feat: add SAF support

src/org/kde/kdeconnect/Plugins/SftpPlugin/saf/RootBasicFileAttributeView.kt

@@ -0,0 +1,25 @@
+/*
+ * SPDX-FileCopyrightText: 2024 ShellWen Chen <me@shellwen.com>
+ *
+ * SPDX-License-Identifier: GPL-2.0-only OR GPL-3.0-only OR LicenseRef-KDE-Accepted-GPL
+ */
+package org.kde.kdeconnect.Plugins.SftpPlugin.saf
+
+import java.io.IOException
+import java.nio.file.attribute.BasicFileAttributeView
+import java.nio.file.attribute.BasicFileAttributes
+import java.nio.file.attribute.FileTime
+
+object RootBasicFileAttributeView : BasicFileAttributeView {
+    override fun name(): String = "basic"
+
+    override fun readAttributes(): BasicFileAttributes = RootFileAttributes
+
+    override fun setTimes(
+        lastModifiedTime: FileTime?,
+        lastAccessTime: FileTime?,
+        createTime: FileTime?
+    ) {
+        throw IOException("Set times of root directory is not supported")
+    }
+}

src/org/kde/kdeconnect/Plugins/SftpPlugin/saf/RootFileAttributes.kt

@@ -0,0 +1,34 @@
+/*
+ * SPDX-FileCopyrightText: 2024 ShellWen Chen <me@shellwen.com>
+ *
+ * SPDX-License-Identifier: GPL-2.0-only OR GPL-3.0-only OR LicenseRef-KDE-Accepted-GPL
+ */
+package org.kde.kdeconnect.Plugins.SftpPlugin.saf
+
+import java.nio.file.attribute.FileTime
+import java.nio.file.attribute.GroupPrincipal
+import java.nio.file.attribute.PosixFileAttributes
+import java.nio.file.attribute.PosixFilePermission
+import java.nio.file.attribute.UserPrincipal
+
+object RootFileAttributes : PosixFileAttributes {
+    override fun lastModifiedTime(): FileTime = FileTime.fromMillis(0)
+    override fun lastAccessTime(): FileTime = FileTime.fromMillis(0)
+    override fun creationTime(): FileTime = FileTime.fromMillis(0)
+    override fun size(): Long = 0
+    override fun fileKey(): Any? = null
+    override fun isDirectory(): Boolean = true
+    override fun isRegularFile(): Boolean = false
+    override fun isSymbolicLink(): Boolean = false
+    override fun isOther(): Boolean = false
+
+    override fun owner(): UserPrincipal? = null
+
+    override fun group(): GroupPrincipal? = null
+
+    override fun permissions(): Set<PosixFilePermission> = // 660 for SAF
+        setOf(
+            PosixFilePermission.OWNER_READ, PosixFilePermission.OWNER_WRITE,
+            PosixFilePermission.GROUP_READ, PosixFilePermission.GROUP_WRITE,
+        )
+}

src/org/kde/kdeconnect/Plugins/SftpPlugin/saf/RootPosixFileAttributeView.kt

@@ -0,0 +1,41 @@
+/*
+ * SPDX-FileCopyrightText: 2024 ShellWen Chen <me@shellwen.com>
+ *
+ * SPDX-License-Identifier: GPL-2.0-only OR GPL-3.0-only OR LicenseRef-KDE-Accepted-GPL
+ */
+package org.kde.kdeconnect.Plugins.SftpPlugin.saf
+
+import java.io.IOException
+import java.nio.file.attribute.FileTime
+import java.nio.file.attribute.GroupPrincipal
+import java.nio.file.attribute.PosixFileAttributeView
+import java.nio.file.attribute.PosixFileAttributes
+import java.nio.file.attribute.PosixFilePermission
+import java.nio.file.attribute.UserPrincipal
+
+object RootPosixFileAttributeView : PosixFileAttributeView {
+    override fun name(): String = "posix"
+
+    override fun readAttributes(): PosixFileAttributes = RootFileAttributes
+    override fun setTimes(
+        lastModifiedTime: FileTime?,
+        lastAccessTime: FileTime?,
+        createTime: FileTime?
+    ) {
+        throw IOException("Set times of root directory is not supported")
+    }
+
+    override fun getOwner(): UserPrincipal? = null
+
+    override fun setOwner(owner: UserPrincipal?) {
+        throw IOException("Set owner of root directory is not supported")
+    }
+
+    override fun setPermissions(perms: MutableSet<PosixFilePermission>?) {
+        throw IOException("Set permissions of root directory is not supported")
+    }
+
+    override fun setGroup(group: GroupPrincipal?) {
+        throw IOException("Set group of root directory is not supported")
+    }
+}

