/**
 * Memory persistence hooks for agentic-flow
 * 
 * Provides cross-provider memory state management with
 * synchronization and persistence capabilities.
 */

import { agenticHookManager } from './hook-manager.js';
import type {
  AgenticHookContext,
  HookHandlerResult,
  MemoryHookPayload,
  SideEffect,
} from './types.js';

// ===== Pre-Memory Store Hook =====

export const preMemoryStoreHook = {
  id: 'agentic-pre-memory-store',
  type: 'pre-memory-store' as const,
  priority: 100,
  handler: async (
    payload: MemoryHookPayload,
    context: AgenticHookContext
  ): Promise<HookHandlerResult> => {
    const { namespace, key, value, ttl, provider } = payload;
    
    const sideEffects: SideEffect[] = [];
    
    // Validate memory constraints
    const validation = await validateMemoryStore(namespace, key, value, context);
    if (!validation.valid) {
      return {
        continue: false,
        sideEffects: [
          {
            type: 'log',
            action: 'write',
            data: {
              level: 'error',
              message: 'Memory store validation failed',
              data: validation,
            },
          },
        ],
      };
    }
    
    // Compress large values
    let processedValue = value;
    if (shouldCompress(value)) {
      processedValue = await compressValue(value);
      sideEffects.push({
        type: 'metric',
        action: 'increment',
        data: { name: 'memory.compressions' },
      });
    }
    
    // Add metadata
    const enrichedValue = {
      data: processedValue,
      metadata: {
        stored: Date.now(),
        provider,
        sessionId: context.sessionId,
        compressed: processedValue !== value,
        size: getValueSize(processedValue),
      },
    };
    
    // Track memory usage
    sideEffects.push({
      type: 'metric',
      action: 'update',
      data: {
        name: `memory.usage.${namespace}`,
        value: getValueSize(enrichedValue),
      },
    });
    
    return {
      continue: true,
      modified: true,
      payload: {
        ...payload,
        value: enrichedValue,
      },
      sideEffects,
    };
  },
};

// ===== Post-Memory Store Hook =====

export const postMemoryStoreHook = {
  id: 'agentic-post-memory-store',
  type: 'post-memory-store' as const,
  priority: 100,
  handler: async (
    payload: MemoryHookPayload,
    context: AgenticHookContext
  ): Promise<HookHandlerResult> => {
    const { namespace, key, value, crossProvider, syncTargets } = payload;
    
    const sideEffects: SideEffect[] = [];
    
    // Cross-provider sync if enabled
    if (crossProvider && syncTargets && syncTargets.length > 0) {
      for (const target of syncTargets) {
        sideEffects.push({
          type: 'memory',
          action: 'sync',
          data: {
            source: payload.provider,
            target,
            namespace,
            key,
            value,
          },
        });
      }
    }
    
    // Update memory index for search
    await updateMemoryIndex(namespace, key, value, context);
    
    // Neural pattern detection
    const patterns = await detectMemoryPatterns(namespace, key, value, context);
    if (patterns.length > 0) {
      sideEffects.push({
        type: 'neural',
        action: 'analyze',
        data: {
          patterns,
          context: { namespace, key },
        },
      });
    }
    
    // Emit memory change event
    sideEffects.push({
      type: 'notification',
      action: 'emit',
      data: {
        event: 'memory:stored',
        data: { namespace, key, size: getValueSize(value) },
      },
    });
    
    return {
      continue: true,
      sideEffects,
    };
  },
};

// ===== Pre-Memory Retrieve Hook =====

export const preMemoryRetrieveHook = {
  id: 'agentic-pre-memory-retrieve',
  type: 'pre-memory-retrieve' as const,
  priority: 100,
  handler: async (
    payload: MemoryHookPayload,
    context: AgenticHookContext
  ): Promise<HookHandlerResult> => {
    const { namespace, key } = payload;
    
