NAME
    Validate::Tiny - Minimalistic data validation

VERSION
    Version 0.31

SYNOPSIS
    Filter and validate user input from forms, etc.

        use Validate::Tiny ':all';

        my $rules = {

            # List of fields to look for
            fields => [qw/name email pass pass2 gender/],

            # Filters to run on all fields
            filters => [

                # Remove spaces from all
                qr/.+/ => filter(qw/trim strip/),

                # Lowercase email
                email => filter('lc'),

                # Remove non-alphanumeric symbols from
                # both passwords
                qr/pass?/ => sub {
                    $_[0] =~ s/\W/./g;
                    $_[0];
                },
            ],

            # Checks to perform on all fields
            checks => [

                # All of these are required
                [qw/name email pass pass2/] => is_required(),

                # pass2 must be equal to pass
                pass2 => is_equal('pass'),

                # custom sub validates an email address
                email => sub {
                    my ( $value, $params ) = @_;
                    Email::Valid->address($value) ? undef : 'Invalid email';
                },

                # custom sub to validate gender
                gender => sub {
                    my ( $value, $params ) = @_;
                    return $value eq 'M'
                      || $value eq 'F' ? undef : 'Invalid gender';
                }

            ]
        };

        # Validate the input agains the rules
        my $result = validate( $input, $rules );

        if ( $result->{success} ) {
            my $values_hash = $result->{data};
            ...
        }
        else {
            my $errors_hash = $result->{error};
            ...
        }

    Or if you prefer an OOP approach:

        use Validate::Tiny;

        my $result = Validate::Tiny->new( $input, $rules );
        if ( $result->success ) {
            my $values_hash = $result->data;
            my $name        = $result->data('name');
            my $email       = $result->data('email');
            ...;
        }
        else {
            my $errors_hash = $result->error;
            my $name_error  = $result->error('name');
            my $email_error = $result->error('email');
        }

DESCRIPTION
    This module provides a simple, light and minimalistic way of validating
    user input. Except perl core modules and some test modules it has no
    other dependencies, which is why it does not implement any complicated
    checks and filters such as email and credit card matching. The basic
    idea of this module is to provide the validation functionality, and
    leave it up to the user to write their own data filters and checks. If
    you need a complete data validation solution that comes with many ready
    features, I recommend you to take a look at Data::FormValidator. If your
    validation logic is not too complicated or your form is relatively
    short, this module is a decent candidate for your project.

LOGIC
    The basic principle of data/form validation is that any user input must
    be sanitized and checked for errors before used in the logic of the
    program. Validate::Tiny breaks this process in three steps:

    1   Specify the fields you want to work with via "fields". All others
        will be disregarded.

    2   Filter the fields' values using "filters". A filter can be as simple
        as changing to lower case or removing excess white space, or very
        complicated such as parsing and removing HTML tags.

    3   Perform a series of "checks" on the filtered values, to make sure
        they match the requirements. Again, the checks can be very simple as
        in checking if the value was defined, or very complicated as in
        checking if the value is a valid credit card number.

    The validation returns a hash ref which contains "success" => 1|0,
    "data" and "error" hashes. If success is 1, "data" will contain the
    filtered values, otherwise "error" will contain the error messages for
    each field.

EXPORT
    This module does not automatically export anything. You can optionally
    request any of the below subroutines or use ':all' to export all.

PROCEDURAL INTERFACE
  validate
        use Validate::Tiny qw/validate/;

        my $result = validate( \%input, \%rules );

    Validates user input against a set of rules. The input is expected to be
    a reference to a hash.

   %rules
        my %rules = (
            fields  => \@field_names,
            filters => \@filters_array,
            checks  => \@checks_array
        );

    "rules" is a hash containing references to the following three arrays:
    "fields", "filters" and "checks".

   fields
    An array containing the names of the fields that must be filtered,
    checked and returned. All others will be disregarded.

        my @field_names = qw/username email password password2/;

   filters
    An array containing name matches and filter subs. The array must have an
    even number of elements. Each *odd* element is a field name match and
    each *even* element is a reference to a filter subroutine or a chain of
    filter subroutines. A filter subroutine takes one parameter - the value
    to be filtered, and returns the modified value.

        my @filters_array = (
            email => sub { return lc $_[0] },    # Lowercase the email
            password =>
              sub { $_[0] =~ s/\s//g; $_[0] }    # Remove spaces from password
        );

    The field name is matched with the perl smart match operator, so you
    could have a regular expression or a reference to an array to match
    several fields:

        my @filters_array = (
            qr/.+/ => sub { lc $_[0] },    # Lowercase ALL

            [qw/password password2/] => sub {    # Remove spaces from both
                $_[0] =~ s/\s//g;                # password and password2
                $_[0];
            }
        );

    Instead of a single filter subroutine, you can pass an array of
    subroutines to provide a chain of filters:

        my @filters_array = (
            qr/.+/ => [ sub { lc $_[0] }, sub { ucfirst $_[0] } ]
        );

    The above example will first lowercase the value then uppercase its
    first letter.

