From 60f7f1c0913c35635ebbab4649a15de2e8310e81 Mon Sep 17 00:00:00 2001
From: Paul Brinkmeier <hallo@pbrinkmeier.de>
Date: Tue, 5 Sep 2023 17:23:25 +0200
Subject: [PATCH] Implement FromField Bool

---
 README.md                                     |  6 ++++--
 lib/Database/PostgreSQL/Opium/FromField.hs    | 12 ++++++++++++
 lib/Database/PostgreSQL/Opium/Oid.hs          |  4 ++++
 .../PostgreSQL/Opium/FromFieldSpec.hs         | 19 +++++++++++++++++++
 4 files changed, 39 insertions(+), 2 deletions(-)

diff --git a/README.md b/README.md
index bd65508..b853ac5 100644
--- a/README.md
+++ b/README.md
@@ -6,6 +6,8 @@
 
 - [x] Implement `String` and `Text` decoding
 - [x] Implement `Int` decoding
-- [ ] Implement error reporting i.e. use `Either OpiumError` instead of `Maybe`
-- [ ] Implement `Float` and `Double` decoding
+- [x] Implement error reporting i.e. use `Either OpiumError` instead of `Maybe`
+- [x] Implement `Float` and `Double` decoding
 - [ ] Implement `UTCTime` and zoned time decoding
+- [ ] Implement `ByteString` decoding (`bytea`)
+  - Can we make let the fromField instance choose whether it wants binary or text?
diff --git a/lib/Database/PostgreSQL/Opium/FromField.hs b/lib/Database/PostgreSQL/Opium/FromField.hs
index 7b63de3..0478e53 100644
--- a/lib/Database/PostgreSQL/Opium/FromField.hs
+++ b/lib/Database/PostgreSQL/Opium/FromField.hs
@@ -85,3 +85,15 @@ instance FromField Double where
   fromField = fromParser
     (Oid.real \/ Oid.doublePrecision)
     floatParser
+
+boolParser :: Parser Bool
+boolParser = choice
+  [ string "t" $> True
+  , string "f" $> False
+  ]
+
+-- | See https://www.postgresql.org/docs/current/datatype-boolean.html.
+instance FromField Bool where
+  fromField = fromParser
+    Oid.boolean
+    boolParser
diff --git a/lib/Database/PostgreSQL/Opium/Oid.hs b/lib/Database/PostgreSQL/Opium/Oid.hs
index 86a3659..3ebe82b 100644
--- a/lib/Database/PostgreSQL/Opium/Oid.hs
+++ b/lib/Database/PostgreSQL/Opium/Oid.hs
@@ -39,3 +39,7 @@ real = eq $ Oid 700
 -- | 64-bit IEEE float
 doublePrecision :: Oid -> Bool
 doublePrecision = eq $ Oid 701
+
+-- | Boolean
+boolean :: Oid -> Bool
+boolean = eq $ Oid 16
diff --git a/test/Database/PostgreSQL/Opium/FromFieldSpec.hs b/test/Database/PostgreSQL/Opium/FromFieldSpec.hs
index 150a68e..5a2968d 100644
--- a/test/Database/PostgreSQL/Opium/FromFieldSpec.hs
+++ b/test/Database/PostgreSQL/Opium/FromFieldSpec.hs
@@ -42,6 +42,12 @@ newtype ADouble = ADouble
 
 instance FromRow ADouble where
 
+newtype ABool = ABool
+  { bool :: Bool
+  } deriving (Eq, Generic, Show)
+
+instance FromRow ABool where
+
 shouldFetch :: (Eq a, FromRow a, Show a) => Connection -> ByteString -> [a] -> IO ()
 shouldFetch conn query expectedRows = do
   actualRows <- Opium.fetch_ conn query
@@ -125,3 +131,16 @@ spec = do
 
       Right [ADouble value1] <- Opium.fetch_ conn "SELECT '-inf'::double precision AS double"
       value1 `shouldSatisfy` (isInfinite /\ (< 0))
+
+  describe "FromField Bool" $ do
+    it "Decodes boolean" $ \conn -> do
+      shouldFetch conn "SELECT true AS bool" [ABool True]
+      shouldFetch conn "SELECT 't'::boolean AS bool" [ABool True]
+      shouldFetch conn "SELECT 'yes'::boolean AS bool" [ABool True]
+      shouldFetch conn "SELECT 'on'::boolean AS bool" [ABool True]
+      shouldFetch conn "SELECT 1::boolean AS bool" [ABool True]
+      shouldFetch conn "SELECT false AS bool" [ABool False]
+      shouldFetch conn "SELECT 'f'::boolean AS bool" [ABool False]
+      shouldFetch conn "SELECT 'no'::boolean AS bool" [ABool False]
+      shouldFetch conn "SELECT 'off'::boolean AS bool" [ABool False]
+      shouldFetch conn "SELECT 0::boolean AS bool" [ABool False]