Refine UniFile and evict lookup cache on delete

Also add comments on functions that rely on implementation details.

app/src/main/kotlin/com/hippo/unifile/DocumentsContractApi21.kt

@@ -40,6 +40,8 @@ object DocumentsContractApi21 {
         )
     }
 
+    // This is not a good approach as the document identifier is an opaque implementation detail of
+    // the provider, but works for ExternalStorageProvider
     fun buildChildUri(uri: Uri, displayName: String): Uri {
         return DocumentsContract.buildDocumentUriUsingTree(
             uri,

app/src/main/kotlin/com/hippo/unifile/MediaFile.kt

@@ -18,7 +18,7 @@ package com.hippo.unifile
 import android.net.Uri
 import java.io.IOException
 
-class MediaFile(override val uri: Uri) : UniFile() {
+class MediaFile(override val uri: Uri) : UniFile {
     override fun createFile(displayName: String) = null
 
     override fun createDirectory(displayName: String) = null
@@ -27,6 +27,7 @@ class MediaFile(override val uri: Uri) : UniFile() {
         get() = MediaContract.getName(uri)
     override val type: String?
         get() = MediaContract.getType(uri)
+    override val parent = null
     override val isDirectory = false
     override val isFile: Boolean
         get() = DocumentsContractApi19.isFile(uri)

app/src/main/kotlin/com/hippo/unifile/RawFile.kt

@@ -23,19 +23,15 @@ import android.webkit.MimeTypeMap
 import java.io.File
 import java.util.Locale
 
-class RawFile(private val parent: RawFile?, private var file: File) : UniFile() {
+class RawFile(override val parent: RawFile?, private var file: File) : UniFile {
 
     private var cachePresent = false
     private val allChildren by lazy {
-        val current = this
         cachePresent = true
-        mutableListOf<RawFile>().apply {
-            val fs = file.listFiles()?.map { RawFile(current, it) }
-            if (fs != null) addAll(fs)
-        }
+        file.listFiles().orEmpty().mapTo(mutableListOf()) { RawFile(this, it) }
     }
 
-    private fun popCacheIfPresent(file: RawFile) = apply {
+    private fun popCacheIfPresent(file: RawFile) {
         if (cachePresent) {
             synchronized(allChildren) {
                 allChildren.add(file)
@@ -43,6 +39,14 @@ class RawFile(private val parent: RawFile?, private var file: File) : UniFile()
         }
     }
 
+    private fun evictCacheIfPresent(file: RawFile) {
+        if (cachePresent) {
+            synchronized(allChildren) {
+                allChildren.remove(file)
+            }
+        }
+    }
+
     override fun createFile(displayName: String): UniFile? {
         val target = RawFile(this, File(file, displayName))
         if (target.exists()) {
@@ -101,7 +105,9 @@ class RawFile(private val parent: RawFile?, private var file: File) : UniFile()
 
     override fun resolve(displayName: String) = RawFile(this, File(file, displayName))
 
-    override fun delete() = file.deleteRecursively()
+    override fun delete() = file.deleteRecursively().also {
+        if (it) parent?.evictCacheIfPresent(this)
+    }
 
     override fun exists() = file.exists()
 

app/src/main/kotlin/com/hippo/unifile/SingleDocumentFile.kt

@@ -17,7 +17,7 @@ package com.hippo.unifile
 
 import android.net.Uri
 
-class SingleDocumentFile(override val uri: Uri) : UniFile() {
+class SingleDocumentFile(override val uri: Uri) : UniFile {
 
     override fun createFile(displayName: String) = null
 
@@ -27,6 +27,7 @@ class SingleDocumentFile(override val uri: Uri) : UniFile() {
         get() = DocumentsContractApi19.getName(uri)
     override val type: String?
         get() = DocumentsContractApi19.getType(uri)
+    override val parent = null
     override val isDirectory: Boolean
         get() = DocumentsContractApi19.isDirectory(uri)
     override val isFile: Boolean

app/src/main/kotlin/com/hippo/unifile/TreeDocumentFile.kt

@@ -20,11 +20,11 @@ import android.provider.DocumentsContract.Document.MIME_TYPE_DIR
 import android.webkit.MimeTypeMap
 
 class TreeDocumentFile(
-    private val parent: UniFile?,
-    override var uri: Uri,
-    override var name: String = getFilenameForUri(uri),
+    override val parent: TreeDocumentFile?,
+    uri: Uri,
+    name: String = getFilenameForUri(uri),
     mimeType: String? = null,
-) : UniFile() {
+) : UniFile {
     private var cachePresent = false
     private val allChildren by lazy {
         cachePresent = true
@@ -33,7 +33,7 @@ class TreeDocumentFile(
         }
     }
 
