module Scenic
  # Methods that are made available in migrations for managing Scenic views.
  module Statements
    # Create a new database view.
    #
    # @param name [String, Symbol] The name of the database view.
    # @param version [Fixnum] The version number of the view, used to find the
    #   definition file in `db/views`. This defaults to `1` if not provided.
    # @param sql_definition [String] The SQL query for the view schema. An error
    #   will be raised if `sql_definition` and `version` are both set,
    #   as they are mutually exclusive.
    # @param materialized [Boolean, Hash] Set to true to create a materialized
    #   view. Set to { no_data: true } to create materialized view without
    #   loading data. Defaults to false.
    # @return The database response from executing the create statement.
    #
    # @example Create from `db/views/searches_v02.sql`
    #   create_view(:searches, version: 2)
    #
    # @example Create from provided SQL string
    #   create_view(:active_users, sql_definition: <<-SQL)
    #     SELECT * FROM users WHERE users.active = 't'
    #   SQL
    #
    def create_view(name, version: nil, sql_definition: nil, materialized: false)
      if version.present? && sql_definition.present?
        raise(
          ArgumentError,
          "sql_definition and version cannot both be set",
        )
      end

      if version.blank? && sql_definition.blank?
        version = 1
      end

      sql_definition ||= definition(name, version)

      if materialized
        Scenic.database.create_materialized_view(
          name,
          sql_definition,
          no_data: no_data(materialized),
        )
      else
        Scenic.database.create_view(name, sql_definition)
      end
    end

    # Drop a database view by name.
    #
    # @param name [String, Symbol] The name of the database view.
    # @param revert_to_version [Fixnum] Used to reverse the `drop_view` command
    #   on `rake db:rollback`. The provided version will be passed as the
    #   `version` argument to {#create_view}.
    # @param materialized [Boolean] Set to true if dropping a meterialized view.
    #   defaults to false.
    # @return The database response from executing the drop statement.
    #
    # @example Drop a view, rolling back to version 3 on rollback
    #   drop_view(:users_who_recently_logged_in, revert_to_version: 3)
    #
    def drop_view(name, revert_to_version: nil, materialized: false)
      if materialized
        Scenic.database.drop_materialized_view(name)
      else
        Scenic.database.drop_view(name)
      end
    end

    # Update a database view to a new version.
    #
    # The existing view is dropped and recreated using the supplied `version`
    # parameter.
    #
    # @param name [String, Symbol] The name of the database view.
    # @param version [Fixnum] The version number of the view.
    # @param sql_definition [String] The SQL query for the view schema. An error
    #   will be raised if `sql_definition` and `version` are both set,
    #   as they are mutually exclusive.
    # @param revert_to_version [Fixnum] The version number to rollback to on
    #   `rake db rollback`
    # @param materialized [Boolean, Hash] True if updating a materialized view.
    #   Set to { no_data: true } to update materialized view without loading
    #   data. Defaults to false.
    # @return The database response from executing the create statement.
    #
    # @example
    #   update_view :engagement_reports, version: 3, revert_to_version: 2
    #
    def update_view(name, version: nil, sql_definition: nil, revert_to_version: nil, materialized: false)
      if version.blank? && sql_definition.blank?
        raise(
          ArgumentError,
          "sql_definition or version must be specified",
        )
      end

      if version.present? && sql_definition.present?
        raise(
          ArgumentError,
          "sql_definition and version cannot both be set",
        )
      end

      sql_definition ||= definition(name, version)

      if materialized
        Scenic.database.update_materialized_view(
          name,
          sql_definition,
          no_data: no_data(materialized),
        )
      else
        Scenic.database.update_view(name, sql_definition)
      end
    end

    # Update a database view to a new version using `CREATE OR REPLACE VIEW`.
    #
    # The existing view is replaced using the supplied `version`
    # parameter.
    #
    # Does not work with materialized views due to lack of database support.
    #
    # @param name [String, Symbol] The name of the database view.
    # @param version [Fixnum] The version number of the view.
    # @param revert_to_version [Fixnum] The version number to rollback to on
    #   `rake db rollback`
    # @return The database response from executing the create statement.
    #
    # @example
    #   replace_view :engagement_reports, version: 3, revert_to_version: 2
    #
    def replace_view(name, version: nil, revert_to_version: nil, materialized: false)
      if version.blank?
        raise ArgumentError, "version is required"
      end

      if materialized
        raise ArgumentError, "Cannot replace materialized views"
      end

      sql_definition = definition(name, version)

      Scenic.database.replace_view(name, sql_definition)
    end

    private

    def definition(name, version)
      Scenic::Definition.new(name, version).to_sql
    end

    def no_data(materialized)
      if materialized.is_a?(Hash)
        materialized.fetch(:no_data, false)
      else
        false
      end
    end
  end
end