module DmIsReflective::PostgresAdapter
  include DataMapper

  def storages
    sql = <<-SQL
      SELECT table_name FROM "information_schema"."tables"
      WHERE table_schema = current_schema()
    SQL

    select(Ext::String.compress_lines(sql))
  end

  private
  def reflective_query_storage storage
    sql = <<-SQL
      SELECT column_name FROM "information_schema"."key_column_usage"
      WHERE table_schema = current_schema() AND table_name = ?
    SQL

    keys = select(Ext::String.compress_lines(sql), storage).to_set

    sql = <<-SQL
      SELECT column_name, column_default, is_nullable,
             character_maximum_length, udt_name
      FROM "information_schema"."columns"
      WHERE table_schema = current_schema() AND table_name = ?
    SQL

    select(Ext::String.compress_lines(sql), storage).map{ |struct|
      struct.instance_eval <<-RUBY
        def key?
          #{keys.member?(struct.column_name)}
        end
      RUBY
      struct
    }
  end

  def reflective_field_name field
    field.column_name
  end

  def reflective_primitive field
    field.udt_name
  end

  def reflective_attributes field, attrs = {}
    # strip data type
    field.column_default.gsub!(/(.*?)::[\w\s]*/, '\1') if
      field.column_default

    attrs[:serial] = true if field.column_default =~ /nextval\('\w+'\)/
    attrs[:key] = true if field.key?
    attrs[:allow_nil] = field.is_nullable == 'YES'
    # strip string quotation
    attrs[:default] = field.column_default.gsub(/^'(.*?)'$/, '\1') if
      field.column_default && !attrs[:serial]

    if field.character_maximum_length
      attrs[:length] = field.character_maximum_length
    elsif field.udt_name.upcase == 'TEXT'
      attrs[:length] = Property::Text.length
    end

    attrs
  end

  def reflective_lookup_primitive primitive
    case primitive.upcase
    when /^INT\d+$/         ; Integer
    when /^FLOAT\d+$/       ; Float
    when 'VARCHAR', 'BPCHAR'; String
    when 'TIMESTAMP', 'DATE'; DateTime
    when 'TEXT'             ; Property::Text
    when 'BOOL'             ; Property::Boolean
    when 'NUMERIC'          ; Property::Decimal
    end || super(primitive)
  end
end