module DmIsReflective::PostgresAdapter
  include DataMapper

  def storages
    sql = <<-SQL
      SELECT table_name FROM "information_schema"."tables"
      WHERE table_schema = current_schema() AND table_type = 'BASE TABLE'
    SQL

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

  def indices storage
    sql = <<-SQL
      SELECT a.attname, i.relname, ix.indisprimary, ix.indisunique
      FROM   pg_class t, pg_class i, pg_index ix, pg_attribute a
      WHERE  t.oid      = ix.indrelid
        AND  i.oid      = ix.indexrelid
        AND  a.attrelid = t.oid
        AND  a.attnum   = ANY(ix.indkey)
        AND  t.relkind  = 'r'
        AND  t.relname  = ?
    SQL

    select(Ext::String.compress_lines(sql), storage).group_by(&:attname).
      inject({}) do |r, (column, idxs)|
        key = !!idxs.find(&:indisprimary)
        idx_uni, idx_com = idxs.partition(&:indisunique).map{ |i|
          if i.empty?
            nil
          elsif i.size == 1
            i.first.relname.to_sym
          else
            i.map{ |ii| ii.relname.to_sym }
          end
        }

        r[column.to_sym] = reflective_indices_hash(key, idx_uni, idx_com)
        r
      end
  end

  private
  def reflective_query_storage storage
    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

    idxs = indices(storage)

    select(Ext::String.compress_lines(sql), storage).map do |f|
      f.define_singleton_method(:indices){ idxs[f.column_name.to_sym] }
      f
    end
  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
    if field.column_default
      field.column_default.gsub!(/(.*?)::[\w\s]*/, '\1')
    end

    attrs.merge!(field.indices) if field.indices

    attrs[:serial] = true if field.column_default =~ /nextval\('\w+'\)/
    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