parse response headers

ARCHITECTURE.md

@@ -0,0 +1,26 @@
+Architecture
+============
+
+
+
+Streaming
+---------
+
+Just because I'm frustrated by how hard it is to implement streaming on Bebop
+the way I've built it so far, properly streaming responses is a core focus of
+Comet, even though I barely encounter streamed pages on Gemini.
+
+This is the streaming process I want to do, not sure if it makes sense.
+
+- `connect/proceed` block and read from the server.
+- Gemtext parts
+- Views are created from Gemtext parts (or a single TextView for text/* files).
+    We need some kind of producer/consumer here.
+- The page view is a vertical LinearLayout (should we use a cursed Recycler?).
+    New views should be passed to the activity and added at the end of the
+    layout (does it work without blinking or other issues?).
+
+The data is received through a buffered SSLSocket object.
+
+1. Receive data
+2. If we can parse a header, do it.

app/src/main/java/dev/lowrespalmtree/comet/MainActivity.kt

@@ -66,18 +66,33 @@ class MainActivity : AppCompatActivity() {
             viewModelScope.launch(Dispatchers.IO) {
                 val uri = Uri.parse(url)
                 if (uri.scheme != "gemini") {
-                    alertLiveData.postValue("Unknown scheme.")
+                    alertLiveData.postValue("Can't process scheme \"${uri.scheme}\".")
                     return@launch
                 }
+
                 val request = Request(uri)
                 val socket = request.connect()
                 val channel = request.proceed(socket, this)
-                val charset = Charset.defaultCharset()
-                for (data in channel) {
-                    val decoded = charset.decode(ByteBuffer.wrap(data)).toString()
-                    source += decoded
-                    sourceLiveData.postValue(source)
+                val response = Response.from(channel, viewModelScope)
+                if (response == null) {
+                    alertLiveData.postValue("Can't parse server response.")
+                    return@launch
                 }
+
+                Log.i(TAG, "sendRequest: got ${response.code} with meta \"${response.meta}\"")
+                when (response.code) {
+                    Response.Code.SUCCESS -> handleRequestSuccess(response)
+                    else -> alertLiveData.postValue("Can't handle code ${response.code}.")
+                }
+            }
+        }
+
+        private suspend fun handleRequestSuccess(response: Response) {
+            val charset = Charset.defaultCharset()
+            for (data in response.data) {
+                val decoded = charset.decode(ByteBuffer.wrap(data)).toString()
+                source += decoded
+                sourceLiveData.postValue(source)
             }
         }
     }

app/src/main/java/dev/lowrespalmtree/comet/Request.kt

@@ -37,6 +37,7 @@ class Request(private val uri: Uri) {
             socket.inputStream.use { socket_input_stream ->
                 BufferedInputStream(socket_input_stream).use { bis ->
                     try {
+                        @Suppress("BlockingMethodInNonBlockingContext")  // what u gonna do
                         while ((bis.read(buffer).also { numRead = it }) >= 0) {
                             Log.d(TAG, "proceed coroutine: received $numRead bytes")
                             val received = buffer.sliceArray(0 until numRead)

app/src/main/java/dev/lowrespalmtree/comet/Response.kt

@@ -0,0 +1,91 @@
+package dev.lowrespalmtree.comet
+
+import android.util.Log
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.channels.Channel
+import kotlinx.coroutines.channels.consumeEach
+import kotlinx.coroutines.launch
+import java.nio.ByteBuffer
+import java.nio.charset.Charset
+
+class Response(val code: Code, val meta: String, val data: Channel<ByteArray>) {
+    @Suppress("unused")
+    enum class Code(val value: Int) {
+        UNKNOWN(0),
+        INPUT(10),
+        SENSITIVE_INPUT(11),
+        SUCCESS(20),
+        REDIRECT_TEMPORARY(30),
+        REDIRECT_PERMANENT(31),
+        TEMPORARY_FAILURE(40),
+        SERVER_UNAVAILABLE(41),
+        CGI_ERROR(42),
+        PROXY_ERROR(43),
+        SLOW_DOWN(44),
+        PERMANENT_FAILURE(50),
+        NOT_FOUND(51),
+        GONE(52),
+        PROXY_REQUEST_REFUSED(53),
+        BAD_REQUEST(59),
+        CLIENT_CERTIFICATE_REQUIRED(60),
+        CERTIFICATE_NOT_AUTHORISED(61),
+        CERTIFICATE_NOT_VALID(62);
+
+        companion object {
+            private val MAP = values().associateBy(Code::value)
+            fun fromInt(type: Int) = MAP[type]
+        }
+    }
+
+    companion object {
+        private const val TAG = "Response"
+
+        /** Return a response object from the incoming server data, served through the channel. */
+        suspend fun from(channel: Channel<ByteArray>, scope: CoroutineScope): Response? {
+            var received = 0
+            val headerBuffer = ByteBuffer.allocate(1024)
+            for (data in channel) {
+                // Push some data into our buffer.
+                headerBuffer.put(data)
+                received += data.size
+                // Check if there is enough data to parse a Gemini header from it (e.g. has \r\n).
+                val lfIndex = headerBuffer.array().indexOf(0x0D)  // \r
+                if (lfIndex == -1)
+                    continue
+                if (headerBuffer.array()[lfIndex + 1] != (0x0A.toByte()))  // \n
+                    continue
+                // We have our header! Parse it to create our Response object.
+                val bytes = headerBuffer.array()
+                val headerData = bytes.sliceArray(0 until lfIndex)
+                val (code, meta) = parseHeader(headerData)
+                    ?: return null.also { Log.e(TAG, "Failed to parse header") }
+                val responseChannel = Channel<ByteArray>()
+                val response = Response(code, meta, responseChannel)
+                scope.launch {
+                    // If we got too much data from the channel: push the trailing data first.
+                    val trailingIndex = lfIndex + 2
+                    if (trailingIndex < received) {
+                        val trailingData = bytes.sliceArray(trailingIndex until received)
+                        responseChannel.send(trailingData)
+                    }
+                    // Forward all incoming data to the Response channel.
+                    channel.consumeEach { responseChannel.send(it) }
+                }
+                // Return the response here; this stops consuming the channel from this for-loop so
+                // that the coroutine above can take care of it.
+                return response
+            }
+            return null
+        }
+
+        /** Return the code and meta from this header if it could be parsed correctly. */
+        private fun parseHeader(data: ByteArray): Pair<Code, String>? {
+            val string = data.toString(Charset.defaultCharset())
+            val parts = string.split(" ", limit = 2)
+            if (parts.size != 2)
+                return null
+            val code = parts[0].toIntOrNull()?.let { Code.fromInt(it) } ?: return null
+            return Pair(code, parts[1])
+        }
+    }
+}

app/src/main/res/values/strings.xml

@@ -1,6 +1,6 @@
 <resources>
     <string name="app_name">Comet</string>
-    <string name="alert_title"></string>
+    <string name="alert_title">Alert</string>
     <string name="action_settings">Settings</string>
     <string name="url">URL</string>
 </resources>