/**
 * Module dependencies
 */
var mysql = require('mysql');

var jdb = require('loopback-datasource-juggler');
var EnumFactory = require('./enumFactory').EnumFactory;

exports.initialize = function initializeDataSource(dataSource, callback) {
    if (!mysql) return;

    var s = dataSource.settings;
    
    if (s.collation) {
        s.charset = s.collation.substr(0,s.collation.indexOf('_')); // Charset should be first 'chunk' of collation.
    } else {
        s.collation = 'utf8_general_ci';
        s.charset = 'utf8';
    }
    
    s.supportBigNumbers = (s.supportBigNumbers || false);
    s.timezone = (s.timezone || 'local');
    
    dataSource.client = mysql.createConnection({
        host: s.host || 'localhost',
        port: s.port || 3306,
        user: s.username,
        password: s.password,
        timezone: s.timezone,
        debug: s.debug,
        socketPath: s.socketPath,
        charset: s.collation.toUpperCase(), // Correct by docs despite seeming odd.
        supportBigNumbers: s.supportBigNumbers
    });

    dataSource.client.on('error', function (err) {
        dataSource.emit('error', err);
    });

    dataSource.connector = new MySQL(dataSource.client);
    dataSource.connector.dataSource = dataSource;
    
    dataSource.client.query('USE `' + s.database + '`', function (err) {
        if (err) {
            if (err.message.match(/(^|: )unknown database/i)) {
                var dbName = s.database;
                var charset = s.charset;
                var collation = s.collation;
                var q = 'CREATE DATABASE ' + dbName + ' CHARACTER SET ' + charset + ' COLLATE ' + collation;
                dataSource.client.query(q, function (error) {
                    if (!error) {
                        dataSource.client.query('USE ' + s.database, callback);
                    } else {
                        throw error;
                    }
                });
            } else throw err;
        } else callback();
    });

    // MySQL specific column types
    dataSource.constructor.registerType(function Point() {});

    dataSource.EnumFactory = EnumFactory; // factory for Enums. Note that currently Enums can not be registered.
    
    
};

exports.MySQL = MySQL;

/**
 * MySQL connector
 */
function MySQL(client) {
    this.name = 'mysql';
    this._models = {};
    this.client = client;
}

require('util').inherits(MySQL, jdb.BaseSQL);

MySQL.prototype.query = function (sql, callback) {
    if (!this.dataSource.connected) {
        return this.dataSource.on('connected', function () {
            this.query(sql, callback);
        }.bind(this));
    }
    var client = this.client;
    var time = Date.now();
    var log = this.log;
    if (typeof callback !== 'function') throw new Error('callback should be a function');
    this.client.query(sql, function (err, data) {
        if (err && err.message.match(/(^|: )unknown database/i)) {
            var dbName = err.message.match(/(^|: )unknown database '(.*?)'/i)[1];
            client.query('CREATE DATABASE ' + dbName, function (error) {
                if (!error) {
                    client.query(sql, callback);
                } else {
                    callback(err);
                }
            });
            return;
        }
        if (log) log(sql, time);
        callback(err, data);
    });
};

/**
 * Must invoke callback(err, id)
 */
MySQL.prototype.create = function (model, data, callback) {
    var fields = this.toFields(model, data);
    var sql = 'INSERT INTO ' + this.tableEscaped(model);
    if (fields) {
        sql += ' SET ' + fields;
    } else {
        sql += ' VALUES ()';
    }
    this.query(sql, function (err, info) {
        callback(err, info && info.insertId);
    });
};

MySQL.prototype.updateOrCreate = function (model, data, callback) {
    var mysql = this;
    var fieldsNames = [];
    var fieldValues = [];
    var combined = [];
    var props = this._models[model].properties;
    Object.keys(data).forEach(function (key) {
        if (props[key] || mysql.id(model, key)) {
            var k = '`' + key + '`';
            var v;
            if (!mysql.id(model, key)) {
                v = mysql.toDatabase(props[key], data[key]);
            } else {
                v = data[key];
            }
            fieldsNames.push(k);
            fieldValues.push(v);
            if (!mysql.id(model, key)) combined.push(k + ' = ' + v);
        }
    });

    var sql = 'INSERT INTO ' + this.tableEscaped(model);
    sql += ' (' + fieldsNames.join(', ') + ')';
    sql += ' VALUES (' + fieldValues.join(', ') + ')';
    sql += ' ON DUPLICATE KEY UPDATE ' + combined.join(', ');

    this.query(sql, function (err, info) {
        if (!err && info && info.insertId) {
            data.id = info.insertId;
        }
        callback(err, data);
    });
};

