pmcp 2.1.0

//! SDK-level task store trait and in-memory implementation.
//!
//! This module provides [`TaskStore`], the core trait for task lifecycle
//! management within the SDK, and [`InMemoryTaskStore`], a thread-safe
//! in-memory implementation suitable for development and testing.
//!
//! # Architecture
//!
//! The SDK defines the trait and a dev/test implementation. Production
//! backends (DynamoDB, Redis) live in the `pmcp-tasks` crate. This
//! follows the TypeScript SDK pattern where task store interfaces and
//! an in-memory implementation are part of core.
//!
//! # Differences from `pmcp-tasks`
//!
//! The SDK [`TaskStore`] trait is intentionally simplified compared to
//! the `pmcp-tasks` [`TaskStore`](https://docs.rs/pmcp-tasks/latest/pmcp_tasks/store/trait.TaskStore.html):
//! - No `set_variables` / `get_result` / `set_result` / `complete_with_result`
//! - No `request_method` parameter on `create`
//! - Returns [`Task`] (wire type) instead of `TaskRecord`
//!
//! These PMCP extensions remain in `pmcp-tasks`. The SDK trait covers
//! the core MCP spec operations only.
//!
//! # Examples
//!
//! ```no_run
//! use pmcp::server::task_store::{InMemoryTaskStore, TaskStore, StoreConfig};
//!
//! # async fn example() {
//! let store = InMemoryTaskStore::new();
//! let task = store.create("session-abc", None).await.unwrap();
//! assert_eq!(task.status, pmcp::types::tasks::TaskStatus::Working);
//! # }
//! ```

use async_trait::async_trait;
use dashmap::DashMap;
use std::time::Instant;

use crate::types::tasks::{Task, TaskStatus};

// ---------------------------------------------------------------------------
// TaskStoreError
// ---------------------------------------------------------------------------

/// Errors returned by [`TaskStore`] operations.
#[derive(Debug)]
pub enum TaskStoreError {
    /// The requested task was not found (or belongs to a different owner).
    NotFound {
        /// The task ID that was looked up.
        task_id: String,
    },
    /// The requested state transition is invalid per the MCP state machine.
    InvalidTransition {
        /// The task ID.
        task_id: String,
        /// Current status.
        from: TaskStatus,
        /// Attempted target status.
        to: TaskStatus,
    },
    /// The task has expired (TTL elapsed).
    Expired {
        /// The task ID.
        task_id: String,
    },
    /// An internal error occurred.
    Internal {
        /// Human-readable error message.
        message: String,
    },
}

impl std::fmt::Display for TaskStoreError {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        match self {
            Self::NotFound { task_id } => write!(f, "task not found: {task_id}"),
            Self::InvalidTransition { task_id, from, to } => {
                write!(f, "invalid transition for task {task_id}: {from} -> {to}")
            },
            Self::Expired { task_id } => write!(f, "task expired: {task_id}"),
            Self::Internal { message } => write!(f, "internal error: {message}"),
        }
    }
}

impl std::error::Error for TaskStoreError {}

impl From<TaskStoreError> for crate::error::Error {
    fn from(err: TaskStoreError) -> Self {
        match &err {
            TaskStoreError::NotFound { .. } => Self::not_found(err.to_string()),
            TaskStoreError::InvalidTransition { .. } => Self::validation(err.to_string()),
            // Expired uses NotFound to avoid leaking existence of expired tasks
            TaskStoreError::Expired { .. } => Self::not_found(err.to_string()),
            TaskStoreError::Internal { .. } => Self::internal(err.to_string()),
        }
    }
}

// ---------------------------------------------------------------------------
// StoreConfig
// ---------------------------------------------------------------------------

