MainActivity: proper alerts for each error type

Also moved the PageViewModel into its own file? What's the norm?

app/build.gradle

@@ -1,6 +1,7 @@
 plugins {
     id 'com.android.application'
     id 'kotlin-android'
+    id 'kotlin-kapt'
 }
 
 android {
@@ -18,10 +19,14 @@ android {
     buildFeatures {
         viewBinding true
     }
+    testOptions {
+        unitTests.returnDefaultValues = true
+    }
     buildTypes {
         release {
             minifyEnabled false
             proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
+            signingConfig signingConfigs.debug
         }
     }
     compileOptions {
@@ -36,9 +41,12 @@ android {
 dependencies {
     implementation 'androidx.core:core-ktx:1.7.0'
     implementation 'androidx.appcompat:appcompat:1.4.0'
-    implementation 'com.google.android.material:material:1.4.0'
     implementation 'androidx.constraintlayout:constraintlayout:2.1.2'
     implementation "androidx.lifecycle:lifecycle-viewmodel-ktx:2.4.0"
+    implementation 'androidx.legacy:legacy-support-v4:1.0.0'
+    implementation "androidx.room:room-runtime:2.3.0"
+    implementation 'com.google.android.material:material:1.4.0'
+    kapt "androidx.room:room-compiler:2.3.0"
     testImplementation 'junit:junit:4.13.2'
     androidTestImplementation 'androidx.test.ext:junit:1.1.3'
     androidTestImplementation 'androidx.test.espresso:espresso-core:3.4.0'

app/src/androidTest/java/dev/lowrespalmtree/comet/ExampleInstrumentedTest.kt

@@ -1,24 +0,0 @@
-package dev.lowrespalmtree.comet
-
-import androidx.test.platform.app.InstrumentationRegistry
-import androidx.test.ext.junit.runners.AndroidJUnit4
-
-import org.junit.Test
-import org.junit.runner.RunWith
-
-import org.junit.Assert.*
-
-/**
- * Instrumented test, which will execute on an Android device.
- *
- * See [testing documentation](http://d.android.com/tools/testing).
- */
-@RunWith(AndroidJUnit4::class)
-class ExampleInstrumentedTest {
-    @Test
-    fun useAppContext() {
-        // Context of the app under test.
-        val appContext = InstrumentationRegistry.getInstrumentation().targetContext
-        assertEquals("dev.lowrespalmtree.comet", appContext.packageName)
-    }
-}

app/src/androidTest/java/dev/lowrespalmtree/comet/UriUtilsTest.kt

@@ -0,0 +1,76 @@
+package dev.lowrespalmtree.comet
+
+import org.junit.Assert.assertEquals
+import org.junit.Test
+
+/**
+ * Example local unit test, which will execute on the development machine (host).
+ *
+ * See [testing documentation](http://d.android.com/tools/testing).
+ */
+class UriUtilsTest {
+    @Test
+    fun joinUrls() {
+        assertEquals(
+            "gemini://dece.space/some-file.gmi",
+            joinUrls("gemini://dece.space/", "some-file.gmi").toString()
+        )
+        assertEquals(
+            "gemini://dece.space/some-file.gmi",
+            joinUrls("gemini://dece.space/", "./some-file.gmi").toString()
+        )
+        assertEquals(
+            "gemini://dece.space/some-file.gmi",
+            joinUrls("gemini://dece.space/dir1", "/some-file.gmi").toString()
+        )
+        assertEquals(
+            "gemini://dece.space/dir1/other-file.gmi",
+            joinUrls("gemini://dece.space/dir1/file.gmi", "other-file.gmi").toString()
+        )
+        assertEquals(
+            "gemini://dece.space/top-level.gmi",
+            joinUrls("gemini://dece.space/dir1/file.gmi", "../top-level.gmi").toString()
+        )
+        assertEquals(
+            "s://hard/test/b/d/a.gmi",
+            joinUrls("s://hard/dir/a", "./../test/b/c/../d/e/f/../.././a.gmi").toString()
+        )
+    }
+
+    @Test
+    fun removeDotSegments() {
+        arrayOf(
+            Pair("index.gmi", "index.gmi"),
+            Pair("/index.gmi", "/index.gmi"),
+            Pair("./index.gmi", "index.gmi"),
+            Pair("/./index.gmi", "/index.gmi"),
+            Pair("/../index.gmi", "/index.gmi"),
+            Pair("/a/b/c/./../../g", "/a/g"),
+            Pair("mid/content=5/../6", "mid/6"),
+            Pair("../../../../g", "g")
+        ).forEach { (path, expected) ->
+            assertEquals(expected, removeDotSegments(path))
+        }
+    }
+
+    @Test
+    fun removeLastSegment() {
+        assertEquals("", removeLastSegment(""))
+        assertEquals("", removeLastSegment("/"))
+        assertEquals("", removeLastSegment("/a"))
+        assertEquals("/a", removeLastSegment("/a/"))
+        assertEquals("/a", removeLastSegment("/a/b"))
+        assertEquals("/a/b/c", removeLastSegment("/a/b/c/d"))
+        assertEquals("//", removeLastSegment("///"))
+    }
+
+    @Test
+    fun popFirstSegment() {
+        assertEquals(Pair("", ""), popFirstSegment(""))
+        assertEquals(Pair("a", ""), popFirstSegment("a"))
+        assertEquals(Pair("/a", ""), popFirstSegment("/a"))
+        assertEquals(Pair("/a", "/"), popFirstSegment("/a/"))
+        assertEquals(Pair("/a", "/b"), popFirstSegment("/a/b"))
+        assertEquals(Pair("a", "/b"), popFirstSegment("a/b"))
+    }
+}

