Allow malformed MIME types: ignore BadContentTypeFormatExceptions (#787)

* Allow malformed MIME types: ignore BadContentTypeFormatExceptions

When fetching calendar data, if the server responds with a malformed
MIME type in the Content-Type header, we now log a warning and proceed
without a content type instead of failing with error message.

* Add space

* Add tests

Author: sunkup

app/src/androidTest/java/at/bitfire/icsdroid/CalendarFetcherTest.kt

@@ -206,4 +206,76 @@ class CalendarFetcherTest {
 
         assertEquals(IOException::class.java, e?.javaClass)
     }
+
+    @Test
+    fun testFetchNetwork_validContentType() {
+        // Test that when a server returns a valid Content-Type header,
+        // the fetcher correctly parses it and processes the calendar data with the proper contentType
+        val icalCorrect = testContext.resources.openRawResource(R.raw.vienna_evolution).use { streamCorrect ->
+            streamCorrect.bufferedReader().use { it.readText() }
+        }
+
+        // create mock response with valid Content-Type header
+        MockServer.enqueue(
+            content = icalCorrect,
+            status = HttpStatusCode.OK,
+            headers = buildHeaders {
+                append(HttpHeaders.ContentType, "text/calendar; charset=utf-8")
+            }
+        )
+
+        // make request to local mock server
+        var ical: String? = null
+        var receivedContentType: ContentType? = null
+        val fetcher = object: CalendarFetcher(appContext, MockServer.uri(), client) {
+            override suspend fun onSuccess(data: InputStream, contentType: ContentType?, eTag: String?, lastModified: Long?, displayName: String?) {
+                ical = data.bufferedReader().use { it.readText() }
+                receivedContentType = contentType
+            }
+        }
+        runBlocking {
+            fetcher.fetch()
+        }
+
+        // assert content is correct and contentType is properly parsed
+        assertEquals(icalCorrect, ical)
+        assertEquals("text/calendar; charset=utf-8", receivedContentType.toString())
+    }
+
+    @Test
+    fun testFetchNetwork_malformedContentType() {
+        // Test that when a server returns a malformed Content-Type header,
+        // the fetcher logs a warning and successfully processes the calendar data with null contentType
+        val icalCorrect = testContext.resources.openRawResource(R.raw.vienna_evolution).use { streamCorrect ->
+            streamCorrect.bufferedReader().use { it.readText() }
+        }
+
+        // create mock response with malformed Content-Type header (containts "-" at start)
+        // that will trigger BadContentTypeFormatException to be thrown
+        MockServer.enqueue(
+            content = icalCorrect,
+            status = HttpStatusCode.OK,
+            headers = buildHeaders {
+                append(HttpHeaders.ContentType, "-Text/calendar charset=utf-8")
+            }
+        )
+
+        // make request to local mock server
+        var ical: String? = null
+        var receivedContentType: ContentType? = null
+        val fetcher = object: CalendarFetcher(appContext, MockServer.uri(), client) {
+            override suspend fun onSuccess(data: InputStream, contentType: ContentType?, eTag: String?, lastModified: Long?, displayName: String?) {
+                ical = data.bufferedReader().use { it.readText() }
+                receivedContentType = contentType
+            }
+        }
+        runBlocking {
+            fetcher.fetch()
+        }
+
+        // assert content is correct and contentType is null (due to malformed header)
+        assertEquals(icalCorrect, ical)
+        assertEquals(null, receivedContentType)
+    }
+
 }

app/src/main/java/at/bitfire/icsdroid/CalendarFetcher.kt

@@ -15,6 +15,7 @@ import io.ktor.client.request.basicAuth
 import io.ktor.client.request.get
 import io.ktor.client.request.header
 import io.ktor.client.statement.bodyAsChannel
+import io.ktor.http.BadContentTypeFormatException
 import io.ktor.http.ContentType
 import io.ktor.http.HttpHeaders
 import io.ktor.http.HttpStatusCode
@@ -154,16 +155,23 @@ open class CalendarFetcher(
                 val statusCode = response.status
                 when {
                     // 20x
-                    statusCode.isSuccess() ->
+                    statusCode.isSuccess() -> {
+                        val contentType: ContentType? = try {
+                            response.contentType()
+                        } catch (e: BadContentTypeFormatException) {
+                            Log.w(Constants.TAG, "Failed to parse content type. Continuing without.", e)
+                            null
+                        }
                         onSuccess(
                             response.bodyAsChannel().toInputStream(),
-                            response.contentType(),
+                            contentType,
                             response.headers[HttpHeaders.ETag],
                             response.headers[HttpHeaders.LastModified]?.let {
                                 HttpUtils.parseDate(it)?.time
                             },
                             null
                         )
+                    }
 
                     // 30x
                     statusCode == HttpStatusCode.NotModified -> onNotModified()