ryo_executor/decider/

deciders.rs

//! Decider implementations
//!
//! Various strategies for agents to decide their next action.

use super::action::{Action, ActionKind};
use super::context::DecisionContext;
use super::state::AgentState;
use std::fmt::Debug;

// ============================================================================
// Decider Trait
// ============================================================================

/// Trait for decision-making strategies
///
/// A Decider takes the current context and state, and returns the next Action.
pub trait Decider: Send + Sync + Debug {
    /// Decide the next action based on context and state
    fn decide(&self, context: &DecisionContext, state: &AgentState) -> Action;

    /// Name of this decider (for logging)
    fn name(&self) -> &'static str;
}

// ============================================================================
// PlainDecider: Pass-through (no autonomous decisions)
// ============================================================================

/// PlainDecider: Just returns the next work item as a read action
///
/// This is for "plain mode" where agents don't make autonomous decisions
/// but simply execute the work assigned to them.
#[derive(Debug, Clone, Default)]
pub struct PlainDecider;

impl Decider for PlainDecider {
    fn decide(&self, context: &DecisionContext, _state: &AgentState) -> Action {
        // If there's remaining work, return the next item as a mutation
        if let Some(target) = context.next_work_item() {
            return Action::mutate("Execute", target.clone());
        }

        // No more work
        Action::done()
    }

    fn name(&self) -> &'static str {
        "PlainDecider"
    }
}

// ============================================================================
// ParameterizedDecider: Uses state for smarter decisions
// ============================================================================

/// ParameterizedDecider: Makes decisions based on current state
///
/// Considers errors, recent results, and other state to make better decisions.
#[derive(Debug, Clone)]
pub struct ParameterizedDecider {
    /// Weight for error-focused decisions (0.0 - 1.0)
    pub error_weight: f64,
    /// Weight for recent-file-focused decisions (0.0 - 1.0)
    pub recency_weight: f64,
}

impl Default for ParameterizedDecider {
    fn default() -> Self {
        Self {
            error_weight: 0.7,
            recency_weight: 0.3,
        }
    }
}

impl ParameterizedDecider {
    /// Create with custom weights
    pub fn with_weights(error_weight: f64, recency_weight: f64) -> Self {
        Self {
            error_weight,
            recency_weight,
        }
    }
}

impl Decider for ParameterizedDecider {
    fn decide(&self, context: &DecisionContext, state: &AgentState) -> Action {
        // 1. If there are errors and error_weight is high, focus on errors
        if state.has_errors() && self.error_weight > 0.5 {
            if let Some(errored_file) = state.most_errored_file() {
                return Action::read(errored_file.to_string_lossy())
                    .with_reason(format!("fixing {} errors", state.error_count()));
            }
        }

        // 2. If last action failed, try something different
        if context.last_failed() {
            // Try a different file or approach
            let available = state.available_files(context.agent_id);
            if let Some(file) = available.first() {
                return Action::read(file.to_string_lossy())
                    .with_reason("trying different file after failure");
            }
        }

        // 3. If success rate is low, consider escalation
        if context.recent_success_rate() < 0.3 && context.recent_results.len() >= 3 {
            return Action::new(ActionKind::Escalate)
                .with_reason("low success rate, requesting help");
        }

        // 4. Normal operation: use remaining work or investigate
        if let Some(target) = context.next_work_item() {
            return Action::mutate("Execute", target.clone());
        }

        let available = state.available_files(context.agent_id);
        if let Some(file) = available.first() {
            return Action::read(file.to_string_lossy())
                .with_reason("investigating available file");
        }

        Action::done()
    }

    fn name(&self) -> &'static str {
        "ParameterizedDecider"
    }
}

// ============================================================================
// MurmurationDecider: Swarm-like behavior with collision avoidance
// ============================================================================