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

@@ -0,0 +1,136 @@
+package dev.lowrespalmtree.comet
+
+import android.annotation.SuppressLint
+import android.text.SpannableString
+import android.text.style.UnderlineSpan
+import android.util.Log
+import android.view.LayoutInflater
+import android.view.View
+import android.view.ViewGroup
+import androidx.recyclerview.widget.RecyclerView
+import dev.lowrespalmtree.comet.databinding.*
+
+class ContentAdapter(private var content: List<Line>, private val listener: ContentAdapterListen) :
+    RecyclerView.Adapter<ContentAdapter.ContentViewHolder>() {
+
+    private var lastLineCount = 0
+
+    interface ContentAdapterListen {
+        fun onLinkClick(url: String)
+    }
+
+    override fun getItemViewType(position: Int): Int =
+        when (content[position]) {
+            is EmptyLine -> TYPE_EMPTY
+            is ParagraphLine -> TYPE_PARAGRAPH
+            is LinkLine -> TYPE_LINK
+            is PreFenceLine -> TYPE_PRE_FENCE
+            is PreTextLine -> TYPE_PRE_TEXT
+            is BlockquoteLine -> TYPE_BLOCKQUOTE
+            is ListItemLine -> TYPE_LIST_ITEM
+            is TitleLine -> when ((content[position] as TitleLine).level) {
+                1 -> TYPE_TITLE_1
+                2 -> TYPE_TITLE_2
+                3 -> TYPE_TITLE_3
+                else -> error("invalid title level")
+            }
+            else -> error("unknown line type")
+        }
+
+    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ContentViewHolder {
+        return LayoutInflater.from(parent.context).let {
+            when (viewType) {
+                TYPE_EMPTY -> ContentViewHolder.Empty(GemtextEmptyBinding.inflate(it))
+                TYPE_PARAGRAPH -> ContentViewHolder.Paragraph(GemtextParagraphBinding.inflate(it))
+                TYPE_TITLE_1 -> ContentViewHolder.Title1(GemtextTitle1Binding.inflate(it))
+                TYPE_TITLE_2 -> ContentViewHolder.Title2(GemtextTitle2Binding.inflate(it))
+                TYPE_TITLE_3 -> ContentViewHolder.Title3(GemtextTitle3Binding.inflate(it))
+                TYPE_LINK -> ContentViewHolder.Link(GemtextLinkBinding.inflate(it))
+                TYPE_PRE_FENCE -> ContentViewHolder.PreFence(GemtextEmptyBinding.inflate(it))
+                TYPE_PRE_TEXT -> ContentViewHolder.PreText(GemtextPreformattedBinding.inflate(it))
+                TYPE_BLOCKQUOTE -> ContentViewHolder.Blockquote(GemtextBlockquoteBinding.inflate(it))
+                TYPE_LIST_ITEM -> ContentViewHolder.ListItem(GemtextListItemBinding.inflate(it))
+                else -> error("invalid view type")
+            }
+        }
+    }
+
+    @SuppressLint("SetTextI18n")
+    override fun onBindViewHolder(holder: ContentViewHolder, position: Int) {
+        val line = content[position]
+        when (holder) {
+            is ContentViewHolder.Paragraph ->
+                holder.binding.textView.text = (line as ParagraphLine).text
+            is ContentViewHolder.Title1 -> holder.binding.textView.text = (line as TitleLine).text
+            is ContentViewHolder.Title2 -> holder.binding.textView.text = (line as TitleLine).text
+            is ContentViewHolder.Title3 -> holder.binding.textView.text = (line as TitleLine).text
+            is ContentViewHolder.Link -> {
+                val text = if ((line as LinkLine).label.isNotEmpty()) line.label else line.url
+                val underlined = SpannableString(text)
+                underlined.setSpan(UnderlineSpan(), 0, underlined.length, 0)
+                holder.binding.textView.text = underlined
+                holder.binding.root.setOnClickListener { listener.onLinkClick(line.url) }
+            }
+            is ContentViewHolder.PreText ->
+                holder.binding.textView.text = (line as PreTextLine).text
+            is ContentViewHolder.Blockquote ->
+                holder.binding.textView.text = (line as BlockquoteLine).text
+            is ContentViewHolder.ListItem ->
+                holder.binding.textView.text = "\u25CF ${(line as ListItemLine).text}"
+            else -> {}
+        }
+    }
+
+    override fun getItemCount(): Int = content.size
+
+    /**
+     * Replace the content rendered by the recycler.
+     *
+     * The new content list may or may not be the same object as the previous one, we don't
+     * assume anything. The assumptions this function do however are:
+     * - If the new content is empty, we are about to load new content, so clear the recycler.
+     * - If it's longer than before, we received new streamed content, so *append* data.
+     * - If it's shorter or the same size than before, we do not notify anything and let the caller
+     *   manage the changes itself.
+     */
+    @SuppressLint("NotifyDataSetChanged")
+    fun setContent(newContent: List<Line>) {
+        content = newContent.toList()  // Shallow copy to avoid concurrent update issues.
+        if (content.isEmpty()) {
+            Log.d(TAG, "setContent: empty content")
+            notifyDataSetChanged()
+        } else if (content.size > lastLineCount) {
+            val numAdded = content.size - lastLineCount
+            Log.d(TAG, "setContent: added $numAdded items")
+            notifyItemRangeInserted(lastLineCount, numAdded)
+        }
+        lastLineCount = content.size
+    }
+
+    sealed class ContentViewHolder(view: View) : RecyclerView.ViewHolder(view) {
+        class Empty(val binding: GemtextEmptyBinding) : ContentViewHolder(binding.root)
+        class Paragraph(val binding: GemtextParagraphBinding) : ContentViewHolder(binding.root)
+        class Title1(val binding: GemtextTitle1Binding) : ContentViewHolder(binding.root)
+        class Title2(val binding: GemtextTitle2Binding) : ContentViewHolder(binding.root)
+        class Title3(val binding: GemtextTitle3Binding) : ContentViewHolder(binding.root)
+        class Link(val binding: GemtextLinkBinding) : ContentViewHolder(binding.root)
+        class PreFence(val binding: GemtextEmptyBinding) : ContentViewHolder(binding.root)
+        class PreText(val binding: GemtextPreformattedBinding) : ContentViewHolder(binding.root)
+        class Blockquote(val binding: GemtextBlockquoteBinding) : ContentViewHolder(binding.root)
+        class ListItem(val binding: GemtextListItemBinding) : ContentViewHolder(binding.root)
+    }
+
+    companion object {
+        const val TAG = "ContentRecycler"
+        const val TYPE_EMPTY = 0
+        const val TYPE_PARAGRAPH = 1
+        const val TYPE_TITLE_1 = 2
+        const val TYPE_TITLE_2 = 3
+        const val TYPE_TITLE_3 = 4
+        const val TYPE_LINK = 5
+        const val TYPE_PRE_FENCE = 6
+        const val TYPE_PRE_TEXT = 7
+        const val TYPE_BLOCKQUOTE = 8
+        const val TYPE_LIST_ITEM = 9
+    }
+}

