const { Collection } = require('../util/');
const path = require('path');
const fs = require('fs');

class StorageManager {

    constructor(manager, options = {}) {

        this.manager = manager;

        this.providers = new Collection();
        this.options = options;

    }

    async initialize() {

        this.manager.logger.write('debug', "Initializing storage providers.");

        const _providers = path.join(process.cwd(), 'storage', 'providers');
        const providers = fs.readdirSync(_providers);

        for(const _provider of providers) {

            let provider = require(path.join(_providers, _provider));
            provider = new provider(this.manager, this.options);

            await provider.init();

            this.providers.set(provider.name, provider);

        }

        return this;

    }

    async _handleStorageRequest(shard, message) {

        // vv TO BE GENERATED ON CLIENT vv
        // Transaction ID concept
        //`${shard.id}-${new Date().getTime().toString(36)}`

        //NULL RESPONSE IF COLLECTION DOES NOT EXIST!!
        //EMPTY OBJECT IF NOTHING MATCHED!!

        /** Message structure
         *  {
         *      provider: string, -- mongodb or mariadb
         *      transactionID: string,
         *      request: {
         *          type: string, -- The function to use from this class, ex. findOne
         *          collection: string, -- Which collection to query from
         *          query: { }, -- Actual search query
         *          data: { } -- If the operation is to update or insert something, this is what to insert
         *      }
         *  }
         */

        if(!message.provider) return this._send(shard, { error: true, message: "Provider not provided", transactionID: message.transactionID });
        if(!this.providers.has(message.provider)) return this._send(shard, { error: true, message: `Invalid provider, expected 'mongodb' or 'mariadb', got '${message.provider}'`, transactionID: message.transactionID });
        if(!message.request) return this._send(shard, { error: true, message: `Missing request.`, transactionID: message.transactionID });

        const response = await this.providers.get(message.provider)._query(message.request)
            .catch((error) => {
                this.manager.logger.write('error', `Provider ${message.provider} errored: ${error}`, shard);
            });

        if(response && response.error) {
            this.manager.logger.write('error', `Provider ${message.provider} errored: ${response.message}`, shard);
            return this._send(shard, response.error);
        }

        this._send(shard, { transactionID: message.transactionID, result: response });

    }
    
    _send(shard, message) {
        shard.send({
            _storage: true,
            transactionID: message.transactionID,
            id: message.id,
            error: message.error,
            message: message.message,
            result: message.result
        });
    }

}

module.exports = StorageManager;