/**
 * VerbEmbeddingSignal - Neural semantic similarity for relationship classification
 *
 * WEIGHT: 35% (second highest after exact match)
 *
 * Uses:
 * 1. 40 pre-computed verb type embeddings (384 dimensions)
 * 2. Cosine similarity against context text
 * 3. Semantic understanding of relationship intent
 *
 */

import type { Brainy } from '../../brainy.js'
import { VerbType } from '../../types/graphTypes.js'
import type { Vector } from '../../coreTypes.js'
import { getVerbTypeEmbeddings } from '../embeddedTypeEmbeddings.js'
import { cosineDistance } from '../../utils/distance.js'

/**
 * Signal result with classification details
 */
export interface VerbSignal {
  type: VerbType
  confidence: number
  evidence: string
  metadata?: {
    similarity?: number
    allScores?: Array<{ type: VerbType; similarity: number }>
  }
}

/**
 * Options for verb embedding signal
 */
export interface VerbEmbeddingSignalOptions {
  minConfidence?: number      // Minimum confidence threshold (default: 0.60)
  minSimilarity?: number       // Minimum cosine similarity (default: 0.55)
  topK?: number               // Number of top candidates to consider (default: 3)
  cacheSize?: number          // LRU cache size (default: 2000)
  enableTemporalBoosting?: boolean  // Boost recently seen relationships (default: true)
}

/**
 * Historical relationship entry for temporal boosting
 */
interface HistoricalEntry {
  text: string
  type: VerbType
  vector: Vector
  timestamp: number
  uses: number
}

/**
 * VerbEmbeddingSignal - Neural relationship type classification
 *
 * Production features:
 * - Uses 40 pre-computed verb type embeddings (zero runtime cost)
 * - Cosine similarity for semantic matching
 * - Temporal boosting for recently seen patterns
 * - LRU cache for hot paths
 * - Confidence calibration based on similarity distribution
 */
export class VerbEmbeddingSignal {
  private brain: Brainy
  private distanceFn: (a: Vector, b: Vector) => number
  private options: Required<VerbEmbeddingSignalOptions>

  // Pre-computed verb type embeddings (loaded once at startup)
  private verbTypeEmbeddings: Map<VerbType, Vector>

  // Historical data for temporal boosting
  private history: HistoricalEntry[] = []
  private readonly MAX_HISTORY = 1000

  // LRU cache
  private cache: Map<string, VerbSignal | null> = new Map()
  private cacheOrder: string[] = []

  // Statistics
  private stats = {
    calls: 0,
    cacheHits: 0,
    matches: 0,
    temporalBoosts: 0,
    averageSimilarity: 0
  }

  constructor(brain: Brainy, options?: VerbEmbeddingSignalOptions) {
    this.brain = brain
    // Visibility boundary: Brainy keeps its distance function in a private
    // field. The signal reuses it when present so verb classification matches
    // the index geometry, falling back to cosine distance otherwise.
    this.distanceFn =
      (brain as unknown as { distance?: (a: Vector, b: Vector) => number }).distance ||
      cosineDistance
    this.options = {
      minConfidence: options?.minConfidence ?? 0.60,
      minSimilarity: options?.minSimilarity ?? 0.55,
      topK: options?.topK ?? 3,
      cacheSize: options?.cacheSize ?? 2000,
      enableTemporalBoosting: options?.enableTemporalBoosting ?? true
    }

    // Load pre-computed verb type embeddings
    this.verbTypeEmbeddings = getVerbTypeEmbeddings()

    // Verify embeddings loaded
    if (this.verbTypeEmbeddings.size === 0) {
      throw new Error('VerbEmbeddingSignal: Failed to load verb type embeddings')
    }
  }

  /**
   * Classify relationship type using semantic similarity
   *
   * @param context Full context text (sentence or paragraph)
   * @param contextVector Optional pre-computed embedding (performance optimization)
   * @returns VerbSignal with classified type or null
   */
  async classify(
    context: string,
    contextVector?: Vector
  ): Promise<VerbSignal | null> {
    this.stats.calls++

    if (!context || context.trim().length === 0) {
      return null
    }

    // Check cache
    const cacheKey = this.getCacheKey(context)
    const cached = this.getFromCache(cacheKey)
    if (cached !== undefined) {
      this.stats.cacheHits++
      return cached
    }

    try {
      // Get context embedding
      const embedding = contextVector ?? await this.getEmbedding(context)

      if (!embedding || embedding.length === 0) {
        return null
      }

      // Compute similarities against all verb types
      const similarities: Array<{ type: VerbType; similarity: number }> = []

      for (const [verbType, typeEmbedding] of this.verbTypeEmbeddings) {
        const distance = this.distanceFn(embedding, typeEmbedding)
        const similarity = 1 - distance  // Convert distance to similarity
        similarities.push({ type: verbType, similarity })
      }

      // Sort by similarity (descending)
      similarities.sort((a, b) => b.similarity - a.similarity)

      // Get top K candidates
      const topCandidates = similarities.slice(0, this.options.topK)

      // Check if best candidate meets threshold
      const best = topCandidates[0]
      if (!best || best.similarity < this.options.minSimilarity) {
        const result = null
        this.addToCache(cacheKey, result)
        return result
      }

      // Apply temporal boosting if enabled
      let boostedSimilarity = best.similarity
      let temporalBoost = 0

      if (this.options.enableTemporalBoosting) {
        const boost = this.getTemporalBoost(context, best.type)
        if (boost > 0) {
          temporalBoost = boost
          boostedSimilarity = Math.min(1.0, best.similarity + boost)
          this.stats.temporalBoosts++
        }
      }