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

@@ -0,0 +1,21 @@
+package dev.lowrespalmtree.comet
+
+import android.content.Context
+import androidx.room.Database
+import androidx.room.Room
+import androidx.room.RoomDatabase
+
+@Database(entities = [History.HistoryEntry::class], version = 1)
+abstract class AppDatabase : RoomDatabase() {
+    abstract fun historyEntryDao(): History.HistoryEntryDao
+}
+
+object Database {
+    lateinit var INSTANCE: AppDatabase
+
+    fun init(context: Context) {
+        if (::INSTANCE.isInitialized)
+            return
+        INSTANCE = Room.databaseBuilder(context, AppDatabase::class.java, "comet").build()
+    }
+}

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

@@ -0,0 +1,69 @@
+package dev.lowrespalmtree.comet
+
+import android.util.Log
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.channels.Channel
+import kotlinx.coroutines.launch
+import java.nio.ByteBuffer
+import java.nio.CharBuffer
+import java.nio.charset.Charset
+
+interface Line
+
+class EmptyLine : Line
+class ParagraphLine(val text: String) : Line
+class TitleLine(val level: Int, val text: String) : Line
+class LinkLine(val url: String, val label: String) : Line
+class PreFenceLine(val caption: String) : Line
+class PreTextLine(val text: String) : Line
+class BlockquoteLine(val text: String) : Line
+class ListItemLine(val text: String) : Line
+
+const val TAG = "Gemtext"
+
+fun parseData(
+    inChannel: Channel<ByteArray>,
+    charset: Charset,
+    scope: CoroutineScope
+): Channel<Line> {
+    val channel = Channel<Line>()
+    scope.launch {
+        var isPref = false
+        var buffer = ByteArray(0)
+        Log.d(TAG, "parseData: start getting data from channel")
+        for (data in inChannel) {
+            buffer += data
+            var nextLineFeed: Int = -1
+            while (buffer.isNotEmpty() && buffer.indexOf(0x0A).also { nextLineFeed = it } > -1) {
+                val lineData = buffer.sliceArray(0 until nextLineFeed)
+                buffer = buffer.sliceArray(nextLineFeed + 1 until buffer.size)
+                val lineString = charset.decode(ByteBuffer.wrap(lineData))
+                val line = parseLine(lineString, isPref)
+                when (line) {
+                    is PreFenceLine -> isPref = !isPref
+                }
+                channel.send(line)
+            }
+        }
+        Log.d(TAG, "parseData: channel closed")
+        channel.close()
+    }
+    return channel
+}
+
+private fun parseLine(line: CharBuffer, isPreformatted: Boolean): Line =
+    when {
+        line.isEmpty() -> EmptyLine()
+        line.startsWith("###") -> TitleLine(3, getCharsFrom(line, 3))
+        line.startsWith("##") -> TitleLine(2, getCharsFrom(line, 2))
+        line.startsWith("#") -> TitleLine(1, getCharsFrom(line, 1))
+        line.startsWith(">") -> BlockquoteLine(getCharsFrom(line, 1))
+        line.startsWith("```") -> PreFenceLine(getCharsFrom(line, 3))
+        line.startsWith("* ") -> ListItemLine(getCharsFrom(line, 2))
+        line.startsWith("=>") -> getCharsFrom(line, 2)
+            .split(" ", limit = 2)
+            .run { LinkLine(get(0), if (size == 2) get(1).trimStart() else "") }
+        else -> if (isPreformatted) PreTextLine(line.toString()) else ParagraphLine(line.toString())
+    }
+
+private fun getCharsFrom(line: CharBuffer, index: Int) = line.substring(index).trim()

