feat(core): appstate

src/core/observable.zig

@@ -0,0 +1,41 @@
+pub fn Observable(T: type) type {
+    return struct {
+        observers: std.ArrayList(*const Observer(T)),
+
+        const Self = @This();
+        pub fn init(allocator: std.mem.Allocator) Self {
+            return .{
+                .observers = std.ArrayList(*const Observer(T)).init(allocator),
+            };
+        }
+
+        pub fn deinit(self: *Self) void {
+            self.observers.deinit();
+        }
+
+        pub fn attach(self: *Self, obs: *const Observer(T)) !void {
+            try self.observers.append(obs);
+        }
+
+        pub fn detach(self: *Self, obs: *const Observer(T)) void {
+            if (std.mem.indexOfScalar(*const Observer, self.observers.items, obs)) |index| {
+                _ = self.observers.swapRemove(index);
+            }
+        }
+
+        pub fn notify(self: Self, args: T) void {
+            for (self.observers.items) |obs| {
+                obs.update(obs.ctx, args);
+            }
+        }
+    };
+}
+
+pub fn Observer(T: type) type {
+    return struct {
+        ctx: *anyopaque,
+        update: *const fn (ctx: *anyopaque, args: T) void,
+    };
+}
+
+const std = @import("std");