//! Local Episteme integration for Aphoria.
//!
//! Provides a simplified interface to the local Episteme instance for:
//! - Ingesting assertions from extracted claims
//! - Querying for conflicts with authoritative sources
//! - Managing the authoritative corpus
//! - Auto-creating aliases when conflicts are detected (Phase 2A.3)

mod corpus;

#[cfg(test)]
mod tests;

use std::collections::HashMap;
use std::path::Path;
use std::sync::Arc;

use ed25519_dalek::SigningKey;
use stemedb_core::types::{AliasOrigin, Assertion, ConceptAlias, ConceptPath, SourceClass};
use stemedb_ingest::{serialize_assertion, Ingestor};
use stemedb_storage::{AliasStore, GenericAliasStore, HybridStore};
use stemedb_wal::Journal;
use tokio::sync::Mutex;
use tracing::{debug, info, instrument, warn};

use crate::bridge::{claim_to_assertion, load_or_generate_key};
use crate::config::AphoriaConfig;
use crate::types::{ConflictResult, ConflictingSource, ExtractedClaim, Verdict};
use crate::AphoriaError;

use corpus::current_timestamp;
pub use corpus::{create_authoritative_assertion, create_authoritative_corpus};

/// In-memory index for concept matching by tail path segments.
///
/// Maps `{tail_seg1}/{tail_seg2}::{predicate}` → `Vec<Assertion>`.
/// This enables matching claims across different URI schemes by their
/// trailing path components.
///
/// # Example
///
/// Both of these subjects produce the same key `"tls/cert_verification::enabled"`:
/// - `rfc://5246/tls/cert_verification`
/// - `code://rust/myapp/client/tls/cert_verification`
pub struct ConceptIndex {
    entries: HashMap<String, Vec<Assertion>>,
}

impl ConceptIndex {
    /// Build a ConceptIndex from a slice of assertions.
    pub fn build(assertions: &[Assertion]) -> Self {
        // Pre-allocate based on expected unique keys
        let mut entries: HashMap<String, Vec<Assertion>> = HashMap::with_capacity(assertions.len());

        for assertion in assertions {
            if let Some(key) = Self::make_key(&assertion.subject, &assertion.predicate) {
                entries.entry(key).or_default().push(assertion.clone());
            }
        }

        Self { entries }
    }

    /// Look up assertions matching the tail segments of a subject and predicate.
    pub fn lookup(&self, subject: &str, predicate: &str) -> Option<&Vec<Assertion>> {
        let key = Self::make_key(subject, predicate)?;
        self.entries.get(&key)
    }

    /// Create a lookup key from subject and predicate.
    ///
    /// Algorithm:
    /// 1. Split subject on `"://"`, take path part
    /// 2. Split path on `"/"` in reverse, get last 2 non-empty segments
    /// 3. If < 2 segments, return None
    /// 4. Return `"{seg[-2]}/{seg[-1]}::{predicate}"`
    pub fn make_key(subject: &str, predicate: &str) -> Option<String> {
        // Split on "://" to separate scheme from path
        let path = subject.find("://").map(|i| &subject[i + 3..]).unwrap_or(subject);

        // Get last two non-empty segments using rsplit (avoids Vec allocation)
        let mut segments = path.rsplit('/').filter(|s| !s.is_empty());

        let tail2 = segments.next()?;
        let tail1 = segments.next()?;

        Some(format!("{}/{}::{}", tail1, tail2, predicate))
    }
}

/// Local Episteme instance for Aphoria.
pub struct LocalEpisteme {
    journal: Arc<Mutex<Journal>>,
    /// Store is owned by this struct but accessed via the Ingestor and AliasStore.
    /// Keeping a reference ensures the store outlives dependent structs.
    #[allow(dead_code)]
    store: Arc<HybridStore>,
    ingestor: Ingestor<HybridStore>,
    signing_key: SigningKey,
    /// AliasStore for persisting cross-scheme aliases discovered during conflict detection.
    alias_store: GenericAliasStore<Arc<HybridStore>>,
}

impl LocalEpisteme {
    /// Open or create a local Episteme instance.
    #[instrument(skip(config), fields(data_dir = %config.episteme.data_dir.display()))]
    pub async fn open(config: &AphoriaConfig, project_root: &Path) -> Result<Self, AphoriaError> {
        let data_dir = &config.episteme.data_dir;

