var util = require('util');
var extend = util._extend;

/*!
 * Module exports
 */
exports.ValidationError = ValidationError;
exports.Validatable = Validatable;

/**
 * Validation mixins for LoopBack models.
 *
 * This class provides methods that add validation cababilities to models.
 * Each of this validations run when `obj.isValid()` method called.
 *
 * Each configurator can accept *n* params (*n*-1 field names and one config). Config
 * is {Object} depends on specific validation, but all of them have a
 * `message` member property. It can be just string, when only one situation possible,
 * For example: `Post.validatesPresenceOf('title', { message: 'can not be blank' });`
 *
 * In more complicated cases it can be {Hash} of messages (for each case):
 * `User.validatesLengthOf('password', { min: 6, max: 20, message: {min: 'too short', max: 'too long'}});`
 * @class Validatable
 */
function Validatable() {
}

/**
 * Validate presence of one or more specified properties. 
 * Requires a model to include a property to be considered valid; fails when validated field is blank.
 *
 * For example, validate presence of title
 * ```
 * Post.validatesPresenceOf('title');
 * ```
 * Validate that model has first, last, and age properties:
 * ```
 * User.validatesPresenceOf('first', 'last', 'age');
 * ```
 * Example with custom message
 * ```
 * Post.validatesPresenceOf('title', {message: 'Cannot be blank'});
 * ```
 *
 * @param {String} propertyName  One or more property names.
 * @options {Object} errMsg Optional custom error message.  Default is "can't be blank"
 * @property {String} message Error message to use instead of default.
 */
Validatable.validatesPresenceOf = getConfigurator('presence');

/**
 * Validate absence of one or more specified properties. 
 * A model should not include a property to be considered valid; fails when validated field not blank.
 *
 * For example, validate absence of reserved
 * ```
 * Post.validatesAbsenceOf('reserved', { unless: 'special' });
 *
 * @param {String} propertyName  One or more property names.
 * @options {Object} errMsg Optional custom error message.  Default is "can't be set"
 * @property {String} message Error message to use instead of default.
 */
Validatable.validatesAbsenceOf = getConfigurator('absence');

/**
 * Validate length. Require a property length to be within a specified range.
 * Three kinds of validations: min, max, is.
 *
 * Default error messages:
 *
 * - min: too short
 * - max: too long
 * - is:  length is wrong
 *
 * Example: length validations
 * ```
 * User.validatesLengthOf('password', {min: 7});
 * User.validatesLengthOf('email', {max: 100});
 * User.validatesLengthOf('state', {is: 2});
 * User.validatesLengthOf('nick', {min: 3, max: 15});
 * ```
 * Example: length validations with custom error messages
 * ```
 * User.validatesLengthOf('password', {min: 7, message: {min: 'too weak'}});
 * User.validatesLengthOf('state', {is: 2, message: {is: 'is not valid state name'}});
 * ```
 * @param {String} propertyName  Property name to validate.
 * @options {Object} Options 
 * @property {Number} is Value that property must equal to validate.
 * @property {Number} min Value that property must be less than to be valid.
 * @property {Number} max Value that property must be less than to be valid.
 * @property {Object} message Optional Object with string properties for custom error message for each validation: is, min, or max
 */
Validatable.validatesLengthOf = getConfigurator('length');

/**
 * Validate numericality.  Requires a value for property to be either an integer or number.
 *
 * Example
 * ```
 * User.validatesNumericalityOf('age', { message: { number: '...' }});
 * User.validatesNumericalityOf('age', {int: true, message: { int: '...' }});
 * ```
 *
 * @param {String} propertyName  Property name to validate.
 * @options {Object} Options 
 * @property {Boolean} int If true, then property must be an integer to be valid.
 * @property {Object} message Optional object with string properties for 'int' for integer validation.  Default error messages:
 * - number: is not a number
 * - int: is not an integer
 */
Validatable.validatesNumericalityOf = getConfigurator('numericality');

/**
 * Validate inclusion in set.  Require a value for property to be in the specified array.
 *
 * Example:
 * ```
 * User.validatesInclusionOf('gender', {in: ['male', 'female']});
 * User.validatesInclusionOf('role', {
 *     in: ['admin', 'moderator', 'user'], message: 'is not allowed'
 * });
 * ```
 *
 * @param {String} propertyName  Property name to validate.
 * @options {Object} Options 
 * @property {Array} in Array Property must match one of the values in the array to be valid.
