Send an email with attachments using SES, postal and selmer

email.clj

ns services.email
  (:require [clojure.tools.logging :as log]
            [clojure.string :as string]
            [clojure.java.io :as io]
            [schema.core :as s]
            [camel-snake-kebab.core :as csk]
            [camel-snake-kebab.extras :as cske]
            [amazonica.core :as aws]
            [amazonica.aws.simpleemail :as ses]
            [selmer.parser :as selmer]
            [postal.message :as msg]
            [clj-time.core :as time]
            [clj-time.periodic :as period]
            [cemerick.url :as url]
            [clj-http.client :as http]
            [cheshire.core :as json]
            [cats.core :as m]
            [cats.builtin]
            [cats.monad.exception :as exc]
            [clj-http.client :as http]
            ...)
  (:import java.io.ByteArrayOutputStream
           java.nio.ByteBuffer
           java.net.URLConnection)
         
(defn render-email
  [opts {:keys [content] :as template}]
  (assoc template
         :content (selmer/render content opts)))

(defn guess-mime
  "Try to guess the mime type, returning default if it cannot."
  [path default]
  (or (URLConnection/guessContentTypeFromName path) default))

(defn normalize-path
  [path]
  (if (= \/ (last path))
    (string/join (drop-last path))
    path))
    
(s/defn workflow-emailer! :- hs/WorkflowStatus
  "Concretely send the email given the input email configuration and workflow.
  Returns the new workflow status or throws if there is an error."
  [email-conf :- hs/EmailConf workflow :- hs/EmailWorkflow]
  (log/debugf "Templating against workflow: %s" workflow)
  (let [subject (selmer/render (get-in email-conf [:templates :subject]) workflow)]
    (log/debugf "Sending email \"%s\"" subject)
    (let [scan-right (-> workflow :scan-right :url normalize-path)
          scan-left (-> workflow :scan-left :url normalize-path)
          photo (-> workflow :photo :url normalize-path)
          msg (msg/make-jmessage
               {:from (:source email-conf)
                :to (:to-addresses email-conf)
                :subject subject
                :body [:mixed
                       [(into [:alternative]
                              (map (partial render-email workflow)
                                   (get-in email-conf [:templates :body])))]
                       {:type :attachment
                        :content-type (guess-mime scan-right "image/jpeg")
                        :content (io/as-url scan-right)}
                       {:type :attachment
                        :content-type (guess-mime scan-left "image/jpeg")
                        :content (io/as-url scan-left)}
                       {:type :attachment
                        :content-type (guess-mime photo "image/jpeg")
                        :content (io/as-url photo)}]})]
      (ses/send-raw-email :source (:source email-conf)
                          :destinations (:to-addresses email-conf)
                          :raw-message {:data (ByteBuffer/wrap
                                               (.toByteArray
                                                (let [baos (ByteArrayOutputStream.)]
                                                  (.writeTo msg baos)
                                                  baos)))})))
  wf/email-submitted-status)