UriUtils: add a bunch of URI utilities

So we can now click on relative links, wow! Fast progress!

app/build.gradle

@@ -18,6 +18,9 @@ android {
     buildFeatures {
         viewBinding true
     }
+    testOptions {
+        unitTests.returnDefaultValues = true
+    }
     buildTypes {
         release {
             minifyEnabled false

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/MainActivity.kt

@@ -61,6 +61,12 @@ class MainActivity : AppCompatActivity(), ContentAdapter.ContentAdapterListen {
 
     private fun openUrl(url: String, base: String? = null) {
         var uri = Uri.parse(url)
+        if (!uri.isAbsolute) {
+            uri = if (!base.isNullOrEmpty()) joinUrls(base, url) else toGeminiUri(uri)
+            Log.d(TAG, "openUrl: '$url' - '$base' - '$uri'")
+            Log.d(TAG, "openUrl: ${uri.authority} - ${uri.path} - ${uri.query}")
+            binding.addressBar.setText(uri.toString())
+        }
 
         when (uri.scheme) {
             "gemini" -> pageViewModel.sendGeminiRequest(uri)

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/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)
-    }
-}