photon-runtime 0.1.0

//! Main Photon runtime handle — publish/subscribe (**Creating topics**) and builder wiring
//! (**Integrating the host**).

use std::sync::Arc;

use futures::stream::Stream;
use photon_core::IdentityFactory;

use photon_backend::{Event, PhotonBackend, ReclaimReport, Result, StoragePort, TopicRegistry, ExecutorServices, BackendCapabilities};

use crate::admin::collect_admin_snapshot;
use crate::admin::AdminSnapshot;

use crate::executor::ExecutorController;

/// Shared storage port, executor services, and handler dispatch controller.
#[derive(Clone)]
pub struct PhotonRuntimeState {
    /// Storage port used by executor checkpoint/retention services.
    pub storage_port: Arc<dyn StoragePort>,
    /// Services used by durable handler executors.
    pub executor_services: Arc<ExecutorServices>,
    /// Handler dispatch controller.
    pub executor: Arc<ExecutorController>,
}

/// Main Photon runtime handle.
#[derive(Clone)]
pub struct Photon {
    backend: Arc<dyn PhotonBackend>,
    runtime: PhotonRuntimeState,
}

static DEFAULT_PHOTON: std::sync::RwLock<Option<Photon>> = std::sync::RwLock::new(None);

/// Configure the default Photon instance used by macro-generated convenience helpers
/// (`Type::publish()` / `Type::subscribe()`).
///
/// Prefer passing an explicit [`Photon`] handle via `publish_on` / `subscribe_on` or
/// [`Photon::publish`]. This process-wide shim is optional sugar for simple hosts.
///
/// # Example
///
/// ```rust,no_run
/// use std::sync::Arc;
///
/// use photon_core::JsonIdentityFactory;
/// use photon_runtime::{configure, Photon};
///
/// # fn main() -> photon_backend::Result<()> {
/// let photon = Photon::builder().auto_registry().build()?;
/// photon.start_executor(Arc::new(JsonIdentityFactory))?;
/// configure(photon);
/// # Ok(())
/// # }
/// ```
///
/// # Panics
///
/// Panics if an internal lock is poisoned.
pub fn configure(photon: Photon) {
    let mut guard = DEFAULT_PHOTON.write().unwrap();
    *guard = Some(photon);
}

/// Clone of the process-wide Photon set by [`configure`], if any.
///
/// Prefer an explicit [`Photon`] handle. This exists for macro convenience helpers.
///
/// # Panics
///
/// Panics if an internal lock is poisoned.
pub fn default() -> Option<Photon> {
    let guard = DEFAULT_PHOTON.read().unwrap();
    guard.clone()
}

impl Photon {
    pub(crate) fn new(backend: Arc<dyn PhotonBackend>, runtime: PhotonRuntimeState) -> Self {
        Self { backend, runtime }
    }

    /// Start building a Photon runtime instance.
    #[must_use]
    pub fn builder() -> crate::builder::PhotonBuilder {
        crate::builder::PhotonBuilder::default()
    }

    /// Telemetry label for the installed backend.
    #[must_use]
    pub fn backend_label(&self) -> &'static str {
        self.backend.telemetry_label()
    }

    pub(crate) fn backend_capabilities(&self) -> BackendCapabilities {
        PhotonBackend::capabilities(self.backend.as_ref())
    }

    /// Compose a read-only ops introspection snapshot for host admin UIs.
    ///
    /// Aggregates the topic catalog, handler inventory, backend capabilities, and checkpoint
    /// cursors for inventory-registered handlers. Does not touch publish/subscribe hot paths.
    ///
    /// # Errors
    ///
    /// Returns an error if a checkpoint load fails.
    pub async fn admin_snapshot(&self) -> Result<AdminSnapshot> {
        collect_admin_snapshot(self).await
    }

    /// Publish a single event to a topic.
    ///
    /// # Errors
    ///
    /// Returns an error if the operation fails.
    pub async fn publish(
        &self,
        topic_name: &str,
        topic_key: Option<&str>,
        actor_json: serde_json::Value,
        payload_json: serde_json::Value,
    ) -> Result<String> {
        PhotonBackend::publish(
            self.backend.as_ref(),
            topic_name,
            topic_key,
            actor_json,
            payload_json,
        )
        .await
    }

    /// Subscribe to topic events as a stream.
    ///
    /// For typed topics, prefer `TopicType::subscribe(opts)` or the `#[subscribe]` macro.
    /// Runnable walkthrough: `cargo run -p uf-photon --example manual_subscribe --features runtime,mem`.
    ///
    /// # Example
    ///
    /// ```rust,no_run
    /// use futures::StreamExt;
    /// use photon_runtime::{configure, default, Photon};
    ///
    /// # async fn demo() -> photon_backend::Result<()> {
    /// configure(Photon::builder().auto_registry().build()?);
    /// let photon = default().expect("configure first");
    /// let mut stream = photon.subscribe("my.topic", None, None);
    /// if let Some(result) = stream.next().await {
    ///     let _event = result?;
    /// }
    /// # Ok(())
    /// # }
    /// ```
    #[must_use]
    pub fn subscribe(
        &self,
        topic_name: &str,
        topic_key_filter: Option<&str>,
        after_seq: Option<i64>,
    ) -> std::pin::Pin<Box<dyn Stream<Item = Result<Event>> + Send>> {
        PhotonBackend::subscribe(
            self.backend.as_ref(),
            topic_name.to_string(),
            topic_key_filter.map(std::string::ToString::to_string),
            after_seq,
        )
    }

