maple-runtime 0.1.1

//! Coupling Fabric - manages coupling relationships and topology
//!
//! Coupling describes the strength and character of interaction between Resonators.

use crate::allocator::AttentionAllocator;
use crate::runtime_core::DecouplingResult;
use crate::types::*;
use dashmap::DashMap;
use petgraph::graph::{DiGraph, NodeIndex};
use std::sync::Arc;
use tokio::sync::RwLock;

/// Coupling Fabric manages all coupling relationships
pub struct CouplingFabric {
    /// Active couplings
    couplings: DashMap<CouplingId, Coupling>,

    /// Coupling graph (directed, weighted)
    graph: Arc<RwLock<CouplingGraph>>,

    /// Attention allocator reference (coupling is bounded by attention)
    attention: Arc<AttentionAllocator>,

    /// Configuration
    config: CouplingConfig,
}

struct CouplingGraph {
    graph: DiGraph<ResonatorId, CouplingId>,
    node_map: std::collections::HashMap<ResonatorId, NodeIndex>,
}

impl CouplingGraph {
    fn new() -> Self {
        Self {
            graph: DiGraph::new(),
            node_map: std::collections::HashMap::new(),
        }
    }

    fn add_node(&mut self, resonator: ResonatorId) -> NodeIndex {
        if let Some(&node) = self.node_map.get(&resonator) {
            return node;
        }

        let node = self.graph.add_node(resonator);
        self.node_map.insert(resonator, node);
        node
    }

    fn add_edge(&mut self, coupling: &Coupling) {
        let source_node = self.add_node(coupling.source);
        let target_node = self.add_node(coupling.target);
        self.graph.add_edge(source_node, target_node, coupling.id);
    }

    fn remove_edge(&mut self, coupling_id: &CouplingId) {
        if let Some(edge_index) = self
            .graph
            .edge_indices()
            .find(|&e| self.graph[e] == *coupling_id)
        {
            self.graph.remove_edge(edge_index);
        }
    }
}

impl CouplingFabric {
    pub fn new(config: &CouplingConfig, attention: Arc<AttentionAllocator>) -> Self {
        Self {
            couplings: DashMap::new(),
            graph: Arc::new(RwLock::new(CouplingGraph::new())),
            attention,
            config: config.clone(),
        }
    }

    /// Register a Resonator in the coupling topology
    pub async fn register(&self, resonator: &ResonatorId) -> Result<(), String> {
        let mut graph = self.graph.write().await;
        graph.add_node(*resonator);
        Ok(())
    }

    /// Establish coupling between Resonators
    ///
    /// ARCHITECTURAL RULE: Couplings MUST strengthen gradually.
    /// Abrupt coupling escalation is a design failure.
    ///
    /// Returns the coupling ID and attention token for handle creation by the runtime.
    pub async fn establish_coupling(
        &self,
        params: CouplingParams,
    ) -> Result<(CouplingId, AllocationToken), CouplingError> {
        // Validate parameters
        params
            .validate()
            .map_err(|e| CouplingError::ValidationFailed(e.to_string()))?;

        // Check attention availability (INVARIANT: Coupling bounded by attention)
        let attention_available = self
            .attention
            .available_for_coupling(&params.source)
            .await?;

        if attention_available < params.initial_attention_cost {
            return Err(CouplingError::InsufficientAttention {
                requested: params.initial_attention_cost,
                available: attention_available,
            });
        }

        // Validate coupling strength is not too aggressive initially
        // (prevent abrupt escalation)
        if params.initial_strength > self.config.max_initial_strength {
            return Err(CouplingError::TooAggressiveInitialStrength);
        }

        // Allocate attention
        let attention_token = self
            .attention
            .allocate(&params.source, params.initial_attention_cost)
            .await?;

        // Create coupling
        let coupling = Coupling {
            id: CouplingId::generate(),
            source: params.source,
            target: params.target,
            strength: params.initial_strength,
            persistence: params.persistence,
            scope: params.scope,
            symmetry: params.symmetry,
            attention_allocated: params.initial_attention_cost,
            meaning_convergence: 0.0,
            interaction_count: 0,
            created_at: TemporalAnchor::now(),
            last_resonance: TemporalAnchor::now(),
        };

        let coupling_id = coupling.id;

