typescript source code of tenancy.factory

import { Provider } from '@nestjs/common';
import { Connection } from 'mongoose';
import { ModelDefinition } from '../interfaces';
import { CONNECTION_MAP, MODEL_DEFINITION_MAP, TENANT_CONNECTION } from '../tenancy.constants';
import { ConnectionMap, ModelDefinitionMap } from '../types';
import { getTenantModelDefinitionToken, getTenantModelToken } from '../utils';

export const createTenancyProviders = (definitions: ModelDefinition[]): Provider[] => {
    const providers: Provider[] = [];

    for (const definition of definitions) {
        // Extract the definition data
        const { name, schema, collection } = definition;

        providers.push({
            provide: getTenantModelDefinitionToken(name),
            useFactory: (
                modelDefinitionMap: ModelDefinitionMap,
                connectionMap: ConnectionMap,
            ) => {
                const exists = modelDefinitionMap.has(name);
                if (!exists) {
                    modelDefinitionMap.set(name, { ...definition });

                    connectionMap.forEach((connection: Connection) => {
                        connection.model(name, schema, collection);
                    });
                }
            },
            inject: [
                MODEL_DEFINITION_MAP,
                CONNECTION_MAP,
            ],
        });

        // Creating Models with connections attached
        providers.push({
            provide: getTenantModelToken(name),
            useFactory(tenantConnection: Connection) {
                return tenantConnection.models[name] || tenantConnection.model(name, schema, collection);
            },
            inject: [TENANT_CONNECTION],
        });
    }

    // Return the list of providers mapping
    return providers;
};