import * as plugins from '../tsmdb.plugins.js';
import type { IStorageAdapter } from './IStorageAdapter.js';
import type { IOpLogEntry, Document, IResumeToken, ChangeStreamOperationType } from '../types/interfaces.js';

/**
 * Operation Log for tracking all mutations
 * Used primarily for change stream support
 */
export class OpLog {
  private storage: IStorageAdapter;
  private counter = 0;
  private listeners: Array<(entry: IOpLogEntry) => void> = [];

  constructor(storage: IStorageAdapter) {
    this.storage = storage;
  }

  /**
   * Generate a new timestamp for oplog entries
   */
  generateTimestamp(): plugins.bson.Timestamp {
    this.counter++;
    return new plugins.bson.Timestamp({ t: Math.floor(Date.now() / 1000), i: this.counter });
  }

  /**
   * Generate a resume token from a timestamp
   */
  generateResumeToken(ts: plugins.bson.Timestamp): IResumeToken {
    // Create a resume token similar to MongoDB's format
    // It's a base64-encoded BSON document containing the timestamp
    const tokenData = {
      _data: Buffer.from(JSON.stringify({
        ts: { t: ts.high, i: ts.low },
        version: 1,
      })).toString('base64'),
    };
    return tokenData;
  }

  /**
   * Parse a resume token to get the timestamp
   */
  parseResumeToken(token: IResumeToken): plugins.bson.Timestamp {
    try {
      const data = JSON.parse(Buffer.from(token._data, 'base64').toString('utf-8'));
      return new plugins.bson.Timestamp({ t: data.ts.t, i: data.ts.i });
    } catch {
      throw new Error('Invalid resume token');
    }
  }

  /**
   * Record an insert operation
   */
  async recordInsert(
    dbName: string,
    collName: string,
    document: Document,
    txnInfo?: { txnNumber?: number; lsid?: { id: plugins.bson.Binary } }
  ): Promise<IOpLogEntry> {
    const entry: IOpLogEntry = {
      ts: this.generateTimestamp(),
      op: 'i',
      ns: `${dbName}.${collName}`,
      o: document,
      ...txnInfo,
    };

    await this.storage.appendOpLog(entry);
    this.notifyListeners(entry);
    return entry;
  }

  /**
   * Record an update operation
   */
  async recordUpdate(
    dbName: string,
    collName: string,
    filter: Document,
    update: Document,
    txnInfo?: { txnNumber?: number; lsid?: { id: plugins.bson.Binary } }
  ): Promise<IOpLogEntry> {
    const entry: IOpLogEntry = {
      ts: this.generateTimestamp(),
      op: 'u',
      ns: `${dbName}.${collName}`,
      o: update,
      o2: filter,
      ...txnInfo,
    };

    await this.storage.appendOpLog(entry);
    this.notifyListeners(entry);
    return entry;
  }

  /**
   * Record a delete operation
   */
  async recordDelete(
    dbName: string,
    collName: string,
    filter: Document,
    txnInfo?: { txnNumber?: number; lsid?: { id: plugins.bson.Binary } }
  ): Promise<IOpLogEntry> {
    const entry: IOpLogEntry = {
      ts: this.generateTimestamp(),
      op: 'd',
      ns: `${dbName}.${collName}`,
      o: filter,
      ...txnInfo,
    };

    await this.storage.appendOpLog(entry);
    this.notifyListeners(entry);
    return entry;
  }

  /**
   * Record a command (drop, rename, etc.)
   */
  async recordCommand(
    dbName: string,
    command: Document
  ): Promise<IOpLogEntry> {
    const entry: IOpLogEntry = {
      ts: this.generateTimestamp(),
      op: 'c',
      ns: `${dbName}.$cmd`,
      o: command,
    };

    await this.storage.appendOpLog(entry);
    this.notifyListeners(entry);
    return entry;
  }

