Merge branch 'fix/off-the-record-outbox' into 'main'

Keep off-the-record messages out of the outbox on disk

See merge request paulhitt/flamenet-messenger-android!143

engine/src/main/kotlin/io/flamenet/e2e/Vault.kt

@@ -1304,7 +1304,33 @@ class Vault(
      */
     fun outbox(): JSONArray = readJson(OUTBOX)?.optJSONArray("pending") ?: JSONArray()
 
-    fun saveOutbox(pending: JSONArray) = writeJson(OUTBOX, JSONObject().put("pending", pending))
+    /**
+     * Write the queue, minus anything for an off-the-record conversation.
+     *
+     * An entry carries `to` and `text`, so this is the message and not a note
+     * about it. Every enqueue writes here directly, so an off-the-record send
+     * queued for later reached disk in plaintext the moment it was typed, for
+     * a conversation §6.28 says is gone when the app closes.
+     *
+     * The filter is here rather than at the four call sites for the same
+     * reason it is on [saveUnreadThreads]: a later caller cannot forget it.
+     * A group entry carries `thread` and no user-thread setting, so it passes
+     * through.
+     *
+     * Dropping a queued send is the promise, not the cost of it. The thread
+     * it belongs to is not kept either, so a message that survived would
+     * arrive into a conversation the app no longer has.
+     */
+    fun saveOutbox(pending: JSONArray) {
+        val kept = JSONArray()
+        for (i in 0 until pending.length()) {
+            val entry = pending.optJSONObject(i) ?: continue
+            val to = entry.optLong("to", 0L)
+            if (to != 0L && offTheRecord(threadForUser(to))) continue
+            kept.put(entry)
+        }
+        writeJson(OUTBOX, JSONObject().put("pending", kept))
+    }
 
     /**
      * Calls placed and received, newest last.

engine/src/test/kotlin/io/flamenet/e2e/OffTheRecordOutboxTest.kt

@@ -0,0 +1,102 @@
+package io.flamenet.e2e
+
+import org.json.JSONArray
+import org.json.JSONObject
+import javax.crypto.KeyGenerator
+import javax.crypto.SecretKey
+import kotlin.test.Test
+import kotlin.test.assertEquals
+import kotlin.test.assertFalse
+import kotlin.test.assertTrue
+
+/**
+ * A queued send for an off-the-record conversation never reaches the vault.
+ *
+ * This is the message, not a note about it: an entry carries `to` and `text`.
+ * Every enqueue writes the whole queue back, so an off-the-record send queued
+ * for later was on disk in plaintext the moment it was typed.
+ */
+class OffTheRecordOutboxTest {
+    private class MapStorage : Vault.Storage {
+        val records = LinkedHashMap<String, ByteArray>()
+
+        override fun read(name: String) = records[name]
+
+        override fun write(
+            name: String,
+            bytes: ByteArray,
+        ) {
+            records[name] = bytes
+        }
+
+        override fun delete(name: String) {
+            records.remove(name)
+        }
+
+        override fun names() = records.keys.toList()
+    }
+
+    private fun key(): SecretKey = KeyGenerator.getInstance("AES").apply { init(256) }.generateKey()
+
+    private fun entry(
+        to: Long,
+        text: String,
+    ) = JSONObject().put("to", to).put("text", text).put("at", 1L)
+
+    private fun texts(array: JSONArray): List<String> =
+        (0 until array.length()).mapNotNull { array.optJSONObject(it)?.optString("text") }
+
+    @Test
+    fun `a send queued in an off the record thread is not written`() {
+        val storage = MapStorage()
+        val k = key()
+        Vault(storage, k).apply {
+            saveOffTheRecord(Vault.threadForUser(7L), true)
+            saveOutbox(JSONArray().put(entry(7L, "meet me at six")).put(entry(8L, "ordinary")))
+        }
+
+        val restored = texts(Vault(storage, k).outbox())
+        assertFalse("meet me at six" in restored, "the off-the-record message text was written to the vault")
+        assertTrue("ordinary" in restored)
+        assertEquals(1, restored.size)
+    }
+
+    @Test
+    fun `nothing is dropped when no thread is off the record`() {
+        val storage = MapStorage()
+        val k = key()
+        Vault(storage, k).saveOutbox(JSONArray().put(entry(7L, "one")).put(entry(8L, "two")))
+        assertEquals(listOf("one", "two"), texts(Vault(storage, k).outbox()))
+    }
+
+    /**
+     * A group entry names the group thread and carries the member it is going
+     * to, and a group has no off-the-record setting of its own.
+     */
+    @Test
+    fun `a group entry passes through`() {
+        val storage = MapStorage()
+        val k = key()
+        Vault(storage, k).saveOutbox(
+            JSONArray().put(entry(8L, "to the group").put("thread", "group:g-1")),
+        )
+        assertEquals(listOf("to the group"), texts(Vault(storage, k).outbox()))
+    }
+
+    /**
+     * Turning it on does not reach back into what was already written, but the
+     * next save must drop it: the queue is rewritten whole every time.
+     */
+    @Test
+    fun `the next save after turning it on clears the queue`() {
+        val storage = MapStorage()
+        val k = key()
+        val v = Vault(storage, k)
+        v.saveOutbox(JSONArray().put(entry(7L, "still here")))
+        assertEquals(listOf("still here"), texts(Vault(storage, k).outbox()))
+
+        v.saveOffTheRecord(Vault.threadForUser(7L), true)
+        v.saveOutbox(v.outbox())
+        assertTrue(texts(Vault(storage, k).outbox()).isEmpty())
+    }
+}