const ParameterizedSQL = require('loopback-connector').ParameterizedSQL;

module.exports = function(Self) {
    Self.ParameterizedSQL = ParameterizedSQL;

    Self.setup = function() {
        Self.super_.setup.call(this);
        /*
        let disableMethods = {
            create: true,
            replaceOrCreate: true,
            patchOrCreate: true,
            upsert: true,
            updateOrCreate: true,
            exists: true,
            find: true,
            findOne: true,
            findById: true,
            deleteById: true,
            replaceById: true,
            updateAttributes: false,
            createChangeStream: true,
            updateAll: true,
            upsertWithWhere: true,
            count: true
        };
        for (let method in disableMethods) {
            // this.disableRemoteMethod(method, disableMethods[method]);
        }
        */
        this.installCrudModel('crud');
    };

    Self.defineScope = function(serverFilter) {
        this.remoteMethodCtx('list', {
            accepts: [
                {
                    arg: 'filter',
                    type: 'object',
                    description: 'Filter defining where'
                }
            ],
            returns: {
                type: [this.modelName],
                root: true
            },
            http: {
                verb: 'get',
                path: '/list'
            }
        });

        this.list = function(ctx, clientFilter, cb) {
            let clientFields = (clientFilter && clientFilter.fields) ? clientFilter.fields : [];
            let serverFields = (serverFilter && serverFilter.fields) ? serverFilter.fields : [];
            let fields = clientFields.filter(itemC => {
                return serverFields.some(itemS => itemS === itemC);
            });
            let and = [];
            let order;
            let limit;
            let filter = {order: order, limit: limit};

            if (clientFilter && clientFilter.where)
                and.push(clientFilter.where);
            if (serverFilter && serverFilter.where)
                and.push(serverFilter.where);

            if (clientFilter && clientFilter.order)
                order = clientFilter.order;
            else if (serverFilter && serverFilter.order)
                order = serverFilter.order;

            if (serverFilter && serverFilter.limit)
                limit = serverFilter.limit;
            else if (clientFilter && clientFilter.limit)
                limit = clientFilter.limit;

            filter.where = (and.length > 0) && {and: and};
            filter.fields = fields;

            this.find(filter, function(err, states) {
                if (err)
                    cb(err, null);
                else
                    cb(null, states);
            });
        };
    };

    Self.remoteMethodCtx = function(methodName, args) {
        var ctx = {
            arg: 'context',
            type: 'object',
            http: function(ctx) {
                return ctx;
            }
        };
        if (args.accepts === undefined)
            args.accepts = [];
        else if (!Array.isArray(args.accepts))
            args.accepts = [args.accepts];
        args.accepts.unshift(ctx);
        this.remoteMethod(methodName, args);
    };

    Self.getConnection = function(cb) {
        this.dataSource.connector.client.getConnection(cb);
    };

    Self.connectToService = function(ctx, dataSource) {
        this.app.dataSources[dataSource].connector.remotes.auth = {
            bearer: new Buffer(ctx.req.accessToken.id).toString('base64'),
            sendImmediately: true
        };
    };

    Self.disconnectFromService = function(dataSource) {
        this.app.dataSources[dataSource].connector.remotes.auth = {
            bearer: new Buffer('').toString('base64'),
            sendImmediately: true
        };
    };

    Self.installCrudModel = function(methodName) {
        this.remoteMethod(methodName, {
            description: 'Create, update or/and delete instances from model in a single request',
            accessType: 'WRITE',
            accepts: [
                {
                    arg: 'actions',
                    type: 'Object',
                    require: true,
                    description: 'Instances to update, example: {create: [instances], update: [instances], delete: [ids]}',
                    http: {source: 'body'}
                }
            ],
            http: {
                path: `/${methodName}`,
                verb: 'POST'
            }
        });
        this[methodName] = async actions => {
            let transaction = await this.beginTransaction({});
            let options = {transaction: transaction};

            try {
                if (actions.delete && actions.delete.length) {
                    await this.destroyAll({id: {inq: actions.delete}}, options);
                }
                if (actions.update) {
                    try {
                        let promises = [];
                        actions.update.forEach(toUpdate => {
                            promises.push(this.upsert(toUpdate, options));
                        });
                        await Promise.all(promises);
                    } catch (error) {
                        throw error;
                    }
                }
                if (actions.create && actions.create.length) {
                    try {
                        await this.create(actions.create, options);
                    } catch (error) {
                        throw error[error.length - 1];
                    }
                }
                await transaction.commit();
            } catch (error) {
                await transaction.rollback();
                throw error;
            }
        };
    };

