1 files changed, 203 insertions, 0 deletions
diff --git a/src/main/kotlin/io/files.kt b/src/main/kotlin/io/files.kt
new file mode 100644
index 0000000..4c53c4e
--- /dev/null
+++ b/src/main/kotlin/io/files.kt
@@ -0,0 +1,203 @@
+package io
+
+import User
+
+sealed interface CreateFileResult {
+	object Created : CreateFileResult
+	sealed interface Failure : CreateFileResult {
+		object NoPermission : Failure
+		object NoParent : Failure
+		object AlreadyExists : Failure
+	}
+}
+
+sealed interface WriteFileResult {
+	object Written : WriteFileResult
+	sealed interface Failure : WriteFileResult {
+		object NoPermission : Failure
+		object NotAFile : Failure
+		data class NotEnoughSpace(
+			val dataSize: Long,
+			val spaceLeft: Long
+		) : Failure
+	}
+}
+
+sealed interface ReadFileResult {
+	data class Read(val data: ByteArray) : ReadFileResult {
+		override fun equals(other: Any?): Boolean = (other as? Read)?.let { it.data.contentEquals(this.data) } ?: false
+
+		override fun hashCode(): Int {
+			return data.contentHashCode()
+		}
+	}
+
+	sealed interface Failure : ReadFileResult {
+		object NoPermission : Failure
+		object NotAFile : Failure
+	}
+}
+
+sealed interface DeleteFileResult {
+	sealed interface Failure : DeleteFileResult {
+		object NoPermission : Failure
+		object NotAFile : Failure
+	}
+
+	object Deleted : DeleteFileResult
+}
+
+interface FileService<INode> {
+	fun getPath(iNode: INode): Path.Absolute
+	fun getINode(path: Path.Absolute): INode
+	fun createFile(iNode: INode, user: User): CreateFileResult
+	fun createSymlink(iNode: INode, user: User, path: Path): CreateFileResult
+	fun createDirectory(iNode: INode, user: User): CreateFileResult
+	fun writeToFile(iNode: INode, user: User, data: ByteArray): WriteFileResult
+	fun readFromFile(iNode: INode, user: User): ReadFileResult
+	fun deleteFile(iNode: INode, user: User): DeleteFileResult
+	fun exists(iNode: INode): Boolean
+	fun isFile(iNode: INode): Boolean
+	fun isDirectory(iNode: INode): Boolean
+	fun isSymlink(iNode: INode): Boolean
+	fun resolve(iNode: INode, fragment: String): INode
+	fun resolve(iNode: INode, path: Path.Relative): INode
+	fun changePermissions(iNode: INode, user: User, permissionUpdate: Map<User, Permission>)
+}
+
+data class Permission(
+	val read: Boolean,
+	val write: Boolean,
+	val execute: Boolean
+) {
+	companion object {
+		val default get() = Permission(read = true, write = true, execute = false)
+	}
+}
+
+sealed interface PrimitiveStorageBlob {
+	val permissions: MutableMap<User, Permission>
+
+	class File(var data: ByteArray, override val permissions: MutableMap<User, Permission>) : PrimitiveStorageBlob
+	class Symlink(val path: Path, override val permissions: MutableMap<User, Permission>) : PrimitiveStorageBlob
+	class Directory(override val permissions: MutableMap<User, Permission>) : PrimitiveStorageBlob
+}
+
+data class PrimitiveINode internal constructor(internal val internalPath: String)
+class PrimitiveFileService : FileService<PrimitiveINode> {
+	private val storageBlobs = mutableMapOf<String, PrimitiveStorageBlob>(
+		"/" to PrimitiveStorageBlob.Directory(mutableMapOf())
+	)
+
+	override fun getPath(iNode: PrimitiveINode): Path.Absolute = Path.of(iNode.internalPath) as Path.Absolute
+
+	override fun getINode(path: Path.Absolute): PrimitiveINode {
+		return resolve(PrimitiveINode("/"), Path.Relative(path.parts))
+	}
+
+	override fun resolve(iNode: PrimitiveINode, fragment: String): PrimitiveINode {
+		if (fragment == "..") {
+			val up = iNode.internalPath.substringBeforeLast('/')
+			if (up.isEmpty()) return PrimitiveINode("/")
+			return PrimitiveINode(up)
+		}
+		if (fragment.isEmpty() || fragment == ".")
