import type { Client as ElasticClient } from '@elastic/elasticsearch';
import { ElasticsearchConnectionManager } from '../../core/connection/connection-manager.js';
import { Logger, defaultLogger } from '../../core/observability/logger.js';
import { MetricsCollector, defaultMetricsCollector } from '../../core/observability/metrics.js';
import { TracingProvider, defaultTracingProvider } from '../../core/observability/tracing.js';
import { DocumentSession } from './document-session.js';
import type {
  DocumentWithMeta,
  SessionConfig,
  SnapshotProcessor,
  SnapshotMeta,
  IteratorOptions,
} from './types.js';
import { IndexNotFoundError } from '../../core/errors/elasticsearch-error.js';

/**
 * Document manager configuration
 */
export interface DocumentManagerConfig {
  /** Index name */
  index: string;

  /** Connection manager (optional, will use singleton if not provided) */
  connectionManager?: ElasticsearchConnectionManager;

  /** Logger (optional, will use default if not provided) */
  logger?: Logger;

  /** Metrics collector (optional) */
  metrics?: MetricsCollector;

  /** Tracing provider (optional) */
  tracing?: TracingProvider;

  /** Auto-create index if it doesn't exist */
  autoCreateIndex?: boolean;

  /** Default batch size for operations */
  defaultBatchSize?: number;
}

/**
 * Fluent document manager for Elasticsearch
 *
 * @example
 * ```typescript
 * const docs = new DocumentManager<Product>('products');
 * await docs.initialize();
 *
 * // Session-based operations
 * await docs
 *   .session()
 *   .start()
 *   .upsert('prod-1', { name: 'Widget', price: 99.99 })
 *   .upsert('prod-2', { name: 'Gadget', price: 149.99 })
 *   .commit();
 *
 * // Get a document
 * const product = await docs.get('prod-1');
 *
 * // Create snapshot
 * const snapshot = await docs.snapshot(async (iterator) => {
 *   const products = [];
 *   for await (const doc of iterator) {
 *     products.push(doc._source);
 *   }
 *   return { totalCount: products.length, products };
 * });
 * ```
 */
export class DocumentManager<T = unknown> {
  private client: ElasticClient;
  private connectionManager: ElasticsearchConnectionManager;
  private logger: Logger;
  private metrics: MetricsCollector;
  private tracing: TracingProvider;
  private index: string;
  private config: DocumentManagerConfig;
  private isInitialized = false;

  constructor(config: DocumentManagerConfig) {
    this.config = config;
    this.index = config.index;

    // Get or create connection manager
    this.connectionManager =
      config.connectionManager || ElasticsearchConnectionManager.getInstance();

    // Set up observability
    this.logger = config.logger || defaultLogger.child(`documents:${this.index}`);
    this.metrics = config.metrics || defaultMetricsCollector;
    this.tracing = config.tracing || defaultTracingProvider;

    // Get client (will throw if connection manager not initialized)
    this.client = this.connectionManager.getClient();
  }

  /**
   * Static factory method for fluent creation
   */
  static create<T = unknown>(index: string, config: Omit<DocumentManagerConfig, 'index'> = {}): DocumentManager<T> {
    return new DocumentManager<T>({ ...config, index });
  }

  /**
   * Initialize the document manager
   */
  async initialize(): Promise<void> {
    if (this.isInitialized) {
      return;
    }

    return this.tracing.withSpan('DocumentManager.initialize', async (span) => {
      span.setAttribute('index', this.index);

      try {
        // Check if index exists
        const exists = await this.client.indices.exists({ index: this.index });

        if (!exists && this.config.autoCreateIndex) {
          this.logger.info('Creating index', { index: this.index });
          await this.client.indices.create({ index: this.index });
          this.logger.info('Index created', { index: this.index });
        } else if (!exists) {
          throw new IndexNotFoundError(this.index);
        }

        this.isInitialized = true;
        this.logger.info('Document manager initialized', { index: this.index });
      } catch (error) {
        this.logger.error('Failed to initialize document manager', error as Error, {
          index: this.index,
        });
        span.recordException(error as Error);
        throw error;
      }
    });
  }

  /**
   * Create a new session for batch operations
   */
  session(config?: SessionConfig): DocumentSession<T> {
    this.ensureInitialized();
    return new DocumentSession<T>(this.client, this.index, this.logger, config);
  }