    /**
     * Executes an SQL query
     * @param {String} query - SQL query
     * @param {Object} params - Query data params
     * @param {Object} options - Query options (Ex: {transaction})
     * @param {Object} cb - Callback
     * @return {Object} Connector promise
     */
    Self.rawSql = function(query, params, options = {}, cb) {
        var connector = this.dataSource.connector;
        return new Promise(function(resolve, reject) {
            connector.execute(query, params, options, function(error, response) {
                if (cb)
                    cb(error, response);
                if (error)
                    reject(error);
                else
                    resolve(response);
            });
        });
    };

    /**
     * Executes an SQL query from an Stmt
     * @param {ParameterizedSql} stmt - Stmt object
     * @param {Object} options - Query options (Ex: {transaction})
     * @return {Object} Connector promise
     */
    Self.rawStmt = function(stmt, options = {}) {
        return this.rawSql(stmt.sql, stmt.params, options);
    };

    Self.escapeName = function(name) {
        return this.dataSource.connector.escapeName(name);
    };

    /**
     * Constructs SQL where clause from Loopback filter
     * @param {Object} filter - filter
     * @param {String} tableAlias - Query main table alias
     * @return {String} Builded SQL where
     */
    Self.buildWhere = function(filter, tableAlias) {
        let connector = this.dataSource.connector;
        let wrappedConnector = Object.create(connector);
        wrappedConnector.columnEscaped = function(model, property) {
            let sql = tableAlias
                ? connector.escapeName(tableAlias) + '.'
                : '';
            return sql + connector.columnEscaped(model, property);
        };

        return wrappedConnector.makeWhere(this.modelName, filter.where);
    };

    /**
     * Constructs SQL limit clause from Loopback filter
     * @param {Object} filter - filter
     * @return {String} Builded SQL limit
     */
    Self.buildLimit = function(filter) {
        let sql = new ParameterizedSQL('');
        this.dataSource.connector.applyPagination(this.modelName, sql, filter);
        return sql;
    };

    /**
     * Constructs SQL order clause from Loopback filter
     * @param {Object} filter - filter
     * @return {String} Builded SQL order
     */
    Self.buildOrderBy = function(filter) {
        let order = filter.order;

        if (!order)
            return '';
        if (typeof order === 'string')
            order = [order];

        let clauses = [];

        for (let clause of order) {
            let sqlOrder = '';
            let t = clause.split(/[\s,]+/);
            let names = t[0].split('.');

            if (names.length > 1)
                sqlOrder += this.escapeName(names[0]) + '.';
            sqlOrder += this.escapeName(names[names.length - 1]);

            if (t.length > 1)
                sqlOrder += ' ' + (t[1].toUpperCase() == 'ASC' ? 'ASC' : 'DESC');

            clauses.push(sqlOrder);
        }

        return `ORDER BY ${clauses.join(', ')}`;
    };

    /**
     * Constructs SQL pagination from Loopback filter
     * @param {Object} filter - filter
     * @return {String} Builded SQL pagination
     */
    Self.buildPagination = function(filter) {
        return ParameterizedSQL.join([
            this.buildOrderBy(filter),
            this.buildLimit(filter)
        ]);
    };

    /**
     * Constructs SQL filter including where, order and limit
     * clauses from Loopback filter
     * @param {Object} filter - filter
     * @param {String} tableAlias - Query main table alias
     * @return {String} Builded SQL limit
     */
    Self.buildSuffix = function(filter, tableAlias) {
        return ParameterizedSQL.join([
            this.buildWhere(filter, tableAlias),
            this.buildPagination(filter)
        ]);
    };

    // Action bindings
    require('../methods/vn-model/validateBinded')(Self);
    // Handle MySql errors
    require('../methods/vn-model/rewriteDbError')(Self);
    // Get table set of values
    require('../methods/vn-model/getSetValues')(Self);
};