exports.Validatable = Validatable;

function Validatable() {
    // validatable class
};

Validatable.validatesPresenceOf = getConfigurator('presence');
Validatable.validatesLengthOf = getConfigurator('length');
Validatable.validatesNumericalityOf = getConfigurator('numericality');
Validatable.validatesInclusionOf = getConfigurator('inclusion');
Validatable.validatesExclusionOf = getConfigurator('exclusion');
Validatable.validatesFormatOf = getConfigurator('format');
Validatable.validate = getConfigurator('custom');
Validatable.validateAsync = getConfigurator('custom', {async: true});
Validatable.validatesUniquenessOf = getConfigurator('uniqueness', {async: true});

// implementation of validators
var validators = {
    presence: function (attr, conf, err) {
        if (blank(this[attr])) {
            err();
        }
    },
    length: function (attr, conf, err) {
        if (nullCheck.call(this, attr, conf, err)) return;

        var len = this[attr].length;
        if (conf.min && len < conf.min) {
            err('min');
        }
        if (conf.max && len > conf.max) {
            err('max');
        }
        if (conf.is && len !== conf.is) {
            err('is');
        }
    },
    numericality: function (attr, conf, err) {
        if (nullCheck.call(this, attr, conf, err)) return;

        if (typeof this[attr] !== 'number') {
            return err('number');
        }
        if (conf.int && this[attr] !== Math.round(this[attr])) {
            return err('int');
        }
    },
    inclusion: function (attr, conf, err) {
        if (nullCheck.call(this, attr, conf, err)) return;

        if (!~conf.in.indexOf(this[attr])) {
            err()
        }
    },
    exclusion: function (attr, conf, err) {
        if (nullCheck.call(this, attr, conf, err)) return;

        if (~conf.in.indexOf(this[attr])) {
            err()
        }
    },
    format: function (attr, conf, err) {
        if (nullCheck.call(this, attr, conf, err)) return;

        if (typeof this[attr] === 'string') {
            if (!this[attr].match(conf['with'])) {
                err();
            }
        } else {
            err();
        }
    },
    custom: function (attr, conf, err, done) {
        conf.customValidator.call(this, err, done);
    },
    uniqueness: function (attr, conf, err, done) {
        var cond = {where: {}};
        cond.where[attr] = this[attr];
        this.constructor.all(cond, function (error, found) {
            if (found.length > 1) {
                err();
            } else if (found.length === 1 && found[0].id !== this.id) {
                err();
            }
            done();
        }.bind(this));
    }
};


function getConfigurator(name, opts) {
    return function () {
        configure(this, name, arguments, opts);
    };
}

Validatable.prototype.isValid = function (callback) {
    var valid = true, inst = this, wait = 0, async = false;

    // exit with success when no errors
    if (!this.constructor._validations) {
        cleanErrors(this);
        if (callback) {
            callback(valid);
        }
        return valid;
    }

    Object.defineProperty(this, 'errors', {
        enumerable: false,
        configurable: true,
        value: new Errors
    });

    this.trigger('validation', function () {
        this.constructor._validations.forEach(function (v) {
            if (v[2] && v[2].async) {
                valid = false;
                async = true;
                wait += 1;
                validationFailed(inst, v, done);
            } else {
                if (validationFailed(inst, v)) {
                    valid = false;
                }
            }
        });
    });

    var asyncFail = false;
    function done(fail) {
        asyncFail = asyncFail || fail;
        if (--wait === 0 && callback) {
            callback(!asyncFail);
        }
    }

    if (valid) cleanErrors(this);
    if (!async && callback) callback(valid);

    return valid;
};

function cleanErrors(inst) {
    Object.defineProperty(inst, 'errors', {
        enumerable: false,
        configurable: true,
        value: false
    });
}

function validationFailed(inst, v, cb) {
    var attr = v[0];
    var conf = v[1];
    var opts = v[2] || {};

    if (typeof attr !== 'string') return false;

    // here we should check skip validation conditions (if, unless)
    // that can be specified in conf
    if (skipValidation(inst, conf, 'if')) return false;
    if (skipValidation(inst, conf, 'unless')) return false;

    var fail = false;
    var validator = validators[conf.validation];
    var validatorArguments = [];
    validatorArguments.push(attr);
    validatorArguments.push(conf);
    validatorArguments.push(function onerror(kind) {
        var message;
        if (conf.message) {
            message = conf.message;
        }
        if (!message && defaultMessages[conf.validation]) {
            message = defaultMessages[conf.validation];
        }
        if (!message) {
            message = 'is invalid';
        }
        if (kind) {
            if (message[kind]) {
                // get deeper
                message = message[kind];
            } else if (defaultMessages.common[kind]) {
                message = defaultMessages.common[kind];
            }
        }
        inst.errors.add(attr, message);
        fail = true;
    });
    if (cb) {
        validatorArguments.push(function () {
            cb(fail);
        });
    }
    validator.apply(inst, validatorArguments);
    return fail;
}

function skipValidation(inst, conf, kind) {
    var doValidate = true;
    if (typeof conf[kind] === 'function') {
        doValidate = conf[kind].call(inst);
        if (kind === 'unless') doValidate = !doValidate;
    } else if (typeof conf[kind] === 'string') {
        if (inst.hasOwnProperty(conf[kind])) {
            doValidate = inst[conf[kind]];
            if (kind === 'unless') doValidate = !doValidate;
        } else if (typeof inst[conf[kind]] === 'function') {
            doValidate = inst[conf[kind]].call(inst);
            if (kind === 'unless') doValidate = !doValidate;
        } else {
            doValidate = kind === 'if';
        }
    }
    return !doValidate;
}

var defaultMessages = {
    presence: 'can\'t be blank',
    length: {
        min: 'too short',
        max: 'too long',
        is: 'length is wrong'
    },
    common: {
        blank: 'is blank',
        'null': 'is null'
    },
    numericality: {
        'int': 'is not an integer',
        'number': 'is not a number'
    },
    inclusion: 'is not included in the list',
    exclusion: 'is reserved',
    uniqueness: 'is not unique'
};

function nullCheck(attr, conf, err) {
    var isNull = this[attr] === null || !(attr in this);
    if (isNull) {
        if (!conf.allowNull) {
            err('null');
        }
        return true;
    } else {
        if (blank(this[attr])) {
            if (!conf.allowBlank) {
                err('blank');
            }
            return true;
        }
    }
    return false;
}

function blank(v) {
    if (typeof v === 'undefined') return true;
    if (v instanceof Array && v.length === 0) return true;
    if (v === null) return true;
    if (typeof v == 'string' && v === '') return true;
    return false;
}

function configure(cls, validation, args, opts) {
    if (!cls._validations) {
        Object.defineProperty(cls, '_validations', {
            writable: true,
            configurable: true,
            enumerable: false,
            value: []
        });
    }
    args = [].slice.call(args);
    var conf;
    if (typeof args[args.length - 1] === 'object') {
        conf = args.pop();
    } else {
        conf = {};
    }
    if (validation === 'custom' && typeof args[args.length - 1] === 'function') {
        conf.customValidator = args.pop();
    }
    conf.validation = validation;
    args.forEach(function (attr) {
        cls._validations.push([attr, conf, opts]);
    });
}

function Errors() {
}

Errors.prototype.add = function (field, message) {
    if (!this[field]) {
        this[field] = [message];
    } else {
        this[field].push(message);
    }
};