        // Create directories if needed
        std::fs::create_dir_all(data_dir)?;

        // Canonicalize paths (required by fjall/lsm-tree)
        let data_dir = data_dir.canonicalize().map_err(|e| {
            AphoriaError::Storage(format!("Failed to canonicalize data_dir: {}", e))
        })?;

        let wal_dir = data_dir.join("wal");
        let store_dir = data_dir.join("store");
        std::fs::create_dir_all(&wal_dir)?;
        std::fs::create_dir_all(&store_dir)?;

        info!("Opening local Episteme at {}", data_dir.display());

        // Open WAL
        let journal = Arc::new(Mutex::new(
            Journal::open(&wal_dir).map_err(|e| AphoriaError::Storage(e.to_string()))?,
        ));

        // Open store
        let store = Arc::new(
            HybridStore::open(&store_dir).map_err(|e| AphoriaError::Storage(e.to_string()))?,
        );

        // Create ingestor
        let mut ingestor = Ingestor::new(journal.clone(), store.clone())
            .await
            .map_err(|e| AphoriaError::Storage(e.to_string()))?;
        ingestor.start();

        // Load or generate signing key
        let signing_key =
            load_or_generate_key(project_root).map_err(|e| AphoriaError::Storage(e.to_string()))?;

        // Create alias store for auto-alias persistence
        let alias_store = GenericAliasStore::new(store.clone());

        Ok(Self { journal, store, ingestor, signing_key, alias_store })
    }

    /// Ingest a batch of extracted claims into Episteme.
    #[instrument(skip(self, claims), fields(claim_count = claims.len()))]
    pub async fn ingest_claims(&self, claims: &[ExtractedClaim]) -> Result<usize, AphoriaError> {
        let timestamp = current_timestamp();
        let mut ingested = 0;

        for claim in claims {
            let assertion = claim_to_assertion(claim, &self.signing_key, timestamp);

            // Serialize and write to WAL
            let record_bytes = serialize_assertion(&assertion)
                .map_err(|e| AphoriaError::Storage(e.to_string()))?;
            let mut journal = self.journal.lock().await;
            journal.append(record_bytes).map_err(|e| AphoriaError::Storage(e.to_string()))?;

            debug!(
                concept_path = %claim.concept_path,
                predicate = %claim.predicate,
                "Ingested claim"
            );
            ingested += 1;
        }

        // Sync WAL
        {
            let mut journal = self.journal.lock().await;
            journal.force_sync().map_err(|e| AphoriaError::Storage(e.to_string()))?;
        }

        // Wait for ingestion to process
        self.ingestor.process_pending().await.map_err(|e| AphoriaError::Storage(e.to_string()))?;

        info!(ingested, "Ingested claims into Episteme");
        Ok(ingested)
    }

    /// Check for conflicts between extracted claims and authoritative sources.
    ///
    /// Uses tail-path matching via `ConceptIndex` to find conflicts across different
    /// URI schemes. For example, a code claim at `code://rust/myapp/tls/cert_verification`
    /// will match authoritative assertions at `rfc://5246/tls/cert_verification`.
    ///
    /// When `config.aliases.auto_create_aliases` is enabled, this method will
    /// automatically persist aliases for matched concepts, enabling faster future
    /// queries via `QueryEngine` with `resolve_aliases: true`.
    #[instrument(skip(self, claims, config, index), fields(claim_count = claims.len()))]
    pub async fn check_conflicts(
        &self,
        claims: &[ExtractedClaim],
        config: &AphoriaConfig,
        index: &ConceptIndex,
    ) -> Result<Vec<ConflictResult>, AphoriaError> {
        let mut results = Vec::new();
        let mut aliases_created = 0usize;
        let timestamp = current_timestamp();
        let agent_id = self.agent_id();

        for claim in claims {
            // Look up authoritative assertions matching this claim's tail path
            let auth_assertions = match index.lookup(&claim.concept_path, &claim.predicate) {
                Some(assertions) => assertions,
                None => continue, // No authoritative coverage for this concept
            };