MySQL.prototype.toFields = function (model, data) {
    var fields = [];
    var props = this._models[model].properties;
    Object.keys(data).forEach(function (key) {
        if (props[key]) {
            var value = this.toDatabase(props[key], data[key]);
            if ('undefined' === typeof value) return;
            fields.push('`' + key.replace(/\./g, '`.`') + '` = ' + value);
        }
    }.bind(this));
    return fields.join(',');
};

function dateToMysql(val) {
    return val.getUTCFullYear() + '-' +
        fillZeros(val.getUTCMonth() + 1) + '-' +
        fillZeros(val.getUTCDate()) + ' ' +
        fillZeros(val.getUTCHours()) + ':' +
        fillZeros(val.getUTCMinutes()) + ':' +
        fillZeros(val.getUTCSeconds());

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

MySQL.prototype.toDatabase = function (prop, val) {
    if (val === null) return 'NULL';
    if (val === undefined) return;
    if (val.constructor.name === 'Object') {
        var operator = Object.keys(val)[0]
        val = val[operator];
        if (operator === 'between') {
            return  this.toDatabase(prop, val[0]) +
                    ' AND ' +
                    this.toDatabase(prop, val[1]);
        } else if (operator == 'inq' || operator == 'nin') {
            if (!(val.propertyIsEnumerable('length')) && typeof val === 'object' && typeof val.length === 'number') { //if value is array
                for (var i = 0; i < val.length; i++) {
                    val[i] = this.client.escape(val[i]);
                }
                return val.join(',');
            } else {
                return val;
            }
        }
    }
    if (!prop) return val;
    if (prop.type.name === 'Number') return Number(val);
    if (prop.type.name === 'Date') {
        if (!val) return 'NULL';
        if (!val.toUTCString) {
            val = new Date(val);
        }
        return '"' + dateToMysql(val) + '"';
    }
    if (prop.type.name == "Boolean") return val ? 1 : 0;
    if (typeof prop.type === 'function') return this.client.escape(prop.type(val));
    return this.client.escape(val.toString());
};

MySQL.prototype.fromDatabase = function (model, data) {
    if (!data) return null;
    var props = this._models[model].properties;
    Object.keys(data).forEach(function (key) {
        var val = data[key];
        if (typeof val === 'undefined' || val === null) {
            return;
        }
        if (props[key]) {
            switch(props[key].type.name) {
                case 'Date':
                val = new Date(val.toString().replace(/GMT.*$/, 'GMT'));
                break;
                case 'Boolean':
                val = Boolean(val);
                break;
            }
        }
        data[key] = val;
    });
    return data;
};

MySQL.prototype.escapeName = function (name) {
    return '`' + name.replace(/\./g, '`.`') + '`';
};

MySQL.prototype.getColumns = function(model, props){
    var cols = this._models[model].properties;
    if(!cols) {
        return '*';
    }
    var self = this;
    var keys = Object.keys(cols);
    if (Array.isArray(props) && props.length > 0) {
        // No empty array, including all the fields
        keys = props;
    } else if ('object' === typeof props && Object.keys(props).length > 0) {
        // { field1: boolean, field2: boolean ... }
        var included = [];
        var excluded = [];
        keys.forEach(function (k) {
            if (props[k]) {
                included.push(k);
            } else if ((k in props) && !props[k]) {
                excluded.push(k);
            }
        });
        if (included.length > 0) {
            keys = included;
        } else if (excluded.length > 0) {
            excluded.forEach(function (e) {
                var index = keys.indexOf(e);
                keys.splice(index, 1);
            });
        }
    }
    var names = keys.map(function(c) {
        return self.columnEscaped(model, c);
    });
    return names.join(', ');
}

