refactor: re-organize backends into separate files

src/types.zig

@@ -0,0 +1,63 @@
+const std = @import("std");
+const builtin = @import("builtin");
+const build_options = @import("build_options");
+
+pub const EventType = enum {
+    created,
+    modified,
+    deleted,
+    /// Only produced on macOS and Windows where the OS gives no pairing info.
+    /// On Linux, paired renames are emitted as a rename event with both paths instead.
+    renamed,
+};
+
+pub const ObjectType = enum {
+    file,
+    dir,
+    /// The object type could not be determined (e.g. a deleted file on Windows
+    /// where the path no longer exists to query).
+    unknown,
+};
+
+pub const Error = error{
+    HandlerFailed,
+    OutOfMemory,
+    WatchFailed,
+};
+
+/// True when the Linux inotify backend runs in poll mode (caller drives the
+/// event loop via poll_fd / handle_read_ready).  False on all other platforms
+/// and on Linux when the `linux_read_thread` build option is set.
+pub const linux_poll_mode = builtin.os.tag == .linux and !build_options.linux_read_thread;
+
+pub const ReadableStatus = enum {
+    // TODO: is_readable, // backend may now read from fd (blocking mode)
+    will_notify, // backend must wait for a handle_read_ready call
+};
+
+pub const Handler = struct {
+    vtable: *const VTable,
+
+    pub const VTable = struct {
+        change: *const fn (handler: *Handler, path: []const u8, event_type: EventType, object_type: ObjectType) error{HandlerFailed}!void,
+        rename: *const fn (handler: *Handler, src_path: []const u8, dst_path: []const u8, object_type: ObjectType) error{HandlerFailed}!void,
+        /// Only present in Linux poll mode (linux_poll_mode == true).
+        wait_readable: if (linux_poll_mode) *const fn (handler: *Handler) error{HandlerFailed}!ReadableStatus else void,
+    };
+
+    pub fn change(handler: *Handler, path: []const u8, event_type: EventType, object_type: ObjectType) error{HandlerFailed}!void {
+        return handler.vtable.change(handler, path, event_type, object_type);
+    }
+
+    pub fn rename(handler: *Handler, src_path: []const u8, dst_path: []const u8, object_type: ObjectType) error{HandlerFailed}!void {
+        return handler.vtable.rename(handler, src_path, dst_path, object_type);
+    }
+
+    pub fn wait_readable(handler: *Handler) error{HandlerFailed}!ReadableStatus {
+        if (comptime linux_poll_mode) {
+            return handler.vtable.wait_readable(handler);
+        } else {
+            unreachable;
+        }
+    }
+};