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1class Sequel::Dataset
2
3  # This makes sure the original Sequel methods are aliased only once.
4  # Since the framework this was built for will reload these pages if they change,
5  # it was necessary. The conditional part of code not required for most other uses
6  # but is not harmful either.
7  if !defined?( DATASET_ALIASED )
8    alias_method :orig_insert_sql, :insert_sql
9    alias_method :orig_update_sql, :update_sql
10    alias_method :orig_delete_sql, :delete_sql
11    DATASET_ALIASED = true
12  end
13
14  # Allows insert_sql method to accept a HyperModel or any object that exposes
15  # a #sequel_values method
16
17  def insert_sql( *args )
18    if ( args.size == 1 ) && args[0].respond_to?( :sequel_values )
19      orig_insert_sql( args[0].sequel_values )
20    else
21      orig_insert_sql( *args )
22    end
23  end
24  
25  # UPDATE AND DELETE SQL MONKEY-PATCH
26  
27  # This code protects us from doing something stupid. Since it is so easy to call the 
28  # update or delete method on a dataset, this patch will throw an error if there is no
29  # filter placed on the dataset. In other words, it won't let you easily update all
30  # the records in a table.
31  #
32  # The workaround is to do this (assumes a dataset named 'scribbles'):
33  #
34  # scribbles.unrestrict.update( :rating => 5 )
35  #
36  # The Dataset#full method is a filter that doesn't restrict anything.
37  
38  def update_sql( *args )
39    validate_where_exists
40    orig_update_sql( *args )
41  end
42  
43  def delete_sql( *args )
44    validate_where_exists
45    orig_delete_sql( *args )
46  end
47  
48  def validate_where_exists
49    if !opts[ :where ]
50      raise 'The Dataset#update and Dataset#delete methods require a filter to be in place. ' +
51        'This protects you from accidentally updating or deleting all records in a database by accident. ' +
52        'The workaround is to apply a filter like dataset.unrestrict.delete that includes all records.'
53    end
54  end
55  
56  # This filter doesn't do anything except make it possible for #update_sql and
57  # #delete_sql to execute without error because a where clause is in place.
58  def unrestrict
59    filter( '1 = 1' )
60  end
61  
62  # CUSTOM ATTRIBUTE READERS
63  # These are mostly convenience methods that lets us pull data out of the
64  # dataset without having to delve into #opts
65  
66  # Returns table name as symbol
67  def table
68    opts[:from].first
69  end
70  
71  # Returns hash of models
72  def models
73    opts[:models]
74  end
75  
76  # If there is only a single model, returns it.
77  def model
78    models[nil]
79  end
80  
81  # Returns true if the table for the given dataset exists
82  def table_exists?
83    db.table_exists?( table )
84  end
85  
86  # CREATE AND DROP TABLE
87
88  def create_table
89    model.create_table( db, table )
90  end
91    
92  def drop_table
93    db.drop_table( table ) if table_exists?
94  end
95  
96  def recreate_table
97    drop_table
98    create_table
99  end
100  
101  # METHOD MISSING
102
103  def method_missing( method, *args )
104  
105    # Creates #find_by_name_and_email like methods
106    if method.to_s.starts_with?( 'find_by_' )
107      columns = method.to_s[8..-1].split('_and_')
108      hash = {}
109      columns.each_with_index do |col,i|
110        hash[col.to_sym] = args[i]
111      end
112      self.filter( hash )
113      
114    # Missing methods are delegated to the model. The model must implement
115    # methods like:
116    # 
117    # def self.dataset_method
118    # end
119    # 
120    # where 'method' is the name of the dataset method to implement
121    else
122      dataset_method = ( 'dataset_' + method.to_s ).to_sym
123      if model.respond_to?( dataset_method )
124        model.send( dataset_method, self, *args )
125      else
126        raise "Couldn't find a Sequel::Dataset##{method} method "+
127          "nor a Hyper::Model##{dataset_method} method"
128      end
129    end
130  end
131  
132end