/// Configuration for the SDK task store.
///
/// Controls TTL defaults, poll intervals, and per-owner task limits.
///
/// # Defaults
///
/// | Setting                  | Default    | Description           |
/// |--------------------------|------------|-----------------------|
/// | `default_ttl_ms`         | 3,600,000  | 1 hour                |
/// | `max_ttl_ms`             | 86,400,000 | 24 hours              |
/// | `default_poll_interval_ms` | 5,000    | 5 seconds             |
/// | `max_tasks_per_owner`    | 100        | Per-owner task limit  |
///
/// # Examples
///
/// ```
/// use pmcp::server::task_store::StoreConfig;
///
/// let config = StoreConfig::default();
/// assert_eq!(config.default_ttl_ms, Some(3_600_000));
/// assert_eq!(config.max_ttl_ms, Some(86_400_000));
/// assert_eq!(config.default_poll_interval_ms, 5000);
/// assert_eq!(config.max_tasks_per_owner, 100);
/// ```
#[derive(Debug, Clone)]
pub struct StoreConfig {
    /// Default TTL in milliseconds. Applied when `create()` receives `None`.
    pub default_ttl_ms: Option<u64>,
    /// Maximum allowed TTL in milliseconds. `None` means no upper bound.
    pub max_ttl_ms: Option<u64>,
    /// Default polling interval suggested to clients, in milliseconds.
    pub default_poll_interval_ms: u64,
    /// Maximum number of active tasks per owner.
    pub max_tasks_per_owner: usize,
}

impl Default for StoreConfig {
    fn default() -> Self {
        Self {
            default_ttl_ms: Some(3_600_000), // 1 hour
            max_ttl_ms: Some(86_400_000),    // 24 hours
            default_poll_interval_ms: 5000,  // 5 seconds
            max_tasks_per_owner: 100,
        }
    }
}

// ---------------------------------------------------------------------------
// TaskStore trait
// ---------------------------------------------------------------------------

/// Core trait for MCP task lifecycle management.
///
/// Implementations must be `Send + Sync` for concurrent access from
/// multiple request handlers.
///
/// # Owner Isolation
///
/// All methods that access a specific task require an `owner_id`. If the
/// task belongs to a different owner, the store returns
/// [`TaskStoreError::NotFound`] (never revealing that the task exists
/// but belongs to someone else).
#[async_trait]
pub trait TaskStore: Send + Sync {
    /// Create a new task in the `Working` state.
    ///
    /// If `ttl` is `None`, the store's `default_ttl_ms` is applied.
    async fn create(&self, owner_id: &str, ttl: Option<u64>) -> Result<Task, TaskStoreError>;

    /// Retrieve a task by ID, scoped to the given owner.
    async fn get(&self, task_id: &str, owner_id: &str) -> Result<Task, TaskStoreError>;

    /// Transition a task to a new status with an optional status message.
    ///
    /// Validates the transition against the MCP state machine before applying.
    async fn update_status(
        &self,
        task_id: &str,
        owner_id: &str,
        status: TaskStatus,
        message: Option<String>,
    ) -> Result<Task, TaskStoreError>;

    /// List tasks for an owner with optional cursor-based pagination.
    ///
    /// Returns `(tasks, next_cursor)`. If `next_cursor` is `None`, there
    /// are no more results.
    async fn list(
        &self,
        owner_id: &str,
        cursor: Option<&str>,
    ) -> Result<(Vec<Task>, Option<String>), TaskStoreError>;

    /// Cancel a task (transition to `Cancelled`).
    async fn cancel(&self, task_id: &str, owner_id: &str) -> Result<Task, TaskStoreError>;

    /// Remove expired tasks. Returns the count of tasks removed.
    async fn cleanup_expired(&self) -> Result<usize, TaskStoreError>;

    /// Returns a reference to the store's configuration.
    fn config(&self) -> &StoreConfig;
}

// ---------------------------------------------------------------------------
// Internal TaskRecord
// ---------------------------------------------------------------------------

