const Provider = require('../Provider.js');
const { MongoClient } = require('mongodb');

class MongoDBProvider extends Provider {

    constructor(manager, config) {
        
        super(manager, {
            name: 'mongodb',
            config
        });

    }

    async init() {

        try {
            this.connection = await MongoClient.connect(this.config.host+this.config.database, { useUnifiedTopology: true });
            this.manager.db = await this.connection.db(this.config.database);
            this.db = this.manager.db;
            this.manager.logger.write('info', `Provider ${this.name} connected.`);
            this._initialized = true;
        } catch(err) {
            this.manager.logger.write('error', `Provider ${this.name} failed to connect: ${err}`);
        }

    }

    _query(request) {
        
        /* Query object structure
        {
            type: '', -- The function to use from this class, ex. findOne
            collection: '', -- Which collection to query from
            query: { }, -- Actual search query
            data: { }, -- If the operation is to update or insert something, this is what to insert
            upsert: bool, -- If true and no matching documents are found, insert a new one
            options: { }, 
            projection: { } -- The fields that should be returned
        }
        */

        if (!this._initialized) return { error: true, message: 'MongoDB not connected' };
        if (!this[request.type]) return { error: true, message: `Invalid request type, got '${request.type}'` };
        if (!request.collection && request.type !== 'stats') return { error: true, message: 'You must specify a collection to query!' };
        return this[request.type](request);


    }

    /**
     * Fetches basic statistics about the database or collection
     *
     * @param {String} collection The collection to query, optional
     * @param {Object} options Optional options for the stats method
     * @returns
     * @memberof MongoDBProvider
     */
    stats({ collection, options = { } }) {

        return new Promise((resolve, reject) => {

            if (!collection || collection.length) {

                this.db.stats(options, (error, stats) => {
                    
                    if (error) return reject(error);
                    else {

                        let { db, collections, objects, averageSize: avgObjSize, dataSize } = stats;
                        return resolve({ db, collections, objects, averageSize: avgObjSize, dataSize });

                    }

                });

            } else {

                this.db.collection(collection).stats(options, (err, stats) => {

                    if (err) return reject(err);
                    else {

                        let { ns, size, count, averageSize: avgObjSize } = stats;
                        return resolve({ index: ns, size, count, averageSize: avgObjSize });

                    }

                });

            }

        });

    }

    /**
     * Count the objects in 
     *
     * @param {String} collection The collection to query
     * @param {Object} query Only documents matching this will be counted, optional
     * @param {Object} options Optional options, see mongo docs for these
     * @returns
     * @memberof MongoDBProvider
     */
    count({ collection, query, options }) {

        return new Promise((resolve, reject) => {

            this.db.collection(collection).countDocuments(query, options, (error, result) => {

                if (error)
                    return reject(error);
                else 
                    return resolve(result);

            });

        });

    }


    /**
     * Remove a document from a collection
     *
     * @param {String} collection The collection to remove from
     * @param {Object} query Any documents matching this will be removed
     * @returns
     * @memberof MongoDBProvider
     */
    remove({ collection, query }) {
        
        return new Promise((resolve, reject) => {
            
            this.db.collection(collection).deleteOne(query, (err, result) => {
                
                if (err) return reject(err);
                return resolve(result);

            });

        });

    }

    /**
     * Insert one document to the collection
     *
     * @param {String} collection The collection to insert into
     * @param {Object} data The document to insert
     * @returns
     * @memberof MongoDBProvider
     */
    insertOne({ collection, data }) {

        return new Promise((resolve, reject) => {

            this.db.collection(collection).insertOne(data, (err, result) => {

                if(err) reject(err);
                resolve(result);

            });

        });

    }

    /**
     * Find and return the first match
     * 
     * @param {String} collection The collection to find from
     * @param {Object} query Documents matching this will be returned
     * @param {Object} projection Defines which fields to return, { 'key': 1, 'key2': 0 } -- key will return, key2 won't, optional
     * @memberof Database
     */

    find({ collection, query, projection }) {

        //if(this.manager.debug) this.manager.logger.debug(`Incoming find query for ${db} with parameters ${JSON.stringify(query)}`);
        return new Promise((resolve, reject) => {

            if(!this._initialized) reject(new Error('MongoDB not connected'));

            this.db.collection(collection).find(query, { projection }, async (error, cursor) => {

                if(error) return reject(error);
                return resolve(await cursor.toArray());