    // Check local cache first
    const cached = await checkLocalCache(namespace, key!, context);
    if (cached) {
      return {
        continue: false,
        modified: true,
        payload: {
          ...payload,
          value: cached,
        },
        sideEffects: [
          {
            type: 'metric',
            action: 'increment',
            data: { name: 'memory.cache.hits' },
          },
        ],
      };
    }
    
    // Pre-fetch related keys
    const relatedKeys = await findRelatedKeys(namespace, key!, context);
    if (relatedKeys.length > 0) {
      // Trigger background fetch
      prefetchKeys(namespace, relatedKeys, context);
    }
    
    return {
      continue: true,
      sideEffects: [
        {
          type: 'metric',
          action: 'increment',
          data: { name: `memory.retrievals.${namespace}` },
        },
      ],
    };
  },
};

// ===== Post-Memory Retrieve Hook =====

export const postMemoryRetrieveHook = {
  id: 'agentic-post-memory-retrieve',
  type: 'post-memory-retrieve' as const,
  priority: 100,
  handler: async (
    payload: MemoryHookPayload,
    context: AgenticHookContext
  ): Promise<HookHandlerResult> => {
    const { namespace, key, value } = payload;
    
    if (!value) {
      return { continue: true };
    }
    
    const sideEffects: SideEffect[] = [];
    
    // Decompress if needed
    let processedValue = value;
    if (value.metadata?.compressed) {
      processedValue = await decompressValue(value.data);
      sideEffects.push({
        type: 'metric',
        action: 'increment',
        data: { name: 'memory.decompressions' },
      });
    }
    
    // Update access patterns
    await updateAccessPattern(namespace, key!, context);
    
    // Cache locally for fast access
    await cacheLocally(namespace, key!, processedValue, context);
    
    // Track retrieval latency
    const latency = Date.now() - context.timestamp;
    sideEffects.push({
      type: 'metric',
      action: 'update',
      data: {
        name: `memory.latency.${namespace}`,
        value: latency,
      },
    });
    
    return {
      continue: true,
      modified: true,
      payload: {
        ...payload,
        value: processedValue.data || processedValue,
      },
      sideEffects,
    };
  },
};

// ===== Memory Sync Hook =====

export const memorySyncHook = {
  id: 'agentic-memory-sync',
  type: 'memory-sync' as const,
  priority: 100,
  handler: async (
    payload: MemoryHookPayload,
    context: AgenticHookContext
  ): Promise<HookHandlerResult> => {
    const { operation, namespace, provider, syncTargets } = payload;
    
    const sideEffects: SideEffect[] = [];
    
    switch (operation) {
      case 'sync':
        // Bidirectional sync
        const changes = await detectMemoryChanges(namespace, provider, context);
        
        if (changes.length > 0) {
          sideEffects.push({
            type: 'log',
            action: 'write',
            data: {
              level: 'info',
              message: `Syncing ${changes.length} memory changes`,
              data: { namespace, provider, targets: syncTargets },
            },
          });
          
          // Apply changes
          for (const change of changes) {
            await applyMemoryChange(change, syncTargets || [], context);
          }
          
          sideEffects.push({
            type: 'metric',
            action: 'update',
            data: {
              name: 'memory.sync.changes',
              value: changes.length,
            },
          });
        }
        break;
        
      case 'persist':
        // Persist to long-term storage
        const snapshot = await createMemorySnapshot(namespace, context);
        
        sideEffects.push({
          type: 'memory',
          action: 'store',
          data: {
            key: `snapshot:${namespace}:${Date.now()}`,
            value: snapshot,
            ttl: 0, // No expiration
          },
        });
        
        sideEffects.push({
          type: 'notification',
          action: 'emit',
          data: {
            event: 'memory:persisted',
            data: { namespace, size: snapshot.size },
          },
        });
        break;
        
      case 'expire':
        // Clean up expired entries
        const expired = await findExpiredEntries(namespace, context);
        
        if (expired.length > 0) {
          for (const key of expired) {
            await removeMemoryEntry(namespace, key, context);
          }
          
          sideEffects.push({
            type: 'metric',
            action: 'update',
            data: {
              name: 'memory.expired',
              value: expired.length,
            },
          });
        }
        break;
    }
    
    return {
      continue: true,
      sideEffects,
    };
  },
};