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

@@ -0,0 +1,37 @@
+package dev.lowrespalmtree.comet
+
+import androidx.room.*
+
+object History {
+    @Entity
+    data class HistoryEntry(
+        @PrimaryKey @ColumnInfo(name = "uri") val uri: String,
+        @ColumnInfo(name = "title") var title: String?,
+        @ColumnInfo(name = "lastVisit") var lastVisit: Long,
+    )
+
+    @Dao
+    interface HistoryEntryDao {
+        @Query("SELECT * FROM HistoryEntry WHERE :uri = uri LIMIT 1")
+        fun get(uri: String): HistoryEntry?
+
+        @Query("SELECT * FROM HistoryEntry ORDER BY lastVisit DESC")
+        fun getAll(): List<HistoryEntry>
+
+        @Insert(onConflict = OnConflictStrategy.IGNORE)
+        fun insert(vararg entries: HistoryEntry)
+
+        @Update
+        fun update(vararg entries: HistoryEntry)
+    }
+
+    fun record(uri: String, title: String?) {
+        val now = System.currentTimeMillis()
+        val dao = Database.INSTANCE.historyEntryDao()
+        val entry = dao.get(uri)
+        if (entry == null)
+            dao.insert(HistoryEntry(uri, title, now))
+        else
+            dao.update(entry.also { it.title = title; it.lastVisit = now })
+    }
+}

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

@@ -1,7 +1,9 @@
 package dev.lowrespalmtree.comet
 
-import android.annotation.SuppressLint
 import android.app.Activity
+import android.content.ActivityNotFoundException
+import android.content.Intent
+import android.content.Intent.ACTION_VIEW
 import android.net.Uri
 import android.os.Bundle
 import android.util.Log
@@ -9,31 +11,41 @@ import android.view.inputmethod.EditorInfo
 import android.view.inputmethod.InputMethodManager
 import androidx.appcompat.app.AlertDialog
 import androidx.appcompat.app.AppCompatActivity
-import androidx.lifecycle.MutableLiveData
-import androidx.lifecycle.ViewModel
 import androidx.lifecycle.ViewModelProvider
-import androidx.lifecycle.viewModelScope
+import androidx.recyclerview.widget.LinearLayoutManager
 import dev.lowrespalmtree.comet.databinding.ActivityMainBinding
-import kotlinx.coroutines.Dispatchers
-import kotlinx.coroutines.launch
-import java.nio.ByteBuffer
-import java.nio.charset.Charset
+import kotlinx.coroutines.ExperimentalCoroutinesApi
 
-class MainActivity : AppCompatActivity() {
+@ExperimentalCoroutinesApi
+class MainActivity : AppCompatActivity(), ContentAdapter.ContentAdapterListen {
     private lateinit var binding: ActivityMainBinding
     private lateinit var pageViewModel: PageViewModel
+    private lateinit var adapter: ContentAdapter
+
+    /** Property to access and set the current address bar URL value. */
+    private var currentUrl
+        get() = binding.addressBar.text.toString()
+        set(value) = binding.addressBar.setText(value)
+
+    /** A non-saved list of visited URLs. Not an history, just used for going back. */
+    private val visitedUrls = mutableListOf<String>()
 
-    @SuppressLint("SetTextI18n")
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
+
+        Database.init(applicationContext)
+
         binding = ActivityMainBinding.inflate(layoutInflater)
         setContentView(binding.root)
 
         pageViewModel = ViewModelProvider(this)[PageViewModel::class.java]
+        adapter = ContentAdapter(listOf(), this)
+        binding.contentRecycler.layoutManager = LinearLayoutManager(this)
+        binding.contentRecycler.adapter = adapter
 
         binding.addressBar.setOnEditorActionListener { view, actionId, _ ->
             if (actionId == EditorInfo.IME_ACTION_DONE) {
-                pageViewModel.sendRequest(view.text.toString())
+                openUrl(view.text.toString())
                 val imm = getSystemService(Activity.INPUT_METHOD_SERVICE) as InputMethodManager
                 imm.hideSoftInputFromWindow(view.windowToken, 0)
                 view.clearFocus()
@@ -43,57 +55,99 @@ class MainActivity : AppCompatActivity() {
             }
         }
 