    Some simple text filters are provided by the "filter()" subroutine.

        use Validate::Tiny qw/validate :util/;

        my @filters_array = (
            name => filter(qw/strip trim lc/)
        );

   checks
    An array ref containing name matches and check subs. The array must have
    an even number of elements. Each *odd* element is a field name match and
    each *even* element is a reference to a check subroutine or a chain of
    check subroutines.

    A check subroutine takes two parameters - the value to be checked and a
    reference to the filtered input hash.

    A check subroutine must return undef if the check passes or a string
    with an error message if the check fails.

    Example:

        # Make sure the password is good
        sub is_good_password {
            my ( $value, $params ) = @_;

            if ( !defined $value ) {
                return undef;
            }

            if ( length($value) < 6 ) {
                return "The password is too short";
            }

            if ( length($value) > 40 ) {
                return "The password is too long";
            }

            if ( $value eq $params->{username} ) {
                return "Your password can not be the same as your username";
            }

            # At this point we're happy with the password
            return undef;
        }

        my $rules = {
            fields => [qw/username password/],
            checks => [
                password => \&is_good_password
            ]
        };

    It may be a bit counter-intuitive for some people to return undef when
    the check passes and a string when it fails. If you have a huge problem
    with this concept, then this module may not be right for you.

    Important! Notice that in the beginning of "is_good_password" we check
    if $value is defined and return undef if it is not. This is because it
    is not the job of "is_good_password" to check if "password" is required.
    Its job is to determine if the password is good. Consider the following
    example:

        my $rules = {
            fields => [qw/username password/],
            checks => [
                password => [ is_required(), \&is_good_password ]
            ]
        };

    and this one too:

        my $rules = {
            fields => [qw/username password/],
            checks => [
                qr/.+/   => is_required(),
                password => \&is_good_password
            ]
        };

    The above examples show how we make sure that "password" is available
    before we check if it is a good password. Of course you can check if
    "password" is defined inside "is_good_password", but it would be
    redundant.

   Chaining
    The above example also shows that chaining check subroutines is
    available in the same fashion as chaining filter subroutines. The
    difference between chaining filters and chaining checks is that a chain
    of filters will always run all filters, and a chain of checks will exit
    after the first failed check and return its error message. This way the
    "$result->{error}" hash always has a single error message per field.

   Using closures
    When writing reusable check subroutines, sometimes you will want to be
    able to pass arguments. Returning closures (anonymous subs) is the
    recommended approach:

        sub is_long_between {
            my ( $min, $max ) = @_;
            return sub {
                my $value = shift;
                return length($value) >= $min && length($value) <= $max
                  ? undef
                  : "Must be between $min and $max symbols";
            };
        }

        my $rules = {
            fields => qw/password/,
            checks => [
                password => is_long_between( 6, 40 )
            ]
        };

   Return value
    "validate" returns a hash ref with three elements:

        my $result = validate(\%input, \%rules);

        # Now $result looks like this
        $result = {
            success => 1,       # or 0 if checks didn't pass
            data    => \%data,
            error   => \%error
        };

    If "success" is 1 all of the filtered input will be in %data, otherwise
    the error messages will be stored in %error. If "success" is 0, %data
    may or may not contain values, but its use is not recommended.

  filter
        filter( $name1, $name2, ... );

    Provides a shortcut to some basic text filters. In reality, it returns a
    list of anonymous subs, so the following:

        my $rules = {
            filters => [
                email => filter('lc', 'ucfirst')
            ]
        };

    is equivalent to this:

        my $rules = {
            filters => [
                email => [ sub{ lc $_[0] }, sub{ ucfirst $_[0] } ]
            ]
        };

    It provides a shortcut for the following filters:

   trim
    Removes leading and trailing white space.

   strip
    Shrinks two or more white spaces to one.

   lc
    Lower case.

   uc
    Upper case.

   ucfirst
    Upper case first letter

  is_required
        is_required( $opt_error_msg );

    "is_required" provides a shortcut to an anonymous subroutine that checks
    if the matched field is defined and it is not an empty string.
    Optionally, you can provide a custom error message to be returned.

  is_equal
        is_equal( $other_field_name, $opt_error_msg )

    "is_equal" checks if the value of the matched field is the same as the
    value of another field within the input hash. Example:

        my $rules = {
            checks => [
                password2 => is_equal("password", "Passwords don't match")
            ]
        };

  is_long_between
        my $rules = {
            checks => [
                username => is_long_between( 6, 25, 'Bad username' )
            ]
        };

