const mongodb = require('mongodb');
const configuration = require('../configuration');
const mongoConfig = configuration.database;

class MongoClient {
    constructor() {
        mongodb.MongoClient.connect(mongoConfig.url, (error, client) => {
            console.log(error);
            if (error !== null) {
                throw new Error(`Unable de connect to Mongo database: ${error}`);
            }

            console.log('Connected successfuly to mongodb');
            this.db = client.db(mongoConfig.database);
        });
    }

    find(collectionName, query, callback) {
        this.db.collection(collectionName).find(query).toArray()
            .then(results => {
                console.log(`Entities ${collectionName} founded.`);
                callback(results);
            })
            .catch(error => {
                throw new Error(`Unable to find entities in collection ${collectionName}: ${error}`);
            });
    }

    insert(collectionName, entity, callback) {
        this.db.collection(collectionName).insertOne(entity, (error, result) => {
            if (error !== null) {
                throw new Error(`Unable to insert ${collectionName} entity: ${error}`);
            }
            
            console.log(`Entity ${collectionName} inserted.`);
            // Return only the inserted document.
            callback(result.ops[0]);
        });
    }

    update(collectionName, entity, callback) {
        this.db.collection(collectionName).updateOne({_id: mongodb.ObjectId(entity._id)}, {$set: entity}, {upsert: true}, (error) => {
            if (error !== null) {
                throw new Error(`Unable to update ${collectionName} entity: ${error}`);
            }

            console.log(`Entity ${collectionName} updated.`);
            callback();
        });
    }

    delete(collectionName, entityId, callback) {
        this.db.collection(collectionName).deleteOne({_id: mongodb.ObjectId(entityId)}, (error) => {
            if (error !== null) {
                throw new Error(`Unable to delete ${collectionName} entity with id ${entityId}: ${error}`);
            }

            console.log(`Entity ${collectionName} with id ${entityId} deleted.`);
            callback();
        });
    }
}

// Define a singleton of class "MongoClient".
const mongoClient = new MongoClient();
module.exports = mongoClient;