 * @property {String} message Optional error message if property is not valid.   Default error message: "is not included in the list".
 */
Validatable.validatesInclusionOf = getConfigurator('inclusion');

/**
 * Validate exclusion.  Require a property value not be in the specified array.
 *
 * Example: `Company.validatesExclusionOf('domain', {in: ['www', 'admin']});`
 *
 * @param {String} propertyName  Property name to validate.
 * @options {Object} Options 
 * @property {Array} in Array Property must match one of the values in the array to be valid.
 * @property {String} message Optional error message if property is not valid.  Default error message: "is reserved".
 */
Validatable.validatesExclusionOf = getConfigurator('exclusion');

/**
 * Validate format. Require a model to include a property that matches the given format.
 *
 * Require a model to include a property that matches the given format.  Example:
 * `User.validatesFormat('name', {with: /\w+/});`
 * 
 * @param {String} propertyName  Property name to validate.
 * @options {Object} Options 
 * @property {RegExp} with Regular expression to validate format.
 * @property {String} message Optional error message if property is not valid.  Default error message: " is invalid".
 */
Validatable.validatesFormatOf = getConfigurator('format');

/**
 * Validate using custom validator
 *
 * Default error message: is invalid
 *
 * Example:
 *
 *     User.validate('name', customValidator, {message: 'Bad name'});
 *     function customValidator(err) {
 *         if (this.name === 'bad') err();
 *     });
 *     var user = new User({name: 'Peter'});
 *     user.isValid(); // true
 *     user.name = 'bad';
 *     user.isValid(); // false
 *
 * @nocode
 * @see helper/validateCustom
 */
Validatable.validate = getConfigurator('custom');

/**
 * Validate using custom async validator
 *
 * Default error message: is invalid
 *
 * Example:
 *```js
 *     User.validateAsync('name', customValidator, {message: 'Bad name'});
 *     function customValidator(err, done) {
 *         process.nextTick(function () {
 *             if (this.name === 'bad') err();
 *             done();
 *         });
 *     });
 *     var user = new User({name: 'Peter'});
 *     user.isValid(); // false (because async validation setup)
 *     user.isValid(function (isValid) {
 *         isValid; // true
 *     })
 *     user.name = 'bad';
 *     user.isValid(); // false
 *     user.isValid(function (isValid) {
 *         isValid; // false
 *     })
 *```
 * @async
 * @nocode
 * @see helper/validateCustom
 */
Validatable.validateAsync = getConfigurator('custom', {async: true});

/**
 * Validate uniqueness. Ensure the value for property is unique in the collection of models.
 * Not available for all connectors. Currently supported with these connectors:
 *  - In Memory
 *  - Oracle
 *  - MongoDB
 *
 * ```
 * // The login must be unique across all User instances.
 * User.validatesUniquenessOf('login');
 *
 * // Assuming SiteUser.belongsTo(Site)
 * // The login must be unique within each Site.
 * SiteUser.validateUniquenessOf('login', { scopedTo: ['siteId'] });
 * ```

 * @param {String} propertyName  Property name to validate.
 * @options {Object} Options 
 * @property {RegExp} with Regular expression to validate format.
 * @property {Array.<String>} scopedTo List of properties defining the scope.
 * @property {String} message Optional error message if property is not valid.  Default error message: "is not unique".
 */
Validatable.validatesUniquenessOf = getConfigurator('uniqueness', {async: true});

// implementation of validators

/*!
 * Presence validator
 */
function validatePresence(attr, conf, err) {
  if (blank(this[attr])) {
    err();
  }
}

/*!
 * Absence validator
 */
function validateAbsence(attr, conf, err) {
  if (!blank(this[attr])) {
    err();
  }
}

/*!
 * Length validator
 */
function validateLength(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 validator
 */
function validateNumericality(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 validator
 */
function validateInclusion(attr, conf, err) {
  if (nullCheck.call(this, attr, conf, err)) return;

  if (!~conf.in.indexOf(this[attr])) {
    err()
  }
}

/*!
 * Exclusion validator
 */
function validateExclusion(attr, conf, err) {
  if (nullCheck.call(this, attr, conf, err)) return;

  if (~conf.in.indexOf(this[attr])) {
    err()
  }
}

/*!
 * Format validator
 */
function validateFormat(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 validator
 */
function validateCustom(attr, conf, err, done) {
  conf.customValidator.call(this, err, done);
}

/*!