    /// Subscribe to assigned virtual shards for a consumer group (multiplexed stream).
    #[must_use]
    pub fn subscribe_consumer_group(
        &self,
        topic_name: &str,
        shard_ids: &[u32],
        after_seq_by_shard: std::collections::HashMap<u32, Option<i64>>,
    ) -> std::pin::Pin<Box<dyn Stream<Item = Result<Event>> + Send>> {
        photon_backend::merge_shard_streams(
            Arc::clone(&self.backend),
            topic_name.to_string(),
            shard_ids,
            after_seq_by_shard,
        )
    }

    /// Load a specific event by ID.
    ///
    /// # Errors
    ///
    /// Returns an error if the operation fails.
    pub async fn get_event(&self, event_id: &str) -> Result<Option<Event>> {
        PhotonBackend::get_event(self.backend.as_ref(), event_id).await
    }

    /// Return the registered topic catalog.
    #[must_use]
    pub fn registry(&self) -> &TopicRegistry {
        PhotonBackend::registry(self.backend.as_ref())
    }

    /// Read the last checkpoint sequence for a subscription/topic pair.
    ///
    /// # Errors
    ///
    /// Returns an error if the operation fails.
    pub async fn get_checkpoint_seq(
        &self,
        subscription_name: &str,
        topic_name: &str,
        topic_key: Option<&str>,
    ) -> Result<Option<i64>> {
        PhotonBackend::get_checkpoint_seq(
            self.backend.as_ref(),
            subscription_name,
            topic_name,
            topic_key,
        )
        .await
    }

    /// Persist an updated checkpoint sequence for a subscription/topic pair.
    ///
    /// # Errors
    ///
    /// Returns an error if the operation fails.
    pub async fn set_checkpoint(
        &self,
        subscription_name: &str,
        topic_name: &str,
        topic_key: Option<&str>,
        last_seq: i64,
    ) -> Result<()> {
        PhotonBackend::set_checkpoint(
            self.backend.as_ref(),
            subscription_name,
            topic_name,
            topic_key,
            last_seq,
        )
        .await
    }

    /// Shared tailer / executor services.
    #[must_use]
    pub const fn runtime(&self) -> &PhotonRuntimeState {
        &self.runtime
    }

    /// Reclaim transport log rows past the safe watermark (headless ops entry point).
    ///
    /// # Errors
    ///
    /// Returns an error if the operation fails.
    pub async fn reclaim_transport(&self) -> Result<Vec<ReclaimReport>> {
        self.runtime
            .executor_services
            .retention_reclaimer
            .sweep_all()
            .await
    }

    /// Start inventory-registered `#[photon::subscribe]` handlers.
    ///
    /// Requires an [`IdentityFactory`] (e.g. [`photon_core::JsonIdentityFactory`]) for actor
    /// resolution. Optionally call [`configure`] so convenience `Type::publish()` helpers work.
    ///
    /// # Example
    ///
    /// ```rust,no_run
    /// use std::sync::Arc;
    ///
    /// use photon_core::JsonIdentityFactory;
    /// use photon_runtime::Photon;
    ///
    /// # async fn boot() -> photon_backend::Result<()> {
    /// let photon = Photon::builder().auto_registry().build()?;
    /// photon.start_executor(Arc::new(JsonIdentityFactory))?;
    /// photon.shutdown_executor();
    /// photon.join_executor().await;
    /// # Ok(())
    /// # }
    /// ```
    ///
    /// # Errors
    ///
    /// Returns an error if the executor was already started on this runtime.
    #[allow(clippy::needless_pass_by_value)] // Arc-by-value is the public ownership API
    pub fn start_executor(&self, identity: Arc<dyn IdentityFactory>) -> Result<()> {
        self.runtime.executor.start(self, &identity)
    }

    /// Signal handler loops to stop accepting new events.
    ///
    /// # Contract
    ///
    /// Idempotent. Pair with [`Self::join_executor`] to await in-flight work.
    pub fn shutdown_executor(&self) {
        self.runtime.executor.shutdown();
    }

    /// Await handler loops and in-flight dispatches after [`Self::shutdown_executor`].
    ///
    /// # Contract
    ///
    /// Safe when the executor was never started. Restart requires a new [`Photon`] build.
    pub async fn join_executor(&self) {
        self.runtime.executor.join().await;
    }
}