            });

        });

    }

    /**
     * Find and return the first match
     *
     * @param {String} collection The collection in which the data is to be updated
     * @param {Object} query The filter that is used to find the data
     * @param {Object} projection Defines which fields to return, { 'key': 1, 'key2': 0 } -- key will return, key2 won't, optional
     * @returns {Object} An object containing the queried data
     * @memberof Database
     */

    findOne({ collection, query, projection }) {

        //if(this.manager.debug) this.manager.logger.debug(`Incoming findOne query for ${db} with parameters ${JSON.stringify(query)}`);
        return new Promise((resolve, reject) => {

            if(!this._initialized) reject(new Error('MongoDB not connected'));

            this.db.collection(collection).findOne(query, { projection }, async (error, item) => {

                if(error) return reject(error);
                return resolve(item);
                
            });

        });

    }

    /**
     * Update the first filter match.
     *
     * @param {String} collection The collection in which the data is to be updated
     * @param {Object} query The filter that is used to find the data
     * @param {Object} data The updated data
     * @param {Boolean} [upsert=true] Create a new entry if no match is found
     * @returns {WriteResult} Object containing the followint counts: Matched, Upserted, Modified
     * @memberof Database
     */
    updateOne({ collection, query, data, upsert = true }) {

        //if(this.manager.debug) this.manager.logger.debug(`Incoming updateOne query for ${db} with parameters ${JSON.stringify(filter)}`);
        return new Promise((resolve, reject) => {

            if(!this._initialized) reject(new Error('MongoDB not connected'));
            
            this.db.collection(collection).updateOne(query, { $set: data }, { upsert: upsert }, async (error, result) => {
                
                if(error) return reject(error);
                else {
                    //return resolve(result)
                    let { matchedCount, upsertedCount, modifiedCount } = result;
                    return resolve({ matched: matchedCount, upserted: upsertedCount, modified: modifiedCount });
                }
            });

        });

    }

    /**
     * Remove a document property
     *
     * @param {String} collection The collection to query
     * @param {Object} query The filter that is used to find the data
     * @param {Array} data Array of fields to remove
     * @returns
     * @memberof MongoDBProvider
     */
    removeProperty({ collection, query, data }) {
        return new Promise((resolve, reject) => {

            let unset = {};
            for (let field in data) unset[field] = '';
            this.db.collection(collection).updateOne(query, { $unset: unset }, async (error, result) => {

                if(error) return reject(error);
                else {

                    let { matchedCount, modifiedCount } = result;
                    return resolve({ matched: matchedCount, modified: modifiedCount });
                
                }

            });

        });

    }

    /**
     * Push data to an array
     *
     * @param {string} collection The collection to query
     * @param {object} query The filter to find the document to update
     * @param {object} data The data to be pushed
     * @param {boolean} [upsert=true] Create a new entry if no match is found
     * @returns
     * @memberof Database
     */
    push({ collection, query, data, upsert = true }) {

        //if(this.manager.debug) this.manager.logger.debug(`Incoming push query for ${db}, with upsert ${upsert} and with parameters ${JSON.stringify(filter)} and data ${JSON.stringify(data)}`);
        return new Promise((resolve, reject) => {

            if(!this._initialized) reject(new Error('MongoDB not connected'));

            this.db.collection(collection).updateOne(query, { $push: data }, { upsert: upsert }, async (error, result) => {

                if(error) return reject(error);
                else return resolve(result);

            });

        });

    }

    /**
     * Find a random element from a database
     *
     * @param {string} collection The collection to query
     * @param {object} [query={}] The filtering object to narrow down the sample pool
     * @param {number} [amount=1] Amount of items to return
     * @returns {object}
     * @memberof Database
     */
    random({ collection, query = {}, amount = 1 }) {

        //if(this.manager.debug) this.manager.logger.debug(`Incoming random query for ${db} with parameters ${JSON.stringify(filter)} and amount ${amount}`);
        if(amount > 100) amount = 100;

        return new Promise((resolve, reject)=>{

            if(!this._initialized) reject(new Error('MongoDB not connected'));

            this.db.collection(collection).aggregate([{ $match: query }, { $sample: {size: amount}}], function(err, item) {

                if(err) return reject(err);
                resolve(item);

            });

        });

    } 

}

module.exports = MongoDBProvider;