NAME
    Validator::Declarative - Declarative parameters validation

VERSION
    version 1.20130719.1300

SYNOPSIS
        sub MakeSomethingCool {
            my $serialized_parameters;
            my ( $ace_id, $upm_id, $year, $week, $timestamp_ms ) = Validator::Declarative->validate(
                \@_ => [
                    ace_id         => 'id',
                    upm_id         => 'id',
                    year           => 'year',
                    week           => 'week',
                    timestamp_ms   => [ 'to_msec', 'mdy', 'timestamp' ],
                ],
            );

            # here all parameters are validated
            # .......

        }

DESCRIPTION
    Almost every function checks the input parameters, in one or other
    manner. But often checking of some parameters are not made at all or are
    made not properly.

    In most cases, checking is done by means of one or more conditional
    statements for each parameter individually. This reduces the readability
    of the code and makes it difficult to maintain.

    Often checking is done using "unless" with several conditions, which
    make things even worse.

    Also, lot of conditional statements increases the cyclomatic complexity
    of the function, which makes it impossible to use automated tests to
    check the quality and complexity of the code.

    To solve these problems, we can use declarative description of function
    parameters.

IMPLEMENTATION
    In general, code for declarative validation definition looks like this:

        my ($param1_name, $param2_name) = Validator::Declarative->validate( \@_ => [
            param1_name => [ validation_definition1    ],
            param2_name => [ validation_definitions2   ],
            ....
        ]);

    This is usual key=>value pairs, but it should be written as array, not
    as hash, because order does matter: one pair represents one parameter,
    and order of pairs should be same as order of parameters in @_.

    Each validation definition is an array ref. For simple cases, when
    validation definition is represented by only one rule, we can type less
    and skip surrounding brackets:

        my ($param1_name, $param2_name, $param3_name, $param4_name) = Validator::Declarative->validate( \@_ => [
            param1_name => 'name_of_rule1',
            param2_name => { 'name_of_rule2' => param_for_rule2 },
            param3_name => { 'name_of_rule3' => [ params_for_rule3 ] },
            param4_name => { 'name_of_rule4' => { hash_of_params_for_rule4 } },
            ....
        ]);

    These are shortcuts for:

        my ($param1_name, $param2_name, $param3_name, $param4_name) = Validator::Declarative->validate( \@_ => [
            param1_name => [ 'name_of_rule1'                                         ],
            param2_name => [ { 'name_of_rule2' => param_for_rule2 }                  ],
            param3_name => [ { 'name_of_rule3' => [ params_for_rule3 ] }             ],
            param4_name => [ { 'name_of_rule4' => { hash_of_params_for_rule4 } }     ],
            ....
        ]);

  Grammars
    Grammars for validation rules are:

   simple
        validation_rule ::= 'rule_name'

   parameterized
        validation_rule ::= { 'rule_name' => 'parameter' }
        validation_rule ::= { 'rule_name' => [ 'parameter' ] }
        validation_rule ::= { 'rule_name' => [ 'param1', 'param2', ... ] }
        validation_rule ::= { 'rule_name' => { 'param1' => 'param2', ... } }

   set of rules
        validation_rule ::= validation_rule, validation_rule, ....

  Rules
    Possible kinds of rules are: types (simple and parametrized),
    converters, constraints.

    Simple and parametrized rules works only on defined values, for undef
    all of them return OK (this is needed to support declarations of
    optional parameters).

  Simple types
   any
    always true, aliases: string

   bool
    qr/^(1|true|yes|0|false|no|)$/i, empty string accepted as false,
    arbitrary data is not allowed

   float
    qr/^[+-]?\d+(:?\.\d*)?$/

   int
    qr/^[+-]?\d+$/, aliases: integer

   positive
    >0

   negative
    <0

   id
    int && positive

   email
    result of Email::Valid->address($_)

  Simple types (date-like)
   year
    int && [1970 .. 3000]

   week
    int && [1 .. 53]

   month
    int && [1 .. 12]

   day
    int && [1 .. 31]

   ymd
    like YYYY-MM-DD

   mdy
    like M/D/Y (M and D can be 1 or 2 digits, Y can be 2 or 4 digits)

   time
    like HH:MM:SS, 00:00:00 ... 23:59:59

   hhmm
    like HH:MM, 00:00 ... 23:59

   timestamp
    almost same as float (because of Time::HiRes), but can't have sign

   msec
    timestamp in milliseconds (ts/1000), alias to timestamp

  Parametrized types
   min => value
    minimal accepted value for parameter

   max => value
    maximal accepted value for parameter

   ref => ref_type | [ref_types]
    ref($_) && ref($_) eq (any of @ref_types)

   class => class_name | [class_names]
    blessed($_) && $_->isa(any of @class_names)

   can => method_name | [method_names]
    blessed($_) && $_->can(all of @method_names), aliases: ducktype

   can_any => method_name | [method_names]
    blessed($_) && $_->can(any of @method_names)

   any_of => [values]
    anything from values provided in array ref, aliases: enum

   list_of => validation_rule
    list of "values with specific validation check", recursive

   hash_of => { simple_type => validation_rule }
    hash of "keys with specific simple type" to "values with specific
    validation check", recursive

   hash_of => [ validation_rule => validation_rule ]
    hash of "keys with specific validation check" to "values with specific
    validation check", recursive

   hash => { key => validation_rule, .... }
    hash with specified key names (not required to exists) and "values with
    specific validation check", recursive

   date => format | [formats]
    date/time in specific format

  
    Types ref and class can be used as simple (without parameter), in this
    case they check whether ref($_) and blessed($_) returns true.

