require "fx/adapters/postgres/connection"
require "fx/adapters/postgres/functions"
require "fx/adapters/postgres/triggers"

module Fx
  # F(x) database adapters.
  #
  # F(x) ships with a Postgres adapter only but can be extended with
  # additional adapters. The {Fx::Adapters::Postgres} adapter provides the
  # interface.
  module Adapters
    # Creates an instance of the F(x) Postgres adapter.
    #
    # This is the default adapter for F(x). Configuring it via
    # {Fx.configure} is not required, but the example below shows how one
    # would explicitly set it.
    #
    # @param [#connection] connectable An object that returns the connection
    #   for F(x) to use. Defaults to `ActiveRecord::Base`.
    #
    # @example
    #  Fx.configure do |config|
    #    config.adapter = Fx::Adapters::Postgres.new
    #  end
    class Postgres
      def initialize(connectable = ActiveRecord::Base)
        @connectable = connectable
      end

      # Returns an array of functions in the database.
      #
      # This collection of functions is used by the [Fx::SchemaDumper] to
      # populate the `schema.rb` file.
      #
      # @return [Array<Fx::Function>]
      def functions
        Functions.all(connection)
      end

      # Returns an array of triggers in the database.
      #
      # This collection of triggers is used by the [Fx::SchemaDumper] to
      # populate the `schema.rb` file.
      #
      # @return [Array<Fx::Trigger>]
      def triggers
        Triggers.all(connection)
      end

      # Creates a function in the database.
      #
      # This is typically called in a migration via
      # {Fx::Statements::Function#create_function}.
      #
      # @param sql_definition The SQL schema for the function.
      #
      # @return [void]
      def create_function(sql_definition)
        execute sql_definition
      end

      # Creates a trigger in the database.
      #
      # This is typically called in a migration via
      # {Fx::Statements::Trigger#create_trigger}.
      #
      # @param sql_definition The SQL schema for the trigger.
      #
      # @return [void]
      def create_trigger(sql_definition)
        execute sql_definition
      end

      # Updates a function in the database.
      #
      # This is typically called in a migration via
      # {Fx::Statements::Function#update_function}.
      #
      # @param name The name of the function.
      # @param sql_definition The SQL schema for the function.
      #
      # @return [void]
      def update_function(name, sql_definition)
        drop_function(name)
        create_function(sql_definition)
      end

      # Updates a trigger in the database.
      #
      # The existing trigger is dropped and recreated using the supplied `on`
      # and `version` parameter.
      #
      # This is typically called in a migration via
      # {Fx::Statements::Function#update_trigger}.
      #
      # @param name The name of the trigger.
      # @param on The associated table for the trigger to drop
      # @param sql_definition The SQL schema for the function.
      #
      # @return [void]
      def update_trigger(name, on:, sql_definition:)
        drop_trigger(name, on: on)
        create_trigger(sql_definition)
      end

      # Drops the function from the database
      #
      # This is typically called in a migration via
      # {Fx::Statements::Function#drop_function}.
      #
      # @param name The name of the function to drop
      #
      # @return [void]
      def drop_function(name)
        execute "DROP FUNCTION #{name}();"
      end

      # Drops the trigger from the database
      #
      # This is typically called in a migration via
      # {Fx::Statements::Trigger#drop_trigger}.
      #
      # @param name The name of the trigger to drop
      # @param on The associated table for the trigger to drop
      #
      # @return [void]
      def drop_trigger(name, on:)
        execute "DROP TRIGGER #{name} ON #{on};"
      end

      private

      attr_reader :connectable

      delegate :execute, to: :connection

      def connection
        Connection.new(connectable.connection)
      end
    end
  end
end