MySQL.prototype.all = function all(model, filter, callback) {
    // Order by id if no order is specified
    filter = filter || {};
    if(!filter.order) {
        var idNames = this.idNames(model);
        if(idNames && idNames.length) {
            filter.order = idNames.join(' ');
        }
    }

    var sql = 'SELECT '+ this.getColumns(model, filter.fields) + ' FROM ' + this.tableEscaped(model);
    var self = this;
    var props = this._models[model].properties;

    if (filter) {

        if (filter.where) {
            sql += ' ' + buildWhere(filter.where);
        }

        if (filter.order) {
            sql += ' ' + buildOrderBy(filter.order);
        }

        if (filter.limit) {
            sql += ' ' + buildLimit(filter.limit, filter.skip || 0);
        }

    }

    this.query(sql, function (err, data) {
        if (err) {
            return callback(err, []);
        }

        var objs = data.map(function (obj) {
            return self.fromDatabase(model, obj);
        });
        if (filter && filter.include) {
            this._models[model].model.include(objs, filter.include, callback);
        } else {
            callback(null, objs);
        }
    }.bind(this));

    return sql;

    function buildWhere(conds) {
        var cs = [];
        Object.keys(conds).forEach(function (key) {
            var keyEscaped = '`' + key.replace(/\./g, '`.`') + '`'
            var val = self.toDatabase(props[key], conds[key]);
            if (conds[key] === null || conds[key] === undefined) {
                cs.push(keyEscaped + ' IS NULL');
            } else if (conds[key] && conds[key].constructor.name === 'Object') {
                var condType = Object.keys(conds[key])[0];
                var sqlCond = keyEscaped;
                if ((condType == 'inq' || condType == 'nin') && val.length == 0) {
                    cs.push(condType == 'inq' ? 0 : 1);
                    return true;
                }
                switch (condType) {
                    case 'gt':
                        sqlCond += ' > ';
                        break;
                    case 'gte':
                        sqlCond += ' >= ';
                        break;
                    case 'lt':
                        sqlCond += ' < ';
                        break;
                    case 'lte':
                        sqlCond += ' <= ';
                        break;
                    case 'between':
                        sqlCond += ' BETWEEN ';
                        break;
                    case 'inq':
                        sqlCond += ' IN ';
                        break;
                    case 'nin':
                        sqlCond += ' NOT IN ';
                        break;
                    case 'neq':
                        sqlCond += ' != ';
                        break;
                }
                sqlCond += (condType == 'inq' || condType == 'nin') ? '(' + val + ')' : val;
                cs.push(sqlCond);
            } else {
                cs.push(keyEscaped + ' = ' + val);
            }
        });
        if (cs.length === 0) {
          return '';
        }
        return 'WHERE ' + cs.join(' AND ');
    }

    function buildOrderBy(order) {
        if (typeof order === 'string') order = [order];
        return 'ORDER BY ' + order.map(function(o) {
            var t = o.split(/\s+/);
            if (t.length === 1) return '`' + o + '`';
            return '`' + t[0] + '` ' + t[1];
        }).join(', ');
    }

    function buildLimit(limit, offset) {
        return 'LIMIT ' + (offset ? (offset + ', ' + limit) : limit);
    }

};

MySQL.prototype.autoupdate = function (models, cb) {
    var self = this;
    var wait = 0;
    if ((!cb) && ('function' === typeof models)) {
        cb = models;
        models = undefined;
    }
    // First argument is a model name
    if ('string' === typeof models) {
        models = [models];
    }

    models = models || Object.keys(this._models);

    models.forEach(function (model) {
        if (model in self._models) {
            wait++;
            self.query('SHOW FIELDS FROM ' + self.tableEscaped(model), function (err, fields) {
                self.query('SHOW INDEXES FROM ' + self.tableEscaped(model), function (err, indexes) {
                    if (!err && fields.length) {
                        self.alterTable(model, fields, indexes, done);
                    } else {
                        self.createTable(model, done);
                    }
                });
            });
        }
    });

    function done(err) {
        if (err) {
            console.error(err);
        }
        if (--wait === 0 && cb) {
            cb();
        }
    }
};

