ona/source/ona/files.zig

const coral = @import("coral");

const ext = @import("./ext.zig");

pub const FileAccessor = struct {
	context: *anyopaque,

	actions: *const struct {
		open_readable: *const fn (context: *anyopaque, file_path: []const u8) OpenError!*ReadableFile,
		open_writable: *const fn (context: *anyopaque, file_path: []const u8) OpenError!*WritableFile,
		query: *const fn (context: *anyopaque, file_path: []const u8) QueryError!FileInfo,
	},

	pub fn bind(comptime State: type, state: *State) FileAccessor {
		const Actions = struct {
			fn as_concrete(context: *anyopaque) *State {
				return @ptrCast(*State, @alignCast(@alignOf(State), context));
			}

			fn open_readable(context: *anyopaque, file_path: []const u8) OpenError!*ReadableFile {
				return as_concrete(context).open_readable(file_path);
			}

			fn open_writable(context: *anyopaque, file_path: []const u8) OpenError!*WritableFile {
				return as_concrete(context).open_writable(file_path);
			}

			fn query(context: *anyopaque, file_path: []const u8) QueryError!FileInfo {
				return as_concrete(context).query(file_path);
			}
		};

		return .{
			.context = @ptrCast(*anyopaque, state),

			.actions = &.{
				.open_readable = Actions.open_readable,
				.open_writable = Actions.open_writable,
				.query = Actions.query,
			},
		};
	}

	pub fn open_readable(self: FileAccessor, file_path: []const u8) OpenError!*ReadableFile {
		return self.actions.open_readable(self.context, file_path);
	}

	pub fn open_writable(self: FileAccessor, file_path: []const u8) OpenError!*WritableFile {
		return self.actions.open_readable(self.context, file_path);
	}

	pub fn query(self: FileAccessor, file_path: []const u8) QueryError!FileInfo {
		return self.actions.query(self.context, file_path);
	}
};

pub const FileInfo = struct {
	size: u64,
};

pub const FileSandbox = struct {
	prefix: []const u8,

	flags: packed struct {
		is_readable: bool = false,
		is_writable: bool = false,
		is_queryable: bool = false,
	},

	const native_path_max = 4095;

	fn native_path_of(file_sandbox: *FileSandbox, file_path: []const u8) [native_path_max + 1]u8 {
		var native_path = [_]u8{0} ** (native_path_max + 1);

		if ((file_sandbox.prefix.len + file_path.len) < native_path_max) {
			coral.io.copy(&native_path, file_sandbox.prefix);
			coral.io.copy(native_path[file_sandbox.prefix.len ..], file_path);
		}

		return native_path;
	}

	pub fn open_readable(file_sandbox: *FileSandbox, file_path: []const u8) OpenError!*ReadableFile {
		if (!file_sandbox.flags.is_readable) return error.AccessDenied;

		return @ptrCast(*ReadableFile, ext.SDL_RWFromFile(&file_sandbox.native_path_of(file_path), "rb") orelse {
			return error.FileNotFound;
		});
	}

	pub fn open_writable(file_sandbox: *FileSandbox, file_path: []const u8) OpenError!*WritableFile {
		if (!file_sandbox.flags.is_writable) return error.AccessDenied;

		return @ptrCast(*WritableFile, ext.SDL_RWFromFile(&file_sandbox.native_path_of(file_path), "wb") orelse {
			return error.FileNotFound;
		});
	}

	pub fn query(file_sandbox: *FileSandbox, file_path: []const u8) QueryError!FileInfo {
		if (!file_sandbox.flags.is_queryable) return error.AccessDenied;

		const rw_ops = ext.SDL_RWFromFile(&file_sandbox.native_path_of(file_path), "rb") orelse {
			return error.FileNotFound;
		};

		defer _ = ext.SDL_RWclose(rw_ops);

		const file_size = ext.SDL_RWsize(rw_ops);

		if (file_size < 0) return error.FileNotFound;

		return FileInfo{
			.size = @intCast(u64, file_size),
		};
	}
};

pub const OpenError = QueryError || error {TooManyFiles};

pub const ReadableFile = opaque {
	pub fn as_reader(self: *ReadableFile) coral.io.Reader {
		return coral.io.Reader.bind(self, read);
	}

	fn as_rw_ops(self: *ReadableFile) *ext.SDL_RWops {
		return @ptrCast(*ext.SDL_RWops, @alignCast(@alignOf(ext.SDL_RWops), self));
	}

	pub fn close(self: *ReadableFile) bool {
		return ext.SDL_RWclose(self.as_rw_ops()) != 0;
	}

	pub fn read(self: *ReadableFile, buffer: []u8) coral.io.ReadError!usize {
		ext.SDL_ClearError();

		const buffer_read = ext.SDL_RWread(self.as_rw_ops(), buffer.ptr, @sizeOf(u8), buffer.len);

		if ((buffer_read == 0) and (ext.SDL_GetError().* != 0)) return error.IoUnavailable;

		return buffer_read;
	}

	pub fn rewind(self: *ReadableFile) SeekError!void {
		return self.seek(0);
	}

	pub fn seek(self: *ReadableFile, absolute: u64) SeekError!void {
		ext.SDL_ClearError();

		// TODO: Fix int cast.
		const sought = ext.SDL_RWseek(self.as_rw_ops(), @intCast(i64, absolute), ext.RW_SEEK_SET);

		if ((sought == -1) and (ext.SDL_GetError().* != 0)) return error.IoUnavailable;
	}
};

pub const QueryError = error {
	FileNotFound,
	AccessDenied,
};

pub const SeekError = error {
	IoUnavailable,
};

pub const WritableFile = opaque {
	pub fn as_writer(self: *WritableFile) coral.io.Writer {
		return coral.io.Writer.bind(WritableFile, self);
	}

	fn as_rw_ops(self: *WritableFile) *ext.SDL_RWops {
		return @ptrCast(*ext.SDL_RWops, @alignCast(@alignOf(ext.SDL_RWops), self));
	}

	pub fn close(self: *WritableFile) bool {
		return ext.SDL_RWclose(self.as_rw_ops()) != 0;
	}

	pub fn rewind(self: *WritableFile) SeekError!void {
		return self.seek(0);
	}

	pub fn seek(self: *WritableFile, absolute: u64) SeekError!void {
		ext.SDL_ClearError();

		// TODO: Fix int cast.
		const sought = ext.SDL_RWseek(self.as_rw_ops(), @intCast(i64, absolute), ext.RW_SEEK_SET);

		if ((sought == -1) and (ext.SDL_GetError().* != 0)) return error.IoUnavailable;
	}

	pub fn write(self: *WritableFile, buffer: []const u8) coral.io.WriteError!usize {
		ext.SDL_ClearError();

		const buffer_read = ext.SDL_RWwrite(self.as_rw_ops(), buffer.ptr, @sizeOf(u8), buffer.len);

		if ((buffer_read == 0) and (ext.SDL_GetError().* != 0)) return error.IoUnavailable;

		return buffer_read;
	}
};