/// Internal record wrapping a [`Task`] with owner and expiration metadata.
#[derive(Debug)]
struct TaskRecord {
    task: Task,
    owner_id: String,
    expires_at: Option<Instant>,
}

// ---------------------------------------------------------------------------
// InMemoryTaskStore
// ---------------------------------------------------------------------------

/// Thread-safe in-memory task store using [`DashMap`].
///
/// Suitable for development and testing. For production use, see the
/// `pmcp-tasks` crate which provides `DynamoDB` and Redis backends.
///
/// # Examples
///
/// ```
/// use pmcp::server::task_store::{InMemoryTaskStore, StoreConfig};
///
/// let store = InMemoryTaskStore::with_config(StoreConfig {
///     default_poll_interval_ms: 3000,
///     ..StoreConfig::default()
/// });
/// ```
#[derive(Debug)]
pub struct InMemoryTaskStore {
    records: DashMap<String, TaskRecord>,
    config: StoreConfig,
}

impl InMemoryTaskStore {
    /// Create an in-memory task store with default configuration.
    pub fn new() -> Self {
        Self {
            records: DashMap::new(),
            config: StoreConfig::default(),
        }
    }

    /// Create an in-memory task store with custom configuration.
    pub fn with_config(config: StoreConfig) -> Self {
        Self {
            records: DashMap::new(),
            config,
        }
    }

    /// Validate owner and expiration for a task record.
    fn validate_access(
        record: &TaskRecord,
        task_id: &str,
        owner_id: &str,
    ) -> Result<(), TaskStoreError> {
        if record.owner_id != owner_id {
            return Err(TaskStoreError::NotFound {
                task_id: task_id.to_string(),
            });
        }
        if let Some(expires_at) = record.expires_at {
            if Instant::now() > expires_at {
                return Err(TaskStoreError::Expired {
                    task_id: task_id.to_string(),
                });
            }
        }
        Ok(())
    }
}

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

#[async_trait]
impl TaskStore for InMemoryTaskStore {
    async fn create(&self, owner_id: &str, ttl: Option<u64>) -> Result<Task, TaskStoreError> {
        // Enforce max_tasks_per_owner (excludes expired tasks)
        let now = Instant::now();
        let owner_count = self
            .records
            .iter()
            .filter(|entry| {
                let v = entry.value();
                v.owner_id == owner_id && v.expires_at.is_none_or(|e| now <= e)
            })
            .count();
        if owner_count >= self.config.max_tasks_per_owner {
            return Err(TaskStoreError::Internal {
                message: format!(
                    "owner {owner_id} has reached the maximum of {} tasks",
                    self.config.max_tasks_per_owner
                ),
            });
        }

        let task_id = uuid::Uuid::new_v4().to_string();
        let now = chrono::Utc::now();
        let now_str = now.to_rfc3339();

        let effective_ttl = ttl.or(self.config.default_ttl_ms);

        // Clamp to max_ttl_ms if configured
        let effective_ttl = match (effective_ttl, self.config.max_ttl_ms) {
            (Some(t), Some(max)) if t > max => Some(max),
            (t, _) => t,
        };

        let expires_at =
            effective_ttl.map(|ms| Instant::now() + std::time::Duration::from_millis(ms));

        let task = Task::new(&task_id, TaskStatus::Working)
            .with_timestamps(&now_str, &now_str)
            .with_poll_interval(self.config.default_poll_interval_ms);

        let task = if let Some(ttl_val) = effective_ttl {
            task.with_ttl(ttl_val)
        } else {
            task
        };

        let record = TaskRecord {
            task: task.clone(),
            owner_id: owner_id.to_string(),
            expires_at,
        };

        self.records.insert(task_id, record);
        Ok(task)
    }

    async fn get(&self, task_id: &str, owner_id: &str) -> Result<Task, TaskStoreError> {
        let entry = self
            .records
            .get(task_id)
            .ok_or_else(|| TaskStoreError::NotFound {
                task_id: task_id.to_string(),
            })?;
        Self::validate_access(entry.value(), task_id, owner_id)?;
        Ok(entry.value().task.clone())
    }

