integrate parser; use parser instead of regex query

lib/text_to_sql_query.rb

@@ -0,0 +1,93 @@
+require './parser'
+
+class TextToSqlQuery
+  def initialize(text, fields, default_field, fields_mappings = {})
+    @text = text.to_s.strip
+    @fields = fields.map(&:to_sym)
+    @default_field = default_field.to_sym
+    @fields_mappings = fields_mappings.merge(@fields.reduce({}) do |mappings, field|
+      _table_name, field_name = field.to_s.split('.')
+      mappings[field_name.to_sym] = field
+      mappings
+    end)
+    fields_mappings.each do |field, value|
+      @fields_mappings[field] = value if @fields_mappings[field]
+    end
+  end
+
+  def where_clause
+    @parser = Query.new
+    @parsed_tree = @parser.parse(@text)
+    generate_sql @parsed_tree
+  end
+
+  private
+
+  def generate_sql(tree)
+    first_key = tree.keys.first
+    node_value = tree[first_key]
+    case first_key
+    when :DEFAULT_COLUMN
+      escaped_node_value = handle_special_chars node_value
+      ["#{@default_field.to_s} ILIKE ?", "%#{escaped_node_value}%"]
+    when :OPERATOR_OR
+      generate_expression_for_logical_operator(:OR, node_value)
+    when :OPERATOR_AND
+      generate_expression_for_logical_operator(:AND, node_value)
+    when :OPERATOR_NOT
+      not_array = generate_sql node_value
+
+      if not_array.length < 2
+        raise "There should be more than 1 element for expression following NOT operator"
+      end
+
+      not_expression = not_array.first
+      not_params = not_array[1..]
+
+      ["NOT #{not_expression}"] + not_params
+
+    else
+      # key is column name
+      escaped_node_value = handle_special_chars node_value
+      mapping = @fields_mappings[first_key.to_sym]
+      if mapping.nil?
+        raise "Unknown field '#{first_key.to_s}'"
+      else
+        ["#{mapping.to_s} ILIKE ?", "%#{escaped_node_value}%"]
+      end
+    end
+  end
+
+  def generate_expression_for_logical_operator(operator, operator_array)
+    if operator_array.length != 2
+      raise "There should be two array elements for #{operator.to_s} operator"
+    end
+
+    first_operand = generate_sql operator_array.first
+    second_operand = generate_sql operator_array.last
+
+    if first_operand.length < 2
+      raise 'There should be more than 1 element in first operand array'
+    end
+
+    if second_operand.length < 2
+      raise 'There should be more than 1 element in second operand array'
+    end
+
+    first_operand_expression = first_operand.first
+    first_operand_params = first_operand[1..]
+
+    second_operand_expression = second_operand.first
+    second_operand_params = second_operand[1..]
+
+    ["(#{first_operand_expression} #{operator.to_s} #{second_operand_expression})"] + first_operand_params + second_operand_params
+  end
+
+  def handle_special_chars(text)
+    result = text.gsub(/\"/, '')
+    result.gsub!(/\_/, '\_')
+    result.tr!('\\', '\\')
+    result.gsub!(/%/, '\%')
+    result
+  end
+end