 * Uniqueness validator
 */
function validateUniqueness(attr, conf, err, done) {
  if (blank(this[attr])) {
    return process.nextTick(done);
  }
  var cond = {where: {}};
  cond.where[attr] = this[attr];

  if (conf && conf.scopedTo) {
    conf.scopedTo.forEach(function(k) {
      var val = this[k];
      if (val !== undefined)
        cond.where[k] = this[k];
    }, this);
  }

  this.constructor.find(cond, function (error, found) {
    if (error) {
      return err();
    }
    if (found.length > 1) {
      err();
    } else if (found.length === 1 && (!this.id || !found[0].id || found[0].id.toString() != this.id.toString())) {
      err();
    }
    done();
  }.bind(this));
}

var validators = {
  presence: validatePresence,
  absence: validateAbsence,
  length: validateLength,
  numericality: validateNumericality,
  inclusion: validateInclusion,
  exclusion: validateExclusion,
  format: validateFormat,
  custom: validateCustom,
  uniqueness: validateUniqueness
};

function getConfigurator(name, opts) {
  return function () {
    var args = Array.prototype.slice.call(arguments);
    args[1] = args[1] || {};
    configure(this, name, args, opts);
  };
}

/**
 * This method performs validation and triggers validation hooks.
 * Before validation the `obj.errors` collection is cleaned.
 * Each validation can add errors to `obj.errors` collection.
 * If collection is not blank, validation failed.
 *
 * NOTE: This method can be called as synchronous only when no asynchronous validation is
 * configured. It's strongly recommended to run all validations as asyncronous.
 *
 * Example: ExpressJS controller: render user if valid, show flash otherwise
 * ```
 * user.isValid(function (valid) {
 *     if (valid) res.render({user: user});
 *     else res.flash('error', 'User is not valid'), console.log(user.errors), res.redirect('/users');
 * });
 * ```
 * Another example:
 * ```
 * user.isValid(function (valid) {
 *     if (!valid) {
 *           console.log(user.errors);
 *         // => hash of errors
 *         // => {
 *         // => username: [errmessage, errmessage, ...],
 *         // => email: ...
 *         // => }
 *     }
 * });
 * ```
 * @param {Function} callback called with (valid)
 * @returns {Boolean} True if no asynchronouse validation is configured and all properties pass validation.
 */
Validatable.prototype.isValid = function (callback, data) {
  var valid = true, inst = this, wait = 0, async = false;
  var validations = this.constructor.validations;

  // exit with success when no errors
  if (typeof validations !== 'object') {
    cleanErrors(this);
    if (callback) {
      this.trigger('validate', function (validationsDone) {
        validationsDone.call(inst, function () {
          callback(valid);
        });
      }, data, callback);
    }
    return valid;
  }

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

  this.trigger('validate', function (validationsDone) {
    var inst = this,
      asyncFail = false;

    var attrs = Object.keys(validations || {});
    
    attrs.forEach(function(attr) {
      var attrValidations = validations[attr] || [];
      attrValidations.forEach(function(v) {
        if (v.options && v.options.async) {
          async = true;
          wait += 1;
          process.nextTick(function () {
            validationFailed(inst, attr, v, done);
          });
        } else {
          if (validationFailed(inst, attr, v)) {
            valid = false;
          }
        }
      });
    });
    
    if (!async) {
      validationsDone.call(inst, function () {
        if (valid) cleanErrors(inst);
        if (callback) {
          callback(valid);
        }
      });
    }

    function done(fail) {
      asyncFail = asyncFail || fail;
      if (--wait === 0) {
        validationsDone.call(inst, function () {
          if (valid && !asyncFail) cleanErrors(inst);
          if (callback) {
            callback(valid && !asyncFail);
          }
        });
      }
    }

  }, data, callback);

  if (async) {
    // in case of async validation we should return undefined here,
    // because not all validations are finished yet
    return;
  } else {
    return valid;
  }

};

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

function validationFailed(inst, attr, conf, cb) {
  var opts = conf.options || {};
  
  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') 
    || skipValidation(inst, conf, 'unless')) {
    if (cb) cb(true);
    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, code = conf.code || conf.validation;
    if (conf.message) {
      message = conf.message;
    }
    if (!message && defaultMessages[conf.validation]) {
      message = defaultMessages[conf.validation];
    }
    if (!message) {
      message = 'is invalid';
    }
    if (kind) {
      code += '.' + kind;
      if (message[kind]) {
        // get deeper
        message = message[kind];
      } else if (defaultMessages.common[kind]) {
        message = defaultMessages.common[kind];
      } else {
        message = 'is invalid';
      }
    }
    if (kind !== false) inst.errors.add(attr, message, code);
    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 (typeof inst[conf[kind]] === 'function') {
      doValidate = inst[conf[kind]].call(inst);
      if (kind === 'unless') doValidate = !doValidate;
    } else if (inst.__data.hasOwnProperty(conf[kind])) {
      doValidate = inst[conf[kind]];
      if (kind === 'unless') doValidate = !doValidate;
    } else {
      doValidate = kind === 'if';
    }
  }
  return !doValidate;
}

var defaultMessages = {
  presence: 'can\'t be blank',
  absence: 'can\'t be set',
  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;
}

/*!