    async fn update_status(
        &self,
        task_id: &str,
        owner_id: &str,
        status: TaskStatus,
        message: Option<String>,
    ) -> Result<Task, TaskStoreError> {
        let mut entry = self
            .records
            .get_mut(task_id)
            .ok_or_else(|| TaskStoreError::NotFound {
                task_id: task_id.to_string(),
            })?;

        let record = entry.value_mut();
        Self::validate_access(record, task_id, owner_id)?;

        // Validate state machine transition
        if !record.task.status.can_transition_to(&status) {
            return Err(TaskStoreError::InvalidTransition {
                task_id: task_id.to_string(),
                from: record.task.status,
                to: status,
            });
        }

        let now_str = chrono::Utc::now().to_rfc3339();
        record.task.status = status;
        record.task.last_updated_at = now_str;
        record.task.status_message = message;

        Ok(record.task.clone())
    }

    async fn list(
        &self,
        owner_id: &str,
        cursor: Option<&str>,
    ) -> Result<(Vec<Task>, Option<String>), TaskStoreError> {
        const PAGE_SIZE: usize = 20;
        let now = Instant::now();
        let mut tasks: Vec<Task> = self
            .records
            .iter()
            .filter(|entry| {
                let v = entry.value();
                v.owner_id == owner_id && v.expires_at.is_none_or(|e| now <= e)
            })
            .map(|entry| entry.value().task.clone())
            .collect();

        // Sort by created_at descending (newest first)
        tasks.sort_by(|a, b| b.created_at.cmp(&a.created_at));

        // Apply cursor-based pagination (cursor = task_id of last item)
        if let Some(cursor_id) = cursor {
            if let Some(pos) = tasks.iter().position(|t| t.task_id == cursor_id) {
                tasks = tasks.into_iter().skip(pos + 1).collect();
            }
        }

        if tasks.len() > PAGE_SIZE {
            let next_cursor = tasks[PAGE_SIZE - 1].task_id.clone();
            tasks.truncate(PAGE_SIZE);
            Ok((tasks, Some(next_cursor)))
        } else {
            Ok((tasks, None))
        }
    }

    async fn cancel(&self, task_id: &str, owner_id: &str) -> Result<Task, TaskStoreError> {
        self.update_status(task_id, owner_id, TaskStatus::Cancelled, None)
            .await
    }

    async fn cleanup_expired(&self) -> Result<usize, TaskStoreError> {
        let now = Instant::now();
        let before = self.records.len();
        self.records
            .retain(|_, record| record.expires_at.is_none_or(|e| now <= e));
        Ok(before - self.records.len())
    }

    fn config(&self) -> &StoreConfig {
        &self.config
    }
}

// ---------------------------------------------------------------------------
// Tests
// ---------------------------------------------------------------------------

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

    // -- Constructor tests --

    #[test]
    fn new_creates_empty_store() {
        let store = InMemoryTaskStore::new();
        assert!(store.records.is_empty());
    }

    #[test]
    fn default_creates_empty_store() {
        let store = InMemoryTaskStore::default();
        assert!(store.records.is_empty());
    }

    #[test]
    fn with_config_applies_custom_config() {
        let config = StoreConfig {
            default_ttl_ms: Some(1_000),
            max_ttl_ms: Some(2_000),
            default_poll_interval_ms: 500,
            max_tasks_per_owner: 10,
        };
        let store = InMemoryTaskStore::with_config(config);
        assert_eq!(store.config().default_ttl_ms, Some(1_000));
        assert_eq!(store.config().max_ttl_ms, Some(2_000));
        assert_eq!(store.config().default_poll_interval_ms, 500);
        assert_eq!(store.config().max_tasks_per_owner, 10);
    }

