module SQL
  module Postgres
    def supports_schema_transactions?
      true
    end

    def table(table_name)
      SQL::Postgres::Table.new(self, table_name)
    end

    def recreate_database
      execute 'DROP SCHEMA IF EXISTS test CASCADE'
      execute 'CREATE SCHEMA test'
      execute 'SET search_path TO test'
    end

    def supports_serial?
      true
    end

    def property_schema_statement(connection, schema)
      if supports_serial? && schema[:serial]
        statement = "#{schema[:quote_column_name]} SERIAL PRIMARY KEY"
      else
        statement = super
        statement << " DEFAULT nextval('#{schema[:sequence_name]}') NOT NULL" if schema.key?(:sequence_name)
        statement
      end
      statement
    end

    def table_options(_opts)
      ''
    end

    def change_column_type_statement(name, column)
      "ALTER TABLE #{quote_name(name)} ALTER COLUMN #{column.to_sql}"
    end

    def rename_column_type_statement(table_name, old_col, new_col)
      "ALTER TABLE #{quote_name(table_name)} RENAME COLUMN #{quote_name(old_col)} TO #{quote_name(new_col)}"
    end

    class Table < SQL::Table
      def initialize(adapter, table_name)
        super()
        @adapter = adapter
        @name = table_name
        @columns = []
        adapter.query_table(table_name).each do |col_struct|
          @columns << SQL::Postgres::Column.new(col_struct)
        end

        query_column_constraints
      end

      def query_column_constraints
        @adapter.select(
          "SELECT * FROM information_schema.table_constraints WHERE table_name='#{@name}' AND table_schema=current_schema()"
        ).each do |table_constraint|
          @adapter.select(
            "SELECT * FROM information_schema.constraint_column_usage WHERE constraint_name='#{table_constraint.constraint_name}' " \
            'AND table_schema=current_schema()'
          ).each do |constrained_column|
            @columns.each do |column|
              next unless column.name == constrained_column.column_name

              case table_constraint.constraint_type
              when 'UNIQUE'       then column.unique = true
              when 'PRIMARY KEY'  then column.primary_key = true
              end
            end
          end
        end
      end
    end

    class Column < SQL::Column
      def initialize(col_struct)
        super()
        @name = col_struct.column_name
        @type = col_struct.data_type
        @default_value = col_struct.column_default

        @not_null = col_struct.is_nullable != 'YES'
      end
    end
  end
end