src/org/kde/kdeconnect/Plugins/SftpPlugin/saf/SafFileSystem.kt

@@ -1,15 +1,21 @@
+/*
+ * SPDX-FileCopyrightText: 2024 ShellWen Chen <me@shellwen.com>
+ *
+ * SPDX-License-Identifier: GPL-2.0-only OR GPL-3.0-only OR LicenseRef-KDE-Accepted-GPL
+ */
 package org.kde.kdeconnect.Plugins.SftpPlugin.saf
 
 import android.content.Context
+import android.net.Uri
 import android.util.Log
+import androidx.documentfile.provider.DocumentFile
 import org.apache.sshd.common.file.util.BaseFileSystem
 import java.nio.file.attribute.UserPrincipalLookupService
 import java.nio.file.spi.FileSystemProvider
 
 class SafFileSystem(
     fileSystemProvider: FileSystemProvider,
-    roots: MutableMap<String, String?>,
-    username: String,
+    private val roots: MutableMap<String, Uri>,
     private val context: Context
 ) : BaseFileSystem<SafPath>(fileSystemProvider) {
     override fun close() {
@@ -19,15 +25,52 @@ class SafFileSystem(
 
     override fun isOpen(): Boolean = true
 
-    override fun supportedFileAttributeViews(): Set<String> = setOf("basic")
+    override fun supportedFileAttributeViews(): Set<String> = setOf("basic", "posix")
 
     override fun getUserPrincipalLookupService(): UserPrincipalLookupService {
         throw UnsupportedOperationException("SAF does not support user principal lookup")
     }
 
-    override fun create(root: String, names: List<String>): SafPath {
+    private tailrec fun getDocumentFileFromPath(
+        docFile: DocumentFile,
+        names: List<String>
+    ): DocumentFile? {
+        if (names.isEmpty()) {
+            return docFile
+        }
+        val nextName = names.first()
+        val nextNames = names.drop(1)
+        val nextDocFile = docFile.findFile(nextName)
+        return if (nextDocFile != null) {
+            getDocumentFileFromPath(nextDocFile, nextNames)
+        } else {
+            null
+        }
+    }
+
+    override fun create(root: String?, names: List<String>): SafPath {
         Log.v(TAG, "create: $root, $names")
-        return SafPath(this, root, names)
+        if ((root == "/") && names.isEmpty()) {
+            return SafPath.newRootPath(this)
+        }
+        val dirName = names.getOrNull(0)
+        if (dirName != null) {
+            roots.forEach { (k, v) ->
+                if (k == dirName) {
+                    if (names.size == 1) {
+                        return SafPath(this, v, root, names)
+                    } else {
+                        val docFile = getDocumentFileFromPath(
+                            DocumentFile.fromTreeUri(context, v)!!,
+                            names.drop(1)
+                        )
+                        return SafPath(this, docFile?.uri, root, names)
+                    }
+                }
+            }
+        }
+
+        return SafPath(this, null, root, names)
     }
 
     companion object {

src/org/kde/kdeconnect/Plugins/SftpPlugin/saf/SafFileSystemFactory.kt

@@ -7,6 +7,7 @@
 package org.kde.kdeconnect.Plugins.SftpPlugin.saf
 
 import android.content.Context
+import android.net.Uri
 import android.util.Log
 import org.apache.sshd.common.file.FileSystemFactory
 import org.apache.sshd.common.session.SessionContext
@@ -15,8 +16,8 @@ import java.nio.file.FileSystem
 import java.nio.file.Path
 
 class SafFileSystemFactory(private val context: Context) : FileSystemFactory {
-    private val provider = SafFileSystemProvider()
-    private val roots: MutableMap<String, String?> = HashMap()
+    private val roots: MutableMap<String, Uri> = HashMap()
+    private val provider = SafFileSystemProvider(context, roots)
 