MySQL.prototype.isActual = function (cb) {
    var ok = false;
    var self = this;
    var wait = 0;
    Object.keys(this._models).forEach(function (model) {
        wait += 1;
        self.query('SHOW FIELDS FROM ' + model, function (err, fields) {
            self.query('SHOW INDEXES FROM ' + model, function (err, indexes) {
                self.alterTable(model, fields, indexes, done, true);
            });
        });
    });

    function done(err, needAlter) {
        if (err) {
            console.log(err);
        }
        ok = ok || needAlter;
        if (--wait === 0 && cb) {
            cb(null, !ok);
        }
    }
};

MySQL.prototype.alterTable = function (model, actualFields, actualIndexes, done, checkOnly) {
    var self = this;
    var m = this._models[model];
    var propNames = Object.keys(m.properties).filter(function (name) {
        return !!m.properties[name];
    });
    var indexNames = m.settings.indexes ? Object.keys(m.settings.indexes).filter(function (name) {
        return !!m.settings.indexes[name];
    }) : [];
    var sql = [];
    var ai = {};

    if (actualIndexes) {
        actualIndexes.forEach(function (i) {
            var name = i.Key_name;
            if (!ai[name]) {
                ai[name] = {
                    info: i,
                    columns: []
                };
            }
            ai[name].columns[i.Seq_in_index - 1] = i.Column_name;
        });
    }
    var aiNames = Object.keys(ai);

    // change/add new fields
    propNames.forEach(function (propName) {
        if (m.properties[propName] && self.id(model, propName)) return;
        var found;
        if (actualFields) {
            actualFields.forEach(function (f) {
                if (f.Field === propName) {
                    found = f;
                }
            });
        }

        if (found) {
            actualize(propName, found);
        } else {
            sql.push('ADD COLUMN `' + propName + '` ' + self.propertySettingsSQL(model, propName));
        }
    });

    // drop columns
    if (actualFields) {
        actualFields.forEach(function (f) {
            var notFound = !~propNames.indexOf(f.Field);
            if (m.properties[f.Field] && self.id(model, f.Field)) return;
            if (notFound || !m.properties[f.Field]) {
                sql.push('DROP COLUMN `' + f.Field + '`');
            }
        });
    }

    // remove indexes
    aiNames.forEach(function (indexName) {
        if (indexName === 'PRIMARY'|| (m.properties[indexName] && self.id(model, indexName))) return;
        if (indexNames.indexOf(indexName) === -1 && !m.properties[indexName] || m.properties[indexName] && !m.properties[indexName].index) {
            sql.push('DROP INDEX `' + indexName + '`');
        } else {
            // first: check single (only type and kind)
            if (m.properties[indexName] && !m.properties[indexName].index) {
                // TODO
                return;
            }
            // second: check multiple indexes
            var orderMatched = true;
            if (indexNames.indexOf(indexName) !== -1) {
                m.settings.indexes[indexName].columns.split(/,\s*/).forEach(function (columnName, i) {
                    if (ai[indexName].columns[i] !== columnName) orderMatched = false;
                });
            }
            if (!orderMatched) {
                sql.push('DROP INDEX `' + indexName + '`');
                delete ai[indexName];
            }
        }
    });

    // add single-column indexes
    propNames.forEach(function (propName) {
        var i = m.properties[propName].index;
        if (!i) {
            return;
        }
        var found = ai[propName] && ai[propName].info;
        if (!found) {
            var type = '';
            var kind = '';
            if (i.type) {
                type = 'USING ' + i.type;
            }
            if (i.kind) {
                // kind = i.kind;
            }
            if (kind && type) {
                sql.push('ADD ' + kind + ' INDEX `' + propName + '` (`' + propName + '`) ' + type);
            } else {
                sql.push('ADD ' + kind + ' INDEX `' + propName + '` ' + type + ' (`' + propName + '`) ');
            }
        }
    });

