#155 refactor and synchronise writing to CodeOcean. (#174)

* #155 refactor and synchronise writing to CodeOcean.

* Reduce complexity of input parsing.

* Update typo in internal/api/ws/codeocean_writer.go

Co-authored-by: Sebastian Serth <MrSerth@users.noreply.github.com>

internal/api/ws/codeocean_reader_test.go

@@ -0,0 +1,75 @@
+package ws
+
+import (
+	"context"
+	"github.com/gorilla/websocket"
+	"github.com/openHPI/poseidon/tests"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/mock"
+	"github.com/stretchr/testify/require"
+	"io"
+	"strings"
+	"testing"
+)
+
+func TestCodeOceanToRawReaderReturnsOnlyAfterOneByteWasRead(t *testing.T) {
+	readingCtx, cancel := context.WithCancel(context.Background())
+	forwardingCtx := readingCtx
+	defer cancel()
+	reader := NewCodeOceanToRawReader(nil, readingCtx, forwardingCtx)
+
+	read := make(chan bool)
+	go func() {
+		//nolint:makezero // we can't make zero initial length here as the reader otherwise doesn't block
+		p := make([]byte, 10)
+		_, err := reader.Read(p)
+		require.NoError(t, err)
+		read <- true
+	}()
+
+	t.Run("Does not return immediately when there is no data", func(t *testing.T) {
+		assert.False(t, tests.ChannelReceivesSomething(read, tests.ShortTimeout))
+	})
+
+	t.Run("Returns when there is data available", func(t *testing.T) {
+		reader.buffer <- byte(42)
+		assert.True(t, tests.ChannelReceivesSomething(read, tests.ShortTimeout))
+	})
+}
+
+func TestCodeOceanToRawReaderReturnsOnlyAfterOneByteWasReadFromConnection(t *testing.T) {
+	messages := make(chan io.Reader)
+
+	connection := &ConnectionMock{}
+	connection.On("WriteMessage", mock.AnythingOfType("int"), mock.AnythingOfType("[]uint8")).Return(nil)
+	connection.On("CloseHandler").Return(nil)
+	connection.On("SetCloseHandler", mock.Anything).Return()
+	call := connection.On("NextReader")
+	call.Run(func(_ mock.Arguments) {
+		call.Return(websocket.TextMessage, <-messages, nil)
+	})
+
+	readingCtx, cancel := context.WithCancel(context.Background())
+	forwardingCtx := readingCtx
+	defer cancel()
+	reader := NewCodeOceanToRawReader(connection, readingCtx, forwardingCtx)
+	reader.Start()
+
+	read := make(chan bool)
+	//nolint:makezero // this is required here to make the Read call blocking
+	message := make([]byte, 10)
+	go func() {
+		_, err := reader.Read(message)
+		require.NoError(t, err)
+		read <- true
+	}()
+
+	t.Run("Does not return immediately when there is no data", func(t *testing.T) {
+		assert.False(t, tests.ChannelReceivesSomething(read, tests.ShortTimeout))
+	})
+
+	t.Run("Returns when there is data available", func(t *testing.T) {
+		messages <- strings.NewReader("Hello")
+		assert.True(t, tests.ChannelReceivesSomething(read, tests.ShortTimeout))
+	})
+}