     fun initRoots(storageInfoList: List<SftpPlugin.StorageInfo>) {
         Log.i(TAG, "initRoots: $storageInfoList")
@@ -29,9 +30,11 @@ class SafFileSystemFactory(private val context: Context) : FileSystemFactory {
 //                        roots[curStorageInfo.displayName] = curStorageInfo.uri.path
 //                    }
                 }
+
                 curStorageInfo.isContentUri -> {
-                    roots[curStorageInfo.displayName] = curStorageInfo.uri.toString()
+                    roots[curStorageInfo.displayName] = curStorageInfo.uri
                 }
+
                 else -> {
                     Log.e(TAG, "Unknown storage URI type: $curStorageInfo")
                 }
@@ -40,7 +43,7 @@ class SafFileSystemFactory(private val context: Context) : FileSystemFactory {
     }
 
     override fun createFileSystem(session: SessionContext?): FileSystem {
-        return SafFileSystem(provider, roots, session!!.username, context)
+        return SafFileSystem(provider, roots, context)
     }
 
     companion object {

src/org/kde/kdeconnect/Plugins/SftpPlugin/saf/SafFileSystemProvider.kt

@@ -1,88 +1,433 @@
+/*
+ * SPDX-FileCopyrightText: 2024 ShellWen Chen <me@shellwen.com>
+ *
+ * SPDX-License-Identifier: GPL-2.0-only OR GPL-3.0-only OR LicenseRef-KDE-Accepted-GPL
+ */
 package org.kde.kdeconnect.Plugins.SftpPlugin.saf
 
+import android.content.ContentValues
+import android.content.Context
+import android.net.Uri
+import android.os.Build
+import android.os.ParcelFileDescriptor
+import android.provider.DocumentsContract
+import android.util.Log
+import java.io.FileNotFoundException
+import java.io.IOException
 import java.net.URI
+import java.nio.channels.FileChannel
 import java.nio.channels.SeekableByteChannel
 import java.nio.file.AccessMode
 import java.nio.file.CopyOption
 import java.nio.file.DirectoryStream
 import java.nio.file.FileStore
 import java.nio.file.FileSystem
+import java.nio.file.Files
 import java.nio.file.LinkOption
 import java.nio.file.OpenOption
 import java.nio.file.Path
+import java.nio.file.StandardOpenOption
+import java.nio.file.attribute.BasicFileAttributeView
 import java.nio.file.attribute.BasicFileAttributes
 import java.nio.file.attribute.FileAttribute
 import java.nio.file.attribute.FileAttributeView
+import java.nio.file.attribute.FileTime
+import java.nio.file.attribute.GroupPrincipal
+import java.nio.file.attribute.PosixFileAttributeView
+import java.nio.file.attribute.PosixFileAttributes
+import java.nio.file.attribute.PosixFilePermission
+import java.nio.file.attribute.UserPrincipal
 import java.nio.file.spi.FileSystemProvider
 
-class SafFileSystemProvider: FileSystemProvider() {
+class SafFileSystemProvider(
+    private val context: Context,
+    val roots: MutableMap<String, Uri>
+) : FileSystemProvider() {
     override fun getScheme(): String = "saf"
 
     override fun newFileSystem(uri: URI, env: MutableMap<String, *>?): FileSystem {
-        TODO("Not yet implemented")
+        // SSHD Core does not use this method, so we can just throw an exception
+        Log.w(TAG, "newFileSystem($uri) not implemented")
+        throw NotImplementedError("newFileSystem($uri) not implemented")
     }
 
     override fun getFileSystem(uri: URI): FileSystem {
-        TODO("Not yet implemented")
+        // SSHD Core does not use this method, so we can just throw an exception
+        Log.w(TAG, "getFileSystem($uri) not implemented")
+        throw NotImplementedError("getFileSystem($uri) not implemented")
     }
 
     override fun getPath(uri: URI): Path {
-        TODO("Not yet implemented")
+        // SSHD Core does not use this method, so we can just throw an exception
+        Log.w(TAG, "getPath($uri) not implemented")
+        throw NotImplementedError("getPath($uri) not implemented")
     }
 
