From: Dale Martenson <dmartenson@...>
Date: 2005-11-01T02:14:12+09:00
Subject: TumbleDRYer (#53) - my solution

I am not sure I understood the quiz this week. When I first read it, I 
thought it might be that one should analyze the input, build a 
dictionary, determine the repetition automatically and generate the 
output using a simplified form. My first thought was to huffman encode 
the dictionary based on entity frequency. The result was great and all 
:-) ... but not very readable.

After rereading the quiz, I took it to mean how would you apply the DRY 
principle to generating this repetitive output. No programmatic analysis 
required.

Here is a solution, using a 'little language' to represent another. My 
idea was to set the defaults so that they reflected the most common 
representation. That way only a few special cases were required.

Sorry, if I misunderstood the quiz.

--Dale

module SqlDsl
    CT_DEFAULTS = {
        :type => 'MyISAM',
        :auto_increment => true,
        :auto_increment_value => 3,
        :auto_id => true
    }

    def ct( name, attributes={} )
        a = CT_DEFAULTS.merge(attributes)
        "CREATE TABLE `#{name}` (\n" +
        "#{"  `id` int(11) NOT NULL auto_increment,\n" if a[:auto_id]}" +
        (( a[:auto_id] ) ? yield : yield.sub( /,\n$/, "\n" ) ) +
        "#{"  PRIMARY KEY (`id`)\n" if a[:auto_id]}" +
        ") TYPE=#{a[:type]} 
#{"AUTO_INCREMENT=#{a[:auto_increment_value]}" if a[:auto_increment]} ;\n\n"
    end

    VC_DEFAULTS = {
        :size => 50,
        :null_allowed => false,
        :default => true,
        :default_value => ''
    }

    def vc( name, attributes={} )
        a = VC_DEFAULTS.merge(attributes)
        "  `#{name}` varchar(#{a[:size]}) " + not_null(a) + default(a) + 
",\n"
    end

    TEXT_DEFAULTS = {
        :null_allowed => false
    }

    def text( name, attributes={} )
        a = TEXT_DEFAULTS.merge(attributes)
        "  `#{name}` text " + not_null(a) + ",\n"
    end

    ID_DEFAULTS = {
        :size => 11,
        :null_allowed => false,
        :default => true,
        :default_value => '0'
    }

    def id( name, attributes={} )
        a = ID_DEFAULTS.merge(attributes)
        "  `#{name}` int(#{a[:size]}) " + not_null(a) + default(a) + ",\n"
    end

    DATE_DEFAULTS = {
        :null_allowed => false,
        :default => true,
        :default_value => '0000-00-00'
    }

    def date( name, attributes={} )
        a = DATE_DEFAULTS.merge(attributes)
        "  `#{name}` date " + not_null(a) +  default(a) + ",\n"
    end

    def pk( name )
        "  PRIMARY KEY (`#{name}`),\n"
    end
   
    def key( name, value )
        "  KEY `#{name}` (`#{value}`),\n"
    end
   
    def not_null( a )
        "#{" NOT NULL" unless a[:null_allowed]}"
    end
   
    def default( a )
        "#{" default '#{a[:default_value]}'" if a[:default]}"
    end
   
    def auto_increment( a )
        "#{" auto_increment" if a[:auto_increment]}"
    end
end

include SqlDsl

print ct( 'authors' ) {
    vc( 'firstname' ) +
    vc( 'name' ) +
    vc( 'nickname' ) +
    vc( 'contact' ) +
    vc( 'password' ) +
    text( 'description' )
} +
ct( 'categories' ) {
    vc( 'name', :size=>20 ) +
    vc( 'description', :size=>70 )
} +
ct( 'categories_documents', :auto_id=>false, :primary_key=>false, 
:auto_increment=>false ) {
    id( 'category_id' ) +
    id( 'document_id' )
} +
ct( 'documents', :auto_id=>false, :auto_increment_value=>14 ) {
    id( 'id', :auto_increment=>true, :default=>false ) +
    vc( 'title' ) +
    text( 'description' ) +
    id( 'author_id' ) +
    date( 'date' ) +
    vc( 'filename' ) +
    pk( 'id' ) +
    key( 'document', 'title' )
}