var mysql = require('mysql');
const loopbackConnector = require('loopback-connector');
const SqlConnector = loopbackConnector.SqlConnector;
const ParameterizedSQL = loopbackConnector.ParameterizedSQL;
var MySQL = require('loopback-connector-mysql').MySQL;
var EnumFactory = require('loopback-connector-mysql').EnumFactory;
var debug = require('debug')('loopback-connector-sql');

exports.initialize = function(dataSource, callback) {
    dataSource.driver = mysql;
    dataSource.connector = new VnMySQL(dataSource.settings);
    dataSource.connector.dataSource = dataSource;

    var modelBuilder = dataSource.modelBuilder;
    var defineType = modelBuilder.defineValueType ?
        modelBuilder.defineValueType.bind(modelBuilder) :
        modelBuilder.constructor.registerType.bind(modelBuilder.constructor);

    defineType(function Point() {});

    dataSource.EnumFactory = EnumFactory;

    if (callback) {
        if (dataSource.settings.lazyConnect) {
            process.nextTick(function() {
                callback();
            });
        } else {
            dataSource.connector.connect(callback);
        }
    }
};

exports.VnMySQL = VnMySQL;

function VnMySQL(settings) {
    SqlConnector.call(this, 'mysql', settings);
}

VnMySQL.prototype = Object.create(MySQL.prototype);
VnMySQL.constructor = VnMySQL;

VnMySQL.prototype.toColumnValue = function(prop, val) {
    if (val == null || !prop || prop.type !== Date)
        return MySQL.prototype.toColumnValue.call(this, prop, val);

    val = new Date(val);

    return val.getFullYear() + '-' +
        fillZeros(val.getMonth() + 1) + '-' +
        fillZeros(val.getDate()) + ' ' +
        fillZeros(val.getHours()) + ':' +
        fillZeros(val.getMinutes()) + ':' +
        fillZeros(val.getSeconds());

    function fillZeros(v) {
        return v < 10 ? '0' + v : v;
    }
};

/**
 * Private make method
 * @param {Object} model Model instance
 * @param {Object} where Where filter
 * @return {ParameterizedSQL} Parametized object
 */
VnMySQL.prototype._makeWhere = function(model, where) {
    let columnValue;
    let sqlExp;

    if (!where) {
        return new ParameterizedSQL('');
    }
    if (typeof where !== 'object' || Array.isArray(where)) {
        debug('Invalid value for where: %j', where);
        return new ParameterizedSQL('');
    }
    var self = this;
    var props = self.getModelDefinition(model).properties;

    var whereStmts = [];
    for (var key in where) {
        var stmt = new ParameterizedSQL('', []);
        // Handle and/or operators
        if (key === 'and' || key === 'or') {
            var branches = [];
            var branchParams = [];
            var clauses = where[key];
            if (Array.isArray(clauses)) {
                for (var i = 0, n = clauses.length; i < n; i++) {
                    var stmtForClause = self._makeWhere(model, clauses[i]);
                    if (stmtForClause.sql) {
                        stmtForClause.sql = '(' + stmtForClause.sql + ')';
                        branchParams = branchParams.concat(stmtForClause.params);
                        branches.push(stmtForClause.sql);
                    }
                }
                stmt.merge({
                    sql: branches.join(' ' + key.toUpperCase() + ' '),
                    params: branchParams
                });
                whereStmts.push(stmt);
                continue;
            }
        // The value is not an array, fall back to regular fields
        }
        var p = props[key];

        // eslint-disable one-var
        var expression = where[key];
        var columnName = self.columnEscaped(model, key);
        // eslint-enable one-var
        if (expression === null || expression === undefined) {
            stmt.merge(columnName + ' IS NULL');
        } else if (expression && expression.constructor === Object) {
            var operator = Object.keys(expression)[0];
            // Get the expression without the operator
            expression = expression[operator];
            if (operator === 'inq' || operator === 'nin' || operator === 'between') {
                columnValue = [];
                if (Array.isArray(expression)) {
                    // Column value is a list
                    for (var j = 0, m = expression.length; j < m; j++) {
                        columnValue.push(this.toColumnValue(p, expression[j]));
                    }
                } else {
                    columnValue.push(this.toColumnValue(p, expression));
                }
                if (operator === 'between') {
                    // BETWEEN v1 AND v2
                    var v1 = columnValue[0] === undefined ? null : columnValue[0];
                    var v2 = columnValue[1] === undefined ? null : columnValue[1];
                    columnValue = [v1, v2];
                } else {
                    // IN (v1,v2,v3) or NOT IN (v1,v2,v3)
                    if (columnValue.length === 0) {
                        if (operator === 'inq') {
                            columnValue = [null];
                        } else {
                        // nin () is true
                            continue;
                        }
                    }
                }
            } else if (operator === 'regexp' && expression instanceof RegExp) {
                // do not coerce RegExp based on property definitions
                columnValue = expression;
            } else {
                columnValue = this.toColumnValue(p, expression);
            }
            sqlExp = self.buildExpression(columnName, operator, columnValue, p);
            stmt.merge(sqlExp);
        } else {
            // The expression is the field value, not a condition
            columnValue = self.toColumnValue(p, expression);
            if (columnValue === null) {
                stmt.merge(columnName + ' IS NULL');
            } else if (columnValue instanceof ParameterizedSQL) {
                stmt.merge(columnName + '=').merge(columnValue);
            } else {
                stmt.merge({
                    sql: columnName + '=?',
                    params: [columnValue]
                });
            }
        }
        whereStmts.push(stmt);
    }
    var params = [];
    var sqls = [];
    for (var k = 0, s = whereStmts.length; k < s; k++) {
        sqls.push(whereStmts[k].sql);
        params = params.concat(whereStmts[k].params);
    }
    var whereStmt = new ParameterizedSQL({
        sql: sqls.join(' AND '),
        params: params
    });
    return whereStmt;
};

/**
 * Build the SQL WHERE clause for the where object
 * @param {string} model Model name
 * @param {object} where An object for the where conditions
 * @return {ParameterizedSQL} The SQL WHERE clause
 */
VnMySQL.prototype.makeWhere = function(model, where) {
    var whereClause = this._makeWhere(model, where);
    if (whereClause.sql) {
        whereClause.sql = 'WHERE ' + whereClause.sql;
    }
    return whereClause;
};