+    /**
+     * @see org.apache.sshd.sftp.server.FileHandle.getOpenOptions
+     */
     override fun newByteChannel(
         path: Path,
-        options: MutableSet<out OpenOption>,
-        vararg attrs: FileAttribute<*>
+        options: Set<OpenOption>,
+        vararg attrs_: FileAttribute<*>
     ): SeekableByteChannel {
-        TODO("Not yet implemented")
+        return newFileChannel(path, options, *attrs_)
+    }
+
+    /**
+     * @see org.apache.sshd.sftp.server.FileHandle.getOpenOptions
+     */
+    override fun newFileChannel(
+        path: Path,
+        options: Set<OpenOption>,
+        vararg attrs_: FileAttribute<*>
+    ): FileChannel {
+        check(path is SafPath)
+        check(!path.isRoot())
+
+        /*
+         * According to https://tools.ietf.org/html/draft-ietf-secsh-filexfer-13#page-33
+         *
+         * The 'attrs' field is ignored if an existing file is opened.
+         */
+        val attrs = if (Files.exists(path)) {
+            emptyArray()
+        } else {
+            attrs_
+        }
+
+        when (options) {
+            // READ
+            setOf(StandardOpenOption.READ) -> {
+                val docFile = path.getDocumentFile(context)!!
+                return ParcelFileDescriptor.AutoCloseInputStream(
+                    context.contentResolver.openFileDescriptor(docFile.uri, "r")!!
+                ).channel
+            }
+            // WRITE, TRUNCATE_EXISTING
+            // WRITE, CREATE
+            // WRITE, TRUNCATE_EXISTING, CREATE
+            // WRITE, CREATE_NEW
+            setOf(
+                StandardOpenOption.WRITE,
+                StandardOpenOption.TRUNCATE_EXISTING,
+            ),
+            setOf(
+                StandardOpenOption.WRITE,
+                StandardOpenOption.CREATE,
+            ),
+            setOf(
+                StandardOpenOption.WRITE,
+                StandardOpenOption.TRUNCATE_EXISTING,
+                StandardOpenOption.CREATE
+            ),
+            setOf(
+                StandardOpenOption.WRITE,
+                StandardOpenOption.CREATE_NEW,
+            ) -> {
+                val docFile = path.getDocumentFile(context) ?: run {
+                    if (options.contains(StandardOpenOption.CREATE) || options.contains(StandardOpenOption.CREATE_NEW)) {
+                        val parent = path.parent.getDocumentFile(context)!!
+                        parent.createFile(Files.probeContentType(path), path.names.last()).apply {
+                            if (this == null) {
+                                throw IOException("Failed to create $path")
+                            }
+                            path.safUri = uri
+                        }
+                    } else {
+                        throw IOException("File not found: $path")
+                    }
+                } ?: throw IOException("Failed to create $path")
+                check(docFile.exists())
+                return ParcelFileDescriptor.AutoCloseOutputStream(
+                    context.contentResolver.openFileDescriptor(docFile.uri, "rw")!!
+                ).channel
+            }
+            // TODO: Implement other options
+        }
+        Log.w(TAG, "newFileChannel($path, $options, $attrs) not implemented")
+        throw IOException("newFileChannel($path, $options, $attrs) not implemented")
     }
 
     override fun newDirectoryStream(
         dir: Path,
         filter: DirectoryStream.Filter<in Path>
     ): DirectoryStream<Path> {
-        TODO("Not yet implemented")
+        check(dir is SafPath)
+
+        if (dir.isRoot()) {
+            return object : DirectoryStream<Path> {
+                override fun iterator(): MutableIterator<Path> {
+                    return roots.mapNotNull { (name, uri) ->
+                        val newPath = SafPath(dir.fileSystem, uri, null, listOf(name))
+                        if (filter.accept(newPath)) newPath else null
+                    }.toMutableList().iterator()
+                }
+
+                override fun close() {
+                    // no-op
+                }
+            }
+        }
+
+        check(dir.names.isNotEmpty())
+
+        return object : DirectoryStream<Path> {
+            override fun iterator(): MutableIterator<Path> {
+                val documentFile = dir.getDocumentFile(context)!!
+                return documentFile.listFiles().mapNotNull {
+                    val newPath = SafPath(dir.fileSystem, it.uri, null, dir.names + it.name!!)
+                    if (filter.accept(newPath)) newPath else null
+                }.toMutableList().iterator()
+            }
+
+            override fun close() {
+                // no-op
+            }
+        }
     }
 