    Type date can be used as simple (without parameter), in this case it
    accept all same formats that accepted by any_to_mdy():

        /^20\d\d\d\d\d\d$/
        /^[+-]?\d{1,10}$/
        /^[+-]?\d{11,13}$/
        /^\d\d\d\d-?\d\d-?\d\d(?:t\d\d:?\d\d:?\d\d(?:z|\+00)?)?$/i
        /\d+\D+\d+\D+\d+/

    When parameter to date is not skipped, it should be name of any of
    date-like simple type ('year', 'week', 'mdy' etc) or formatting string
    for DateTime::Format::Strptime::parse_datetime (example:
    '%e/%b/%Y:%H:%M:%S %z', see DateTime::Format::Strptime for details).
    There is no strict requirement for installed DateTime::Format::Strptime
    - if module can't be loaded, checking with the appropriate format will
    always lead to a positive result.

  Converters
   default => value
    substitute $_ with provided value (only when actual parameter is undef)

  Constraints
   required
    result of defined($_), applied by default

   optional
    OK if !defined($_)

   not_empty
    for list_of/hash_of/hash: has at least one element

    for any/string: length($_) > 0

  Order of execution
    Order of rules in validation definition doesn't matters.

    All specified rules will be executed in this order:

   1. Actual parameter is checked to satisfy all constraints.
    It's error to specify both required and optional at the same time.

    If none of required and optional were specified, then required is
    implied.

   2. Actual parameter is passed thru converter (if any).
    It's error to specify more than one converter, except for default. If
    present, default will be executed at first place.

    It's error to specify default if there is no optional constraint.

   3. Parameter (actual or modified by converter, if any) is checked to satisfy any type (simple or parametrized).
    If no one type were specified, then any is implied.

    Order of types in checking is not defined and doesn't matter.

    First successful check will finish entire validation for this parameter.

  Errors and logging
    For any calls all parameters will be checked, and in case of any errors
    exception should be thrown.

    Description of all errors will be included into exception text message.

METHODS
  validate(\@params => \@rules)
  register_type( $name => $code, ...)
  register_converter( $name => $code, ...)
  register_constraint( $name => $code, ...)
EXAMPLES
        # Parameter is optional, and can be any type
        field_name => [ 'any', 'optional' ]

        # Parameter is optional, and it's id in database
        field_name => [ 'id',  'optional' ]

        # Parameter is optional, and it's id in database, with default value
        field_name => [ 'id',  'optional', {default => undef} ]

        # Parameter is optional, and it's id or list of ids in database
        field_name => [ 'id',  'optional', {list_of => 'id'}  ]

        # Parameter is mandatory, and can be any type
        field_name => 'any'     # full form:     [ 'required', 'any' ]

        # Parameter is mandatory, and it's id in database
        field_name => 'id'      # full form:     [ 'required', 'id'  ]

        # Parameter is mandatory, and it's id or list of ids in database
        field_name => [ 'id', {list_of => 'id'} ]
        # full form:  [ 'required', 'id', {list_of => 'id'} ]

        # Parameter is bool and optional
        field_name => [ 'bool', 'optional' ]

        # Parameter is bool and optional, and default is true
        field_name => [ 'bool', 'optional', {default => 1} ]

        # Parameter args is mandatory, and it's hash with keys:
        #   - suspensions: not required, hash with keys:
        #       - cssnote_ref: not required, id
        #       - review_deadline: not required, timestamp
        #       - reasons: required, can be id or list of ids
        #   - resumptions: not required, hash with keys:
        #       - cssnote_ref: not required, id
        #       - reasons: required, can be id, list of ids or hash "id to id"
        # At least one key (suspensions or resumptions) should exists in args.
        args => [ 'not_empty', { hash => {
            suspensions => { hash => {
                cssnote_ref     => [ 'optional', 'id' ],
                review_deadline => [ 'optional', 'timestamp' ],
                reasons         => [ 'id', {list_of => 'id'} ],
            }},
            resumptions => { hash => {
                cssnote_ref     => [ 'optional', 'id' ],
                reasons         => [ 'id', {list_of => 'id'}, {hash_of => {'id' => 'id'}} ],
            }},
        }}]

SEE ALSO
    Inspired by Validator::LIVR -
    <https://github.com/koorchik/Validator-LIVR>

AUTHOR
    Oleg Kostyuk, "<cub at cpan.org>"

TODO
    Implement types list_of, hash_of, hash and date.

    Implement additional converters, like to_ts, to_mdy and several others.

BUGS
    Please report any bugs or feature requests to Github
    <https://github.com/cub-uanic/Validator-Declarative>

AUTHOR
    Oleg Kostyuk <cub@cpan.org>

COPYRIGHT AND LICENSE
    This software is Copyright (c) 2013 by Oleg Kostyuk.

    This is free software, licensed under:

      The (three-clause) BSD License