    #[test]
    fn store_config_default_values() {
        let config = StoreConfig::default();
        assert_eq!(config.default_ttl_ms, Some(3_600_000));
        assert_eq!(config.max_ttl_ms, Some(86_400_000));
        assert_eq!(config.default_poll_interval_ms, 5000);
        assert_eq!(config.max_tasks_per_owner, 100);
    }

    // -- Create tests --

    #[tokio::test]
    async fn create_returns_working_task() {
        let store = InMemoryTaskStore::new();
        let task = store.create("owner-1", None).await.unwrap();
        assert_eq!(task.status, TaskStatus::Working);
        assert!(!task.task_id.is_empty());
        assert!(!task.created_at.is_empty());
        assert!(!task.last_updated_at.is_empty());
    }

    #[tokio::test]
    async fn create_with_default_ttl() {
        let store = InMemoryTaskStore::new();
        let task = store.create("owner-1", None).await.unwrap();
        // Default TTL from StoreConfig is 3_600_000 (1 hour)
        assert_eq!(task.ttl, Some(3_600_000));
    }

    #[tokio::test]
    async fn create_with_explicit_ttl() {
        let store = InMemoryTaskStore::new();
        let task = store.create("owner-1", Some(60_000)).await.unwrap();
        assert_eq!(task.ttl, Some(60_000));
    }

    #[tokio::test]
    async fn create_clamps_ttl_to_max() {
        let store = InMemoryTaskStore::with_config(StoreConfig {
            max_ttl_ms: Some(10_000),
            ..StoreConfig::default()
        });
        let task = store.create("owner-1", Some(999_999)).await.unwrap();
        assert_eq!(task.ttl, Some(10_000));
    }

    #[tokio::test]
    async fn create_sets_poll_interval() {
        let store = InMemoryTaskStore::with_config(StoreConfig {
            default_poll_interval_ms: 3000,
            ..StoreConfig::default()
        });
        let task = store.create("owner-1", None).await.unwrap();
        assert_eq!(task.poll_interval, Some(3000));
    }

    // -- Get tests --

    #[tokio::test]
    async fn get_returns_created_task() {
        let store = InMemoryTaskStore::new();
        let created = store.create("owner-1", None).await.unwrap();
        let fetched = store.get(&created.task_id, "owner-1").await.unwrap();
        assert_eq!(fetched.task_id, created.task_id);
        assert_eq!(fetched.status, TaskStatus::Working);
    }

    #[tokio::test]
    async fn get_owner_mismatch_returns_not_found() {
        let store = InMemoryTaskStore::new();
        let created = store.create("owner-1", None).await.unwrap();
        let result = store.get(&created.task_id, "owner-2").await;
        assert!(
            matches!(&result, Err(TaskStoreError::NotFound { task_id }) if task_id == &created.task_id),
            "expected NotFound, got: {result:?}"
        );
    }

    #[tokio::test]
    async fn get_nonexistent_returns_not_found() {
        let store = InMemoryTaskStore::new();
        let result = store.get("nonexistent", "owner-1").await;
        assert!(matches!(result, Err(TaskStoreError::NotFound { .. })));
    }

    // -- List tests --

    #[tokio::test]
    async fn list_returns_owner_tasks_only() {
        let store = InMemoryTaskStore::new();
        store.create("owner-1", None).await.unwrap();
        store.create("owner-1", None).await.unwrap();
        store.create("owner-2", None).await.unwrap();

        let (tasks, _) = store.list("owner-1", None).await.unwrap();
        assert_eq!(tasks.len(), 2);
    }

    #[tokio::test]
    async fn list_empty_for_unknown_owner() {
        let store = InMemoryTaskStore::new();
        store.create("owner-1", None).await.unwrap();
        let (tasks, _) = store.list("owner-unknown", None).await.unwrap();
        assert!(tasks.is_empty());
    }

