Implement robust file downloading, uploading and opening

Signed-off-by: denis0001-dev <denis0001.dev@ya.ru>

utils/shared/src/androidMain/kotlin/com/pr0gramm3r101/utils/files/PlatformFileSystem.android.kt

@@ -12,6 +12,17 @@ internal actual fun expectWriteBytes(path: String, bytes: ByteArray) {
     file.writeBytes(bytes)
 }
 
+internal actual fun expectAppendBytes(path: String, bytes: ByteArray) {
+    val file = File(path)
+    file.parentFile?.mkdirs()
+    file.appendBytes(bytes)
+}
+
+internal actual fun expectFileSize(path: String): Long {
+    val file = File(path)
+    return if (file.isFile) file.length() else 0L
+}
+
 internal actual fun expectDelete(path: String) {
     File(path).delete()
 }
@@ -26,6 +37,12 @@ internal actual fun expectDeleteFilesWithPrefix(dirPath: String, namePrefix: Str
     }
 }
 
+internal actual fun expectListFileNamesInDirectory(dirPath: String): List<String> {
+    val dir = File(dirPath)
+    if (!dir.isDirectory) return emptyList()
+    return dir.listFiles()?.map { it.name } ?: emptyList()
+}
+
 internal actual fun expectGetAppCacheDirectory(): String =
     UtilsLibrary.context.cacheDir.absolutePath
 

utils/shared/src/commonMain/kotlin/com/pr0gramm3r101/utils/files/PlatformFileSystem.kt

@@ -18,6 +18,15 @@ object PlatformFileSystem {
         expectWriteBytes(path, bytes)
     }
 
+    /** Appends [bytes] to the file at [path], creating it when missing. */
+    fun appendBytes(path: String, bytes: ByteArray) {
+        if (bytes.isEmpty()) return
+        expectAppendBytes(path, bytes)
+    }
+
+    /** Size in bytes, or 0 when the file does not exist. */
+    fun fileSize(path: String): Long = expectFileSize(path)
+
     /**
      * Deletes the file at [path]. No-op if the file does not exist.
      */
@@ -32,6 +41,10 @@ object PlatformFileSystem {
         expectDeleteFilesWithPrefix(dirPath, namePrefix)
     }
 
+    /** Returns filenames (not paths) in [dirPath], or empty if the directory is missing. */
+    fun listFileNamesInDirectory(dirPath: String): List<String> =
+        expectListFileNamesInDirectory(dirPath)
+
     /**
      * Returns the platform-specific application cache directory path.
      * On Android: context.cacheDir (requires UtilsLibrary.init to be called).
@@ -51,7 +64,10 @@ object PlatformFileSystem {
 
 internal expect fun expectExists(path: String): Boolean
 internal expect fun expectWriteBytes(path: String, bytes: ByteArray)
+internal expect fun expectAppendBytes(path: String, bytes: ByteArray)
+internal expect fun expectFileSize(path: String): Long
 internal expect fun expectDelete(path: String)
 internal expect fun expectDeleteFilesWithPrefix(dirPath: String, namePrefix: String)
+internal expect fun expectListFileNamesInDirectory(dirPath: String): List<String>
 internal expect fun expectGetAppCacheDirectory(): String
 internal expect fun expectEnsureDirectory(path: String)

utils/shared/src/iosMain/kotlin/com/pr0gramm3r101/utils/files/PlatformFileSystem.ios.kt

@@ -7,11 +7,18 @@ import kotlinx.cinterop.addressOf
 import kotlinx.cinterop.usePinned
 import platform.Foundation.NSData
 import platform.Foundation.NSFileManager
+import platform.Foundation.NSNumber
 import platform.Foundation.NSCachesDirectory
 import platform.Foundation.NSSearchPathForDirectoriesInDomains
 import platform.Foundation.NSUserDomainMask
 import platform.Foundation.create
 import platform.Foundation.writeToFile
+import platform.posix.fclose
+import platform.posix.fopen
+import platform.posix.fwrite
+import kotlinx.cinterop.addressOf
+import kotlinx.cinterop.convert
+import kotlinx.cinterop.usePinned
 
 @OptIn(ExperimentalForeignApi::class)
 internal actual fun expectExists(path: String): Boolean =
@@ -29,6 +36,32 @@ internal actual fun expectWriteBytes(path: String, bytes: ByteArray) {
     nsData?.writeToFile(path, true)
 }
 
+@OptIn(ExperimentalForeignApi::class)
+internal actual fun expectAppendBytes(path: String, bytes: ByteArray) {
+    val parent = path.substringBeforeLast('/', missingDelimiterValue = "")
+    if (parent.isNotEmpty()) {
+        NSFileManager.defaultManager.createDirectoryAtPath(parent, true, null, null)
+    }
+    val file = fopen(path, "ab") ?: error("Failed to open file for append")
+    try {
+        bytes.usePinned { pinned ->
+            val written = fwrite(pinned.addressOf(0), 1.convert(), bytes.size.convert(), file).toInt()
+            if (written != bytes.size) {
+                error("Short write")
+            }
+        }
+    } finally {
+        fclose(file)
+    }
+}
+
+@OptIn(ExperimentalForeignApi::class)
+internal actual fun expectFileSize(path: String): Long {
+    if (!NSFileManager.defaultManager.fileExistsAtPath(path)) return 0L
+    val attrs = NSFileManager.defaultManager.attributesOfItemAtPath(path, null) ?: return 0L
+    return (attrs["NSFileSize"] as? NSNumber)?.longValue ?: 0L
+}
+
 internal actual fun expectDelete(path: String) {
     NSFileManager.defaultManager.removeItemAtPath(path, null)
 }
@@ -43,6 +76,12 @@ internal actual fun expectDeleteFilesWithPrefix(dirPath: String, namePrefix: Str
     }
 }
 
+internal actual fun expectListFileNamesInDirectory(dirPath: String): List<String> {
+    val contents = NSFileManager.defaultManager.contentsOfDirectoryAtPath(dirPath, null)
+        ?: return emptyList()
+    return (contents as List<*>).filterIsInstance<String>()
+}
+
 internal actual fun expectGetAppCacheDirectory(): String {
     val paths = NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, true)
     return (paths.firstOrNull() as? String) ?: ""