-    private fun popCacheIfPresent(file: TreeDocumentFile) = apply {
+    private fun popCacheIfPresent(file: TreeDocumentFile) {
         if (cachePresent) {
             synchronized(allChildren) {
                 allChildren.add(file)
@@ -41,6 +41,14 @@ class TreeDocumentFile(
         }
     }
 
+    private fun evictCacheIfPresent(file: TreeDocumentFile) {
+        if (cachePresent) {
+            synchronized(allChildren) {
+                allChildren.remove(file)
+            }
+        }
+    }
+
     override fun createFile(displayName: String): UniFile? {
         val child = findFile(displayName)
         if (child != null) {
@@ -73,14 +81,22 @@ class TreeDocumentFile(
         return null
     }
 
-    private val rawType by lazy {
-        mimeType ?: DocumentsContractApi19.getRawType(uri)
-    }
+    private var mimeType = mimeType
+        get() {
+            if (field == null) {
+                field = DocumentsContractApi19.getRawType(uri)
+            }
+            return field
+        }
 
+    override var uri = uri
+        private set
+    override var name = name
+        private set
     override val type: String?
-        get() = rawType.takeUnless { isDirectory }
+        get() = mimeType.takeUnless { isDirectory }
     override val isDirectory: Boolean
-        get() = rawType == MIME_TYPE_DIR
+        get() = mimeType == MIME_TYPE_DIR
     override val isFile: Boolean
         get() = !type.isNullOrEmpty()
 
@@ -117,7 +133,9 @@ class TreeDocumentFile(
         return TreeDocumentFile(this, childUri, displayName)
     }
 
-    override fun delete() = DocumentsContractApi19.delete(uri)
+    override fun delete() = DocumentsContractApi19.delete(uri).also {
+        if (it) parent?.evictCacheIfPresent(this)
+    }
 
     override fun exists() = DocumentsContractApi19.exists(uri)
 
@@ -134,18 +152,15 @@ class TreeDocumentFile(
         if (result != null) {
             uri = result
             name = displayName
+            mimeType = null
             return true
         }
         return false
     }
 }
 
+// Technically the Uris should be treated as opaque, but it works for ExternalStorageProvider
 private fun getFilenameForUri(uri: Uri): String {
     val path = requireNotNull(uri.path)
-    val index = path.lastIndexOf('/')
-    return if (index >= 0) {
-        path.substring(index + 1)
-    } else {
-        return path
-    }
+    return path.substringAfterLast('/')
 }

app/src/main/kotlin/com/hippo/unifile/UniFile.kt

@@ -28,7 +28,7 @@ import splitties.init.appCtx
  * In Android files can be accessed via [java.io.File] and [android.net.Uri].
  * The UniFile is designed to emulate File interface for both File and Uri.
  */
-sealed class UniFile {
+sealed interface UniFile {
     /**
      * Create a new file as a direct child of this directory.
      *
@@ -36,7 +36,7 @@ sealed class UniFile {
      * @return file representing newly created document, or null if failed
      * @see android.provider.DocumentsContract.createDocument
      */
-    abstract fun createFile(displayName: String): UniFile?
+    fun createFile(displayName: String): UniFile?
 
     /**
      * Create a new directory as a direct child of this directory.
@@ -45,7 +45,7 @@ sealed class UniFile {
      * @return file representing newly created directory, or null if failed
      * @see android.provider.DocumentsContract.createDocument
      */
-    abstract fun createDirectory(displayName: String): UniFile?
+    fun createDirectory(displayName: String): UniFile?
 
     /**
      * Return a Uri for the underlying document represented by this file. This
@@ -61,7 +61,7 @@ sealed class UniFile {
      * @see ContentResolver.openOutputStream
      * @see ContentResolver.openFileDescriptor
      */
-    abstract val uri: Uri
+    val uri: Uri
 
     /**
      * Return the display name of this file.
@@ -69,7 +69,7 @@ sealed class UniFile {
      * @return name of the file, or null if failed
      * @see android.provider.DocumentsContract.Document.COLUMN_DISPLAY_NAME
      */
-    abstract val name: String?
+    val name: String?
 
     /**
      * Return the MIME type of this file.
@@ -77,7 +77,21 @@ sealed class UniFile {
      * @return MIME type of the file, or null if failed
      * @see android.provider.DocumentsContract.Document.COLUMN_MIME_TYPE
      */
-    abstract val type: String?
+    val type: String?
+
+    /**
+     * Return the parent file of this file. Only defined inside of the
+     * user-selected tree; you can never escape above the top of the tree.
+     *
+     *
+     * The underlying [android.provider.DocumentsProvider] only defines a
+     * forward mapping from parent to child, so the reverse mapping of child to
+     * parent offered here is purely a convenience method, and it may be
+     * incorrect if the underlying tree structure changes.
+     *
+     * @return parent of the file, or null if it is the top of the file tree
+     */
+    val parent: UniFile?
 