     override fun createDirectory(dir: Path, vararg attrs: FileAttribute<*>) {
-        TODO("Not yet implemented")
+        check(dir is SafPath)
+        if (dir.isRoot()) {
+            throw IOException("Cannot create root directory")
+        }
+        if (dir.parent == null) {
+            throw IOException("Parent directory does not exist")
+        }
+        val parent = dir.parent.getDocumentFile(context)
+            ?: throw IOException("Parent directory does not exist")
+        parent.createDirectory(dir.names.last())
     }
 
     override fun delete(path: Path) {
-        TODO("Not yet implemented")
+        check(path is SafPath)
+        val docFile = path.getDocumentFile(context)
+            ?: throw java.nio.file.NoSuchFileException(
+                path.toString(),
+            ) // No kotlin.NoSuchFileException, they are different
+        if (!docFile.delete()) {
+            throw IOException("Failed to delete $path")
+        }
     }
 
     override fun copy(source: Path, target: Path, vararg options: CopyOption) {
-        TODO("Not yet implemented")
+        check(source is SafPath)
+        check(target is SafPath)
+
+        val sourceDocFile = source.getDocumentFile(context)
+            ?: throw java.nio.file.NoSuchFileException(
+                source.toString(),
+            ) // No kotlin.NoSuchFileException, they are different
+
+        val targetDocFile = target.parent.getDocumentFile(context)!!
+            .createFile(Files.probeContentType(source), target.names.last())
+            ?: throw IOException("Failed to create $target")
+
+        context.contentResolver.openOutputStream(targetDocFile.uri)?.use { os ->
+            context.contentResolver.openInputStream(sourceDocFile.uri)?.use { is_ ->
+                is_.copyTo(os)
+            }
+        }
     }
 
     override fun move(source: Path, target: Path, vararg options: CopyOption) {
-        TODO("Not yet implemented")
+        check(source is SafPath)
+        check(target is SafPath)
+
+        val sourceUri = source.getDocumentFile(context)!!.uri
+        val parentUri = source.parent.getDocumentFile(context)!!.uri
+        val destParentUri = target.parent.getDocumentFile(context)!!.uri
+
+        // 1. If dest parent is the same as source parent, rename the file
+        if (parentUri == destParentUri) {
+            try {
+                val newUri = DocumentsContract.renameDocument(
+                    context.contentResolver,
+                    sourceUri,
+                    target.names.last()
+                )
+                source.safUri = newUri!!
+                return
+            } catch (ignored: FileNotFoundException) {
+                // no-op: fallback to the next method
+            }
         }
 
-    override fun isSameFile(path: Path, path2: Path): Boolean {
-        TODO("Not yet implemented")
+        val sourceTreeDocumentId = DocumentsContract.getTreeDocumentId(parentUri)
+        val destTreeDocumentId = DocumentsContract.getTreeDocumentId(destParentUri)
+
+        // 2. If source and dest are in the same tree, and the API level is high enough, move the file
+        if (sourceTreeDocumentId == destTreeDocumentId &&
+            Build.VERSION.SDK_INT >= Build.VERSION_CODES.N
+        ) {
+            val newUri = DocumentsContract.moveDocument(
+                context.contentResolver,
+                sourceUri,
+                parentUri,
+                destParentUri
+            )
+            source.safUri = newUri!!
+            return
+        }
+
+        // 3. Else copy and delete the file
+        copy(source, target, *options)
+        delete(source)
+    }
+
+    override fun isSameFile(p1: Path, p2: Path): Boolean {
+        check(p1 is SafPath)
+        check(p2 is SafPath)
+        return p1.root == p2.root && p1.names == p2.names &&
+                p1.getDocumentFile(context)!!.uri == p2.getDocumentFile(context)!!.uri
     }
 
     override fun isHidden(path: Path): Boolean {
-        TODO("Not yet implemented")
+        check(path is SafPath)
+
+        if (path.isRoot()) {
+            return false
         }
 