    #[tokio::test]
    async fn list_sorted_newest_first() {
        let store = InMemoryTaskStore::new();
        let first = store.create("owner-1", None).await.unwrap();
        // Small delay to ensure different timestamps
        tokio::time::sleep(std::time::Duration::from_millis(2)).await;
        let second = store.create("owner-1", None).await.unwrap();

        let (tasks, _) = store.list("owner-1", None).await.unwrap();
        assert_eq!(tasks.len(), 2);
        assert_eq!(tasks[0].task_id, second.task_id);
        assert_eq!(tasks[1].task_id, first.task_id);
    }

    // -- Cancel tests --

    #[tokio::test]
    async fn cancel_transitions_to_cancelled() {
        let store = InMemoryTaskStore::new();
        let created = store.create("owner-1", None).await.unwrap();
        let cancelled = store.cancel(&created.task_id, "owner-1").await.unwrap();
        assert_eq!(cancelled.status, TaskStatus::Cancelled);
    }

    #[tokio::test]
    async fn cancel_completed_task_returns_invalid_transition() {
        let store = InMemoryTaskStore::new();
        let created = store.create("owner-1", None).await.unwrap();

        // Complete the task first
        store
            .update_status(
                &created.task_id,
                "owner-1",
                TaskStatus::Completed,
                Some("Done".to_string()),
            )
            .await
            .unwrap();

        // Cancel should fail
        let result = store.cancel(&created.task_id, "owner-1").await;
        assert!(
            matches!(result, Err(TaskStoreError::InvalidTransition { .. })),
            "expected InvalidTransition, got: {result:?}"
        );
    }

    // -- Update status tests --

    #[tokio::test]
    async fn update_status_working_to_completed() {
        let store = InMemoryTaskStore::new();
        let created = store.create("owner-1", None).await.unwrap();
        let updated = store
            .update_status(
                &created.task_id,
                "owner-1",
                TaskStatus::Completed,
                Some("Done".to_string()),
            )
            .await
            .unwrap();
        assert_eq!(updated.status, TaskStatus::Completed);
        assert_eq!(updated.status_message.as_deref(), Some("Done"));
    }

    #[tokio::test]
    async fn update_status_from_terminal_returns_invalid_transition() {
        let store = InMemoryTaskStore::new();
        let created = store.create("owner-1", None).await.unwrap();

        // Complete first
        store
            .update_status(&created.task_id, "owner-1", TaskStatus::Completed, None)
            .await
            .unwrap();

        // Try to go back to Working
        let result = store
            .update_status(&created.task_id, "owner-1", TaskStatus::Working, None)
            .await;
        assert!(
            matches!(result, Err(TaskStoreError::InvalidTransition { .. })),
            "expected InvalidTransition, got: {result:?}"
        );
    }

    #[tokio::test]
    async fn update_status_self_transition_rejected() {
        let store = InMemoryTaskStore::new();
        let created = store.create("owner-1", None).await.unwrap();
        let result = store
            .update_status(&created.task_id, "owner-1", TaskStatus::Working, None)
            .await;
        assert!(
            matches!(result, Err(TaskStoreError::InvalidTransition { .. })),
            "expected InvalidTransition, got: {result:?}"
        );
    }

    // -- TTL / expiration tests --

    #[tokio::test]
    async fn task_created_with_explicit_ttl_has_correct_field() {
        let store = InMemoryTaskStore::new();
        let task = store.create("owner-1", Some(60_000)).await.unwrap();
        assert_eq!(task.ttl, Some(60_000));
    }

    #[tokio::test]
    async fn task_created_with_none_ttl_gets_default() {
        let config = StoreConfig {
            default_ttl_ms: Some(120_000),
            ..StoreConfig::default()
        };
        let store = InMemoryTaskStore::with_config(config);
        let task = store.create("owner-1", None).await.unwrap();
        assert_eq!(task.ttl, Some(120_000));
    }