 * Return true when v is undefined, blank array, null or empty string
 * otherwise returns false
 *
 * @param {Mix} v
 * Returns true if `v` is blank.
 */
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) {
    if (typeof attr === 'string') {
      var validation = extend({}, conf);
      validation.options = opts || {};
      cls.validations[attr] = cls.validations[attr] || [];
      cls.validations[attr].push(validation);
    }
  });
}

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

Errors.prototype.add = function (field, message, code) {
  code = code || 'invalid';
  if (!this[field]) {
    this[field] = [];
    this.codes[field] = [];
  }
  this[field].push(message);
  this.codes[field].push(code);
};

function ErrorCodes(messages) {
  var c = this;
  Object.keys(messages).forEach(function (field) {
    c[field] = messages[field].codes;
  });
}

/**
 * ValidationError is raised when the application attempts to save an invalid model instance.
 * Example:
 * ```
 * {
 *   "name": "ValidationError",
 *   "status": 422,
 *   "message": "The Model instance is not valid. \
 *  See `details` property of the error object for more info.",
 *   "statusCode": 422,
 *   "details": {
 *     "context": "user",
  *    "codes": {
  *      "password": [
 *         "presence"
 *       ],
 *       "email": [
 *         "uniqueness"
 *       ]
 *    },
 *     "messages": {
 *       "password": [
 *        "can't be blank"
 *      ],
 *       "email": [
 *         "Email already exists"
 *       ]
 *     }
 *   },
 * }
 * ```
 * You might run into situations where you need to raise a validation error yourself, for example in a "before" hook or a
 * custom model method.
 * ```
 * MyModel.prototype.preflight = function(changes, callback) {
 *   // Update properties, do not save to db
 *   for (var key in changes) {
 *     model[key] = changes[key];
 *   }
 * 
 *   if (model.isValid()) {
 *     return callback(null, { success: true });
 *   }
 * 
 *   // This line shows how to create a ValidationError
 *   err = new ValidationError(model);
 *   callback(err);
 * }
 * ```
*/
function ValidationError(obj) {
  if (!(this instanceof ValidationError)) return new ValidationError(obj);

  this.name = 'ValidationError';

  var context = obj && obj.constructor && obj.constructor.modelName;
  this.message = util.format(
    'The %s instance is not valid. Details: %s.',
      context ? '`' + context + '`' : 'model',
      formatErrors(obj.errors) || '(unknown)'
  );

  this.statusCode = 422;

  this.details = {
    context: context,
    codes: obj.errors && obj.errors.codes,
    messages: obj.errors
  };

  if (Error.captureStackTrace) {
    // V8 (Chrome, Opera, Node)
    Error.captureStackTrace(this, this.constructor);
  } else if (errorHasStackProperty) {
    // Firefox
    this.stack = (new Error).stack;
  }
  // Safari and PhantomJS initializes `error.stack` on throw
  // Internet Explorer does not support `error.stack`
}

util.inherits(ValidationError, Error);

var errorHasStackProperty = !!(new Error).stack;

function formatErrors(errors) {
  var DELIM = '; ';
  errors = errors || {};
  return Object.getOwnPropertyNames(errors)
    .filter(function(propertyName) {
      return Array.isArray(errors[propertyName]);
    })
    .map(function(propertyName) {
      var messages = errors[propertyName];
      return messages.map(function(msg) {
        return '`' + propertyName + '` ' + msg;
      }).join(DELIM);
    })
    .join(DELIM);
}