-    override fun getFileStore(path: Path): FileStore {
-        TODO("Not yet implemented")
+        return path.names.last().startsWith(".")
+    }
+
+    override fun getFileStore(path: Path): FileStore? {
+        // SAF does not support file store
+        Log.i(TAG, "getFileStore($path) not implemented")
+        return null
     }
 
     override fun checkAccess(path: Path, vararg modes: AccessMode) {
-        TODO("Not yet implemented")
+        check(path is SafPath)
+        if (path.isRoot()) {
+            modes.forEach {
+                when (it) {
+                    AccessMode.READ -> {
+                        // Root is always readable
+                    }
+
+                    AccessMode.WRITE -> {
+                        // Root is not writable
+                        throw java.nio.file.AccessDeniedException("/") // No kotlin.AccessDeniedException, they are different
+                    }
+
+                    AccessMode.EXECUTE -> {
+                        // Root is not executable
+                        throw java.nio.file.AccessDeniedException("/") // No kotlin.AccessDeniedException, they are different
+                    }
+                }
+            }
+            return
+        }
+        val docFile = path.getDocumentFile(context)
+            ?: throw java.nio.file.NoSuchFileException(
+                path.toString(),
+            ) // No kotlin.NoSuchFileException, they are different
+        if (!docFile.exists()) {
+            throw java.nio.file.NoSuchFileException(
+                docFile.uri.toString(),
+            ) // No kotlin.NoSuchFileException, they are different
+        }
+        modes.forEach {
+            when (it) {
+                AccessMode.READ -> {
+                    if (!docFile.canRead()) {
+                        throw java.nio.file.AccessDeniedException(docFile.uri.toString()) // No kotlin.AccessDeniedException, they are different
+                    }
+                }
+
+                AccessMode.WRITE -> {
+                    if (!docFile.canWrite()) {
+                        throw java.nio.file.AccessDeniedException(docFile.uri.toString()) // No kotlin.AccessDeniedException, they are different
+                    }
+                }
+
+                AccessMode.EXECUTE -> {
+                    // SAF files is not executable
+                    throw java.nio.file.AccessDeniedException(docFile.uri.toString()) // No kotlin.AccessDeniedException, they are different
+                }
+            }
+        }
     }
 
     override fun <V : FileAttributeView> getFileAttributeView(
         path: Path,
         type: Class<V>,
         vararg options: LinkOption?
-    ): V {
-        TODO("Not yet implemented")
+    ): V? {
+        check(path is SafPath)
+        if (path.isRoot()) {
+            if (type == BasicFileAttributeView::class.java) {
+                @Suppress("UNCHECKED_CAST")
+                return RootBasicFileAttributeView as V
+            }
+            if (type == PosixFileAttributeView::class.java) {
+                @Suppress("UNCHECKED_CAST")
+                return RootPosixFileAttributeView as V
+            }
+        }
+
+        if (type == BasicFileAttributeView::class.java) {
+            @Suppress("UNCHECKED_CAST")
+            return object : BasicFileAttributeView {
+                override fun name(): String = "basic"
+
+                override fun readAttributes(): BasicFileAttributes =
+                    readAttributes(path, BasicFileAttributes::class.java)
+
+                override fun setTimes(
+                    lastModifiedTime: FileTime?,
+                    lastAccessTime: FileTime?,
+                    createTime: FileTime?
+                ) {
+                    Log.w(
+                        TAG,
+                        "setTimes($path, $lastModifiedTime, $lastAccessTime, $createTime) not implemented"
+                    )
+                }
+            } as V
+        }
+        if (type == PosixFileAttributeView::class.java) {
+            @Suppress("UNCHECKED_CAST")
+            return object : PosixFileAttributeView {
+                override fun name(): String = "posix"
+
+                override fun readAttributes(): PosixFileAttributes =
+                    readAttributes(path, PosixFileAttributes::class.java)
+
+                override fun setTimes(
+                    lastModifiedTime: FileTime?,
+                    lastAccessTime: FileTime?,
+                    createTime: FileTime?
+                ) {
+                    Log.w(
+                        TAG,
+                        "setTimes($path, $lastModifiedTime, $lastAccessTime, $createTime) not implemented"
+                    )
+                }
+
+                override fun getOwner(): UserPrincipal? {
+                    Log.i(TAG, "getOwner($path) not implemented")
+                    return null
+                }
+
+                override fun setOwner(owner: UserPrincipal?) {
+                    Log.i(TAG, "setOwner($path, $owner) not implemented")
+                }
+
+                override fun setPermissions(perms: MutableSet<PosixFilePermission>?) {
+                    Log.i(TAG, "setPermissions($path, $perms) not implemented")
+                }
+
+                override fun setGroup(group: GroupPrincipal?) {
+                    Log.i(TAG, "setGroup($path, $group) not implemented")
+                }
+            } as V
+        }
+        Log.w(TAG, "getFileAttributeView($path)[${type.getSimpleName()}] not implemented")
+        return null
     }
 