+			return iNode
+		val blob = storageBlobs[iNode.internalPath]
+		return when (blob) {
+			is PrimitiveStorageBlob.Symlink -> {
+				when (blob.path) {
+					is Path.Absolute -> getINode(blob.path)
+					is Path.Relative -> resolve(resolve(iNode, ".."), blob.path)
+				}
+			}
+			else -> {
+				PrimitiveINode(iNode.internalPath + "/" + fragment)
+			}
+		}
+	}
+
+	override fun resolve(iNode: PrimitiveINode, path: Path.Relative): PrimitiveINode =
+		path.parts.fold(iNode) { node, fragment -> resolve(node, fragment) }
+
+	private fun getStorageBlob(iNode: PrimitiveINode): PrimitiveStorageBlob? = storageBlobs[iNode.internalPath]
+
+	override fun writeToFile(iNode: PrimitiveINode, user: User, data: ByteArray): WriteFileResult {
+		val file = getStorageBlob(iNode) as? PrimitiveStorageBlob.File ?: return WriteFileResult.Failure.NotAFile
+		if (!hasPermission(user, file) { read })
+			return WriteFileResult.Failure.NoPermission
+		file.data = data
+		return WriteFileResult.Written
+	}
+
+	override fun readFromFile(iNode: PrimitiveINode, user: User): ReadFileResult {
+		val file = getStorageBlob(iNode) as? PrimitiveStorageBlob.File ?: return ReadFileResult.Failure.NotAFile
+		if (!hasPermission(user, file) { read })
+			return ReadFileResult.Failure.NoPermission
+		return ReadFileResult.Read(file.data)
+	}
+
+	override fun exists(iNode: PrimitiveINode): Boolean =
+		getStorageBlob(iNode) != null
+
+	override fun isFile(iNode: PrimitiveINode): Boolean =
+		getStorageBlob(iNode) is PrimitiveStorageBlob.File
+
+	override fun isDirectory(iNode: PrimitiveINode): Boolean =
+		getStorageBlob(iNode) is PrimitiveStorageBlob.Directory
+
+	override fun isSymlink(iNode: PrimitiveINode): Boolean =
+		getStorageBlob(iNode) is PrimitiveStorageBlob.Symlink
+
+	override fun changePermissions(iNode: PrimitiveINode, user: User, permissionUpdate: Map<User, Permission>) {
+		val file = getStorageBlob(iNode) ?: return // TODO Results
+		if (!hasPermission(user, file) { write })
+			return  // TODO Results
+		file.permissions.putAll(permissionUpdate)
+		return // TODO Results
+	}
+
+	override fun deleteFile(iNode: PrimitiveINode, user: User): DeleteFileResult {
+		val file = getStorageBlob(iNode) ?: return DeleteFileResult.Failure.NotAFile
+		if (!hasPermission(user, file) { write })
+			return DeleteFileResult.Failure.NoPermission
+		(storageBlobs.keys.filter { it.startsWith(iNode.internalPath + "/") } + listOf(iNode.internalPath)).forEach {
+			storageBlobs.remove(it)
+		}
+		return DeleteFileResult.Deleted
+	}
+
+	private fun hasPermission(user: User, blob: PrimitiveStorageBlob, check: Permission.() -> Boolean): Boolean {
+		return user.isRoot || blob.permissions[user]?.let(check) ?: false
+	}
+
+	private fun checkCreationPreconditions(iNode: PrimitiveINode, user: User): CreateFileResult? {
+		if (storageBlobs.containsKey(iNode.internalPath)) return CreateFileResult.Failure.AlreadyExists
+		val parent = getStorageBlob(resolve(iNode, ".."))
+		if (parent !is PrimitiveStorageBlob.Directory) return CreateFileResult.Failure.NoParent
+		if (!hasPermission(user, parent) { write }) return CreateFileResult.Failure.NoPermission
+		return null
+	}
+
+	override fun createFile(iNode: PrimitiveINode, user: User): CreateFileResult {
+		val preconditions = checkCreationPreconditions(iNode, user)
+		if (preconditions != null) return preconditions
+		storageBlobs[iNode.internalPath] = PrimitiveStorageBlob.File(byteArrayOf(), mutableMapOf(user to Permission.default))
+		return CreateFileResult.Created
+	}
+
+	override fun createSymlink(iNode: PrimitiveINode, user: User, path: Path): CreateFileResult {
+		val preconditions = checkCreationPreconditions(iNode, user)
+		if (preconditions != null) return preconditions
+		storageBlobs[iNode.internalPath] = PrimitiveStorageBlob.Symlink(path, mutableMapOf(user to Permission.default))
+		return CreateFileResult.Created
+	}
+
+	override fun createDirectory(iNode: PrimitiveINode, user: User): CreateFileResult {
+		val preconditions = checkCreationPreconditions(iNode, user)
+		if (preconditions != null) return preconditions
+		storageBlobs[iNode.internalPath] = PrimitiveStorageBlob.Directory(mutableMapOf(user to Permission.default))
+		return CreateFileResult.Created
+	}
+
+}