Uri: add resolveLinkUri with tests

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

@@ -1,14 +1,46 @@
 package dev.lowrespalmtree.comet
 
+import dev.lowrespalmtree.comet.utils.*
 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).
- */
+/** Test utils.Uri functions. Runs of the device due to the Uri functions being Android-only .*/
 class UriUtilsTest {
+    @Test
+    fun resolveLinkUri() {
+        // Absolute URLs.
+        assertEquals(
+            "gemini://example.com/",
+            resolveLinkUri("gemini://example.com", "gemini://dece.space/").toString()
+        )
+        // Relative links.
+        assertEquals(
+            "gemini://example.com/",
+            resolveLinkUri(".", "gemini://example.com/").toString()
+        )
+        assertEquals(
+            "gemini://example.com/",
+            resolveLinkUri("..", "gemini://example.com/").toString()
+        )
+        assertEquals(
+            "gemini://example.com/page",
+            resolveLinkUri("./page", "gemini://example.com/").toString()
+        )
+        assertEquals(
+            "gemini://example.com/page",
+            resolveLinkUri("page", "gemini://example.com/").toString()
+        )
+        assertEquals(
+            "gemini://example.com/page.com",
+            resolveLinkUri("page.com", "gemini://example.com/").toString()
+        )
+        // Scheme-less URLs.
+        assertEquals(
+            "gemini://someone.smol.pub/somepage",
+            resolveLinkUri("//someone.smol.pub/somepage", "gemini://smol.pub/feed").toString()
+        )
+    }
+
     @Test
     fun joinUrls() {
         assertEquals(

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

@@ -20,6 +20,7 @@ import androidx.recyclerview.widget.LinearLayoutManager
 import dev.lowrespalmtree.comet.databinding.FragmentPageViewBinding
 import dev.lowrespalmtree.comet.utils.isConnectedToNetwork
 import dev.lowrespalmtree.comet.utils.joinUrls
+import dev.lowrespalmtree.comet.utils.resolveLinkUri
 import dev.lowrespalmtree.comet.utils.toGeminiUri
 import kotlinx.coroutines.ExperimentalCoroutinesApi
 
@@ -107,13 +108,7 @@ class PageFragment : Fragment(), PageAdapter.Listener {
             return
         }
 
-        var uri = Uri.parse(url)
-        if (!uri.isAbsolute) {
-            uri = if (!base.isNullOrEmpty()) joinUrls(base, url) else toGeminiUri(uri)
-        } else if (uri.scheme == "gemini" && uri.path.isNullOrEmpty()) {
-            uri = uri.buildUpon().path("/").build()
-        }
-
+        val uri = resolveLinkUri(url, base)
         when (uri.scheme) {
             "gemini" -> vm.sendGeminiRequest(uri, requireContext())
             else -> openUnknownScheme(uri)

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

@@ -9,6 +9,7 @@ import androidx.lifecycle.ViewModel
 import androidx.lifecycle.viewModelScope
 import androidx.preference.PreferenceManager
 import dev.lowrespalmtree.comet.utils.joinUrls
+import dev.lowrespalmtree.comet.utils.resolveLinkUri
 import kotlinx.coroutines.*
 import kotlinx.coroutines.channels.onSuccess
 import java.net.ConnectException
@@ -163,9 +164,7 @@ class PageViewModel(@Suppress("unused") private val savedStateHandle: SavedState
                 lineChannelResult.onSuccess { line ->
                     if (line is LinkLine) {
                         // Mark visited links here as we have a access to the history.
-                        val fullUrl =
-                            if (Uri.parse(line.url).isAbsolute) line.url
-                            else joinUrls(uriString, line.url).toString()
+                        val fullUrl = resolveLinkUri(line.url, uriString).toString()
                         if (History.contains(fullUrl))
                             line.visited = true
                     }

app/src/main/java/dev/lowrespalmtree/comet/utils/Uri.kt

@@ -2,6 +2,26 @@ package dev.lowrespalmtree.comet.utils
 
 import android.net.Uri
 
+/**
+ * Resolve the URI of a link found on a page.
+ *
+ * Links can take various forms: absolute links to a page on a capsule, relative links on the same
+ * capsule, but also fancy scheme-less absolute URLs (i.e. starting with "//") for cross-protocol
+ * linking. This function returns the resolved URI from any type of link, opt. using current URL.
+ */
+fun resolveLinkUri(url: String, base: String?): Uri {
+    var uri = Uri.parse(url)
+    if (!uri.isAbsolute) {
+        uri =
+            if (url.startsWith("//")) uri.buildUpon().scheme("gemini").build()
+            else if (!base.isNullOrEmpty()) joinUrls(base, url)
+            else toGeminiUri(uri)
+    } else if (uri.scheme == "gemini" && uri.path.isNullOrEmpty()) {
+        uri = uri.buildUpon().path("/").build()
+    }
+    return uri
+}
+
 /**
  * Transform a relative URI to an absolute Gemini URI
  *