llmosafe 0.7.3

//! LLMOSAFE Tier 2 Working Memory
//!
//! Surprise-gated ring buffer. Rejects updates where the entropy value is too
//! unexpected relative to history (via `WorkingMemory::<SIZE>::new(threshold)`).
//!
//! Stores `CognitiveEntropy` values in a fixed-size ring buffer with:
//! - `mean()`, `variance()` — running statistics
//! - `trend()` — linear regression slope over the buffer window
//!
//! Entropy values are in [0, 65535]. The `new()` threshold determines how
//! surprising a value must be (relative to mean) before rejection. Typical
//! threshold: 58000 for classifier output.

// Arithmetic in this module operates on bounded ring-buffer index values
// [0, SIZE-1] where modulo/offset semantics are the intended behavior.
// DO-178C: these operations are verified safe by compile-time const bounds.
#![allow(clippy::arithmetic_side_effects)]

use crate::control_types::ControlSignal;
use crate::llmosafe_kernel::{
    CognitiveEntropy, KernelError, SiftedProof, SiftedSynapse, ValidatedProof, ValidatedSynapse,
};

/// Memory Control Loop output.
///
/// # Control Signal
///
/// - Setpoint: `μ = mean_entropy` (self-adjusting — ring buffer running mean)
/// - Actual: `entropy_n` (current observation's raw entropy)
/// - Error: `e_mem = |entropy_n - mean_entropy| / 65535.0` (normalised to `[0, 1]`)
/// - Gain: `K_mem = 1.0 + 0.3 × tanh(|trend| / 1000.0)` (gain-scheduled by trend)
///
/// # DAL B
///
/// Memory loop gates on surprise — missed escalation allows unsafe
/// observations to propagate to the kernel. DAL B because failure
/// causes hazardous behaviour (missed escalation), not catastrophic.
///
/// # Invariants
///
/// - `0.0 ≤ error_mem ≤ 1.0`
/// - Ring buffer size = SIZE (const generic, compile-time bound)
/// - Surprise gate: `error_mem > surprise_threshold/65535` → HallucinationDetected
///
/// Fields:
/// - `error_mem: f32` — normalised surprise error [0.0, 1.0].
/// - `trend: f64` — linear regression slope over buffer window.
/// - `mean_entropy: f64` — running mean entropy of ring buffer.
#[derive(Debug, Clone, Copy)]
pub struct MemoryOutput {
    /// Normalised surprise error `[0.0, 1.0]`.
    pub error_mem: f32,
    /// Linear regression slope over buffer window.
    pub trend: f64,
    /// Running mean entropy of ring buffer.
    pub mean_entropy: f64,
}

impl ControlSignal for MemoryOutput {
    fn error(&self) -> f32 {
        self.error_mem
    }

    fn setpoint(&self) -> f32 {
        (self.mean_entropy / 65535.0) as f32
    }
}

/// Fixed-size working memory stack buffer.
///
/// Holds up to SIZE entropy values in a ring buffer.
/// Default capacity is 64 entries (stack-allocated).
pub struct WorkingMemory<const SIZE: usize = 64> {
    state: [CognitiveEntropy<28, 2>; SIZE],
    current_index: usize,
    surprise_threshold: i128,
}

impl<const SIZE: usize> WorkingMemory<SIZE> {
    const _SIZE_CHECK: () = assert!(SIZE > 0, "WorkingMemory size must be > 0");

    /// Initialize with a fixed surprise threshold (e.g. 5.00)
    ///
    /// # Examples
    ///
    /// ```
    /// use llmosafe::WorkingMemory;
    /// let memory = WorkingMemory::<64>::new(1000);
    /// ```
    pub const fn new(threshold: i128) -> Self {
        Self {
            state: [CognitiveEntropy::new(0); SIZE],
            current_index: 0,
            surprise_threshold: threshold,
        }
    }

    /// Updated: Uses the SiftedSynapse protocol for state transitions.
    ///
    /// # Errors
    ///
    /// Returns `CognitiveInstability` or `BiasHaloDetected` if `sifted.validate()` fails.
    /// Returns `HallucinationDetected` if the synapse surprise exceeds the memory threshold.
    ///
    /// # Examples
    ///
    /// ```
    /// use llmosafe::{WorkingMemory, sift_perceptions};
    /// let mut memory = WorkingMemory::<64>::new(65535);
    /// let (sifted, proof) = sift_perceptions(&["the weather is nice today"], "test");
    /// let result = memory.update(sifted, proof);
    /// assert!(result.is_ok());
    /// ```
    pub fn update(
        &mut self,
        sifted: SiftedSynapse,
        _proof: SiftedProof,
    ) -> Result<(ValidatedSynapse, ValidatedProof), KernelError> {
        sifted.validate()?;

        if sifted.surprise() > self.surprise_threshold {
            return Err(KernelError::HallucinationDetected);
        }

        self.state[self.current_index] = sifted.entropy();
        let prev_index = self.current_index;
        self.current_index = (self.current_index + 1) % SIZE;

        let validated = ValidatedSynapse::new(sifted.into_inner());
        let validated_proof = ValidatedProof(());