    // add multi-column indexes
    indexNames.forEach(function (indexName) {
        var i = m.settings.indexes[indexName];
        var found = ai[indexName] && ai[indexName].info;
        if (!found) {
            var type = '';
            var kind = '';
            if (i.type) {
                type = 'USING ' + i.type;
            }
            if (i.kind) {
                kind = i.kind;
            }
            if (kind && type) {
                sql.push('ADD ' + kind + ' INDEX `' + indexName + '` (' + i.columns + ') ' + type);
            } else {
                sql.push('ADD ' + kind + ' INDEX ' + type + ' `' + indexName + '` (' + i.columns + ')');
            }
        }
    });

    if (sql.length) {
        var query = 'ALTER TABLE ' + self.tableEscaped(model) + ' ' + sql.join(',\n');
        if (checkOnly) {
            done(null, true, {statements: sql, query: query});
        } else {
            this.query(query, done);
        }
    } else {
        done();
    }

    function actualize(propName, oldSettings) {
        var newSettings = m.properties[propName];
        if (newSettings && changed(newSettings, oldSettings)) {
            sql.push('CHANGE COLUMN `' + propName + '` `' + propName + '` ' + self.propertySettingsSQL(model, propName));
        }
    }

    function changed(newSettings, oldSettings) {
        if (oldSettings.Null === 'YES') { // Used to allow null and does not now.
            if(newSettings.allowNull === false) return true;
            if(newSettings.null === false) return true;
        }
        if (oldSettings.Null === 'NO') { // Did not allow null and now does.
            if(newSettings.allowNull === true) return true;
            if(newSettings.null === true) return true;
            if(newSettings.null === undefined && newSettings.allowNull === undefined) return true;
        }
        
        if (oldSettings.Type.toUpperCase() !== datatype(newSettings).toUpperCase()) return true;
        return false;
    }
};

MySQL.prototype.propertiesSQL = function (model) {
    var self = this;
    var sql = ['`id` INT(11) NOT NULL AUTO_INCREMENT PRIMARY KEY'];
    Object.keys(this._models[model].properties).forEach(function (prop) {
        if (self.id(model, prop)) return;
        sql.push('`' + prop + '` ' + self.propertySettingsSQL(model, prop));
    });
    // Declared in model index property indexes.
    Object.keys(this._models[model].properties).forEach(function (prop) {
        var i = self._models[model].properties[prop].index;
        if (i) {
            sql.push(self.singleIndexSettingsSQL(model, prop));
        }
    });
    // Settings might not have an indexes property.
    var dxs = this._models[model].settings.indexes;
    if(dxs){
        Object.keys(this._models[model].settings.indexes).forEach(function(prop){
            sql.push(self.indexSettingsSQL(model, prop));
        });
    }
    return sql.join(',\n  ');
};

MySQL.prototype.singleIndexSettingsSQL = function (model, prop) {
    // Recycled from alterTable single indexes above, more or less.
    var i = this._models[model].properties[prop].index;
    var type = '';
    var kind = '';
    if (i.type) {
        type = 'USING ' + i.type;
    }
    if (i.kind) {
        kind = i.kind;
    }
    if (kind && type) {
        return (kind + ' INDEX `' + prop + '` (`' + prop + '`) ' + type);
    } else {
        return (kind + ' INDEX `' + prop + '` ' + type + ' (`' + prop + '`) ');
    }
};

MySQL.prototype.indexSettingsSQL = function (model, prop) {
    // Recycled from alterTable multi-column indexes above, more or less.
    var i = this._models[model].settings.indexes[prop];
    var type = '';
    var kind = '';
    if (i.type) {
        type = 'USING ' + i.type;
    }
    if (i.kind) {
        kind = i.kind;
    }
    if (kind && type) {
        return (kind + ' INDEX `' + prop + '` (' + i.columns + ') ' + type);
    } else {
        return (kind + ' INDEX ' + type + ' `' + prop + '` (' + i.columns + ')');
    }
};