/// MurmurationDecider: Swarm behavior for parallel agents
///
/// Implements three rules:
/// 1. Separation: Don't work on the same file as other agents
/// 2. Alignment: Coordinate with nearby agents
/// 3. Cohesion: Move towards the overall goal
#[derive(Debug, Clone)]
pub struct MurmurationDecider {
    /// Weight for separation behavior (0.0 - 1.0)
    pub separation_weight: f64,
}

impl Default for MurmurationDecider {
    fn default() -> Self {
        Self {
            separation_weight: 1.0,
        }
    }
}

impl MurmurationDecider {
    /// Create with custom separation weight
    pub fn with_separation(separation_weight: f64) -> Self {
        Self { separation_weight }
    }
}

impl Decider for MurmurationDecider {
    fn decide(&self, context: &DecisionContext, state: &AgentState) -> Action {
        // 1. Separation: Find an unoccupied, uninvestigated file
        let available = state.available_files(context.agent_id);

        if let Some(file) = available.first() {
            return Action::read(file.to_string_lossy()).with_reason(format!(
                "agent #{} investigating (separation)",
                context.agent_id
            ));
        }

        // 2. All files are occupied or investigated
        if !state.uninvestigated_files().is_empty() {
            // Some files are being investigated by others, wait
            return Action::rest("waiting for other agents");
        }

        // 3. Cohesion: All done, contribute to final goal
        if let Some(target) = context.next_work_item() {
            return Action::mutate("Execute", target.clone())
                .with_reason("cohesion: executing final work");
        }

        Action::done()
    }

    fn name(&self) -> &'static str {
        "MurmurationDecider"
    }
}

// ============================================================================
// Decision Modifier: Adjusts decisions based on conditions
// ============================================================================

/// Trait for modifying decisions based on conditions
///
/// Modifiers are applied after the base decider makes its decision,
/// allowing for layered behavior like "weather awareness" on top of
/// "flocking behavior".
pub trait DecisionModifier: Send + Sync + Debug {
    /// Modify an action based on context and state
    ///
    /// Can return the same action unchanged, modify it, or replace it entirely.
    fn modify(&self, action: Action, context: &DecisionContext, state: &AgentState) -> Action;

    /// Name of this modifier (for logging)
    fn name(&self) -> &'static str;
}

// ============================================================================
// Pre-built Modifiers
// ============================================================================

/// ErrorAwareModifier: Prioritizes files with errors
///
/// Like birds avoiding storms - if there are errors, focus on fixing them.
#[derive(Debug, Clone)]
pub struct ErrorAwareModifier {
    /// Weight for error prioritization (0.0 - 1.0)
    pub weight: f64,
}

impl ErrorAwareModifier {
    pub fn new(weight: f64) -> Self {
        Self { weight }
    }
}

impl DecisionModifier for ErrorAwareModifier {
    fn modify(&self, action: Action, _context: &DecisionContext, state: &AgentState) -> Action {
        // If weight is high and there are errors, redirect to error file
        if self.weight > 0.5 && state.has_errors() {
            if let Some(errored_file) = state.most_errored_file() {
                return Action::read(errored_file.to_string_lossy()).with_reason(format!(
                    "error-aware: {} errors in file",
                    state.error_count()
                ));
            }
        }
        action
    }

    fn name(&self) -> &'static str {
        "ErrorAwareModifier"
    }
}

/// StallDetectionModifier: Escalates when progress stalls
///
/// Like birds changing course when stuck in a thermal.
#[derive(Debug, Clone)]
pub struct StallDetectionModifier {
    /// Number of ticks without progress before escalating
    pub threshold: u64,
}

impl StallDetectionModifier {
    pub fn new(threshold: u64) -> Self {
        Self { threshold }
    }
}

impl DecisionModifier for StallDetectionModifier {
    fn modify(&self, action: Action, context: &DecisionContext, state: &AgentState) -> Action {
        if state.is_stalled(context.tick, self.threshold) {
            return Action::new(ActionKind::Escalate).with_reason(format!(
                "stall-detection: no progress for {} ticks",
                self.threshold
            ));
        }
        action
    }

    fn name(&self) -> &'static str {
        "StallDetectionModifier"
    }
}

/// SuccessRateModifier: Escalates on low success rate
///
/// Like birds seeking shelter when conditions are bad.
#[derive(Debug, Clone)]
pub struct SuccessRateModifier {
    /// Minimum success rate before escalating (0.0 - 1.0)
    pub threshold: f64,
    /// Minimum number of results before checking
    pub min_samples: usize,
}

impl SuccessRateModifier {
    pub fn new(threshold: f64) -> Self {
        Self {
            threshold,
            min_samples: 3,
        }
    }
}

