package Mojo::Base;

use strict;
use warnings;
use utf8;
use feature ();

# No imports because we get subclassed, a lot!
use Carp ();

# Only Perl 5.14+ requires it on demand
use IO::Handle ();

sub import {
  my $class = shift;
  return unless my $flag = shift;

  # Base
  if ($flag eq '-base') { $flag = $class }

  # Strict
  elsif ($flag eq '-strict') { $flag = undef }

  # Module
  elsif ((my $file = $flag) && !$flag->can('new')) {
    $file =~ s!::|'!/!g;
    require "$file.pm";
  }

  # ISA
  if ($flag) {
    my $caller = caller;
    no strict 'refs';
    push @{"${caller}::ISA"}, $flag;
    *{"${caller}::has"} = sub { attr($caller, @_) };
  }

  # Mojo modules are strict!
  strict->import;
  warnings->import;
  utf8->import;
  feature->import(':5.10');
}

sub new {
  my $class = shift;
  bless @_ ? @_ > 1 ? {@_} : {%{$_[0]}} : {}, ref $class || $class;
}

sub attr {
  my ($class, $attrs, $default) = @_;
  return unless ($class = ref $class || $class) && $attrs;

  Carp::croak 'Default has to be a code reference or constant value'
    if ref $default && ref $default ne 'CODE';

  for my $attr (@{ref $attrs eq 'ARRAY' ? $attrs : [$attrs]}) {
    Carp::croak qq{Attribute "$attr" invalid} unless $attr =~ /^[a-zA-Z_]\w*$/;

    # Header (check arguments)
    my $code = "package $class;\nsub $attr {\n  if (\@_ == 1) {\n";

    # No default value (return value)
    unless (defined $default) { $code .= "    return \$_[0]{'$attr'};" }

    # Default value
    else {

      # Return value
      $code .= "    return \$_[0]{'$attr'} if exists \$_[0]{'$attr'};\n";

      # Return default value
      $code .= "    return \$_[0]{'$attr'} = ";
      $code .= ref $default eq 'CODE' ? '$default->($_[0]);' : '$default;';
    }

    # Store value
    $code .= "\n  }\n  \$_[0]{'$attr'} = \$_[1];\n";

    # Footer (return invocant)
    $code .= "  \$_[0];\n}";

    warn "-- Attribute $attr in $class\n$code\n\n" if $ENV{MOJO_BASE_DEBUG};
    Carp::croak "Mojo::Base error: $@" unless eval "$code;1";
  }
}

sub tap {
  my ($self, $cb) = @_;
  $_->$cb for $self;
  return $self;
}

1;

=encoding utf8

=head1 NAME

Mojo::Base - Minimal base class for Mojo projects

=head1 SYNOPSIS

  package Cat;
  use Mojo::Base -base;

  has name => 'Nyan';
  has [qw(birds mice)] => 2;

  package Tiger;
  use Mojo::Base 'Cat';

  has friend  => sub { Cat->new };
  has stripes => 42;

  package main;
  use Mojo::Base -strict;

  my $mew = Cat->new(name => 'Longcat');
  say $mew->mice;
  say $mew->mice(3)->birds(4)->mice;

  my $rawr = Tiger->new(stripes => 23, mice => 0);
  say $rawr->tap(sub { $_->friend->name('Tacgnol') })->mice;

=head1 DESCRIPTION

L<Mojo::Base> is a simple base class for L<Mojo> projects.

  # Automatically enables "strict", "warnings", "utf8" and Perl 5.10 features
  use Mojo::Base -strict;
  use Mojo::Base -base;
  use Mojo::Base 'SomeBaseClass';

All three forms save a lot of typing.

  # use Mojo::Base -strict;
  use strict;
  use warnings;
  use utf8;
  use feature ':5.10';
  use IO::Handle ();

  # use Mojo::Base -base;
  use strict;
  use warnings;
  use utf8;
  use feature ':5.10';
  use IO::Handle ();
  use Mojo::Base;
  push @ISA, 'Mojo::Base';
  sub has { Mojo::Base::attr(__PACKAGE__, @_) }

  # use Mojo::Base 'SomeBaseClass';
  use strict;
  use warnings;
  use utf8;
  use feature ':5.10';
  use IO::Handle ();
  require SomeBaseClass;
  push @ISA, 'SomeBaseClass';
  use Mojo::Base;
  sub has { Mojo::Base::attr(__PACKAGE__, @_) }

=head1 FUNCTIONS

L<Mojo::Base> exports the following functions if imported with the C<-base>
flag or a base class.

=head2 has

  has 'name';
  has [qw(name1 name2 name3)];
  has name => 'foo';
  has name => sub {...};
  has [qw(name1 name2 name3)] => 'foo';
  has [qw(name1 name2 name3)] => sub {...};

Create attributes for hash-based objects, just like the L</"attr"> method.

=head1 METHODS

L<Mojo::Base> implements the following methods.

=head2 new

  my $object = BaseSubClass->new;
  my $object = BaseSubClass->new(name => 'value');
  my $object = BaseSubClass->new({name => 'value'});

This base class provides a basic constructor for hash-based objects. You can
pass it either a hash or a hash reference with attribute values.

=head2 attr

  $object->attr('name');
  BaseSubClass->attr('name');
  BaseSubClass->attr([qw(name1 name2 name3)]);
  BaseSubClass->attr(name => 'foo');
  BaseSubClass->attr(name => sub {...});
  BaseSubClass->attr([qw(name1 name2 name3)] => 'foo');
  BaseSubClass->attr([qw(name1 name2 name3)] => sub {...});

Create attribute accessor for hash-based objects, an array reference can be
used to create more than one at a time. Pass an optional second argument to
set a default value, it should be a constant or a callback. The callback will
be executed at accessor read time if there's no set value. Accessors can be
chained, that means they return their invocant when they are called with an
argument.

=head2 tap

  $object = $object->tap(sub {...});

K combinator, tap into a method chain to perform operations on an object
within the chain. The object will be the first argument passed to the callback
and is also available as C<$_>.

=head1 DEBUGGING

You can set the MOJO_BASE_DEBUG environment variable to get some advanced
diagnostics information printed to C<STDERR>.

  MOJO_BASE_DEBUG=1

=head1 SEE ALSO

L<Mojolicious>, L<Mojolicious::Guides>, L<http://mojolicio.us>.

=cut