    #[tokio::test]
    async fn cleanup_expired_removes_expired_tasks() {
        let store = InMemoryTaskStore::with_config(StoreConfig {
            default_ttl_ms: Some(1), // 1ms TTL
            ..StoreConfig::default()
        });
        store.create("owner-1", Some(1)).await.unwrap();

        // Wait for expiration
        tokio::time::sleep(std::time::Duration::from_millis(10)).await;

        let removed = store.cleanup_expired().await.unwrap();
        assert_eq!(removed, 1);
        assert!(store.records.is_empty());
    }

    #[tokio::test]
    async fn cleanup_expired_keeps_non_expired() {
        let store = InMemoryTaskStore::new();
        store.create("owner-1", Some(3_600_000)).await.unwrap();
        let removed = store.cleanup_expired().await.unwrap();
        assert_eq!(removed, 0);
        assert_eq!(store.records.len(), 1);
    }

    #[tokio::test]
    async fn get_expired_task_returns_expired_error() {
        let store = InMemoryTaskStore::with_config(StoreConfig {
            default_ttl_ms: Some(1), // 1ms TTL
            ..StoreConfig::default()
        });
        let created = store.create("owner-1", Some(1)).await.unwrap();

        // Wait for expiration
        tokio::time::sleep(std::time::Duration::from_millis(10)).await;

        let result = store.get(&created.task_id, "owner-1").await;
        assert!(
            matches!(result, Err(TaskStoreError::Expired { .. })),
            "expected Expired, got: {result:?}"
        );
    }

    // -- Error display tests --

    #[test]
    fn task_store_error_display_not_found() {
        let err = TaskStoreError::NotFound {
            task_id: "t-123".to_string(),
        };
        assert_eq!(err.to_string(), "task not found: t-123");
    }

    #[test]
    fn task_store_error_display_invalid_transition() {
        let err = TaskStoreError::InvalidTransition {
            task_id: "t-123".to_string(),
            from: TaskStatus::Completed,
            to: TaskStatus::Working,
        };
        let msg = err.to_string();
        assert!(msg.contains("invalid transition"));
        assert!(msg.contains("t-123"));
    }

    #[test]
    fn task_store_error_display_expired() {
        let err = TaskStoreError::Expired {
            task_id: "t-123".to_string(),
        };
        assert_eq!(err.to_string(), "task expired: t-123");
    }

    #[test]
    fn task_store_error_display_internal() {
        let err = TaskStoreError::Internal {
            message: "something broke".to_string(),
        };
        assert_eq!(err.to_string(), "internal error: something broke");
    }

    #[test]
    fn task_store_error_converts_to_sdk_error() {
        let err = TaskStoreError::NotFound {
            task_id: "t-123".to_string(),
        };
        let sdk_err: crate::error::Error = err.into();
        let msg = sdk_err.to_string();
        assert!(msg.contains("task not found: t-123"));
    }

    // -- Max tasks per owner --

    #[tokio::test]
    async fn max_tasks_per_owner_enforced() {
        let store = InMemoryTaskStore::with_config(StoreConfig {
            max_tasks_per_owner: 2,
            ..StoreConfig::default()
        });
        store.create("owner-1", None).await.unwrap();
        store.create("owner-1", None).await.unwrap();
        let result = store.create("owner-1", None).await;
        assert!(
            matches!(result, Err(TaskStoreError::Internal { .. })),
            "expected Internal error for max tasks, got: {result:?}"
        );
    }

    #[tokio::test]
    async fn max_tasks_scoped_to_owner() {
        let store = InMemoryTaskStore::with_config(StoreConfig {
            max_tasks_per_owner: 2,
            ..StoreConfig::default()
        });
        store.create("owner-a", None).await.unwrap();
        store.create("owner-a", None).await.unwrap();
        // Owner B should still be able to create
        let result = store.create("owner-b", None).await;
        assert!(result.is_ok());
    }
}