        // Shadow validator: invariants at memory → kernel boundary
        debug_assert!(
            prev_index < SIZE,
            "CMIT: memory index {} overflowed SIZE={}",
            prev_index,
            SIZE,
        );

        Ok((validated, validated_proof))
    }
    /// Returns the running mean entropy of the ring buffer.
    pub fn mean_entropy(&self) -> f64 {
        let sum: i128 = self.state.iter().map(CognitiveEntropy::mantissa).sum();
        sum as f64 / SIZE as f64
    }

    /// Returns the variance of entropy values in the ring buffer.
    pub fn entropy_variance(&self) -> f64 {
        let mean = self.mean_entropy();
        let variance_sum: f64 = self
            .state
            .iter()
            .map(|e| {
                let diff = e.mantissa() as f64 - mean;
                diff * diff
            })
            .sum();
        variance_sum / SIZE as f64
    }

    /// Returns the linear regression slope over the buffer window.
    pub fn trend(&self) -> f64 {
        let n = SIZE as f64;
        let mut sum_y = 0.0;
        let mut sum_x_times_y = 0.0;

        // Walk the ring buffer in temporal order: oldest first, newest last.
        // After wraparound, buffer order is [current_index, ..., SIZE-1, 0, ..., current_index-1].
        // Assign x=0 to oldest, x=SIZE-1 to newest.
        for offset in 0..SIZE {
            let idx = (self.current_index + offset) % SIZE;
            let x = offset as f64;
            let y = self.state[idx].mantissa() as f64;
            sum_y += y;
            sum_x_times_y += x * y;
        }

        let sum_x = (n * (n - 1.0)) / 2.0;
        let sum_xx = (n * (n - 1.0) * (2.0 * n - 1.0)) / 6.0;

        let denominator = n * sum_xx - sum_x * sum_x;
        if denominator == 0.0 {
            return 0.0;
        }
        (n * sum_x_times_y - sum_x * sum_y) / denominator
    }

    /// Returns true if the absolute trend exceeds the given threshold.
    pub fn is_drifting(&self, threshold: f64) -> bool {
        self.trend().abs() > threshold
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::llmosafe_kernel::{SiftedProof, Synapse};

    #[test]
    fn test_homeostatic_stats() {
        let mut memory = WorkingMemory::<4>::new(1000);
        for i in 0..4 {
            let mut synapse = Synapse::new();
            synapse.set_raw_entropy(100 * (i + 1) as u16);
            let sifted = SiftedSynapse::new(synapse);
            memory.update(sifted, SiftedProof::for_testing()).unwrap();
        }
        // Buffer after 4 updates (all values present):
        // Entropy stored: 100, 200, 300, 400
        // Temporal order (oldest→newest): 100, 200, 300, 400
        assert_eq!(memory.mean_entropy(), 250.0);
        // Slope = 100.0 (rising from 100 to 400)
        assert!((memory.trend() - 100.0).abs() < 0.01);
        assert!(memory.is_drifting(10.0));
    }
    #[test]
    fn test_memory_update_gating() {
        let mut memory = WorkingMemory::<4>::new(500); // Threshold 5.00

        // 1. Valid update (Low surprise, no bias, stable entropy)
        let mut synapse = Synapse::new();
        synapse.set_raw_entropy(400);
        synapse.set_raw_surprise(100);
        synapse.set_has_bias(false);
        let sifted = SiftedSynapse::new(synapse);
        assert!(memory.update(sifted, SiftedProof::for_testing()).is_ok());

        // 2. Invalid update: Surprise too high (Hallucination)
        let mut synapse = Synapse::new();
        synapse.set_raw_entropy(400);
        synapse.set_raw_surprise(600);
        synapse.set_has_bias(false);
        let sifted = SiftedSynapse::new(synapse);
        assert_eq!(
            memory
                .update(sifted, SiftedProof::for_testing())
                .unwrap_err(),
            KernelError::HallucinationDetected
        );

        // 3. Invalid update: Bias detected
        let mut synapse = Synapse::new();
        synapse.set_raw_entropy(400);
        synapse.set_raw_surprise(100);
        synapse.set_has_bias(true);
        let sifted = SiftedSynapse::new(synapse);
        assert_eq!(
            memory
                .update(sifted, SiftedProof::for_testing())
                .unwrap_err(),
            KernelError::BiasHaloDetected
        );

        // 4. Invalid update: Cognitive Instability
        let mut synapse = Synapse::new();
        synapse.set_raw_entropy(50001);
        synapse.set_raw_surprise(100);
        synapse.set_has_bias(false);
        let sifted = SiftedSynapse::new(synapse);
        assert_eq!(
            memory
                .update(sifted, SiftedProof::for_testing())
                .unwrap_err(),
            KernelError::CognitiveInstability
        );
    }