  /**
   * Get oplog entries after a timestamp
   */
  async getEntriesAfter(ts: plugins.bson.Timestamp, limit?: number): Promise<IOpLogEntry[]> {
    return this.storage.getOpLogAfter(ts, limit);
  }

  /**
   * Get the latest timestamp
   */
  async getLatestTimestamp(): Promise<plugins.bson.Timestamp | null> {
    return this.storage.getLatestOpLogTimestamp();
  }

  /**
   * Subscribe to oplog changes (for change streams)
   */
  subscribe(listener: (entry: IOpLogEntry) => void): () => void {
    this.listeners.push(listener);
    return () => {
      const idx = this.listeners.indexOf(listener);
      if (idx >= 0) {
        this.listeners.splice(idx, 1);
      }
    };
  }

  /**
   * Notify all listeners of a new entry
   */
  private notifyListeners(entry: IOpLogEntry): void {
    for (const listener of this.listeners) {
      try {
        listener(entry);
      } catch (error) {
        console.error('Error in oplog listener:', error);
      }
    }
  }

  /**
   * Convert an oplog entry to a change stream document
   */
  opLogEntryToChangeEvent(
    entry: IOpLogEntry,
    fullDocument?: Document,
    fullDocumentBeforeChange?: Document
  ): {
    _id: IResumeToken;
    operationType: ChangeStreamOperationType;
    fullDocument?: Document;
    fullDocumentBeforeChange?: Document;
    ns: { db: string; coll?: string };
    documentKey?: { _id: plugins.bson.ObjectId };
    updateDescription?: {
      updatedFields?: Document;
      removedFields?: string[];
    };
    clusterTime: plugins.bson.Timestamp;
  } {
    const [db, coll] = entry.ns.split('.');
    const resumeToken = this.generateResumeToken(entry.ts);

    const baseEvent = {
      _id: resumeToken,
      ns: { db, coll: coll === '$cmd' ? undefined : coll },
      clusterTime: entry.ts,
    };

    switch (entry.op) {
      case 'i':
        return {
          ...baseEvent,
          operationType: 'insert' as ChangeStreamOperationType,
          fullDocument: fullDocument || entry.o,
          documentKey: entry.o._id ? { _id: entry.o._id } : undefined,
        };

      case 'u':
        const updateEvent: any = {
          ...baseEvent,
          operationType: 'update' as ChangeStreamOperationType,
          documentKey: entry.o2?._id ? { _id: entry.o2._id } : undefined,
        };

        if (fullDocument) {
          updateEvent.fullDocument = fullDocument;
        }
        if (fullDocumentBeforeChange) {
          updateEvent.fullDocumentBeforeChange = fullDocumentBeforeChange;
        }

        // Parse update description
        if (entry.o.$set || entry.o.$unset) {
          updateEvent.updateDescription = {
            updatedFields: entry.o.$set || {},
            removedFields: entry.o.$unset ? Object.keys(entry.o.$unset) : [],
          };
        }

        return updateEvent;

      case 'd':
        return {
          ...baseEvent,
          operationType: 'delete' as ChangeStreamOperationType,
          documentKey: entry.o._id ? { _id: entry.o._id } : undefined,
          fullDocumentBeforeChange,
        };

      case 'c':
        if (entry.o.drop) {
          return {
            ...baseEvent,
            operationType: 'drop' as ChangeStreamOperationType,
            ns: { db, coll: entry.o.drop },
          };
        }
        if (entry.o.dropDatabase) {
          return {
            ...baseEvent,
            operationType: 'dropDatabase' as ChangeStreamOperationType,
          };
        }
        if (entry.o.renameCollection) {
          return {
            ...baseEvent,
            operationType: 'rename' as ChangeStreamOperationType,
          };
        }
        return {
          ...baseEvent,
          operationType: 'invalidate' as ChangeStreamOperationType,
        };

      default:
        return {
          ...baseEvent,
          operationType: 'invalidate' as ChangeStreamOperationType,
        };
    }
  }
}