add provider for data directory

app/src/main/AndroidManifest.xml

@@ -55,6 +55,16 @@
                 <category android:name="android.intent.category.LAUNCHER" />
             </intent-filter>
         </activity>
+        <provider
+            android:authorities="com.geode.launcher.user"
+            android:name=".UserDirectoryProvider"
+            android:grantUriPermissions="true"
+            android:exported="true"
+            android:permission="android.permission.MANAGE_DOCUMENTS">
+            <intent-filter>
+                <action android:name="android.content.action.DOCUMENTS_PROVIDER" />
+            </intent-filter>
+        </provider>
     </application>
 
 </manifest>

app/src/main/java/com/geode/launcher/UserDirectoryProvider.kt

@@ -0,0 +1,116 @@
+package com.geode.launcher
+
+import android.database.Cursor
+import android.database.MatrixCursor
+import android.os.CancellationSignal
+import android.os.ParcelFileDescriptor
+import android.provider.DocumentsContract
+import android.provider.DocumentsProvider
+import android.webkit.MimeTypeMap
+import java.io.File
+
+private const val ROOT = "root"
+
+private val DEFAULT_ROOT_PROJECTION: Array<String> = arrayOf(
+    DocumentsContract.Root.COLUMN_ROOT_ID,
+    DocumentsContract.Root.COLUMN_FLAGS,
+    DocumentsContract.Root.COLUMN_ICON,
+    DocumentsContract.Root.COLUMN_TITLE,
+    DocumentsContract.Root.COLUMN_DOCUMENT_ID,
+)
+
+private val DEFAULT_DOCUMENT_PROJECTION: Array<String> = arrayOf(
+    DocumentsContract.Document.COLUMN_DOCUMENT_ID,
+    DocumentsContract.Document.COLUMN_MIME_TYPE,
+    DocumentsContract.Document.COLUMN_DISPLAY_NAME,
+    DocumentsContract.Document.COLUMN_LAST_MODIFIED,
+    DocumentsContract.Document.COLUMN_FLAGS,
+    DocumentsContract.Document.COLUMN_SIZE
+)
+
+class UserDirectoryProvider : DocumentsProvider() {
+    private lateinit var rootDir: File
+
+    override fun onCreate(): Boolean {
+        val context = context ?: return false
+        rootDir = context.filesDir
+
+        return true
+    }
+
+    override fun queryRoots(projection: Array<out String>?): Cursor {
+        val result = MatrixCursor(projection ?: DEFAULT_ROOT_PROJECTION)
+
+        // assert context is nonnull
+        val context = context ?: return result
+
+        result.newRow().apply {
+            add(DocumentsContract.Root.COLUMN_ROOT_ID, ROOT)
+            add(DocumentsContract.Root.COLUMN_DOCUMENT_ID, ROOT)
+            add(
+                DocumentsContract.Root.COLUMN_FLAGS,
+                DocumentsContract.Root.FLAG_SUPPORTS_CREATE or
+                        DocumentsContract.Root.FLAG_SUPPORTS_RECENTS or
+                        DocumentsContract.Root.FLAG_SUPPORTS_SEARCH
+            )
+            add(DocumentsContract.Root.COLUMN_TITLE, context.getString(R.string.app_name))
+            add(DocumentsContract.Root.COLUMN_ICON, R.drawable.geode_logo)
+        }
+
+        return result
+    }
+
+    override fun queryDocument(documentId: String?, projection: Array<out String>?): Cursor {
+        return MatrixCursor(projection ?: DEFAULT_DOCUMENT_PROJECTION).apply {
+            val file = getFileForDocumentId(documentId ?: ROOT)
+            addDocument(this, file)
+        }
+    }
+
+    override fun queryChildDocuments(
+        parentDocumentId: String?,
+        projection: Array<out String>?,
+        sortOrder: String?
+    ): Cursor {
+        return MatrixCursor(projection ?: DEFAULT_DOCUMENT_PROJECTION).apply {
+            val parent = getFileForDocumentId(parentDocumentId ?: ROOT)
+            parent.listFiles()?.forEach { file -> addDocument(this, file) }
+        }
+    }
+
+    override fun openDocument(
+        documentId: String?,
+        mode: String?,
+        signal: CancellationSignal?
+    ): ParcelFileDescriptor {
+        val file = getFileForDocumentId(documentId ?: ROOT)
+        return ParcelFileDescriptor.open(file, ParcelFileDescriptor.parseMode(mode))
+    }
+
+    private fun addDocument(cursor: MatrixCursor, file: File) {
+        cursor.newRow().apply {
+            add(DocumentsContract.Document.COLUMN_DOCUMENT_ID, getDocumentIdForFile(file))
+            add(DocumentsContract.Document.COLUMN_MIME_TYPE, typeForFile(file))
+            add(DocumentsContract.Document.COLUMN_DISPLAY_NAME, file.name)
+            add(DocumentsContract.Document.COLUMN_LAST_MODIFIED, file.lastModified())
+            add(DocumentsContract.Document.COLUMN_SIZE, file.length())
+        }
+    }
+
+    private fun typeForFile(file: File): String {
+        if (file.isDirectory) {
+            return DocumentsContract.Document.MIME_TYPE_DIR
+        }
+
+        return MimeTypeMap.getSingleton()
+            .getMimeTypeFromExtension(file.extension) ?: "application/octet-stream"
+    }
+
+    private fun getFileForDocumentId(documentId: String): File {
+        return File(rootDir, documentId.removePrefix(ROOT))
+    }
+
+    private fun getDocumentIdForFile(file: File): String {
+        return ROOT + file.toRelativeString(rootDir)
+    }
+}