     /**
      * Indicates if this file represents a *directory*.
@@ -86,7 +100,7 @@ sealed class UniFile {
      * otherwise.
      * @see android.provider.DocumentsContract.Document.MIME_TYPE_DIR
      */
-    abstract val isDirectory: Boolean
+    val isDirectory: Boolean
 
     /**
      * Indicates if this file represents a *file*.
@@ -94,7 +108,7 @@ sealed class UniFile {
      * @return `true` if this file is a file, `false` otherwise.
      * @see android.provider.DocumentsContract.Document.COLUMN_MIME_TYPE
      */
-    abstract val isFile: Boolean
+    val isFile: Boolean
 
     /**
      * Returns the time when this file was last modified, measured in
@@ -104,7 +118,7 @@ sealed class UniFile {
      * @return the time when this file was last modified, `-1L` if can't get it
      * @see android.provider.DocumentsContract.Document.COLUMN_LAST_MODIFIED
      */
-    abstract fun lastModified(): Long
+    fun lastModified(): Long
 
     /**
      * Returns the length of this file in bytes. Returns -1 if the file does not
@@ -114,14 +128,14 @@ sealed class UniFile {
      * @return the number of bytes in this file, `-1L` if can't get it
      * @see android.provider.DocumentsContract.Document.COLUMN_SIZE
      */
-    abstract fun length(): Long
+    fun length(): Long
 
     /**
      * Indicates whether the current context is allowed to read from this file.
      *
      * @return `true` if this file can be read, `false` otherwise.
      */
-    abstract fun canRead(): Boolean
+    fun canRead(): Boolean
 
     /**
      * Indicates whether the current context is allowed to write to this file.
@@ -136,7 +150,7 @@ sealed class UniFile {
      *
      * @see android.provider.DocumentsContract.Document.FLAG_DIR_SUPPORTS_CREATE
      */
-    abstract fun canWrite(): Boolean
+    fun canWrite(): Boolean
 
     /**
      * It works like mkdirs, but it will return true if the UniFile is directory
@@ -144,7 +158,7 @@ sealed class UniFile {
      * @return `true` if the directory was created
      * or if the directory already existed.
      */
-    abstract fun ensureDir(): Boolean
+    fun ensureDir(): Boolean
 
     /**
      * Make sure the UniFile is file
@@ -152,14 +166,14 @@ sealed class UniFile {
      * @return `true` if the file can be created
      * or if the file already existed.
      */
-    abstract fun ensureFile(): Boolean
+    fun ensureFile(): Boolean
 
     /**
      * Get child file of this directory, the child might not exist.
      *
      * @return the child file
      */
-    abstract fun resolve(displayName: String): UniFile
+    fun resolve(displayName: String): UniFile
 
     operator fun div(name: String) = resolve(name)
 
@@ -173,20 +187,20 @@ sealed class UniFile {
      * @return `true` if this file was deleted, `false` otherwise.
      * @see android.provider.DocumentsContract.deleteDocument
      */
-    abstract fun delete(): Boolean
+    fun delete(): Boolean
 
     /**
      * Returns a boolean indicating whether this file can be found.
      *
      * @return `true` if this file exists, `false` otherwise.
      */
-    abstract fun exists(): Boolean
+    fun exists(): Boolean
 
-    abstract fun listFiles(): List<UniFile>
+    fun listFiles(): List<UniFile>
 
-    abstract fun findFirst(filter: (String) -> Boolean): UniFile?
+    fun findFirst(filter: (String) -> Boolean): UniFile?
 
-    open fun openFileDescriptor(mode: String) = appCtx.contentResolver.openFileDescriptor(uri, mode) ?: error("Can't open ParcelFileDescriptor")
+    fun openFileDescriptor(mode: String) = appCtx.contentResolver.openFileDescriptor(uri, mode) ?: error("Can't open ParcelFileDescriptor")
 
     /**
      * Test there is a file with the display name in the directory.
@@ -215,7 +229,7 @@ sealed class UniFile {
      * @return true on success.
      * @see android.provider.DocumentsContract.renameDocument
      */
-    abstract fun renameTo(displayName: String): Boolean
+    fun renameTo(displayName: String): Boolean
 
     companion object {
         fun fromFile(file: File) = RawFile(null, file)