Optional configuration to use an existing Awscr::S3::Client (#8)

fixes #5

Author: philipp-classen

spec/s3/client_spec.cr

@@ -66,6 +66,19 @@ def with_client(*, auto_close = true, & : EasyAwscr::S3::Client -> Nil)
   end
 end
 
+def with_native_awscr_s3_client(& : Awscr::S3::Client -> Nil)
+  with_aws_api do |api|
+    cred = api.credential_provider.credentials
+    yield Awscr::S3::Client.new(
+      api.region,
+      cred.access_key_id,
+      cred.secret_access_key,
+      cred.session_token,
+      endpoint: api.endpoint
+    )
+  end
+end
+
 class SafeKeyGen
   getter keys_used
 
@@ -283,4 +296,51 @@ describe EasyAwscr::S3::Client do
       end
     end
   end
+
+  describe "allow to use your own awscr-s3 client" do
+    describe "#constructor" do
+      it "should use the client_provider if configured" do
+        with_native_awscr_s3_client do |awscr_s3_client|
+          call_count = 0
+          client_provider = ->(_force_new : Bool) do
+            call_count += 1
+            awscr_s3_client
+          end
+
+          client = EasyAwscr::S3::Client.new(client_provider: client_provider, region: "us-east-1", lazy_init: true)
+          call_count.should eq(0)
+
+          list1 = client.list_buckets
+          call_count.should eq(1)
+          list2 = client.list_buckets
+          call_count.should eq(2)
+
+          list1.buckets.should eq(list2.buckets)
+        end
+      end
+    end
+
+    describe "#from_native_client" do
+      it "should be support to wrap a single call" do
+        with_native_awscr_s3_client do |awscr_s3_client|
+          list1 = EasyAwscr::S3::Client.from_native_client(awscr_s3_client).list_buckets
+          list2 = EasyAwscr::S3::Client.from_native_client(awscr_s3_client).list_buckets
+          list1.buckets.should eq(list2.buckets)
+        end
+      end
+
+      it "should integrate with the normal client" do
+        with_client do |client|
+          with_temp_test_bucket(client) do |bucket|
+            with_native_awscr_s3_client do |awscr_s3_client|
+              native_client = EasyAwscr::S3::Client.from_native_client(awscr_s3_client)
+
+              client.head_bucket(bucket).should be_true
+              native_client.head_bucket(bucket).should be_true
+            end
+          end
+        end
+      end
+    end
+  end
 end

src/easy-awscr/s3/client.cr

@@ -7,6 +7,13 @@ module EasyAwscr::S3
     @s3_client : Awscr::S3::Client?
     @client_factory : Internals::ConnectionPool?
 
+    # An optional hook for managing the native S3 client ("awscr-s3" library)
+    # yourself, instead of letting "easy-aws" handle it internally.
+    #
+    # The first parameter is a hint whether the connections or credentials should
+    # be refreshed. It is only a hint, and implementations are allowed to ignore it.
+    alias ClientProvider = Proc(Bool, Awscr::S3::Client)
+
     # This is a hard limit enforced by AWS for multipart uploads:
     # each part must be at least 5 MB.
     MINIMUM_PART_SIZE_5MB = 5242880
@@ -18,12 +25,18 @@ module EasyAwscr::S3
     def initialize(*,
                    @region = EasyAwscr::Config.default_region!,
                    @credential_provider = EasyAwscr::Config.default_credential_provider,
+                   @client_provider : ClientProvider? = nil,
                    @endpoint : String? = nil,
                    lazy_init = false)
       @mutex = Mutex.new(:unchecked)
       client unless lazy_init
     end
 
+    # Converts an existing client from "awscr-s3" to use the "easy-awscr" client interface.
+    def self.from_native_client(native_client : Awscr::S3::Client) : self
+      new(client_provider: ->(_force_new : Bool) { native_client }, region: "us-east-1", lazy_init: false)
+    end
+
     # Closes this client. If used again, a new connection will be opened.
     def close
       @mutex.synchronize do
@@ -288,6 +301,8 @@ module EasyAwscr::S3
     end
 
     private def client(*, force_new = false) : Awscr::S3::Client
+      @client_provider.try { |provider| return provider.call(force_new) }
+
       dead_client_factory = nil
       @mutex.synchronize do
         s3_client = @s3_client