before_insert.clj

(ns toucan2.tools.before-insert
  (:require
   [clojure.spec.alpha :as s]
   [methodical.core :as m]
   [toucan2.connection :as conn]
   [toucan2.log :as log]
   [toucan2.pipeline :as pipeline]
   [toucan2.util :as u]))

(m/defmulti before-insert
  {:arglists '([model row])}
  u/dispatch-on-first-arg)

(defn- do-before-insert-to-rows [rows model]
  (mapv
   (fn [row]
     (u/try-with-error-context [`before-insert {::model model, ::row row}]
       (log/tracef :compile "Do before-insert for %s %s" model row)
       (let [result (before-insert model row)]
         (log/tracef :compile "[before insert] => %s" row)
         result)))
   rows))

;;; make sure we transform rows whether it's in the parsed args or in the resolved query.

(m/defmethod pipeline/transduce-query :around [#_query-type     :toucan.query-type/insert.*
                                               #_model          ::before-insert
                                               #_resolved-query :default]
  "Execute [[before-insert]] methods and the INSERT query inside a transaction."
  [rf query-type model parsed-args resolved-query]
  (conn/with-transaction [_conn nil {:nested-transaction-rule :ignore}]
    (next-method rf query-type model parsed-args resolved-query)))

(m/defmethod pipeline/build [#_query-type     :toucan.query-type/insert.*
                             #_model          ::before-insert
                             #_resolved-query :toucan.map-backend/honeysql2]
  "Apply [[before-insert]] to `:rows` in the `resolved-query` or `parsed-args` for Honey SQL queries."
  [query-type model parsed-args resolved-query]
  ;; not 100% sure why either `parsed-args` OR `resolved-query` can have `:rows` but I guess we have to update either
  ;; one
  (let [parsed-args    (cond-> parsed-args
                         (:rows parsed-args) (update :rows do-before-insert-to-rows model))
        resolved-query (cond-> resolved-query
                         (:rows resolved-query) (update :rows do-before-insert-to-rows model))]
    (next-method query-type model parsed-args resolved-query)))

;;; Important! before-insert should be done BEFORE any [[toucan2.tools.transformed/transforms]]. Transforms are often
;;; for serializing and deserializing values; we don't want before insert methods to have to work with
;;; already-serialized values.
;;;
;;; By marking `::before-insert` as preferred over `:toucan2.tools.transformed/transformed` it will be done first (see
;;; https://github.com/camsaul/methodical#before-methods)
#_(m/prefer-method! #'pipeline/transduce-with-model
                  [:toucan.query-type/insert.* ::before-insert]
                  [:toucan.query-type/insert.* :toucan2.tools.transformed/transformed.model])

(defmacro define-before-insert
  {:style/indent :defn}
  [model [instance-binding] & body]
  `(do
     (u/maybe-derive ~model ::before-insert)
     (m/defmethod before-insert ~model
       [~'&model ~instance-binding]
       (cond->> (do ~@body)
         ~'next-method (~'next-method ~'&model)))))

(s/fdef define-before-insert
  :args (s/cat :model    some?
               :bindings (s/spec (s/cat :instance :clojure.core.specs.alpha/binding-form))
               :body     (s/+ any?))
  :ret any?)