var safeRequire = require('../utils').safeRequire;

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

exports.initialize = function initializeSchema(schema, callback) {
    if (!mysql) return;

    var s = schema.settings;
    schema.client = mysql.createClient({
        host: s.host || 'localhost',
        port: s.port || 3306,
        user: s.username,
        password: s.password,
        database: s.database,
        debug: s.debug
    });

    schema.adapter = new MySQL(schema.client);
    // schema.client.query('SET TIME_ZONE = "+04:00"', callback);
    process.nextTick(callback);
};

function MySQL(client) {
    this._models = {};
    this.client = client;
}

MySQL.prototype.define = function (descr) {
    this._models[descr.model.modelName] = descr;
};

MySQL.prototype.defineProperty = function (model, prop, params) {
    this._models[model].properties[prop] = params;
};

MySQL.prototype.query = function (sql, callback) {
    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) {
        log(sql, time);
        callback(err, data);
    });
};

MySQL.prototype.save = function (model, data, callback) {
    var sql = 'UPDATE ' + model + ' SET ' + this.toFields(model, data) +
        ' WHERE id = ' + data.id;

    this.query(sql, function (err) {
        callback(err);
    });
};

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

MySQL.prototype.toFields = function (model, data) {
    var fields = [];
    var props = this._models[model].properties;
    Object.keys(data).forEach(function (key) {
        if (props[key]) {
            fields.push('`' + key.replace(/\./g, '`.`') + '` = ' + this.toDatabase(props[key], data[key]));
        }
    }.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 (prop.type.name === 'Number') return val;
    if (val === null) return 'NULL';
    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;
    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 (props[key]) {
            if (props[key].type.name === 'Date') {
                val = new Date(val.toString().replace(/GMT.*$/, 'GMT'));
            }
        }
        data[key] = val;
    });
    return data;
};

MySQL.prototype.exists = function (model, id, callback) {
    var sql = 'SELECT 1 FROM ' + model + ' WHERE id = ' + id + ' LIMIT 1';
    this.query(sql, function (err, data) {
        if (err) return callback(err);
        callback(null, data.length === 1);
    });
};

MySQL.prototype.find = function find(model, id, callback) {
    var sql = 'SELECT * FROM ' + model + ' WHERE id = ' + id + ' LIMIT 1';
    this.query(sql, function (err, data) {
        if (data && data.length === 1) {
            data[0].id = id;
        } else {
            data = [null];
        }
        callback(err, this.fromDatabase(model, data[0]));
    }.bind(this));
};

MySQL.prototype.destroy = function destroy(model, id, callback) {
    var sql = 'DELETE FROM ' + model + ' WHERE id = ' + id + ' LIMIT 1';
    this.query(sql, function (err) {
        callback(err);
    });
};

MySQL.prototype.all = function all(model, filter, callback) {

    var sql = 'SELECT * FROM ' + 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.offset || 0);
        }

    }

    this.query(sql, function (err, data) {
        if (err) {
            return callback(err, []);
        }
        callback(null, data.map(function (obj) {
            return self.fromDatabase(model, obj);
        }));
    }.bind(this));

    return sql;

    function buildWhere(conds) {
        var cs = [];
        Object.keys(conds).forEach(function (key) {
            var keyEscaped = '`' + key.replace(/\./g, '`.`') + '`'
            if (conds[key] === null) {
                cs.push(keyEscaped + ' IS NULL');
            } else {
                cs.push(keyEscaped + ' = ' + self.toDatabase(props[key], conds[key]));
            }
        });
        return 'WHERE ' + cs.join(' AND ');
    }

    function buildOrderBy(order) {
        if (typeof order === 'string') order = [order];
        return 'ORDER BY ' + order.join(', ');
    }

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

};

MySQL.prototype.destroyAll = function destroyAll(model, callback) {
    this.query('DELETE FROM ' + model, function (err) {
        if (err) {
            return callback(err, []);
        }
        callback(err);
    }.bind(this));
};

MySQL.prototype.count = function count(model, callback, where) {
    var self = this;
    var props = this._models[model].properties;

    this.query('SELECT count(*) as cnt FROM ' + model + buildWhere(where), function (err, res) {
        callback(err, err ? null : res[0].cnt);
    });

    function buildWhere(conds) {
        var cs = [];
        Object.keys(conds || {}).forEach(function (key) {
            var keyEscaped = '`' + key.replace(/\./g, '`.`') + '`'
            if (conds[key] === null) {
                cs.push(keyEscaped + ' IS NULL');
            } else {
                cs.push(keyEscaped + ' = ' + self.toDatabase(props[key], conds[key]));
            }
        });
        return cs.length ? ' WHERE ' + cs.join(' AND ') : '';
    }
};

MySQL.prototype.updateAttributes = function updateAttrs(model, id, data, cb) {
    data.id = id;
    this.save(model, data, cb);
};

MySQL.prototype.disconnect = function disconnect() {
    this.client.end();
};

MySQL.prototype.automigrate = function (cb) {
    var self = this;
    var wait = 0;
    Object.keys(this._models).forEach(function (model) {
        wait += 1;
        self.dropTable(model, function () {
            self.createTable(model, function (err) {
                if (err) console.log(err);
                done();
            });
        });
    });

    function done() {
        if (--wait === 0 && cb) {
            cb();
        }
    }
};

MySQL.prototype.autoupdate = function (cb) {
    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.alterTable(model, fields, done);
        });
    });

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

MySQL.prototype.alterTable = function (model, actualFields, done) {
    var self = this;
    var m = this._models[model];
    var propNames = Object.keys(m.properties);
    var sql = [];

    // change/add new fields
    propNames.forEach(function (propName) {
        var found;
        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
    actualFields.forEach(function (f) {
        var notFound = !~propNames.indexOf(f.Field);
        if (f.Field === 'id') return;
        if (notFound || !m.properties[f.Field]) {
            sql.push('DROP COLUMN `' + f.Field + '`');
        }
    });

    if (sql.length) {
        this.query('ALTER TABLE `' + model + '` ' + sql.join(',\n'), 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' && (newSettings.allowNull === false || newSettings.null === false)) return true;
        if (oldSettings.Null === 'NO' && !(newSettings.allowNull === false || newSettings.null === false)) return true;
        if (oldSettings.Type.toUpperCase() !== datatype(newSettings)) return true;
        return false;
    }
};

MySQL.prototype.dropTable = function (model, cb) {
    this.query('DROP TABLE IF EXISTS ' + model, cb);
};

MySQL.prototype.createTable = function (model, cb) {
    this.query('CREATE TABLE ' + model +
        ' (\n  ' + this.propertiesSQL(model) + '\n)', cb);
};

MySQL.prototype.propertiesSQL = function (model) {
    var self = this;
    var sql = ['`id` INT(11) NOT NULL AUTO_INCREMENT UNIQUE PRIMARY KEY'];
    Object.keys(this._models[model].properties).forEach(function (prop) {
        sql.push('`' + prop + '` ' + self.propertySettingsSQL(model, prop));
    });
    return sql.join(',\n  ');

};

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

function datatype(p) {
    switch (p.type.name) {
        case 'String':
        return 'VARCHAR(' + (p.limit || 255) + ')';
        case 'Text':
        return 'TEXT';
        case 'Number':
        return 'INT(11)';
        case 'Date':
        return 'DATETIME';
        case 'Boolean':
        return 'TINYINT(1)';
    }
}