     override fun <A : BasicFileAttributes> readAttributes(
@@ -90,16 +435,110 @@ class SafFileSystemProvider: FileSystemProvider() {
         type: Class<A>,
         vararg options: LinkOption?
     ): A {
-        // TODO
-        throw UnsupportedOperationException("readAttributes($path)[${type.getSimpleName()}] N/A");
+        check(path is SafPath)
+
+        if (path.isRoot()) {
+            if (type == BasicFileAttributes::class.java || type == PosixFileAttributes::class.java) {
+                @Suppress("UNCHECKED_CAST")
+                return RootFileAttributes as A
+            }
+        }
+
+        path.getDocumentFile(context).let {
+            if (it == null) {
+                throw java.nio.file.NoSuchFileException(
+                    path.toString(),
+                ) // No kotlin.NoSuchFileException, they are different
+            }
+            if (type == BasicFileAttributes::class.java || type == PosixFileAttributes::class.java) {
+                @Suppress("UNCHECKED_CAST")
+                return object : PosixFileAttributes {
+                    override fun lastModifiedTime(): FileTime =
+                        FileTime.fromMillis(it.lastModified())
+
+                    override fun lastAccessTime(): FileTime = FileTime.fromMillis(it.lastModified())
+                    override fun creationTime(): FileTime = FileTime.fromMillis(it.lastModified())
+                    override fun size(): Long = it.length()
+                    override fun fileKey(): Any? = null
+                    override fun isDirectory(): Boolean = it.isDirectory
+                    override fun isRegularFile(): Boolean = it.isFile
+                    override fun isSymbolicLink(): Boolean = false
+                    override fun isOther(): Boolean = false
+
+                    override fun owner(): UserPrincipal? = null
+                    override fun group(): GroupPrincipal? = null
+                    override fun permissions(): Set<PosixFilePermission> = // 660 for SAF
+                        setOf(
+                            PosixFilePermission.OWNER_READ, PosixFilePermission.OWNER_WRITE,
+                            PosixFilePermission.GROUP_READ, PosixFilePermission.GROUP_WRITE,
+                        )
+                } as A
+            }
+        }
+
+        Log.w(TAG, "readAttributes($path)[${type.getSimpleName()}] not implemented")
+        throw UnsupportedOperationException("readAttributes($path)[${type.getSimpleName()}] N/A")
     }
 
     override fun readAttributes(
         path: Path,
         attributes: String,
         vararg options: LinkOption?
-    ): MutableMap<String, Any?> {
-        TODO("Not yet implemented")
+    ): Map<String, Any?> {
+        // TODO: Implement readAttributes
+        check(path is SafPath)
+        if (path.isRoot()) {
+            if (attributes == "basic" || attributes.startsWith("basic:")) {
+                return mapOf(
+                    "isDirectory" to true,
+                    "isRegularFile" to false,
+                    "isSymbolicLink" to false,
+                    "isOther" to false,
+                    "size" to 0L,
+                    "fileKey" to null,
+                    "lastModifiedTime" to FileTime.fromMillis(0),
+                    "lastAccessTime" to FileTime.fromMillis(0),
+                    "creationTime" to FileTime.fromMillis(0)
+                )
+            }
+            if (attributes == "posix" || attributes.startsWith("posix:")) {
+                return mapOf(
+                    "owner" to null,
+                    "group" to null,
+                    "permissions" to setOf(
+                        PosixFilePermission.OWNER_READ, PosixFilePermission.OWNER_WRITE,
+                        PosixFilePermission.GROUP_READ, PosixFilePermission.GROUP_WRITE,
+                    )
+                )
+            }
+        }
+        val documentFile = path.getDocumentFile(context)
+        check(documentFile != null)
+        if (attributes == "basic" || attributes.startsWith("basic:")) {
+            return mapOf(
+                "isDirectory" to documentFile.isDirectory,
+                "isRegularFile" to documentFile.isFile,
+                "isSymbolicLink" to false,
+                "isOther" to false,
+                "size" to documentFile.length(),
+                "fileKey" to null,
+                "lastModifiedTime" to FileTime.fromMillis(documentFile.lastModified()),
+                "lastAccessTime" to FileTime.fromMillis(documentFile.lastModified()),
+                "creationTime" to FileTime.fromMillis(documentFile.lastModified())
+            )
+        }
+        if (attributes == "posix" || attributes.startsWith("posix:")) {
+            return mapOf(
+                "owner" to null,
+                "group" to null,
+                "permissions" to setOf(
+                    PosixFilePermission.OWNER_READ, PosixFilePermission.OWNER_WRITE,
+                    PosixFilePermission.GROUP_READ, PosixFilePermission.GROUP_WRITE,
+                )
+            )
+        }
+        Log.w(TAG, "readAttributes($path, $attributes) not implemented")
+        throw UnsupportedOperationException("readAttributes($path, $attributes) N/A")
     }
 
