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SendGrid

Haskell interface to the SendGrid API.

Quick Start

tl;dr:

• install with Stack
• use mkSingleRecip email to construct an email
• use Lenses to update properties of the email (such as templates, categories, or unsubscribe groups.
• run the reader monad with the ApiKey

Requirements:

• Stack

Installation:

Add the following to your stack.yaml under packages:

packages:
- location:
    git: git://github.com/frontrowed/sendgrid
    commit: <COMMIT>

Usage

The primary data type is SendEmail, which represents the components of an email message that may be sent via SendGrid. Properties of a SendEmail include the standard email components such as sender, CC and BCC recipients, attachements, and so forth. Additionally, SendGrid-specific attributes include templates, categories, and unsubscribe groups.

Consider the following definition of a simple email from sender@source.com to receiver@person.com. It has the subject "Coming via sendgrid" and contents "Text body". The type indicates that the message categories are Text, one recipient (Vector 1), and no CC or BCC recipients (Vector 0).

email1 :: SendEmail Text (Vector 1) (Vector 0) (Vector 0)
email1 =
  let [sender, recipient] = map (uncurry unsafeEmailAddress) [
        ("sender", "source.com"),
        ("receiver", "person.com")
      ]
  in
  mkSingleRecipEmail
    recipient
    "Coming via sendgrid"
    (That "Text body")
    sender

SendEMail types can additionaly be modified using Lenses to modify the components. Use the SendEmail lenses and lens operator set the desired attributes. For instance, to set the categories and unsubscribe group:

email2 :: SendMail Text (Vector 1) (Vector 0) (Vector 0)
email2 = email1
  & categories .~ ["email", "test", "foo", "bar"]
  & templateId .~ Just "ff469da0-4a45-4263-2414-5ac770565e4d"

We use type indices to typecheck the number of CC and BCC recipients. To set and add to each of these, you need to construct a typechecked vector

To add CC and BCC recipients you can use the ccsAll and ``bccsAll` lens, which accepts a tuple of type-indexed vectors where the second is wrapped with Maybe.

email3 =
  let cc1 = unsafeEmailAddress "cc1" "example.com"
      cc2 = unsafeEmailAddress "cc2" "example.com"
      n1  = "CC 1 name"
      n2  = "CC 2 name"
  in email2
     & ccsAll .~ (cc2 #: cc1 #: empty, Just $ n2 #: n1 #: empty)

This can be rather unwieldy, so the ccsWipe and bccsWipe lenses are provided. As the names hint at, these "wipe" the names list so make sure to use the paired ccNames and bccNames lenses to set the names.

email4 :: SendMail Text (Vector 1) (Vector 2) (Vector 0)
email4 =
  let cc1 = unsafeEmailAddress "cc1" "example.com"
      cc2 = unsafeEmailAddress "cc2" "example.com"
      n1  = "CC 1"
      n2  = "CC 2"
  in email2
     & ccsWipe .~ (cc2 #: cc1 #: empty)
     & ccNames .~ (Just $ n2 #: n1 #: empty)

Finally, to actually send an email, you'll need to use an ApiKey and construct a Wreq session. One approach is to set this as an environmental variable and then load it using System.Environment.lookupEnv

main = do
  key <- fmap (Tagged . T.pack) <$> lookupEnv "API_KEY"
  maybe
    (fail "Could not lookup API_KEY in environment")
    sendMyEmail
    key

The sendEmail function operates in the Reader Monad with configuration given as 2-tuple type (Tagged ApiKey Text, Session).

sendMyEmail :: Tagged ApiKey Text -> IO ()
sendMyEmail apikey = do
  result <- withSession $ \session ->
    runReaderT (sendEmail email4) (apikey, session)
  print result