      // Calibrate confidence based on similarity distribution
      const confidence = this.calibrateConfidence(boostedSimilarity, topCandidates)

      if (confidence < this.options.minConfidence) {
        const result = null
        this.addToCache(cacheKey, result)
        return result
      }

      // Update rolling average similarity
      this.stats.averageSimilarity =
        (this.stats.averageSimilarity * (this.stats.calls - 1) + best.similarity) / this.stats.calls

      this.stats.matches++

      const result: VerbSignal = {
        type: best.type,
        confidence,
        evidence: `Semantic similarity: ${(best.similarity * 100).toFixed(1)}%${temporalBoost > 0 ? ` (temporal boost: +${(temporalBoost * 100).toFixed(1)}%)` : ''}`,
        metadata: {
          similarity: best.similarity,
          allScores: topCandidates
        }
      }

      this.addToCache(cacheKey, result)
      return result
    } catch (error) {
      return null
    }
  }

  /**
   * Get embedding for context text
   */
  private async getEmbedding(text: string): Promise<Vector | null> {
    try {
      // Use brain's embedding service
      const embedding = await this.brain.embed(text)
      return embedding
    } catch (error) {
      return null
    }
  }

  /**
   * Calibrate confidence based on similarity distribution
   *
   * Higher confidence when:
   * - Top similarity is high
   * - Clear gap between top and second-best
   * - Top K candidates agree on same type
   */
  private calibrateConfidence(
    topSimilarity: number,
    topCandidates: Array<{ type: VerbType; similarity: number }>
  ): number {
    let confidence = topSimilarity

    // Boost confidence if there's a clear gap to second-best
    if (topCandidates.length >= 2) {
      const gap = topSimilarity - topCandidates[1].similarity
      if (gap > 0.15) {
        confidence = Math.min(1.0, confidence + 0.05)  // Clear winner bonus
      } else if (gap < 0.05) {
        confidence = Math.max(0.0, confidence - 0.05)  // Ambiguous penalty
      }
    }

    // Boost confidence if multiple candidates agree on same type
    const topType = topCandidates[0].type
    const agreementCount = topCandidates.filter(c => c.type === topType).length
    if (agreementCount > 1) {
      confidence = Math.min(1.0, confidence + 0.03 * (agreementCount - 1))
    }

    return confidence
  }

  /**
   * Get temporal boost for recently seen patterns
   *
   * Boosts confidence if similar context was recently classified as the same type
   */
  private getTemporalBoost(context: string, type: VerbType): number {
    if (this.history.length === 0) {
      return 0
    }

    const now = Date.now()
    const recentThreshold = 60000  // 1 minute

    // Find recent similar patterns with same type
    for (const entry of this.history) {
      if (entry.type !== type) continue
      if (now - entry.timestamp > recentThreshold) continue

      // Check text similarity (simple substring check for now)
      const normalized = context.toLowerCase()
      const histNormalized = entry.text.toLowerCase()

      if (normalized.includes(histNormalized) || histNormalized.includes(normalized)) {
        // Boost decays with age
        const age = now - entry.timestamp
        const decay = 1 - (age / recentThreshold)
        return 0.05 * decay  // Max 5% boost
      }
    }

    return 0
  }

  /**
   * Add pattern to history for temporal boosting
   */
  addToHistory(text: string, type: VerbType, vector: Vector): void {
    // Check if pattern already exists
    const existing = this.history.find(
      e => e.text.toLowerCase() === text.toLowerCase() && e.type === type
    )

    if (existing) {
      existing.timestamp = Date.now()
      existing.uses++
      return
    }

    // Add new entry
    this.history.push({
      text,
      type,
      vector,
      timestamp: Date.now(),
      uses: 1
    })

    // Evict oldest if over limit
    if (this.history.length > this.MAX_HISTORY) {
      this.history.sort((a, b) => b.timestamp - a.timestamp)
      this.history = this.history.slice(0, this.MAX_HISTORY)
    }
  }

  /**
   * Clear history
   */
  clearHistory(): void {
    this.history = []
  }

  /**
   * Get cache key
   */
  private getCacheKey(context: string): string {
    return context.toLowerCase().trim().substring(0, 200)
  }

  /**
   * Get from LRU cache
   */
  private getFromCache(key: string): VerbSignal | null | undefined {
    if (!this.cache.has(key)) {
      return undefined
    }

    const cached = this.cache.get(key)

    // Move to end (most recently used)
    this.cacheOrder = this.cacheOrder.filter(k => k !== key)
    this.cacheOrder.push(key)

    return cached ?? null
  }

  /**
   * Add to LRU cache with eviction
   */
  private addToCache(key: string, value: VerbSignal | null): void {
    this.cache.set(key, value)
    this.cacheOrder.push(key)

    // Evict oldest if over limit
    if (this.cache.size > this.options.cacheSize) {
      const oldest = this.cacheOrder.shift()
      if (oldest) {
        this.cache.delete(oldest)
      }
    }
  }

  /**
   * Get statistics
   */
  getStats() {
    return {
      ...this.stats,
      verbTypeCount: this.verbTypeEmbeddings.size,
      historySize: this.history.length,
      cacheSize: this.cache.size,
      cacheHitRate: this.stats.calls > 0 ? this.stats.cacheHits / this.stats.calls : 0,
      matchRate: this.stats.calls > 0 ? this.stats.matches / this.stats.calls : 0
    }
  }

  /**
   * Reset statistics
   */
  resetStats(): void {
    this.stats = {
      calls: 0,
      cacheHits: 0,
      matches: 0,
      temporalBoosts: 0,
      averageSimilarity: 0
    }
  }

  /**
   * Clear cache
   */
  clearCache(): void {
    this.cache.clear()
    this.cacheOrder = []
  }
}