     override fun setAttribute(
@@ -108,6 +547,40 @@ class SafFileSystemProvider: FileSystemProvider() {
         value: Any?,
         vararg options: LinkOption?
     ) {
-        TODO("Not yet implemented")
+        check(path is SafPath)
+        when (attribute) {
+            "basic:lastModifiedTime" -> {
+                check(value is FileTime)
+                path.getDocumentFile(context)?.let {
+                    val updateValues = ContentValues().apply {
+                        put(DocumentsContract.Document.COLUMN_LAST_MODIFIED, value.toMillis())
+                    }
+                    if (context.contentResolver.update(it.uri, updateValues, null, null) == 0) {
+                        throw IOException("Failed to set lastModifiedTime of $path")
+                    }
+                } ?: throw java.nio.file.NoSuchFileException(
+                    path.toString(),
+                ) // No kotlin.NoSuchFileException, they are different
+            }
+
+            "basic:lastAccessTime", "basic:creationTime" -> {
+                check(value is FileTime)
+                throw UnsupportedOperationException("$attribute is read-only")
+            }
+
+            "posix:owner", "posix:group", "posix:permissions" -> {
+                Log.w(TAG, "set posix attribute $attribute not implemented")
+            }
+
+            else -> {
+                Log.w(TAG, "setAttribute($path, $attribute, $value) not implemented")
+            }
+        }
+        // TODO: Implement setAttribute
+        Log.w(TAG, "setAttribute($path, $attribute, $value) not implemented")
+    }
+
+    companion object {
+        private const val TAG = "SafFileSystemProvider"
     }
 }

src/org/kde/kdeconnect/Plugins/SftpPlugin/saf/SafPath.kt

@@ -1,14 +1,38 @@
+/*
+ * SPDX-FileCopyrightText: 2024 ShellWen Chen <me@shellwen.com>
+ *
+ * SPDX-License-Identifier: GPL-2.0-only OR GPL-3.0-only OR LicenseRef-KDE-Accepted-GPL
+ */
 package org.kde.kdeconnect.Plugins.SftpPlugin.saf
 
+import android.content.Context
+import android.net.Uri
+import android.util.Log
+import androidx.documentfile.provider.DocumentFile
 import org.apache.sshd.common.file.util.BasePath
 import java.nio.file.LinkOption
-import java.nio.file.Path
 
 class SafPath(
     fileSystem: SafFileSystem,
-    root: String, names: List<String>
+    var safUri: Uri?,
+    val root: String?, val names: List<String>
 ) : BasePath<SafPath, SafFileSystem>(fileSystem, root, names) {
-    override fun toRealPath(vararg options: LinkOption?): Path {
-        return this // FIXME
+    override fun toRealPath(vararg options: LinkOption?): SafPath {
+        return this.normalize()
+    }
+
+    fun getDocumentFile(ctx: Context): DocumentFile? {
+        if (safUri == null) return null
+        return DocumentFile.fromTreeUri(ctx, safUri!!)
+    }
+
+    fun isRoot(): Boolean {
+        return (root == "/") && names.isEmpty()
+    }
+
+    companion object {
+        fun newRootPath(fileSystem: SafFileSystem): SafPath {
+            return SafPath(fileSystem, null, "/", emptyList())
+        }
     }
 }