    Checks if the length of the value is >= $min and <= $max. Optionally you
    can provide a custom error message. The default is *Invalid value*.

  is_long_at_least
        my $rules = {
            checks => [
                zip_code => is_long_at_least( 5, 'Bad zip code' )
            ]
        };

    Checks if the length of the value is >= $length. Optionally you can
    provide a custom error message. The default is *Must be at least %i
    symbols*.

  is_long_at_most
        my $rules = {
            checks => [
                city_name => is_long_at_most( 40, 'City name is too long' )
            ]
        };

    Checks if the length of the value is <= $length. Optionally you can
    provide a custom error message. The default is *Must be at the most %i
    symbols*.

  is_a
        use DateTime::Format::Natural;
        use Try::Tiny;

        my $parser = DateTime::Format::Natural->new;

        my $rules = {
            fields  => ['date'],

            filters => [
                date => sub {
                    try {
                        $parser->parse_datetime( $_[0] );
                    }
                    catch {
                        $_[0]
                    }
                }
            ],

            checks => [
                date => is_a("DateTime", "Ivalid date")
            ]
        };

    Checks if the value is an instance of a class. This can be particularly
    useful, when you need to parse dates or other user input that needs to
    get converted to an object. Since the filters get executed before
    checks, you can use them to instantiate the data, then use "is_a" to
    check if you got a successful object.

  is_like
        my $rules = {
            checks => [
                username => is_like( qr/^[a-z0-9_]{6,20}$/, "Bad username" )
            ]
        };

    Checks if the value matches a regular expression. Optionally you can
    provide a custom error message.

  is_in
        my @cities = qw/Alchevsk Kiev Odessa/;
        my $rules = {
            checks => [
                city => is_in( \@cities, "We only deliver to " . join(',', @cities))
            ]
        };

    Checks if the value matches a set of values. Optionally you can provide
    a custom error message.

OBJECT INTERFACE
  new
    Validates the input against the rules and returns a class instance.

        use Validate::Tiny;

        my $result = Validate::Tiny->new( $input, $rules );
        if ( $result->success ) {

            # Do something with the data
            $result->data->{name};
            $result->data('name');
        }
        else {

            # Do something with the errors
            $result->error->{name};
            $result->error('name');
        }

  success
    Returns a true value if the input passed all the rules.

  data
    Returns a hash reference to all filtered fields. If called with a
    parameter, it will return the value of that field or croak if there is
    no such field defined in the fields array.

        my $all_fields = $result->data;
        my $email      = $result->data('email');

  error
    Returns a hash reference to all error messages. If called with a
    parameter, it will return the error message of that field, or croak if
    there is no such field.

        my $errors = $result->error;
        my $email = $result->error('email');

  error_string
    Returns a string with all errors. Sometimes you may want to display all
    errors together in a string. This function makes that easy.

        my $str = $result->error_string;    # return a string with all errors
        my $str = $result->error_string(
            template  => '%s is %s',
            separator => '<br>',
            names     => {
                f_name => 'First name',
                l_name => 'Last name'
            }
        );

        # An example output for the above would be:
        # "First name is required<br>Last name is required"

    "error_string" takes the following optional parameters:

   template
    A string for the "sprintf" function. It has to have two %s's in it: one
    for the field name and one for the error message.

        my $str = $result->error_string(
            template => '(%s)%s'
        );

        # Result: "(field_name):Error message"

    The default value is "[%s] %s".

   separator
    A character or a string which will be used to join all error messages.
    The default value is ";".

   names
    A HASH reference, which contains field_name => "Field description"
    values, so instead of "field_name" your users will see a meaningful
    description for the field.

        my $str = $result->error_string(
            template => '%s %s',
            names => {
                pass  => 'Chosen password',
                pass2 => 'Password verification'
            }
        );

        # Result: "Password verification does not match."

    If a field description is not defined then the field name will be used.
    The default value for "names" is an empty hash.

   single
    If this is non-zero, the result will contain the error message only for
    one of the fields. This can be useful when you want to display a single
    error at a time. The value of "separator" in this case is disregarded.
    Default value 0.

  to_hash
    Return a result hash, much like using the procedural interface. See the
    output of "validate" for more information.

SEE ALSO
    Data::FormValidator, Validation::Class

AUTHOR
    minimalist, "<minimalist at lavabit.com>"

CREDITS
    "natatime" borrowed from Adam Kennedy's List::MoreUtils.

BUGS
    Bug reports and patches are welcome. Reports which include a failing
    Test::More style test are helpful and will receive priority.

    You may also fork the module on Github:
    https://github.com/naturalist/Validate--Tiny

LICENSE AND COPYRIGHT
    Copyright 2011 minimalist.

    This program is free software; you can redistribute it and/or modify it
    under the terms as perl itself.