  /**
   * Get a single document by ID
   */
  async get(documentId: string): Promise<DocumentWithMeta<T> | null> {
    this.ensureInitialized();

    return this.tracing.withSpan('DocumentManager.get', async (span) => {
      span.setAttributes({
        'document.id': documentId,
        'document.index': this.index,
      });

      const startTime = Date.now();

      try {
        const result = await this.client.get({
          index: this.index,
          id: documentId,
        });

        const duration = (Date.now() - startTime) / 1000;
        this.metrics.requestDuration.observe(duration, {
          operation: 'get',
          index: this.index,
        });

        return {
          _id: result._id,
          _source: result._source as T,
          _version: result._version,
          _seq_no: result._seq_no,
          _primary_term: result._primary_term,
          _index: result._index,
        };
      } catch (error: any) {
        if (error.statusCode === 404) {
          this.logger.debug('Document not found', { documentId, index: this.index });
          return null;
        }

        this.logger.error('Failed to get document', error, { documentId, index: this.index });
        span.recordException(error);
        throw error;
      }
    });
  }

  /**
   * Create a document
   */
  async create(documentId: string, document: T): Promise<void> {
    this.ensureInitialized();

    return this.tracing.withSpan('DocumentManager.create', async (span) => {
      span.setAttributes({
        'document.id': documentId,
        'document.index': this.index,
      });

      const startTime = Date.now();

      try {
        await this.client.create({
          index: this.index,
          id: documentId,
          document: document as Record<string, unknown>,
          refresh: true,
        });

        const duration = (Date.now() - startTime) / 1000;
        this.metrics.requestDuration.observe(duration, {
          operation: 'create',
          index: this.index,
        });

        this.logger.debug('Document created', { documentId, index: this.index });
      } catch (error) {
        this.logger.error('Failed to create document', error as Error, {
          documentId,
          index: this.index,
        });
        span.recordException(error as Error);
        throw error;
      }
    });
  }

  /**
   * Update a document
   */
  async update(
    documentId: string,
    document: Partial<T>,
    options?: { seqNo?: number; primaryTerm?: number }
  ): Promise<void> {
    this.ensureInitialized();

    return this.tracing.withSpan('DocumentManager.update', async (span) => {
      span.setAttributes({
        'document.id': documentId,
        'document.index': this.index,
      });

      const startTime = Date.now();

      try {
        await this.client.update({
          index: this.index,
          id: documentId,
          doc: document as Record<string, unknown>,
          refresh: true,
          ...(options?.seqNo !== undefined && { if_seq_no: options.seqNo }),
          ...(options?.primaryTerm !== undefined && { if_primary_term: options.primaryTerm }),
        });

        const duration = (Date.now() - startTime) / 1000;
        this.metrics.requestDuration.observe(duration, {
          operation: 'update',
          index: this.index,
        });

        this.logger.debug('Document updated', { documentId, index: this.index });
      } catch (error) {
        this.logger.error('Failed to update document', error as Error, {
          documentId,
          index: this.index,
        });
        span.recordException(error as Error);
        throw error;
      }
    });
  }

  /**
   * Upsert a document (create or update)
   */
  async upsert(documentId: string, document: T): Promise<void> {
    this.ensureInitialized();

    return this.tracing.withSpan('DocumentManager.upsert', async (span) => {
      span.setAttributes({
        'document.id': documentId,
        'document.index': this.index,
      });

      const startTime = Date.now();

      try {
        await this.client.index({
          index: this.index,
          id: documentId,
          document: document as Record<string, unknown>,
          refresh: true,
        });

        const duration = (Date.now() - startTime) / 1000;
        this.metrics.requestDuration.observe(duration, {
          operation: 'upsert',
          index: this.index,
        });

        this.logger.debug('Document upserted', { documentId, index: this.index });
      } catch (error) {
        this.logger.error('Failed to upsert document', error as Error, {
          documentId,
          index: this.index,
        });
        span.recordException(error as Error);
        throw error;
      }
    });
  }

  /**
   * Delete a document
   */
  async delete(documentId: string): Promise<void> {
    this.ensureInitialized();

    return this.tracing.withSpan('DocumentManager.delete', async (span) => {
      span.setAttributes({
        'document.id': documentId,
        'document.index': this.index,
      });

      const startTime = Date.now();

      try {
        await this.client.delete({
          index: this.index,
          id: documentId,
          refresh: true,
        });

        const duration = (Date.now() - startTime) / 1000;
        this.metrics.requestDuration.observe(duration, {
          operation: 'delete',
          index: this.index,
        });

        this.logger.debug('Document deleted', { documentId, index: this.index });
      } catch (error: any) {
        if (error.statusCode === 404) {
          this.logger.debug('Document not found for deletion', { documentId, index: this.index });
          return; // Idempotent delete
        }

        this.logger.error('Failed to delete document', error, { documentId, index: this.index });
        span.recordException(error);
        throw error;
      }
    });
  }

  /**
   * Check if index exists
   */
  async exists(): Promise<boolean> {
    try {
      return await this.client.indices.exists({ index: this.index });
    } catch (error) {
      this.logger.error('Failed to check if index exists', error as Error, {
        index: this.index,
      });
      return false;
    }
  }

