add Node

src/main.zig

@@ -222,8 +222,6 @@ pub const Circuit = struct {
     const UpdateOrder = []*Component;
 };
 
-var null_signal = Signal{};
-
 pub const Component = struct {
     name: []const u8,
 
@@ -402,6 +400,77 @@ pub const Microchip = struct {
     }
 };
 
+pub const Node = struct {
+    component: Component,
+
+    pub fn init(allocator: std.mem.Allocator) !*Node {
+        var self = try allocator.create(Node);
+        errdefer allocator.destroy(self);
+        try Component.init(&self.component, allocator, "Circuit Node", 2, 1, &update, &deinit);
+        return self;
+    }
+
+    pub fn deinit(component: *Component, allocator: std.mem.Allocator) void {
+        const self: *Node = @fieldParentPtr("component", component);
+        allocator.destroy(self);
+    }
+
+    pub fn update(component: *Component) AllocatorError!void {
+        const output = component.getOutput(0);
+        const activate = component.getInput(0) orelse &Signal{ .digital = 1 };
+        const trigger = component.getInput(1) orelse &Signal{};
+
+        if (activate.digital == 0) {
+            output.digital = 0;
+            output.analog = 0.0;
+        } else {
+            output.digital = trigger.digital;
+            output.analog = trigger.analog;
+        }
+    }
+};
+
+test "Node" {
+    var trigger = Signal{ .digital = 1, .analog = 1.0 };
+    var activate = Signal{};
+
+    var node = try Node.init(std.testing.allocator);
+    defer node.component.deinit(std.testing.allocator);
+    node.component.inputs.items[1].signal = &trigger;
+
+    // should always pass trigger signal if activate is disconnected
+    try node.component.update();
+    try std.testing.expectEqual(Signal{ .digital = 1, .analog = 1.0 }, node.component.getOutput(0).*);
+
+    node.component.inputs.items[0].signal = &activate;
+
+    // should not pass trigger signal if activate is 0
+    activate.digital = 0;
+    activate.analog = 0.0;
+    try node.component.update();
+    try std.testing.expectEqual(Signal{ .digital = 0, .analog = 0.0 }, node.component.getOutput(0).*);
+
+    // should pass trigger signal if activate is 1 ...
+    activate.digital = 1;
+    activate.analog = 0.0;
+    try node.component.update();
+    try std.testing.expectEqual(Signal{ .digital = 1, .analog = 1.0 }, node.component.getOutput(0).*);
+
+    // should not pass trigger signal if activate.digital is 0
+    // even if activate.analog is not 0.0
+    activate.digital = 0;
+    activate.analog = 1.0;
+    try node.component.update();
+    try std.testing.expectEqual(Signal{ .digital = 0, .analog = 0.0 }, node.component.getOutput(0).*);
+
+    // should preserve the trigger signal polarity and analog strength
+    activate.digital = 1;
+    trigger.digital = -1;
+    trigger.analog = -0.69;
+    try node.component.update();
+    try std.testing.expectEqual(Signal{ .digital = -1, .analog = -0.69 }, node.component.getOutput(0).*);
+}
+
 pub const Battery = struct {
     component: Component,