impl DecisionModifier for SuccessRateModifier {
    fn modify(&self, action: Action, context: &DecisionContext, _state: &AgentState) -> Action {
        if context.recent_results.len() >= self.min_samples
            && context.recent_success_rate() < self.threshold
        {
            return Action::new(ActionKind::Escalate).with_reason(format!(
                "success-rate: {:.0}% below threshold",
                context.recent_success_rate() * 100.0
            ));
        }
        action
    }

    fn name(&self) -> &'static str {
        "SuccessRateModifier"
    }
}

/// RetryModifier: Retries on failure with backoff
#[derive(Debug, Clone)]
pub struct RetryModifier {
    /// Maximum retries
    pub max_retries: u32,
}

impl RetryModifier {
    pub fn new(max_retries: u32) -> Self {
        Self { max_retries }
    }
}

impl DecisionModifier for RetryModifier {
    fn modify(&self, action: Action, context: &DecisionContext, _state: &AgentState) -> Action {
        // If last action failed and we haven't exceeded retries, retry
        if context.last_failed() {
            let consecutive_failures = context
                .recent_results
                .iter()
                .rev()
                .take_while(|r| !r.success)
                .count() as u32;

            if consecutive_failures < self.max_retries {
                // Retry the same action
                if let Some(last) = context.last_result() {
                    return last
                        .action
                        .clone()
                        .with_reason(format!("retry: attempt {}", consecutive_failures + 1));
                }
            }
        }
        action
    }

    fn name(&self) -> &'static str {
        "RetryModifier"
    }
}

// ============================================================================
// Composable Decider: Base + Modifiers
// ============================================================================

/// ComposableDecider: Combines a base decider with modifiers
///
/// This enables layered decision-making:
/// - Base decider handles target selection (WHERE to act)
/// - Modifiers adjust behavior based on conditions (HOW to act)
///
/// # Example
///
/// ```rust,ignore
/// let decider = ComposableDecider::new(MurmurationDecider::default())
///     .with_modifier(ErrorAwareModifier::new(0.7))
///     .with_modifier(StallDetectionModifier::new(5));
/// ```
#[derive(Debug)]
pub struct ComposableDecider {
    base: Box<dyn Decider>,
    modifiers: Vec<Box<dyn DecisionModifier>>,
}

impl ComposableDecider {
    /// Create a new composable decider with the given base
    pub fn new(base: impl Decider + 'static) -> Self {
        Self {
            base: Box::new(base),
            modifiers: Vec::new(),
        }
    }

    /// Add a modifier to the chain
    pub fn with_modifier(mut self, modifier: impl DecisionModifier + 'static) -> Self {
        self.modifiers.push(Box::new(modifier));
        self
    }

    /// Add an error-aware modifier
    pub fn error_aware(self, weight: f64) -> Self {
        self.with_modifier(ErrorAwareModifier::new(weight))
    }

    /// Add a stall detection modifier
    pub fn stall_detection(self, threshold: u64) -> Self {
        self.with_modifier(StallDetectionModifier::new(threshold))
    }

    /// Add a success rate modifier
    pub fn success_rate(self, threshold: f64) -> Self {
        self.with_modifier(SuccessRateModifier::new(threshold))
    }

    /// Add a retry modifier
    pub fn with_retry(self, max_retries: u32) -> Self {
        self.with_modifier(RetryModifier::new(max_retries))
    }
}

impl Decider for ComposableDecider {
    fn decide(&self, context: &DecisionContext, state: &AgentState) -> Action {
        // 1. Get base decision
        let mut action = self.base.decide(context, state);

        // 2. Apply modifiers in order
        for modifier in &self.modifiers {
            action = modifier.modify(action, context, state);
        }

        action
    }

    fn name(&self) -> &'static str {
        "ComposableDecider"
    }
}

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

    fn create_test_context() -> DecisionContext {
        DecisionContext::new(0, "rename foo to bar")
            .with_tick(1)
            .with_remaining_work(vec!["task1".to_string(), "task2".to_string()])
    }

    fn create_test_state() -> AgentState {
        let mut state = AgentState::new();
        state.update_file(
            PathBuf::from("a.rs"),
            super::super::state::FileState::new(100, 2000),
        );
        state.update_file(
            PathBuf::from("b.rs"),
            super::super::state::FileState::new(50, 1000),
        );
        state
    }