  /**
   * Delete the index
   */
  async deleteIndex(): Promise<void> {
    return this.tracing.withSpan('DocumentManager.deleteIndex', async (span) => {
      span.setAttribute('index', this.index);

      try {
        await this.client.indices.delete({ index: this.index });
        this.isInitialized = false;
        this.logger.info('Index deleted', { index: this.index });
      } catch (error) {
        this.logger.error('Failed to delete index', error as Error, { index: this.index });
        span.recordException(error as Error);
        throw error;
      }
    });
  }

  /**
   * Get document count
   */
  async count(query?: unknown): Promise<number> {
    this.ensureInitialized();

    try {
      const queryObj = query as Record<string, unknown> | undefined;
      const result = await this.client.count({
        index: this.index,
        ...(queryObj ? { query: queryObj } : {}),
      });

      return result.count;
    } catch (error) {
      this.logger.error('Failed to count documents', error as Error, { index: this.index });
      throw error;
    }
  }

  /**
   * Create a snapshot with custom processor
   */
  async snapshot<R>(processor: SnapshotProcessor<T, R>): Promise<SnapshotMeta<R>> {
    this.ensureInitialized();

    return this.tracing.withSpan('DocumentManager.snapshot', async (span) => {
      span.setAttribute('index', this.index);

      const startTime = Date.now();
      const snapshotIndex = `${this.index}-snapshots`;

      try {
        // Get previous snapshot
        const previousSnapshot = await this.getLatestSnapshot<R>(snapshotIndex);

        // Create iterator for all documents
        const iterator = this.iterate();

        // Process snapshot
        const snapshotData = await processor(iterator, previousSnapshot);

        // Count documents
        const documentCount = await this.count();

        // Store snapshot
        const snapshot: SnapshotMeta<R> = {
          date: new Date(),
          data: snapshotData,
          documentCount,
          processingTime: Date.now() - startTime,
        };

        await this.storeSnapshot(snapshotIndex, snapshot);

        this.logger.info('Snapshot created', {
          index: this.index,
          documentCount,
          processingTime: snapshot.processingTime,
        });

        return snapshot;
      } catch (error) {
        this.logger.error('Failed to create snapshot', error as Error, { index: this.index });
        span.recordException(error as Error);
        throw error;
      }
    });
  }

  /**
   * Iterate over all documents
   */
  async *iterate(options: IteratorOptions = {}): AsyncIterableIterator<DocumentWithMeta<T>> {
    this.ensureInitialized();

    const batchSize = options.batchSize || this.config.defaultBatchSize || 1000;

    // TODO: Use Point-in-Time API for better performance
    // For now, use basic search with search_after

    let searchAfter: any[] | undefined;
    let hasMore = true;

    while (hasMore) {
      const searchQuery = options.query as Record<string, unknown> | undefined;
      const result = await this.client.search({
        index: this.index,
        size: batchSize,
        ...(searchAfter ? { search_after: searchAfter } : {}),
        sort: options.sort || [{ _id: 'asc' }],
        ...(searchQuery ? { query: searchQuery } : {}),
      });

      const hits = result.hits.hits;

      if (hits.length === 0) {
        hasMore = false;
        break;
      }

      for (const hit of hits) {
        yield {
          _id: hit._id ?? '',
          _source: hit._source as T,
          _version: hit._version,
          _seq_no: hit._seq_no,
          _primary_term: hit._primary_term,
          _index: hit._index,
          _score: hit._score ?? undefined,
        };
      }

      // Get last sort value for pagination
      const lastHit = hits[hits.length - 1];
      if (lastHit) {
        searchAfter = lastHit.sort;
      }

      if (hits.length < batchSize) {
        hasMore = false;
      }
    }
  }

  /**
   * Get latest snapshot
   */
  private async getLatestSnapshot<R>(snapshotIndex: string): Promise<R | null> {
    try {
      const result = await this.client.search({
        index: snapshotIndex,
        size: 1,
        sort: [{ 'date': 'desc' }] as unknown as Array<string | { [key: string]: 'asc' | 'desc' }>,
      });

      const firstHit = result.hits.hits[0];
      if (!firstHit) {
        return null;
      }

      const snapshot = firstHit._source as SnapshotMeta<R>;
      return snapshot.data;
    } catch (error: any) {
      if (error.statusCode === 404) {
        return null; // Index doesn't exist yet
      }
      throw error;
    }
  }

  /**
   * Store snapshot
   */
  private async storeSnapshot<R>(snapshotIndex: string, snapshot: SnapshotMeta<R>): Promise<void> {
    await this.client.index({
      index: snapshotIndex,
      document: snapshot as unknown as Record<string, unknown>,
      refresh: true,
    });
  }

  /**
   * Ensure manager is initialized
   */
  private ensureInitialized(): void {
    if (!this.isInitialized) {
      throw new Error('DocumentManager not initialized. Call initialize() first.');
    }
  }

  /**
   * Get index name
   */
  getIndex(): string {
    return this.index;
  }
}