MySQL.prototype.propertySettingsSQL = function (model, prop) {
    var p = this._models[model].properties[prop];
    var line =  datatype(p) + ' ' +
    (p.allowNull === false || p['null'] === false ? 'NOT NULL' : 'NULL');
    return line;
};

function datatype(p) {
    var dt = '';
    switch (p.type.name) {
        default:
        case 'String':
        case 'JSON':
            dt = columnType(p, 'VARCHAR');
            dt = stringOptionsByType(p, dt);
        break;
        case 'Text':
            dt = columnType(p, 'TEXT');
            dt = stringOptionsByType(p, dt);
        break;
        case 'Number':
            dt = columnType(p, 'INT');
            dt = numericOptionsByType(p, dt);
        break;
        case 'Date':
            dt = columnType(p, 'DATETIME'); // Currently doesn't need options.
        break;
        case 'Boolean':
            dt = 'TINYINT(1)';
        break;
        case 'Point':
            dt = 'POINT';
        break;
        case 'Enum':
            dt = 'ENUM(' + p.type._string + ')';
            dt = stringOptions(p, dt); // Enum columns can have charset/collation.
        break;
    }
    return dt;
}

function columnType(p, defaultType) {
    var dt = defaultType;
    if(p.dataType){
        dt = String(p.dataType);
    }
    return dt;
}

function stringOptionsByType(p, dt) {
    switch (dt.toLowerCase()) {
        default:
        case 'varchar':
        case 'char':
            dt += '(' + (p.limit || 255) + ')';
        break;
        
        case 'text':
        case 'tinytext':
        case 'mediumtext':
        case 'longtext':
        
        break;
    }
    dt = stringOptions(p, dt);
    return dt;
}

function stringOptions(p, dt){
    if(p.charset){
        dt += " CHARACTER SET " + p.charset;
    }
    if(p.collation){
        dt += " COLLATE " + p.collation;
    }
    return dt;
}

function numericOptionsByType(p, dt) {
    switch (dt.toLowerCase()) {
        default:
        case 'tinyint':
        case 'smallint':
        case 'mediumint':
        case 'int':
        case 'integer':
        case 'bigint':
            dt = integerOptions(p, dt);
        break;
        
        case 'decimal':
        case 'numeric':
            dt = fixedPointOptions(p, dt);
        break;
        
        case 'float':
        case 'double':
            dt = floatingPointOptions(p, dt);
        break;
    }
    dt = unsigned(p, dt);
    return dt;
}

function floatingPointOptions(p, dt) {
    var precision = 16;
    var scale = 8;
    if(p.precision){
        precision = Number(p.precision);
    }
    if(p.scale){
        scale = Number(p.scale);
    }
    if (p.precision && p.scale) {
        dt += '(' + precision + ',' + scale + ')';
    } else if(p.precision){
        dt += '(' + precision + ')';
    } 
    return dt;
}

/*  @TODO: Change fixed point to use an arbitrary precision arithmetic library.     */
/*  Currently fixed point will lose precision because it's turned to non-fixed in   */
/*  JS. Also, defaulting column to (9,2) and not allowing non-specified 'DECIMAL'   */
/*  declaration which would default to DECIMAL(10,0). Instead defaulting to (9,2).  */
function fixedPointOptions(p, dt) {
    var precision = 9;
    var scale = 2;
    if(p.precision){
        precision = Number(p.precision);
    }
    if(p.scale){
        scale = Number(p.scale);
    }
    dt += '(' + precision + ',' + scale + ')';
    return dt;
}

function integerOptions(p, dt) {
    var tmp = 0;
    if (p.display || p.limit) {
        tmp = Number(p.display || p.limit);
    }
    if(tmp > 0){
        dt += '(' + tmp + ')';
    } else if(p.unsigned){
        switch (dt.toLowerCase()) {
            default:
            case 'int':
                dt += '(10)';
            break;
            case 'mediumint':
                dt += '(8)';
            break;
            case 'smallint':
                dt += '(5)';
            break;
            case 'tinyint':
                dt += '(3)';
            break;
            case 'bigint':
                dt += '(20)';
            break;
        }
    } else {
        switch (dt.toLowerCase()) {
            default:
            case 'int':
                dt += '(11)';
            break;
            case 'mediumint':
                dt += '(9)';
            break;
            case 'smallint':
                dt += '(6)';
            break;
            case 'tinyint':
                dt += '(4)';
            break;
            case 'bigint':
                dt += '(20)';
            break;
        }
    }
    return dt;
}

function unsigned(p, dt){
    if (p.unsigned) {
        dt += ' UNSIGNED';
    }
    return dt;
}

require('./discovery')(MySQL);