FIXME in MiniSQL#tables

lib/minisql.rb

@@ -37,12 +37,20 @@ def drop_index name
 
   # Idea:
   #
-  # select('*').from(:table).where do
-  #   column[:co1] = ...
+  # rows = select['*'].from(:table)
+  #
+  # or
+  #
+  # rows = select['*'].from(:table).where do
+  #   column[:co1] == ...
   #   column[:co2] < ...
-  #   column[:co3] > ...
+  #   column[:co3] >= ...
   # end
-  def select columns
+  #
+  # rows.each ... # no sql are executed until here
+  def select
+    require 'selector'
+    Selector.new self
   end
 
   def insert_into
@@ -56,9 +64,8 @@ def execute command, &block
   end
 
   def tables
-    # FIXME: use self#select
     result = []
-    execute 'select name from sqlite_master' do |row|
+    select[:name].from(:sqlite_master) do |row|
       result << row[0].to_sym
     end
     result

lib/selector.rb

@@ -0,0 +1,119 @@
+class Selector
+
+  def initialize db
+    @db = db
+    @columns = []
+    @from = nil
+    @where = nil
+    @result_set = nil
+  end
+
+  def [] *columns
+    raise 'already defined columns' unless @columns.empty?
+    @columns = columns
+    self
+  end
+
+  def from table, &block
+    raise 'more than one from clause' unless @from.nil?
+    @from = table
+    block_given? ? self.each(&block) : self
+  end
+
+  def where &block
+    raise 'more than one where clause' unless @where.nil?
+    @where = Where.new
+    @where.instance_eval(block)
+    self
+  end
+
+  def dump
+    sql = 'SELECT ' + @columns.join(', ') + " FROM #{@from}"
+    sql += ' ' + @where.dump unless @where.nil?
+    sql += ' ;'
+    sql
+  end
+
+  def each &block
+    @result_set = @db.execute dump if @result_set.nil?
+    @result_set.each &block
+  end
+
+  include Enumerable
+
+  class Where
+
+    def initialize
+      @columns = []
+    end
+
+    def column
+      col = Column.new
+      @columns << col
+      col
+    end
+
+    def dump
+      raise 'empty where clause' if @columns.empty?
+      'WHERE ' + @columns.map{|c| c.dump }.join(' and ')
+    end
+
+    class Column
+
+      def initialize
+        @name = nil
+        @op = nil # can be '=', '<>' '<', '>', '<=', '>='
+        @rval = nil
+        @result_set = nil
+      end
+
+      def [] name
+        raise 'named again' unless @name.nil?
+        @name=name
+        self
+      end
+
+      def == rval
+        cmp '=', rval
+      end
+
+      def != rval
+        cmp '<>', rval
+      end
+
+      def < rval
+        cmp '<', rval
+      end
+
+      def > rval
+        cmp '>', rval
+      end
+
+      def <= rval
+        cmp '<=', rval
+      end
+
+      def >= rval
+        cmp '>=', rval
+      end
+
+      def dump
+        raise 'column has no name' if @name.nil?
+        raise "column #{@name} has no comparison operator" if @op.nil?
+        "#{@name} #{@op} #{@rval}"
+      end
+
+      protected
+
+      def cmp op, rval
+        raise "more than one comparison operator detected, already have #{@op}" unless @op.nil?
+        @op=op
+        @rval=rval
+        self
+      end
+
+    end
+
+  end
+
+end