            // Find conflicting authoritative sources
            let mut conflicts = Vec::new();
            for assertion in auth_assertions {
                // Skip if it's our own assertion (same source class)
                if assertion.source_class == SourceClass::Expert {
                    continue;
                }

                // Auto-create alias if enabled (regardless of value conflict)
                // This bridges the code path to the authoritative path for future queries
                if config.aliases.auto_create_aliases {
                    if let Err(e) = self
                        .create_alias_if_new(
                            &claim.concept_path,
                            &assertion.subject,
                            agent_id,
                            timestamp,
                        )
                        .await
                    {
                        warn!(
                            code_path = %claim.concept_path,
                            auth_path = %assertion.subject,
                            error = %e,
                            "Failed to create alias"
                        );
                    } else {
                        aliases_created += 1;
                    }
                }

                // Check if value differs (for conflict reporting)
                if assertion.object != claim.value {
                    // Only consider Tier 0-2 as authoritative
                    if assertion.source_class.tier() <= 2 {
                        conflicts.push(ConflictingSource {
                            path: assertion.subject.clone(),
                            source_class: assertion.source_class,
                            value: assertion.object.clone(),
                            confidence: assertion.confidence,
                        });
                    }
                }
            }

            if conflicts.is_empty() {
                continue;
            }

            // Compute conflict score
            let conflict_score = compute_conflict_score(&conflicts, claim.confidence);

            // Determine verdict
            let verdict = if conflict_score >= config.thresholds.block {
                Verdict::Block
            } else if conflict_score >= config.thresholds.flag {
                Verdict::Flag
            } else {
                Verdict::Pass
            };

            results.push(ConflictResult {
                claim: claim.clone(),
                conflicts,
                conflict_score,
                verdict,
                acknowledged: None,
            });
        }

        info!(
            conflicts = results.len(),
            blocks = results.iter().filter(|r| r.verdict == Verdict::Block).count(),
            flags = results.iter().filter(|r| r.verdict == Verdict::Flag).count(),
            aliases_created,
            "Conflict check complete"
        );

        Ok(results)
    }

    /// Ingest authoritative assertions (RFC, OWASP, etc.).
    #[instrument(skip(self, assertions), fields(count = assertions.len()))]
    pub async fn ingest_authoritative(
        &self,
        assertions: &[Assertion],
    ) -> Result<usize, AphoriaError> {
        let mut ingested = 0;

        for assertion in assertions {
            let record_bytes =
                serialize_assertion(assertion).map_err(|e| AphoriaError::Storage(e.to_string()))?;
            let mut journal = self.journal.lock().await;
            journal.append(record_bytes).map_err(|e| AphoriaError::Storage(e.to_string()))?;
            ingested += 1;
        }

        // Sync and process
        {
            let mut journal = self.journal.lock().await;
            journal.force_sync().map_err(|e| AphoriaError::Storage(e.to_string()))?;
        }
        self.ingestor.process_pending().await.map_err(|e| AphoriaError::Storage(e.to_string()))?;

        info!(ingested, "Ingested authoritative assertions");
        Ok(ingested)
    }

    /// Shut down the Episteme instance gracefully.
    pub async fn shutdown(&mut self) {
        info!("Shutting down local Episteme");
        self.ingestor.shutdown(std::time::Duration::from_secs(2)).await;
    }

    /// Get the signing key's public key bytes for alias creation.
    pub fn agent_id(&self) -> [u8; 32] {
        self.signing_key.verifying_key().to_bytes()
    }

