Add top level APIs for fetching secrets

- Adds top level APIs for fetching secrets (`getSecret` and `getSecretEither`)
- Removes call to `defaultAzureCredentials` in client. Users need to supply `AccessToken`
- Split types and functions.

azure-key-vault/Azure/Secret.hs

@@ -1,37 +1,58 @@
-{-# LANGUAGE DeriveGeneric #-}
 {-# LANGUAGE TypeApplications #-}
 {-# LANGUAGE TypeOperators #-}
 
 module Azure.Secret
-    ( KeyVaultResponse (..)
-    , GetSecretFromVaultApi
-    , getSecretFromVault
-    , callKeyVaultClient
+    ( getSecret
+    , getSecretEither
     ) where
 
-import Data.Aeson (FromJSON (..), withObject, (.:))
 import Data.Data (Proxy (..))
 import Data.Text (Text)
-import GHC.Generics (Generic)
 import Network.HTTP.Client.TLS (newTlsManager)
 import Servant.API (Capture, Get, Header', JSON, QueryParam', Required, Strict, (:>))
 import Servant.Client (BaseUrl (..), ClientM, Scheme (..), client, mkClientEnv, runClientM)
-import UnliftIO (MonadIO (..), throwIO)
+import UnliftIO (MonadIO (..), throwString)
 
-import Azure.Auth (defaultAzureCredential)
-import Azure.Types (AccessToken (..), Token)
+import Azure.Secret.Types (KeyVaultHost (..), KeyVaultResponse (..), SecretName (..))
+import Azure.Types (AccessToken (..))
 
 import qualified Data.Text as Text
 
-newtype KeyVaultResponse = KeyVaultResponse
-    { unKeyValueReponse :: Text
-    }
-    deriving stock (Eq, Show, Generic)
+{- | Fetches a secret from Key vault.
 
-instance FromJSON KeyVaultResponse where
-    parseJSON = withObject "KeyVaultResponse" $ \o -> do
-        unKeyValueReponse <- o .: "value"
-        pure KeyVaultResponse{..}
+All errors are thrown in IO. For variant where error is
+caught in a @Left@ branch, see @getSecretEither@
+-}
+getSecret ::
+    MonadIO m =>
+    -- | Name of the secret
+    SecretName ->
+    -- | Host to identify the key vault. This is where all the request will be
+    -- made. It is of the form @{keyvault-name}.vault.azure.net@
+    KeyVaultHost ->
+    -- | Access token which will form part of the authentication header
+    AccessToken ->
+    m KeyVaultResponse
+getSecret secretName host accessToken = do
+    res <- getSecretEither secretName host accessToken
+    case res of
+        Left err -> throwString $ show err
+        Right value -> pure value
+
+{- | Fetches a secret from key vault provided the name of the secret and the key vault host.
+These secrets can be found under @/secrets@ path under key vault section in Azure portal.
+-}
+getSecretEither ::
+    MonadIO m =>
+    -- | Name of the secret
+    SecretName ->
+    -- | Host to identify the key vault. This is where all the request will be
+    -- made. It is of the form @{keyvault-name}.vault.azure.net@
+    KeyVaultHost ->
+    -- | Access token which will form part of the authentication header
+    AccessToken ->
+    m (Either Text KeyVaultResponse)
+getSecretEither = callKeyVaultClient getSecretFromVault
 
 {-
 Path: GET {vaultBaseUrl}/secrets/{secret-name}/{secret-version}?api-version=7.4
@@ -52,20 +73,19 @@ getSecretFromVault = client (Proxy @GetSecretFromVaultApi)
 callKeyVaultClient ::
     MonadIO m =>
     (Text -> Float -> Text -> ClientM KeyVaultResponse) ->
-    Text ->
-    Text ->
-    Token ->
-    m KeyVaultResponse
-callKeyVaultClient action secretName vaultHost tokenStore = do
+    SecretName ->
+    KeyVaultHost ->
+    AccessToken ->
+    m (Either Text KeyVaultResponse)
+callKeyVaultClient action (SecretName secretName) (KeyVaultHost vaultHost) accessToken = do
     manager <- liftIO newTlsManager
-    authHeader <- defaultAzureCredential Nothing vaultHost tokenStore
     res <-
         liftIO $
             runClientM
-                (action secretName 7.4 ("Bearer " <> atAccessToken authHeader))
+                (action secretName 7.4 ("Bearer " <> atAccessToken accessToken))
                 (mkClientEnv manager $ BaseUrl Https (Text.unpack vaultHost) 443 "")
-    case res of
+    pure $ case res of
         Left err ->
-            throwIO err
+            Left . Text.pack $ show err
         Right response ->
-            pure response
+            Right response

azure-key-vault/Azure/Secret/Types.hs

@@ -0,0 +1,25 @@
+{-# LANGUAGE DeriveGeneric #-}
+
+module Azure.Secret.Types
+    ( KeyVaultResponse (..)
+    , SecretName (..)
+    , KeyVaultHost (..)
+    ) where
+
+import Data.Aeson (FromJSON (..), withObject, (.:))
+import Data.Text (Text)
+import GHC.Generics (Generic)
+
+newtype KeyVaultResponse = KeyVaultResponse
+    { unKeyValueReponse :: Text
+    }
+    deriving stock (Eq, Show, Generic)
+
+instance FromJSON KeyVaultResponse where
+    parseJSON = withObject "KeyVaultResponse" $ \o -> do
+        unKeyValueReponse <- o .: "value"
+        pure KeyVaultResponse{..}
+
+newtype SecretName = SecretName {unSecretName :: Text} deriving stock (Eq, Show)
+
+newtype KeyVaultHost = KeyVaultHost {unKeyVaultHost :: Text} deriving stock (Eq, Show)

azure-key-vault/azure-key-vault.cabal

@@ -52,7 +52,8 @@ common common-options
 
 library
     import:           common-options
-    exposed-modules:  Azure.Secret
+    exposed-modules:  Azure.Secret.Types
+                      Azure.Secret
     build-depends:    aeson
                     , azure-auth
                     , http-client-tls
@@ -61,3 +62,13 @@ library
                     , text
                     , unliftio
     default-language: Haskell2010
+
+executable example
+  main-is: Main.hs
+  hs-source-dirs: example
+  ghc-options: -Wall
+  default-language: Haskell2010
+  build-depends:
+      base >= 4.7 && < 5
+    , azure-auth
+    , azure-key-vault

azure-key-vault/example/Main.hs

@@ -0,0 +1,16 @@
+{-# LANGUAGE OverloadedStrings #-}
+
+module Main where
+
+import Azure.Secret (getSecret)
+import Azure.Secret.Types (KeyVaultHost (..), SecretName (..))
+import Azure.Types (newEmptyToken)
+import Azure.Auth (defaultAzureCredential)
+
+main :: IO ()
+main = do
+    tok <- newEmptyToken
+    cred <- defaultAzureCredential Nothing "https://vault.azure.net" tok
+    -- In order to run this, you need to replace @SecretName@ and @KeyVaultHost@ with
+    -- appropriate values in your resource group. These are just dummy values.
+    getSecret (SecretName "radiohead") (KeyVaultHost "albums") cred >>= print