-        pageViewModel.sourceLiveData.observe(this, {
-            binding.sourceBlock.text = it
-        })
-        pageViewModel.alertLiveData.observe(this, {
-            AlertDialog.Builder(this)
-                .setTitle(R.string.alert_title)
-                .setMessage(it)
-                .create()
-                .show()
-        })
+        binding.contentSwipeLayout.setOnRefreshListener { openUrl(currentUrl) }
+
+        pageViewModel.state.observe(this, { updateState(it) })
+        pageViewModel.lines.observe(this, { updateLines(it) })
+        pageViewModel.event.observe(this, { handleEvent(it) })
     }
 
-    class PageViewModel : ViewModel() {
-        var source = ""
-        val sourceLiveData: MutableLiveData<String> by lazy { MutableLiveData<String>() }
-        val alertLiveData: MutableLiveData<String> by lazy { MutableLiveData<String>() }
+    override fun onBackPressed() {
+        visitedUrls.removeLastOrNull()  // Always remove current page first.
+        val previousUrl = visitedUrls.removeLastOrNull()
+        if (previousUrl != null)
+            openUrl(previousUrl)
+        else
+            super.onBackPressed()
+    }
 
-        fun sendRequest(url: String) {
-            Log.d(TAG, "sendRequest: $url")
-            source = ""
-            viewModelScope.launch(Dispatchers.IO) {
-                val uri = Uri.parse(url)
-                if (uri.scheme != "gemini") {
-                    alertLiveData.postValue("Can't process scheme \"${uri.scheme}\".")
-                    return@launch
-                }
+    override fun onLinkClick(url: String) {
+        openUrl(url, base = if (currentUrl.isNotEmpty()) currentUrl else null)
+    }
 
-                val request = Request(uri)
-                val socket = request.connect()
-                val channel = request.proceed(socket, this)
-                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 fun openUrl(url: String, base: String? = null, redirections: Int = 0) {
+        if (redirections >= 5) {
+            alert("Too many redirections.")
+            return
         }
 
-        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)
+        var uri = Uri.parse(url)
+        if (!uri.isAbsolute) {
+            uri = if (!base.isNullOrEmpty()) joinUrls(base, url) else toGeminiUri(uri)
+        }
+
+        when (uri.scheme) {
+            "gemini" -> pageViewModel.sendGeminiRequest(uri)
+            else -> openUnknownScheme(uri)
+        }
+    }
+
+    private fun updateState(state: PageViewModel.State) {
+        Log.d(TAG, "updateState: $state")
+        when (state) {
+            PageViewModel.State.IDLE -> {
+                binding.contentProgressBar.hide()
+                binding.contentSwipeLayout.isRefreshing = false
             }
+            PageViewModel.State.CONNECTING -> {
+                binding.contentProgressBar.show()
+            }
+            PageViewModel.State.RECEIVING -> {
+                binding.contentSwipeLayout.isRefreshing = false
+            }
+        }
+    }
+
+    private fun updateLines(lines: List<Line>) {
+        Log.d(TAG, "updateLines: ${lines.size} lines")
+        adapter.setContent(lines)
+    }
+
+    private fun handleEvent(event: PageViewModel.Event) {
+        Log.d(TAG, "handleEvent: $event")
+        if (!event.handled) {
+            when (event) {
+                is PageViewModel.SuccessEvent -> {
+                    currentUrl = event.uri
+                    visitedUrls.add(event.uri)
+                }
+                is PageViewModel.RedirectEvent -> {
+                    openUrl(event.uri, base = currentUrl, redirections = event.redirects)
+                }
+                is PageViewModel.FailureEvent -> {
+                    var message = event.details
+                    if (!event.serverDetails.isNullOrEmpty())
+                        message += "\n\n" + "Server details: ${event.serverDetails}"
+                    alert(message, title = event.short)
+                }
+            }
+            event.handled = true
+        }
+    }
+
+    private fun alert(message: String, title: String? = null) {
+        AlertDialog.Builder(this)
+            .setTitle(title ?: getString(R.string.error_alert_title))
+            .setMessage(message)
+            .create()
+            .show()
+    }
+
+    private fun openUnknownScheme(uri: Uri) {
+        try {
+            startActivity(Intent(ACTION_VIEW, uri))
+        } catch (e: ActivityNotFoundException) {
+            alert("Can't open this URL.")
         }
     }
 

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

@@ -7,6 +7,7 @@ import kotlinx.coroutines.CoroutineScope
 import kotlinx.coroutines.channels.Channel
 import kotlinx.coroutines.launch
 import java.io.BufferedInputStream
+import java.net.InetSocketAddress
 import java.net.SocketTimeoutException
 import java.security.cert.X509Certificate
 import javax.net.ssl.SSLContext
@@ -20,8 +21,9 @@ class Request(private val uri: Uri) {
         Log.d(TAG, "connect")
         val context = SSLContext.getInstance("TLSv1.2")
         context.init(null, arrayOf(TrustManager()), null)
-        val socket = context.socketFactory.createSocket(uri.host, port) as SSLSocket
+        val socket = context.socketFactory.createSocket() as SSLSocket
         socket.soTimeout = 10000
+        socket.connect(InetSocketAddress(uri.host, port), 10000)
         socket.startHandshake()
         return socket
     }
@@ -39,25 +41,25 @@ class Request(private val uri: Uri) {
                     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)
                             channel.send(received)
                         }
                     } catch (e: SocketTimeoutException) {
-                        Log.i(TAG, "Socket timeout.")
-                        channel.cancel()
+                        Log.i(TAG, "proceed coroutine: socket timeout.")
                     }
                 }
             }
             Log.d(TAG, "proceed coroutine: reading completed")
+            channel.close()
         }
         return channel
     }
 
