module PgSearch
  module Multisearch
    REBUILD_SQL_TEMPLATE = <<-SQL
INSERT INTO :documents_table (searchable_type, searchable_id, content, created_at, updated_at)
  SELECT :model_name AS searchable_type,
         :model_table.id AS searchable_id,
         (
           :content_expressions
         ) AS content,
         :current_time AS created_at,
         :current_time AS updated_at
  FROM :model_table
SQL

    class << self
      def rebuild(model, clean_up=true)
        model.transaction do
          PgSearch::Document.where(:searchable_type => model.name).delete_all if clean_up
          if model.respond_to?(:rebuild_pg_search_documents)
            model.rebuild_pg_search_documents
          else
            model.connection.execute(rebuild_sql(model))
          end
        end
      end

      def rebuild_sql(model)
        connection = model.connection

        unless model.respond_to?(:pg_search_multisearchable_options)
          raise ModelNotMultisearchable.new(model)
        end

        columns = Array.wrap(
          model.pg_search_multisearchable_options[:against]
        )

        content_expressions = columns.map { |column|
          %Q{coalesce(:model_table.#{column}::text, '')}
        }.join(" || ' ' || ")

        REBUILD_SQL_TEMPLATE.gsub(
          ":content_expressions", content_expressions
        ).gsub(
          ":model_name", connection.quote(model.name)
        ).gsub(
          ":model_table", model.quoted_table_name
        ).gsub(
          ":documents_table", PgSearch::Document.quoted_table_name
        ).gsub(
          ":current_time", connection.quote(connection.quoted_date(Time.now))
        )
      end
    end

    class ModelNotMultisearchable < StandardError
      def initialize(model_class)
        @model_class = model_class
      end

      def message
        "#{@model_class.name} is not multisearchable. See PgSearch::ClassMethods#multisearchable"
      end
    end
  end
end