fix: fail on malformed board detail responses

app/src/main/java/space/hackenslacker/kanbn4droid/app/auth/KanbnApiClient.kt

@@ -227,7 +227,9 @@ class HttpKanbnApiClient : KanbnApiClient {
                 apiKey = apiKey,
             ) { code, body ->
                 if (code in 200..299) {
-                    BoardsApiResult.Success(parseBoardDetail(body, boardId))
+                    parseBoardDetail(body, boardId)
+                        ?.let { BoardsApiResult.Success(it) }
+                        ?: BoardsApiResult.Failure("Malformed board detail response.")
                 } else {
                     BoardsApiResult.Failure(serverMessage(body, code))
                 }
@@ -482,9 +484,13 @@ class HttpKanbnApiClient : KanbnApiClient {
         return workspaces
     }
 
-    private fun parseBoardDetail(body: String, fallbackId: String): BoardDetail {
+    private fun parseBoardDetail(body: String, fallbackId: String): BoardDetail? {
+        if (body.isBlank()) {
+            return BoardDetail(id = fallbackId, title = "Board", lists = emptyList())
+        }
+
         val root = parseJsonObject(body)
-            ?: return BoardDetail(id = fallbackId, title = "Board", lists = emptyList())
+            ?: return null
         val data = root["data"] as? Map<*, *>
         val board = (data?.get("board") as? Map<*, *>)
             ?: data
@@ -592,17 +598,23 @@ class HttpKanbnApiClient : KanbnApiClient {
     private fun jsonEscape(value: String): String {
         val builder = StringBuilder()
         value.forEach { ch ->
+            if (ch.code in 0x00..0x1F) {
                 when (ch) {
-                '\\' -> builder.append("\\\\")
-                '"' -> builder.append("\\\"")
                     '\b' -> builder.append("\\b")
                     '\u000C' -> builder.append("\\f")
                     '\n' -> builder.append("\\n")
                     '\r' -> builder.append("\\r")
                     '\t' -> builder.append("\\t")
+                    else -> builder.append("\\u%04x".format(ch.code))
+                }
+            } else {
+                when (ch) {
+                    '\\' -> builder.append("\\\\")
+                    '"' -> builder.append("\\\"")
                     else -> builder.append(ch)
                 }
             }
+        }
         return builder.toString()
     }
 

app/src/test/java/space/hackenslacker/kanbn4droid/app/auth/HttpKanbnApiClientBoardDetailParsingTest.kt

@@ -186,6 +186,25 @@ class HttpKanbnApiClientBoardDetailParsingTest {
         }
     }
 
+    @Test
+    fun getBoardDetailFailsOnMalformedJsonPayload() = runTest {
+        TestServer().use { server ->
+            server.register(
+                path = "/api/v1/boards/malformed",
+                status = 200,
+                responseBody = "{\"data\": {\"id\": \"broken\"",
+            )
+
+            val result = HttpKanbnApiClient().getBoardDetail(server.baseUrl, "key", "malformed")
+
+            assertTrue(result is BoardsApiResult.Failure)
+            assertEquals(
+                "Malformed board detail response.",
+                (result as BoardsApiResult.Failure).message,
+            )
+        }
+    }
+
     @Test
     fun requestMappingMatchesContractForBoardDetailAndMutations() = runTest {
         TestServer().use { server ->
@@ -229,6 +248,24 @@ class HttpKanbnApiClientBoardDetailParsingTest {
         }
     }
 
+    @Test
+    fun renameListEscapesControlCharactersInRequestBody() = runTest {
+        TestServer().use { server ->
+            server.register(path = "/api/v1/lists/l-esc", status = 200, responseBody = "{}")
+
+            val raw = "name\u0000line\u001f\n\tend"
+            val result = HttpKanbnApiClient().renameList(server.baseUrl, "api", "l-esc", raw)
+
+            assertTrue(result is BoardsApiResult.Success<*>)
+            val request = server.findRequest("PATCH", "/api/v1/lists/l-esc")
+            assertNotNull(request)
+            assertEquals(
+                "{\"name\":\"name\\u0000line\\u001f\\n\\tend\"}",
+                request?.body,
+            )
+        }
+    }
+
     @Test
     fun serverMessageIsPropagatedWithFallbackWhenMissing() = runTest {
         TestServer().use { server ->