     @SuppressLint("CustomX509TrustManager")
-    class TrustManager: X509TrustManager {
+    class TrustManager : X509TrustManager {
         @SuppressLint("TrustAllX509TrustManager")
-        override fun checkClientTrusted(chain: Array<out X509Certificate>?, authType: String?) {}
+        override fun checkClientTrusted(chain: Array<out X509Certificate>?, authType: String?) {
+        }
 
         override fun checkServerTrusted(chain: Array<out X509Certificate>?, authType: String?) {
             Log.d(TAG, "cool cert, please continue")

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

@@ -3,7 +3,7 @@ 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.channels.ClosedReceiveChannelException
 import kotlinx.coroutines.launch
 import java.nio.ByteBuffer
 import java.nio.charset.Charset
@@ -31,6 +31,18 @@ class Response(val code: Code, val meta: String, val data: Channel<ByteArray>) {
         CERTIFICATE_NOT_AUTHORISED(61),
         CERTIFICATE_NOT_VALID(62);
 
+        enum class Category(val value: Int) {
+            UNKNOWN(0),
+            INPUT(1),
+            SUCCESS(2),
+            REDIRECT(3),
+            SERVER_ERROR(4),
+            CLIENT_ERROR(5),
+            CERTIFICATE(6);
+        }
+
+        fun getCategory(): Category? = Category.values().associateBy(Category::value)[value / 10]
+
         companion object {
             private val MAP = values().associateBy(Code::value)
             fun fromInt(type: Int) = MAP[type]
@@ -39,43 +51,56 @@ class Response(val code: Code, val meta: String, val data: Channel<ByteArray>) {
 
     companion object {
         private const val TAG = "Response"
+        private const val MAX_META_LEN = 1024
+        private const val MAX_HEADER_LEN = 2 + 1 + MAX_META_LEN + 2
 
         /** 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) {
+            var lfIndex: Int
+            // While we don't have a response object (i.e. no header parsed), keep reading.
+            while (true) {
+                val data = try {
+                    channel.receive()
+                } catch (e: ClosedReceiveChannelException) {
+                    Log.i(TAG, "companion from: channel closed during initial receive")
+                    return null
+                }
+                if (received + data.size > MAX_HEADER_LEN) {
+                    Log.i(TAG, "companion from: received too much data for a valid header")
+                    return null
+                }
                 // 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
+                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
+                break
             }
-            return null
+            // 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.i(TAG, "companion from: can't parse header") }
+            val response = Response(code, meta, Channel())
+            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)
+                    response.data.send(trailingData)
+                }
+                // Forward all incoming data to the Response channel.
+                for (data in channel)
+                    response.data.send(data)
+                response.data.close()
+            }
+            return response
         }
 
         /** Return the code and meta from this header if it could be parsed correctly. */

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

@@ -0,0 +1,88 @@
+package dev.lowrespalmtree.comet
+
+import android.net.Uri
+import android.util.Log
+
+/**
+ * Transform a relative URI to an absolute Gemini URI
+ *
+ * This is mostly to translate user-friendly URLs such as "medusae.space" into
+ * "gemini://medusae.space". This assumes that the Uri parsing put what the user probably intended
+ * as the hostname into the path field instead of the authority. Thus, it will NOT merely translate
+ * any absolute URI into a gemini-scheme URI.
+ */
+fun toGeminiUri(uri: Uri): Uri =
+    Uri.Builder()
+        .scheme("gemini")
+        .authority(uri.path)
+        .query(uri.query)
+        .fragment(uri.fragment)
+        .build()
+
+/** Return the URI obtained from considering the relative part of an URI wrt/ a base URI. */
+fun joinUrls(base: String, relative: String): Uri {
+    val baseUri = Uri.parse(base)
+    val relUri = Uri.parse(relative)
+    val newPath = removeDotSegments(
+        if (relative.startsWith("/")) {
+            relUri.path ?: ""
+        } else {
+            removeLastSegment(
+                baseUri.path ?: ""
+            ) + "/" +
+                    (relUri.path ?: "")
+        }
+    )
+    return Uri.Builder()
+        .scheme(baseUri.scheme)
+        .authority(baseUri.authority)
+        .path(newPath)
+        .query(relUri.query)
+        .fragment(relUri.fragment)
+        .build()
+}
+
+/** Remove all the sneaky dot segments from the path. */
+internal fun removeDotSegments(path: String): String {
+    var output = ""
+    var slice = path
+    while (slice.isNotEmpty()) {
+        if (slice.startsWith("../")) {
+            slice = slice.substring(3)
+        } else if (slice.startsWith("./") || slice.startsWith("/./")) {
+            slice = slice.substring(2)
+        } else if (slice == "/.") {
+            slice = "/"
+        } else if (slice.startsWith("/../")) {
+            slice = "/" + slice.substring(4)
+            output = removeLastSegment(output)
+        } else if (slice == "/..") {
+            slice = "/"
+            output = removeLastSegment(output)
+        } else if (slice == "." || slice == "..") {
+            slice = ""
+        } else {
+            val (firstSegment, remaining) = popFirstSegment(slice)
+            output += firstSegment
+            slice = remaining
+        }
+    }
+    return output
+}
+
+/** Remove the last segment of that path, including preceding "/" if any. */
+internal fun removeLastSegment(path: String): String {
+    val lastSlashIndex = path.indexOfLast { it == '/' }
+    return if (lastSlashIndex > -1) path.slice(0 until lastSlashIndex) else path
+}
+
+/** Return first segment and the rest. */
+internal fun popFirstSegment(path: String): Pair<String, String> {
+    if (path.isEmpty())
+        return Pair(path, "")
+    var nextSlash = path.substring(1).indexOf("/")
+    if (nextSlash == -1)
+        return Pair(path, "")
+    nextSlash++
+    return Pair(path.substring(0, nextSlash), path.substring(nextSlash))
+}