        // Add to topology
        self.graph.write().await.add_edge(&coupling);
        self.couplings.insert(coupling.id, coupling.clone());

        tracing::debug!(
            "Established coupling {} -> {} (strength: {})",
            params.source,
            params.target,
            params.initial_strength
        );

        Ok((coupling_id, attention_token))
    }

    /// Strengthen coupling gradually
    pub async fn strengthen(
        &self,
        coupling_id: CouplingId,
        delta: f64,
    ) -> Result<(), CouplingError> {
        // RULE: Maximum strengthening rate
        if delta > self.config.max_strengthening_rate {
            return Err(CouplingError::StrengtheningTooRapid);
        }

        if let Some(mut coupling) = self.couplings.get_mut(&coupling_id) {
            let new_strength = (coupling.strength + delta).min(1.0);
            coupling.strength = new_strength;

            // May need more attention for stronger coupling
            let additional_attention = (delta * 10.0) as u64;
            self.attention
                .allocate_more(&coupling.source, additional_attention)
                .await?;
            coupling.attention_allocated += additional_attention;

            tracing::debug!("Strengthened coupling {} to {}", coupling_id, new_strength);
        }

        Ok(())
    }

    /// Weaken coupling without severing
    pub async fn weaken(&self, coupling_id: CouplingId, factor: f64) -> Result<(), CouplingError> {
        if let Some(mut coupling) = self.couplings.get_mut(&coupling_id) {
            coupling.strength *= 1.0 - factor;

            // Release some attention
            let attention_release = (coupling.attention_allocated as f64 * factor) as u64;
            self.attention
                .release_partial(&coupling.source, attention_release)
                .await;
            coupling.attention_allocated -= attention_release;

            tracing::debug!("Weakened coupling {} by factor {}", coupling_id, factor);
        }

        Ok(())
    }

    /// Safe decoupling that preserves commitments
    ///
    /// ARCHITECTURAL RULE: Coupling MUST be severed safely without
    /// violating existing commitments.
    pub async fn decouple_safely(
        &self,
        coupling_id: CouplingId,
    ) -> Result<DecouplingResult, CouplingError> {
        let coupling = self
            .couplings
            .get(&coupling_id)
            .ok_or(CouplingError::NotFound)?
            .clone();

        // Check for active commitments through this coupling
        // (would be checked via CommitmentManager in real implementation)

        // Remove from graph
        self.graph.write().await.remove_edge(&coupling_id);

        // Release attention
        self.attention
            .release_all(&coupling.source, coupling.attention_allocated)
            .await;

        // Remove coupling
        self.couplings.remove(&coupling_id);

        tracing::debug!("Decoupled {}", coupling_id);

        Ok(DecouplingResult::Success)
    }

    /// Get coupling by ID
    pub fn get_coupling(&self, id: &CouplingId) -> Option<Coupling> {
        self.couplings.get(id).map(|r| r.clone())
    }

    /// Get all couplings for a Resonator
    pub fn get_couplings_for(&self, resonator: &ResonatorId) -> Vec<Coupling> {
        self.couplings
            .iter()
            .filter(|entry| entry.source == *resonator || entry.target == *resonator)
            .map(|entry| entry.clone())
            .collect()
    }

    /// Restore couplings from continuity record
    pub async fn restore_couplings(
        &self,
        _resonator: &ResonatorId,
        couplings: &[Coupling],
    ) -> Result<(), String> {
        for coupling in couplings {
            self.graph.write().await.add_edge(coupling);
            self.couplings.insert(coupling.id, coupling.clone());
        }

        tracing::debug!("Restored {} couplings", couplings.len());
        Ok(())
    }

    /// Persist coupling topology
    pub async fn persist_topology(&self) -> Result<(), String> {
        // Placeholder: In real implementation, would persist to durable storage
        tracing::info!("Persisting {} couplings", self.couplings.len());
        Ok(())
    }

    /// Count of active couplings
    pub fn count(&self) -> usize {
        self.couplings.len()
    }
}