import * as plugins from '../../congodb.plugins.js';
import type { ICommandHandler, IHandlerContext } from '../CommandRouter.js';
import { QueryEngine } from '../../engine/QueryEngine.js';

/**
 * DeleteHandler - Handles delete commands
 */
export class DeleteHandler implements ICommandHandler {
  async handle(context: IHandlerContext): Promise<plugins.bson.Document> {
    const { storage, database, command, documentSequences } = context;

    const collection = command.delete;
    if (typeof collection !== 'string') {
      return {
        ok: 0,
        errmsg: 'delete command requires a collection name',
        code: 2,
        codeName: 'BadValue',
      };
    }

    // Get deletes from command or document sequences
    let deletes: plugins.bson.Document[] = command.deletes || [];

    // Check for OP_MSG document sequences
    if (documentSequences && documentSequences.has('deletes')) {
      deletes = documentSequences.get('deletes')!;
    }

    if (!Array.isArray(deletes) || deletes.length === 0) {
      return {
        ok: 0,
        errmsg: 'delete command requires deletes array',
        code: 2,
        codeName: 'BadValue',
      };
    }

    const ordered = command.ordered !== false;
    const writeErrors: plugins.bson.Document[] = [];
    let totalDeleted = 0;

    // Check if collection exists
    const exists = await storage.collectionExists(database, collection);
    if (!exists) {
      // Collection doesn't exist, return success with 0 deleted
      return { ok: 1, n: 0 };
    }

    for (let i = 0; i < deletes.length; i++) {
      const deleteSpec = deletes[i];
      const filter = deleteSpec.q || deleteSpec.filter || {};
      const limit = deleteSpec.limit;

      // limit: 0 means delete all matching, limit: 1 means delete one
      const deleteAll = limit === 0;

      try {
        // Get all documents
        const documents = await storage.findAll(database, collection);

        // Apply filter
        const matchingDocs = QueryEngine.filter(documents, filter);

        if (matchingDocs.length === 0) {
          continue;
        }

        // Determine which documents to delete
        const docsToDelete = deleteAll ? matchingDocs : matchingDocs.slice(0, 1);

        // Delete the documents
        const idsToDelete = docsToDelete.map(doc => doc._id);
        const deleted = await storage.deleteByIds(database, collection, idsToDelete);
        totalDeleted += deleted;
      } catch (error: any) {
        writeErrors.push({
          index: i,
          code: error.code || 1,
          errmsg: error.message || 'Delete failed',
        });

        if (ordered) {
          break;
        }
      }
    }

    const response: plugins.bson.Document = {
      ok: 1,
      n: totalDeleted,
    };

    if (writeErrors.length > 0) {
      response.writeErrors = writeErrors;
    }

    return response;
  }
}