    #[test]
    fn test_working_memory_size_1() {
        let mut memory = WorkingMemory::<1>::new(1000);
        let mut s1 = Synapse::new();
        s1.set_raw_entropy(100);
        let sifted1 = SiftedSynapse::new(s1);

        memory.update(sifted1, SiftedProof::for_testing()).unwrap();
        assert!(memory.state[0].is_stable(100));

        let mut s2 = Synapse::new();
        s2.set_raw_entropy(200);
        let sifted2 = SiftedSynapse::new(s2);

        memory.update(sifted2, SiftedProof::for_testing()).unwrap();
        assert!(memory.state[0].is_stable(200));
        assert_eq!(memory.current_index, 0);
    }

    #[test]
    fn test_memory_new_max_threshold() {
        let memory = WorkingMemory::<64>::new(i128::MAX);
        assert_eq!(memory.surprise_threshold, i128::MAX);
    }

    #[test]
    fn test_memory_zero_threshold() {
        let mut memory = WorkingMemory::<64>::new(0);
        let mut synapse = Synapse::new();
        synapse.set_raw_surprise(1);
        let sifted = SiftedSynapse::new(synapse);
        // Any surprise > 0 should fail
        assert_eq!(
            memory
                .update(sifted, SiftedProof::for_testing())
                .unwrap_err(),
            KernelError::HallucinationDetected
        );
    }

    #[test]
    fn test_memory_negative_threshold() {
        let mut memory = WorkingMemory::<64>::new(-1);
        let synapse = Synapse::new();
        let sifted = SiftedSynapse::new(synapse);
        // Even surprise 0 > -1, so it should fail
        assert_eq!(
            memory
                .update(sifted, SiftedProof::for_testing())
                .unwrap_err(),
            KernelError::HallucinationDetected
        );
    }
}

#[cfg(test)]
mod proptests {
    use super::*;
    use crate::llmosafe_kernel::{SiftedProof, Synapse};
    use proptest::prelude::*;

    proptest! {
        #[test]
        fn test_working_memory_random_synapse_sequence(
            entropies in prop::collection::vec(0u16..800u16, 1..200)
        ) {
            let mut memory = WorkingMemory::<64>::new(1000);
            for e in entropies {
                let mut synapse = Synapse::new();
                synapse.set_raw_entropy(e);
                let sifted = SiftedSynapse::new(synapse);
                prop_assert!(memory.update(sifted, SiftedProof::for_testing()).is_ok());
            }
        }
    }
}

#[cfg(feature = "std")]
pub mod cognitive_memory {
    use super::*;
    use crate::llmosafe_kernel::Synapse;
    use std::sync::Mutex;

    // Threshold=58000 matches the classifier surprise range [0,65535].
    // C-ABI callers set raw_surprise directly in the Synapse bits;
    // values >58000 will be rejected as HallucinationDetected (-4).
    static GLOBAL_MEMORY: Mutex<WorkingMemory<64>> = Mutex::new(WorkingMemory::<64>::new(58000));

    pub fn process_state_update(synapse_bits: u128) -> i32 {
        let synapse = Synapse::from_raw_u128(synapse_bits);
        let sifted = SiftedSynapse::new(synapse);
        // C-ABI callers bypass the Rust-side sifter; the caller is responsible
        // for pre-sifting on their side. We mint the proof via the explicit
        // bypass path — this is a documented FFI boundary exception, not a
        // proof-system violation.
        let proof = SiftedProof::from_raw_bits_bypass();

        let mut memory = GLOBAL_MEMORY
            .lock()
            .unwrap_or_else(std::sync::PoisonError::into_inner);

        match memory.update(sifted, proof) {
            Ok(_) => 0,
            Err(KernelError::DepthExceeded) => -1,
            Err(KernelError::CognitiveInstability) => -2,
            Err(KernelError::BiasHaloDetected) => -3,
            Err(KernelError::HallucinationDetected) => -4,
            Err(KernelError::ResourceExhaustion) => -5,
            Err(KernelError::SelfMemoryExceeded) => -6,
            Err(KernelError::DeadlineExceeded) => -7,
        }
    }

    /// Returns (mean_entropy, entropy_variance, trend, is_drifting) from the global WorkingMemory.
    ///
    /// `is_drifting` uses a fixed threshold of 10.0.
    pub fn get_memory_stats() -> (f64, f64, f64, bool) {
        let memory = GLOBAL_MEMORY
            .lock()
            .unwrap_or_else(std::sync::PoisonError::into_inner);
        let mean = memory.mean_entropy();
        let variance = memory.entropy_variance();
        let trend = memory.trend();
        let is_drifting = memory.is_drifting(10.0);
        (mean, variance, trend, is_drifting)
    }
}