Add debug and testing apis to Spinner.

lib/spinner/src/main/java/org/signal/spinner/PluginResult.kt

@@ -28,6 +28,48 @@ sealed class PluginResult(val type: String) {
     val json: String
   ) : PluginResult("json")
 
+  class TsvResult(
+    private val columns: List<String>,
+    private val rows: Iterator<List<String?>>
+  ) : PluginResult("tsv") {
+    fun toInputStream(): InputStream = object : InputStream() {
+      private var buffer: ByteArray = columns.joinToString("\t").toByteArray()
+      private var pos: Int = 0
+      private var done: Boolean = false
+
+      override fun read(): Int {
+        if (!fill()) return -1
+        return buffer[pos++].toInt() and 0xFF
+      }
+
+      override fun read(b: ByteArray, off: Int, len: Int): Int {
+        if (!fill()) return -1
+        val toRead = minOf(buffer.size - pos, len)
+        System.arraycopy(buffer, pos, b, off, toRead)
+        pos += toRead
+        return toRead
+      }
+
+      override fun close() {
+        (rows as? AutoCloseable)?.close()
+      }
+
+      private fun fill(): Boolean {
+        while (pos >= buffer.size) {
+          if (done) return false
+          if (rows.hasNext()) {
+            buffer = ("\n" + rows.next().joinToString("\t") { it ?: "" }).toByteArray()
+            pos = 0
+          } else {
+            done = true
+            return false
+          }
+        }
+        return true
+      }
+    }
+  }
+
   data class ErrorResult(
     val status: Response.Status = Response.Status.INTERNAL_ERROR,
     val message: String

lib/spinner/src/main/java/org/signal/spinner/SpinnerServer.kt

@@ -286,6 +286,9 @@ internal class SpinnerServer(
       is PluginResult.JsonResult -> {
         return newFixedLengthResponse(Response.Status.OK, "application/json", pluginResult.json)
       }
+      is PluginResult.TsvResult -> {
+        return newChunkedResponse(Response.Status.OK, "text/tab-separated-values", pluginResult.toInputStream())
+      }
       is PluginResult.RawFileResult -> {
         return newFixedLengthResponse(Response.Status.OK, pluginResult.mimeType, pluginResult.data, pluginResult.length)
       }