fix api host being overwritten by default value (#80)

* fix apiHost being overwritten by default value

* add unit tests

* address comment

Author: wenxi-zeng

core/src/main/java/com/segment/analytics/kotlin/core/platform/plugins/SegmentDestination.kt

@@ -18,7 +18,7 @@ import kotlinx.serialization.json.jsonPrimitive
 @Serializable
 data class SegmentSettings(
     var apiKey: String,
-    var apiHost: String = DEFAULT_API_HOST,
+    var apiHost: String? = null
 )
 
 /**
@@ -95,8 +95,9 @@ class SegmentDestination : DestinationPlugin(), VersionedPlugin {
     override fun update(settings: Settings, type: Plugin.UpdateType) {
         super.update(settings, type)
         if (settings.hasIntegrationSettings(this)) {
-            settings.destinationSettings<SegmentSettings>(key)?.let {
-                pipeline.apiHost = it.apiHost
+            // only populate the apiHost value if it exists
+            settings.destinationSettings<SegmentSettings>(key)?.apiHost?.let {
+                pipeline.apiHost = it
             }
         }
     }

core/src/test/kotlin/com/segment/analytics/kotlin/core/AnalyticsTests.kt

@@ -18,6 +18,8 @@ import org.junit.jupiter.api.Test
 import org.junit.jupiter.api.TestInstance
 import org.junit.jupiter.api.*
 import org.junit.jupiter.api.Assertions.*
+import java.io.ByteArrayInputStream
+import java.net.HttpURLConnection
 import java.time.Instant
 import java.util.Date
 import java.util.UUID
@@ -43,12 +45,12 @@ class AnalyticsTests {
         every { Instant.now() } returns Date(0).toInstant()
         mockkStatic(UUID::class)
         every { UUID.randomUUID().toString() } returns "qwerty-qwerty-123"
-        mockHTTPClient()
     }
 
     @BeforeEach
     fun setup() {
         clearPersistentStorage()
+        mockHTTPClient()
         val config = Configuration(
             writeKey = "123",
             application = "Test"
@@ -84,6 +86,48 @@ class AnalyticsTests {
 
             assertEquals(exception.message?.contains("Android"), true)
         }
+
+        @Test
+        fun `analytics should respect remote apiHost`() {
+            // need the following block in `init` to inject mock before analytics gets instantiate
+            val settingsStream = ByteArrayInputStream(
+                """
+                {"integrations":{"Segment.io":{"apiKey":"1vNgUqwJeCHmqgI9S1sOm9UHCyfYqbaQ","apiHost":"remote"}},"plan":{},"edgeFunction":{}}
+            """.trimIndent().toByteArray()
+            )
+            val httpConnection: HttpURLConnection = mockk()
+            val connection = object : Connection(httpConnection, settingsStream, null) {}
+            every { anyConstructed<HTTPClient>().settings("cdn-settings.segment.com/v1") } returns connection
+
+            val config = Configuration(
+                writeKey = "123",
+                application = "Test",
+                apiHost = "local"
+            )
+            analytics = testAnalytics(config, testScope, testDispatcher)
+            analytics.track("test")
+            analytics.flush()
+
+            val apiHost = slot<String>()
+            verify { anyConstructed<HTTPClient>().upload(capture(apiHost)) }
+            assertEquals("remote", apiHost.captured)
+        }
+
+        @Test
+        fun `analytics should respect local modified apiHost if remote not presented`() {
+            val config = Configuration(
+                writeKey = "123",
+                application = "Test",
+                apiHost = "local"
+            )
+            analytics = testAnalytics(config, testScope, testDispatcher)
+            analytics.track("test")
+            analytics.flush()
+
+            val apiHost = slot<String>()
+            verify { anyConstructed<HTTPClient>().upload(capture(apiHost)) }
+            assertEquals("local", apiHost.captured)
+        }
     }
 
     @Nested