// ===== Memory Persist Hook =====

export const memoryPersistHook = {
  id: 'agentic-memory-persist',
  type: 'memory-persist' as const,
  priority: 90,
  handler: async (
    payload: MemoryHookPayload,
    context: AgenticHookContext
  ): Promise<HookHandlerResult> => {
    const { namespace } = payload;
    
    // Create full memory backup
    const backup = await createFullBackup(namespace, context);
    
    // Store backup with metadata
    const backupData = {
      timestamp: Date.now(),
      sessionId: context.sessionId,
      namespace,
      entries: backup.entries,
      size: backup.size,
      checksum: calculateChecksum(backup),
    };
    
    return {
      continue: true,
      sideEffects: [
        {
          type: 'memory',
          action: 'store',
          data: {
            key: `backup:${namespace}:${context.sessionId}`,
            value: backupData,
            ttl: 604800, // 7 days
          },
        },
        {
          type: 'notification',
          action: 'emit',
          data: {
            event: 'memory:backup:created',
            data: {
              namespace,
              size: backup.size,
              entries: backup.entries.length,
            },
          },
        },
      ],
    };
  },
};

// ===== Helper Functions =====

async function validateMemoryStore(
  namespace: string,
  key: string | undefined,
  value: any,
  context: AgenticHookContext
): Promise<{ valid: boolean; reason?: string }> {
  // Check size limits
  const size = getValueSize(value);
  const maxSize = 10 * 1024 * 1024; // 10MB
  
  if (size > maxSize) {
    return {
      valid: false,
      reason: `Value size ${size} exceeds limit ${maxSize}`,
    };
  }
  
  // Check namespace quota
  const quota = await getNamespaceQuota(namespace, context);
  const usage = await getNamespaceUsage(namespace, context);
  
  if (usage + size > quota) {
    return {
      valid: false,
      reason: `Namespace quota exceeded: ${usage + size} > ${quota}`,
    };
  }
  
  // Validate key format
  if (key && !isValidKey(key)) {
    return {
      valid: false,
      reason: `Invalid key format: ${key}`,
    };
  }
  
  return { valid: true };
}

function shouldCompress(value: any): boolean {
  const size = getValueSize(value);
  return size > 1024; // Compress if larger than 1KB
}

async function compressValue(value: any): Promise<any> {
  // Implement compression (placeholder)
  // In real implementation, use zlib or similar
  return {
    compressed: true,
    data: JSON.stringify(value),
  };
}

async function decompressValue(value: any): Promise<any> {
  // Implement decompression (placeholder)
  if (value.compressed) {
    return JSON.parse(value.data);
  }
  return value;
}

function getValueSize(value: any): number {
  return Buffer.byteLength(JSON.stringify(value), 'utf8');
}

async function updateMemoryIndex(
  namespace: string,
  key: string,
  value: any,
  context: AgenticHookContext
): Promise<void> {
  // Update search index (placeholder)
  // In real implementation, update inverted index for search
}

async function detectMemoryPatterns(
  namespace: string,
  key: string,
  value: any,
  context: AgenticHookContext
): Promise<any[]> {
  // Detect patterns in memory usage
  const patterns = [];
  
  // Check for sequential access pattern
  const accessHistory = await getAccessHistory(namespace, context);
  if (isSequentialPattern(accessHistory)) {
    patterns.push({
      type: 'sequential',
      confidence: 0.8,
      suggestion: 'prefetch-next',
    });
  }
  
