Use connection pooling and add disconnect for disconnecting all connections

Fixes #4, but requires some work on configuring the pool.

Author: anttih

MODULE.md

@@ -119,6 +119,13 @@ end :: forall eff. Client -> Eff (db :: DB | eff) Unit
 ```
 
 
+#### `disconnect`
+
+``` purescript
+disconnect :: forall eff. Eff (db :: DB | eff) Unit
+```
+
+
 
 ## Module Database.Postgres.SqlValue
 

src/Database/Postgres.purs

@@ -6,6 +6,7 @@ module Database.Postgres
   , ConnectionString()
   , mkConnectionString
   , connect
+  , disconnect
   , end
   , execute, execute_
   , query, query_
@@ -18,6 +19,7 @@ import Control.Alt
 import Control.Monad.Eff
 import Control.Monad.Trans
 import Data.Either
+import Data.Function (Fn2(), runFn2)
 import Data.Array
 import Data.Foreign
 import Data.Foreign.Class
@@ -115,20 +117,11 @@ withConnection :: forall eff a
   . ConnectionInfo
   -> (Client -> Aff (db :: DB | eff) a)
   -> Aff (db :: DB | eff) a
-withConnection info p = do
-  client <- connect info
-  finally (p client) $ liftEff (end client)
+withConnection info p = runFn2 _withConnection (mkConnectionString info) p
 
 liftError :: forall e a. ForeignError -> Aff e a
 liftError err = throwError $ error (show err)
 
-finally :: forall eff a. Aff eff a -> Aff eff Unit -> Aff eff a
-finally a sequel = do
-  res <- attempt a
-  sequel
-  either throwError pure res
-
-
 foreign import connect' """
   function connect$prime(conString) {
     return function(success, error) {
@@ -146,6 +139,32 @@ foreign import connect' """
   }
   """ :: forall eff. String -> Aff (db :: DB | eff) Client
 
+foreign import _withConnection
+  """
+  function _withConnection(conString, cb) {
+    return function(success, error) {
+      var pg = require('pg');
+      pg.connect(conString, function(err, client, done) {
+        if (err) {
+          done(true);
+          return error(err);
+        }
+        cb(client)(function(v) {
+          done();
+          success(v);
+        }, function(err) {
+          done();
+          error(err);
+        })
+      });
+    };
+  }
+  """ :: forall eff a.
+      Fn2
+      ConnectionString
+      (Client -> Aff (db :: DB | eff) a)
+      (Aff (db :: DB | eff) a)
+
 foreign import runQuery_ """
   function runQuery_(queryStr) {
     return function(client) {
@@ -212,3 +231,11 @@ foreign import end """
     };
   }
   """ :: forall eff. Client -> Eff (db :: DB | eff) Unit
+
+foreign import disconnect
+  """
+  function disconnect() {
+    var pg = require('pg');
+    pg.end();
+  }
+  """ :: forall eff. Eff (db :: DB | eff) Unit

test/Main.purs

@@ -26,6 +26,8 @@ main = runAff (trace <<< show) (const $ trace "All ok") $ do
 
   exampleQueries
 
+  liftEff $ disconnect
+
 data Artist = Artist
   { name :: String
   , year :: Number