    /// Create an alias from a code path to an authoritative path, if it doesn't already exist.
    ///
    /// This is used during conflict detection to persist the relationship between
    /// code concepts and their authoritative counterparts.
    #[instrument(skip(self), fields(code_path = %code_path, auth_path = %auth_path))]
    async fn create_alias_if_new(
        &self,
        code_path: &str,
        auth_path: &str,
        agent_id: [u8; 32],
        timestamp: u64,
    ) -> Result<(), AphoriaError> {
        // Check if alias already exists
        let existing = self
            .alias_store
            .get_canonical(code_path)
            .await
            .map_err(|e| AphoriaError::Storage(e.to_string()))?;

        if existing.is_some() {
            debug!("Alias already exists, skipping");
            return Ok(());
        }

        // Parse paths
        let alias_path = ConceptPath::parse(code_path)
            .map_err(|e| AphoriaError::Storage(format!("Invalid code path: {}", e)))?;
        let canonical_path = ConceptPath::parse(auth_path)
            .map_err(|e| AphoriaError::Storage(format!("Invalid auth path: {}", e)))?;

        // Create and persist alias
        let alias = ConceptAlias::new(
            alias_path,
            canonical_path,
            agent_id,
            timestamp,
            AliasOrigin::AutoDetected,
        );

        self.alias_store
            .set_alias(&alias)
            .await
            .map_err(|e| AphoriaError::Storage(e.to_string()))?;

        debug!("Created auto-detected alias");
        Ok(())
    }

    /// Get a reference to the alias store for querying created aliases.
    #[allow(dead_code)]
    pub fn alias_store(&self) -> &GenericAliasStore<Arc<HybridStore>> {
        &self.alias_store
    }
}

/// Compute conflict score based on authoritative sources and claim confidence.
///
/// The score uses two approaches and takes the maximum:
///
/// 1. **Boosted score**: `max_tier_weight * (1.0 - code_weight) * max_confidence`
///    where code_weight = Expert (Tier 3) = 0.5. This is low unless the
///    authoritative source has very high authority weight.
///
/// 2. **Normalized score**: Linear mapping from tier distance to score:
///    - Tier 0 (Regulatory) vs code → 0.95 (above BLOCK threshold 0.7)
///    - Tier 1 (Clinical)   vs code → 0.77 (above BLOCK threshold 0.7)
///    - Tier 2 (Observational) vs code → 0.58 (above FLAG threshold 0.4)
///    - Tier 3 (same tier)  vs code → 0.40 (at FLAG threshold)
///
/// The final score is capped at 1.0.
fn compute_conflict_score(conflicts: &[ConflictingSource], _claim_confidence: f32) -> f32 {
    if conflicts.is_empty() {
        return 0.0;
    }

    // Get max tier weight from conflicting sources
    let max_tier_weight = conflicts
        .iter()
        .map(|c| c.source_class.authority_weight())
        .max_by(|a, b| a.partial_cmp(b).unwrap_or(std::cmp::Ordering::Equal))
        .unwrap_or(0.0);

    // Code claims are Expert (Tier 3) = 0.5 weight
    let code_weight = SourceClass::Expert.authority_weight();

    // Base conflict score from tier spread
    let base_score = max_tier_weight * (1.0 - code_weight);

    // Boost by authoritative source confidence
    let max_confidence = conflicts
        .iter()
        .map(|c| c.confidence)
        .max_by(|a, b| a.partial_cmp(b).unwrap_or(std::cmp::Ordering::Equal))
        .unwrap_or(1.0);

    let boosted_score = base_score * max_confidence;

    // Normalize: tier spread 0→3 maps to 0.4→0.95
    let min_tier = conflicts.iter().map(|c| c.source_class.tier()).min().unwrap_or(3) as f32;
    let normalized = 0.4 + (3.0 - min_tier) / 3.0 * 0.55;

    normalized.max(boosted_score).min(1.0)
}