app/src/main/res/layout/activity_main.xml

@@ -24,40 +24,48 @@
                 android:layout_width="match_parent"
                 android:layout_height="match_parent"
                 android:layout_margin="4dp"
-                android:ems="10"
                 android:hint="@string/url"
                 android:imeOptions="actionDone|actionGo"
                 android:importantForAutofill="no"
                 android:inputType="textUri"
-                android:text="" />
+                android:text=""
+                tools:ignore="TextContrastCheck" />
 
         </com.google.android.material.appbar.CollapsingToolbarLayout>
 
     </com.google.android.material.appbar.AppBarLayout>
 
-    <androidx.core.widget.NestedScrollView
-        android:id="@+id/scroll_view"
+    <androidx.swiperefreshlayout.widget.SwipeRefreshLayout
+        android:id="@+id/content_swipe_layout"
         android:layout_width="match_parent"
-        android:layout_height="match_parent"
-        app:layout_behavior="com.google.android.material.appbar.AppBarLayout$ScrollingViewBehavior">
+        android:layout_height="wrap_content"
+        app:layout_behavior="@string/appbar_scrolling_view_behavior">
 
-        <LinearLayout
+        <RelativeLayout
+            android:id="@+id/content_inner_layout"
             android:layout_width="match_parent"
             android:layout_height="match_parent"
-            android:orientation="vertical">
+            app:layout_behavior="@string/appbar_scrolling_view_behavior">
 
-            <TextView
-                android:id="@+id/source_block"
+            <androidx.recyclerview.widget.RecyclerView
+                android:id="@+id/content_recycler"
                 android:layout_width="match_parent"
                 android:layout_height="wrap_content"
-                android:layout_marginStart="16dp"
-                android:layout_marginEnd="16dp"
-                android:text=""
-                android:textAlignment="textStart"
-                app:layout_constraintEnd_toEndOf="parent"
-                app:layout_constraintStart_toStartOf="parent" />
+                android:orientation="vertical"
+                app:layout_constraintTop_toTopOf="parent" />
 
-        </LinearLayout>
-    </androidx.core.widget.NestedScrollView>
+            <androidx.core.widget.ContentLoadingProgressBar
+                android:id="@+id/content_progress_bar"
+                style="?android:attr/progressBarStyleHorizontal"
+                android:layout_width="match_parent"
+                android:layout_height="16dp"
+                android:layout_alignParentTop="true"
+                android:layout_marginTop="-8dp"
+                android:indeterminate="true"
+                android:visibility="gone" />
+
+        </RelativeLayout>
+
+    </androidx.swiperefreshlayout.widget.SwipeRefreshLayout>
 
 </androidx.coordinatorlayout.widget.CoordinatorLayout>

app/src/main/res/layout/gemtext_blockquote.xml

@@ -0,0 +1,12 @@
+<?xml version="1.0" encoding="utf-8"?>
+<TextView xmlns:android="http://schemas.android.com/apk/res/android"
+    android:id="@+id/text_view"
+    android:textSize="16sp"
+    android:textColor="@color/text"
+    android:textStyle="italic"
+    android:layout_width="match_parent"
+    android:layout_height="wrap_content"
+    android:paddingStart="32dp"
+    android:paddingEnd="16dp"
+    android:paddingTop="2dp"
+    android:paddingBottom="4dp" />

app/src/main/res/layout/gemtext_empty.xml

@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="utf-8"?>
+<TextView xmlns:android="http://schemas.android.com/apk/res/android"
+    android:layout_width="0dp"
+    android:layout_height="4dp" />

app/src/main/res/layout/gemtext_link.xml

@@ -0,0 +1,12 @@
+<?xml version="1.0" encoding="utf-8"?>
+<TextView xmlns:android="http://schemas.android.com/apk/res/android"
+    android:id="@+id/text_view"
+    android:textSize="16sp"
+    android:textColor="@color/teal_700"
+    android:layout_width="match_parent"
+    android:layout_height="wrap_content"
+    android:paddingStart="16dp"
+    android:paddingEnd="16dp"
+    android:paddingTop="2dp"
+    android:paddingBottom="4dp"
+    android:textIsSelectable="false" />

