derive host from region

lib/ex_aws/config.ex

@@ -13,6 +13,7 @@ defmodule ExAws.Config do
     config = client
     |> ExAws.Config.get
     |> Map.merge(Enum.into(opts, %{}))
+    |> parse_host_for_region
 
     %{client | config: config}
     |> retrieve_runtime_config
@@ -62,4 +63,15 @@ defmodule ExAws.Config do
   end
   def retrieve_runtime_value(value, _), do: value
 
+  def parse_host_for_region(%{host: {stub, host}, region: region} = config) do
+    %{config | host: String.replace(host, stub, region)}
+  end
+  def parse_host_for_region(%{host: map, region: region} = config) when is_map(map) do
+    case Map.fetch(map, region) do
+      {:ok, host} -> %{config | host: host}
+      :error      -> "A host for region #{region} was not found in host map #{inspect(map)}"
+    end
+  end
+  def parse_host_for_region(config), do: config
+
 end

mix.exs

@@ -52,30 +52,40 @@ defmodule ExAws.Mixfile do
       json_codec: Poison,
       kinesis: [
         scheme: "https://",
-        host: "kinesis.us-east-1.amazonaws.com",
+        host: {"$region", "kinesis.$region.amazonaws.com"},
         region: "us-east-1",
         port: 80
       ],
       dynamodb: [
         scheme: "https://",
-        host: "dynamodb.us-east-1.amazonaws.com",
+        host: {"$region", "dynamodb.$region.amazonaws.com"},
         region: "us-east-1",
         port: 80
       ],
       lambda: [
-        host: "lambda.us-east-1.amazonaws.com",
+        host: {"$region", "lambda.$region.amazonaws.com"},
         scheme: "https://",
         region: "us-east-1",
         port: 80
       ],
       s3: [
         scheme: "https://",
-        host: "s3.amazonaws.com",
+        host: %{
+          "us-east-1" => "s3.amazonaws.com",
+          "us-west-1" => "s3-us-west-1.amazonaws.com",
+          "us-west-2" => "s3-us-west-2.amazonaws.com",
+          "eu-west-1" => "s3-eu-west-1.amazonaws.com",
+          "eu-central-1" => "s3-eu-central-1.amazonaws.com",
+          "ap-southeast-1" => "s3-ap-southeast-1.amazonaws.com",
+          "ap-southeast-2" => "s3-ap-southeast-2.amazonaws.com",
+          "ap-northeast-1" => "s3-ap-southeast-1.amazonaws.com",
+          "sa-east-1" => "s3-sa-east-1.amazonaws.com",
+        },
         region: "us-east-1"
       ],
       sqs: [
         scheme: "https://",
-        host: "sqs.us-east-1.amazonaws.com",
+        host: {"$region", "sqs.$region.amazonaws.com"},
         region: "us-east-1"
       ]
     ]