Paperless: poll consume task for real upload confirmation; v0.1.2

After POST /api/documents/post_document/ the client now polls /api/tasks/
until the document is consumed, so the app shows 'Toegevoegd ✓', 'Duplicaat',
or a failure message instead of just 'queued'. A 'Niet wachten' button lets
the user stop waiting (the POST itself is NonCancellable, so the document is
always really sent). Bump versionCode 3 / versionName 0.1.2.

Fixes #3

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

app/src/main/java/eu/geyskens/pdfscan/paperless/PaperlessClient.kt

@@ -1,12 +1,16 @@
 package eu.geyskens.pdfscan.paperless
 
 import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.NonCancellable
+import kotlinx.coroutines.delay
 import kotlinx.coroutines.withContext
 import okhttp3.MediaType.Companion.toMediaType
 import okhttp3.MultipartBody
 import okhttp3.OkHttpClient
 import okhttp3.Request
 import okhttp3.RequestBody.Companion.asRequestBody
+import org.json.JSONArray
+import org.json.JSONObject
 import java.io.File
 import java.util.concurrent.TimeUnit
 
@@ -28,7 +32,12 @@ class PaperlessClient(
     private val root = baseUrl.trim().trimEnd('/')
 
     sealed interface Result {
+        /** Document was consumed and created in Paperless. */
         data object Success : Result
+        /** Paperless rejected it as a duplicate of an existing document. */
+        data object Duplicate : Result
+        /** Upload was accepted but still processing when we stopped waiting. */
+        data object Pending : Result
         data class Failure(val message: String) : Result
     }
 
@@ -51,7 +60,11 @@ class PaperlessClient(
         }.getOrElse { Result.Failure(it.message ?: "Verbinding mislukt.") }
     }
 
-    /** Uploads a PDF to the Paperless consume/inbox pipeline. */
+    /**
+     * Uploads a PDF and then waits for Paperless to actually consume it. The upload
+     * endpoint only queues the document and returns a task UUID; we poll the task so the
+     * user learns whether it was added, was a duplicate, or failed.
+     */
     suspend fun upload(pdf: File, title: String): Result = withContext(Dispatchers.IO) {
         val body = MultipartBody.Builder()
             .setType(MultipartBody.FORM)
@@ -66,11 +79,70 @@ class PaperlessClient(
             .header("Authorization", "Token $token")
             .post(body)
             .build()
-        runCatching {
-            client.newCall(request).execute().use { resp ->
-                if (resp.isSuccessful) Result.Success
-                else Result.Failure("Upload mislukt: ${resp.code} ${resp.message}")
+
+        // The POST runs NonCancellable so that "stop waiting" only skips the status poll —
+        // the document is always really queued. post_document returns the task UUID string.
+        val posted: kotlin.Result<String?> = withContext(NonCancellable) {
+            runCatching {
+                client.newCall(request).execute().use { resp ->
+                    if (!resp.isSuccessful) error("Upload mislukt: ${resp.code} ${resp.message}")
+                    resp.body?.string()?.trim()?.trim('"')?.takeIf { it.isNotBlank() }
+                }
             }
-        }.getOrElse { Result.Failure(it.message ?: "Upload mislukt.") }
+        }
+        val taskId = posted.getOrElse { return@withContext Result.Failure(it.message ?: "Upload mislukt.") }
+
+        // Older servers may not return a usable id; then we can only confirm acceptance.
+        if (taskId == null || taskId.equals("OK", ignoreCase = true)) return@withContext Result.Pending
+
+        pollTask(taskId)
+    }
+
+    /** Polls /api/tasks/ until the consume task finishes, or gives up after ~45s. */
+    private suspend fun pollTask(taskId: String): Result {
+        val deadline = System.currentTimeMillis() + 45_000
+        while (System.currentTimeMillis() < deadline) {
+            val task = runCatching {
+                val req = Request.Builder()
+                    .url("$root/api/tasks/?task_id=$taskId")
+                    .header("Authorization", "Token $token")
+                    .header("Accept", "application/json")
+                    .get()
+                    .build()
+                client.newCall(req).execute().use { resp ->
+                    if (resp.isSuccessful) firstTask(resp.body?.string()) else null
+                }
+            }.getOrNull()
+
+            when (task?.status?.uppercase()) {
+                "SUCCESS" -> return Result.Success
+                "FAILURE" -> {
+                    val msg = task.result.orEmpty()
+                    return if (msg.contains("duplicate", ignoreCase = true)) Result.Duplicate
+                    else Result.Failure(msg.ifBlank { "Paperless kon het document niet verwerken." })
+                }
+                // PENDING / STARTED / RETRY / unknown → keep waiting.
+            }
+            delay(1500)
+        }
+        return Result.Pending
+    }
+
+    private data class Task(val status: String?, val result: String?)
+
+    /** Parses the first task object from the /api/tasks/ response (a plain array). */
+    private fun firstTask(json: String?): Task? {
+        if (json.isNullOrBlank()) return null
+        return runCatching {
+            val trimmed = json.trim()
+            val arr = if (trimmed.startsWith("[")) JSONArray(trimmed)
+            else JSONObject(trimmed).optJSONArray("results")
+            if (arr == null || arr.length() == 0) return null
+            val o = arr.getJSONObject(0)
+            Task(
+                status = o.optString("status").takeIf { it.isNotBlank() && it != "null" },
+                result = o.optString("result").takeIf { it.isNotBlank() && it != "null" },
+            )
+        }.getOrNull()
     }
 }