    #[test]
    fn test_plain_decider() {
        let decider = PlainDecider;
        let context = create_test_context();
        let state = create_test_state();

        let action = decider.decide(&context, &state);
        assert_eq!(action.kind, ActionKind::Mutate);
        assert_eq!(action.target, Some("task1".to_string()));
    }

    #[test]
    fn test_murmuration_decider() {
        let decider = MurmurationDecider::default();
        let context = DecisionContext::new(0, "investigate").with_tick(1);
        let state = create_test_state();

        let action = decider.decide(&context, &state);
        assert_eq!(action.kind, ActionKind::Read);
        assert!(action.target.is_some());
    }

    #[test]
    fn test_parameterized_decider_with_errors() {
        let decider = ParameterizedDecider::default();
        let context = DecisionContext::new(0, "fix errors");

        let mut state = create_test_state();
        state.add_error(super::super::state::ErrorInfo::new(
            PathBuf::from("a.rs"),
            10,
            "error",
        ));

        let action = decider.decide(&context, &state);
        assert_eq!(action.kind, ActionKind::Read);
        // Should target the file with errors
        assert!(action.target.unwrap().contains("a.rs"));
    }

    #[test]
    fn test_composable_decider_basic() {
        // Base: MurmurationDecider
        let decider = ComposableDecider::new(MurmurationDecider::default());

        let context = DecisionContext::new(0, "investigate").with_tick(1);
        let state = create_test_state();

        let action = decider.decide(&context, &state);
        assert_eq!(action.kind, ActionKind::Read);
    }

    #[test]
    fn test_composable_decider_with_error_modifier() {
        // Base: Murmuration + Error awareness
        let decider = ComposableDecider::new(MurmurationDecider::default()).error_aware(0.8);

        let context = DecisionContext::new(0, "investigate").with_tick(1);
        let mut state = create_test_state();

        // Add error to a.rs
        state.add_error(super::super::state::ErrorInfo::new(
            PathBuf::from("a.rs"),
            10,
            "compile error",
        ));

        let action = decider.decide(&context, &state);
        // Should redirect to error file
        assert_eq!(action.kind, ActionKind::Read);
        assert!(action.target.unwrap().contains("a.rs"));
        assert!(action.reason.unwrap().contains("error-aware"));
    }

    #[test]
    fn test_composable_decider_stall_detection() {
        let decider = ComposableDecider::new(PlainDecider).stall_detection(5);

        let context = DecisionContext::new(0, "task")
            .with_tick(10)
            .with_remaining_work(vec!["task1".to_string()]);

        let mut state = create_test_state();
        // Simulate stall: last progress was at tick 0
        state.last_progress_tick = 0;

        let action = decider.decide(&context, &state);
        // Should escalate due to stall
        assert_eq!(action.kind, ActionKind::Escalate);
        assert!(action.reason.unwrap().contains("stall"));
    }

    #[test]
    fn test_composable_decider_chain() {
        // Full chain: Murmuration + Error + Stall + Retry
        let decider = ComposableDecider::new(MurmurationDecider::default())
            .error_aware(0.7)
            .stall_detection(10)
            .with_retry(3);

        let context = DecisionContext::new(0, "investigate").with_tick(1);
        let state = create_test_state();

        // Normal operation - should use base decider
        let action = decider.decide(&context, &state);
        assert_eq!(action.kind, ActionKind::Read);
    }

    #[test]
    fn test_success_rate_modifier() {
        use super::super::action::ActionResult;

        let decider = ComposableDecider::new(PlainDecider).success_rate(0.5);

        // Create context with many failures
        let mut context =
            DecisionContext::new(0, "task").with_remaining_work(vec!["task1".to_string()]);

        // Add 4 failures
        for _ in 0..4 {
            context.add_result(ActionResult::failure(Action::read("test.rs"), "error"));
        }

        let state = create_test_state();
        let action = decider.decide(&context, &state);

        // Should escalate due to low success rate
        assert_eq!(action.kind, ActionKind::Escalate);
        assert!(action.reason.unwrap().contains("success-rate"));
    }
}