  // Check for temporal patterns
  if (isTemporalPattern(accessHistory)) {
    patterns.push({
      type: 'temporal',
      confidence: 0.7,
      suggestion: 'cache-duration',
    });
  }
  
  return patterns;
}

async function checkLocalCache(
  namespace: string,
  key: string,
  context: AgenticHookContext
): Promise<any | null> {
  const cacheKey = `${namespace}:${key}`;
  return context.memory.cache.get(cacheKey);
}

async function findRelatedKeys(
  namespace: string,
  key: string,
  context: AgenticHookContext
): Promise<string[]> {
  // Find related keys based on patterns
  // Placeholder implementation
  return [];
}

async function prefetchKeys(
  namespace: string,
  keys: string[],
  context: AgenticHookContext
): Promise<void> {
  // Trigger background prefetch
  // Placeholder implementation
}

async function updateAccessPattern(
  namespace: string,
  key: string,
  context: AgenticHookContext
): Promise<void> {
  // Track access patterns for optimization
  const patternKey = `pattern:${namespace}:${key}`;
  const pattern = await context.memory.cache.get(patternKey) || {
    accesses: [],
    lastAccess: 0,
  };
  
  pattern.accesses.push(Date.now());
  pattern.lastAccess = Date.now();
  
  // Keep last 100 accesses
  if (pattern.accesses.length > 100) {
    pattern.accesses = pattern.accesses.slice(-100);
  }
  
  await context.memory.cache.set(patternKey, pattern);
}

async function cacheLocally(
  namespace: string,
  key: string,
  value: any,
  context: AgenticHookContext
): Promise<void> {
  const cacheKey = `${namespace}:${key}`;
  context.memory.cache.set(cacheKey, value);
}

async function detectMemoryChanges(
  namespace: string,
  provider: string,
  context: AgenticHookContext
): Promise<any[]> {
  // Detect changes for sync
  // Placeholder implementation
  return [];
}

async function applyMemoryChange(
  change: any,
  targets: string[],
  context: AgenticHookContext
): Promise<void> {
  // Apply memory change to targets
  // Placeholder implementation
}

async function createMemorySnapshot(
  namespace: string,
  context: AgenticHookContext
): Promise<any> {
  // Create snapshot of namespace
  // Placeholder implementation
  return {
    namespace,
    timestamp: Date.now(),
    entries: [],
    size: 0,
  };
}

async function findExpiredEntries(
  namespace: string,
  context: AgenticHookContext
): Promise<string[]> {
  // Find expired entries
  // Placeholder implementation
  return [];
}

async function removeMemoryEntry(
  namespace: string,
  key: string,
  context: AgenticHookContext
): Promise<void> {
  // Remove memory entry
  // Placeholder implementation
}

async function createFullBackup(
  namespace: string,
  context: AgenticHookContext
): Promise<any> {
  // Create full backup
  // Placeholder implementation
  return {
    entries: [],
    size: 0,
  };
}

function calculateChecksum(data: any): string {
  // Calculate checksum
  // Placeholder implementation
  return 'checksum';
}

async function getNamespaceQuota(
  namespace: string,
  context: AgenticHookContext
): Promise<number> {
  // Get namespace quota
  return 100 * 1024 * 1024; // 100MB default
}

async function getNamespaceUsage(
  namespace: string,
  context: AgenticHookContext
): Promise<number> {
  // Get current usage
  // Placeholder implementation
  return 0;
}

function isValidKey(key: string): boolean {
  // Validate key format
  return /^[a-zA-Z0-9:_\-./]+$/.test(key);
}

async function getAccessHistory(
  namespace: string,
  context: AgenticHookContext
): Promise<any[]> {
  // Get access history
  // Placeholder implementation
  return [];
}

function isSequentialPattern(history: any[]): boolean {
  // Check for sequential access
  // Placeholder implementation
  return false;
}

function isTemporalPattern(history: any[]): boolean {
  // Check for temporal patterns
  // Placeholder implementation
  return false;
}

// ===== Register Hooks =====

export function registerMemoryHooks(): void {
  agenticHookManager.register(preMemoryStoreHook);
  agenticHookManager.register(postMemoryStoreHook);
  agenticHookManager.register(preMemoryRetrieveHook);
  agenticHookManager.register(postMemoryRetrieveHook);
  agenticHookManager.register(memorySyncHook);
  agenticHookManager.register(memoryPersistHook);
}