app/src/main/res/layout/gemtext_list_item.xml

@@ -0,0 +1,11 @@
+<?xml version="1.0" encoding="utf-8"?>
+<TextView xmlns:android="http://schemas.android.com/apk/res/android"
+    android:id="@+id/text_view"
+    android:textSize="16sp"
+    android:textColor="@color/text"
+    android:layout_width="match_parent"
+    android:layout_height="wrap_content"
+    android:paddingStart="32dp"
+    android:paddingEnd="16dp"
+    android:paddingTop="2dp"
+    android:paddingBottom="4dp" />

app/src/main/res/layout/gemtext_paragraph.xml

@@ -0,0 +1,11 @@
+<?xml version="1.0" encoding="utf-8"?>
+<TextView xmlns:android="http://schemas.android.com/apk/res/android"
+    android:id="@+id/text_view"
+    android:textSize="16sp"
+    android:textColor="@color/text"
+    android:layout_width="match_parent"
+    android:layout_height="wrap_content"
+    android:paddingStart="16dp"
+    android:paddingEnd="16dp"
+    android:paddingTop="2dp"
+    android:paddingBottom="4dp" />

app/src/main/res/layout/gemtext_preformatted.xml

@@ -0,0 +1,13 @@
+<?xml version="1.0" encoding="utf-8"?>
+<TextView xmlns:android="http://schemas.android.com/apk/res/android"
+    android:id="@+id/text_view"
+    android:textSize="14sp"
+    android:textColor="@color/text"
+    android:typeface="monospace"
+    android:layout_width="match_parent"
+    android:layout_height="wrap_content"
+    android:paddingStart="16dp"
+    android:paddingEnd="8dp"
+    android:paddingTop="2dp"
+    android:paddingBottom="2dp"
+    android:background="@color/purple_200" />

app/src/main/res/layout/gemtext_title1.xml

@@ -0,0 +1,12 @@
+<?xml version="1.0" encoding="utf-8"?>
+<TextView xmlns:android="http://schemas.android.com/apk/res/android"
+    android:id="@+id/text_view"
+    android:textSize="30sp"
+    android:textColor="@color/text"
+    android:textStyle="bold"
+    android:layout_width="match_parent"
+    android:layout_height="wrap_content"
+    android:paddingStart="16dp"
+    android:paddingEnd="16dp"
+    android:paddingTop="16dp"
+    android:paddingBottom="4dp" />

app/src/main/res/layout/gemtext_title2.xml

@@ -0,0 +1,12 @@
+<?xml version="1.0" encoding="utf-8"?>
+<TextView xmlns:android="http://schemas.android.com/apk/res/android"
+    android:id="@+id/text_view"
+    android:textSize="24sp"
+    android:textColor="@color/text"
+    android:textStyle="bold"
+    android:layout_width="match_parent"
+    android:layout_height="wrap_content"
+    android:paddingStart="16dp"
+    android:paddingEnd="16dp"
+    android:paddingTop="8dp"
+    android:paddingBottom="4dp" />

app/src/main/res/layout/gemtext_title3.xml

@@ -0,0 +1,12 @@
+<?xml version="1.0" encoding="utf-8"?>
+<TextView xmlns:android="http://schemas.android.com/apk/res/android"
+    android:id="@+id/text_view"
+    android:textSize="18sp"
+    android:textColor="@color/text"
+    android:textStyle="bold"
+    android:layout_width="match_parent"
+    android:layout_height="wrap_content"
+    android:paddingStart="16dp"
+    android:paddingEnd="16dp"
+    android:paddingTop="8dp"
+    android:paddingBottom="4dp" />

app/src/main/res/values-night/themes.xml

@@ -1,6 +1,6 @@
 <resources xmlns:tools="http://schemas.android.com/tools">
     <!-- Base application theme. -->
-    <style name="Theme.Comet" parent="Theme.MaterialComponents.DayNight.DarkActionBar">
+    <style name="Theme.Comet" parent="Theme.MaterialComponents.DayNight.NoActionBar">
         <!-- Primary brand color. -->
         <item name="colorPrimary">@color/purple_200</item>
         <item name="colorPrimaryVariant">@color/purple_700</item>

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

@@ -7,4 +7,5 @@
     <color name="teal_700">#FF018786</color>
     <color name="black">#FF000000</color>
     <color name="white">#FFFFFFFF</color>
+    <color name="text">#222222</color>
 </resources>

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

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

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

@@ -9,6 +9,8 @@
         <item name="colorSecondary">@color/teal_200</item>
         <item name="colorSecondaryVariant">@color/teal_700</item>
         <item name="colorOnSecondary">@color/black</item>
+        <!-- Status bar color. -->
+        <item name="android:statusBarColor" tools:targetApi="l">?attr/colorPrimaryVariant</item>
         <!-- Customize your theme here. -->
     </style>
 </resources>

app/src/test/java/dev/lowrespalmtree/comet/ExampleUnitTest.kt

@@ -1,17 +0,0 @@
-package dev.lowrespalmtree.comet
-
-import org.junit.Test
-
-import org.junit.Assert.*
-
-/**
- * Example local unit test, which will execute on the development machine (host).
- *
- * See [testing documentation](http://d.android.com/tools/testing).
- */
-class ExampleUnitTest {
-    @Test
-    fun addition_isCorrect() {
-        assertEquals(4, 2 + 2)
-    }
-}