = turn_number {
                metadata.insert("turn_number".into(), json!(turn));
            }
        }

        client::track(&event_name, &request_id, &user_ctx, metadata).await;
    });
}

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

    /// The debug-log firehose router (`debug_log`) finds the session span by its
    /// `session_id` field (not by name). That field name is a literal in
    /// `session_span` (tracing field names can't be a const), so pin it against the
    /// shared const here — a rename of either breaks this test instead of silently
    /// degrading routing to the per-pid fallback.
    #[test]
    fn session_span_exposes_router_field() {
        // A bare registry enables every callsite, so the span has live metadata.
        let subscriber = tracing_subscriber::registry();
        tracing::subscriber::with_default(subscriber, || {
            let span = session_span("test-id");
            let meta = span
                .metadata()
                .expect("session span must have metadata under an enabling subscriber");
            assert!(
                meta.fields().field(SESSION_ID_FIELD).is_some(),
                "session span must expose `{SESSION_ID_FIELD}` for debug-log routing",
            );
        });
    }

    /// Event-name prefixes are wire contract — analytics queries match on them, so
    /// they must not drift.
    #[test]
    fn event_prefix_is_stable_per_origin() {
        assert_eq!(EmitterOrigin::Shell.event_prefix(), "grok-shell-");
        assert_eq!(EmitterOrigin::Workspace.event_prefix(), "grok-workspace-");
    }

    /// The `Shell` reroute must reproduce the historical
    /// `format!("grok-shell-{suffix}")` event name byte-for-byte, since every
    /// existing `log_session_event` / `log_event` / `emit_event` call funnels
    /// through `EmitterOrigin::Shell`.
    #[test]
    fn shell_origin_event_name_matches_legacy_format() {
        let suffix = "trace_upload_attempted";
        let rerouted = format!("{}{}", EmitterOrigin::Shell.event_prefix(), suffix);
        let legacy = format!("grok-shell-{suffix}");
        assert_eq!(rerouted, legacy);
    }

    #[test]
    fn workspace_origin_event_name_uses_workspace_prefix() {
        let name = format!("{}turn", EmitterOrigin::Workspace.event_prefix());
        assert_eq!(name, "grok-workspace-turn");
    }

    /// `ALL` must enumerate every variant so the stripper in `client` can
    /// recover the `event_value` for any origin the emitter produces. Length
    /// completeness is also compiler-enforced by the `const _` assertion in
    /// this module (via `strum::EnumCount`); this test additionally pins that
    /// the known variants are present and that every origin yields a distinct,
    /// non-empty prefix (which `EnumCount` alone does not guarantee).
    #[test]
    fn all_covers_every_origin_with_distinct_nonempty_prefixes() {
        assert!(EmitterOrigin::ALL.contains(&EmitterOrigin::Shell));
        assert!(EmitterOrigin::ALL.contains(&EmitterOrigin::Workspace));
        assert_eq!(
            EmitterOrigin::ALL.len(),
            <EmitterOrigin as strum::EnumCount>::COUNT,
            "ALL must list every EmitterOrigin variant",
        );

        let mut prefixes: Vec<&str> = EmitterOrigin::ALL
            .iter()
            .map(|o| o.event_prefix())
            .collect();
        assert!(
            prefixes.iter().all(|p| !p.is_empty()),
            "every origin must have a non-empty prefix",
        );
        let total = prefixes.len();
        prefixes.sort_unstable();
        prefixes.dedup();
        assert_eq!(
            prefixes.len(),
            total,
            "every origin must yield a distinct prefix",
        );
    }
}