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)
  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
    case @first_key
    when :DEFAULT_COLUMN
      ["#{@default_field.to_s} LIKE ?", "%#{tree[@first_key]}%"]
    when :OPERATOR_OR
      generate_expression_for_logical_operator(:OR, tree[@first_key])
    when :OPERATOR_AND
      generate_expression_for_logical_operator(:AND, tree[@first_key])
    when :OPERATOR_NOT
      @not_array = generate_sql tree[@first_key]

      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
      @mapping = @fields_mappings[@first_key.to_sym]
      if @mapping.nil?
        ["#{@default_field.to_s} LIKE ?", "%#{tree[@first_key]}%"]
      else
        ["#{@mapping.to_s} LIKE ?", "%#{tree[@first_key]}%"]
      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
end