require 'ardb'
require 'ardb/adapter/base'

class Ardb::Adapter

  class Postgresql < Base

    def public_schema_settings
      self.config_settings.merge({
        'database'           => 'postgres',
        'schema_search_path' => 'public'
      })
    end

    def create_db
      ActiveRecord::Base.establish_connection(self.public_schema_settings)
      ActiveRecord::Base.connection.create_database(self.database, self.config_settings)
      ActiveRecord::Base.establish_connection(self.config_settings)
    end

    def drop_db
      begin
        ActiveRecord::Base.establish_connection(self.public_schema_settings)
        ActiveRecord::Base.connection.tap do |conn|
          conn.execute "UPDATE pg_catalog.pg_database"\
                       " SET datallowconn=false WHERE datname='#{self.database}'"
          # this SELECT actually runs a command: it terminates all the connections
          # http://www.postgresql.org/docs/9.2/static/functions-admin.html#FUNCTIONS-ADMIN-SIGNAL-TABLE
          conn.execute "SELECT pg_terminate_backend(pid)"\
                       " FROM pg_stat_activity WHERE datname='#{self.database}'"
          conn.execute "DROP DATABASE IF EXISTS #{self.database}"
        end
      rescue PG::Error => e
        raise e unless e.message =~ /does not exist/
      end
    end

    def drop_tables
      ActiveRecord::Base.connection.tap do |conn|
        tables = conn.execute "SELECT table_name"\
                              " FROM information_schema.tables"\
                              " WHERE table_schema = 'public';"
        tables.each{ |row| conn.execute "DROP TABLE #{row['table_name']} CASCADE" }
      end
    end

    def foreign_key_add_sql
      "ALTER TABLE :from_table"\
      " ADD CONSTRAINT :name"\
      " FOREIGN KEY (:from_column)"\
      " REFERENCES :to_table (:to_column)"
    end

    def foreign_key_drop_sql
      "ALTER TABLE :from_table"\
      " DROP CONSTRAINT :name"
    end

    def load_sql_schema
      require 'scmd'
      cmd_str = "psql -f \"#{self.sql_schema_path}\" #{self.database}"
      cmd = Scmd.new(cmd_str, :env => env_var_hash).tap(&:run)
      raise 'Error loading database' unless cmd.success?
    end

    def dump_sql_schema
      require 'scmd'
      cmd_str = "pg_dump -i -s -x -O -f \"#{self.sql_schema_path}\" #{self.database}"
      cmd = Scmd.new(cmd_str, :env => env_var_hash).tap(&:run)
      raise 'Error dumping database' unless cmd.success?
    end

    private

    def env_var_hash
      @env_var_hash ||= {
        'PGHOST'     => self.config_settings['host'],
        'PGPORT'     => self.config_settings['port'],
        'PGUSER'     => self.config_settings['username'],
        'PGPASSWORD' => self.config_settings['password']
      }
    end

  end

end