feat: 🚧 add triggers API

adds a trigger API that allows composing different triggers (base triggers triggered by an event, triggers that combine two triggers) to allow events that use multiple buttons

include/gamepad/triggers.hpp

@@ -0,0 +1,85 @@
+#pragma once
+
+namespace Gamepad {
+
+class AbstractTrigger;
+class ConstantTrigger;
+
+class Trigger final {
+    public:
+    Trigger (bool val): impl(new ConstantTrigger(val)) {}
+    explicit Trigger(std::unique_ptr<AbstractTrigger> _impl) : impl(std::move(_impl)) {}
+    bool eval() { return impl.eval(); }
+    //private:
+    std::unique_ptr<AbstractTrigger> impl;
+}
+
+class AbstractTrigger {
+    public:
+    virtual bool eval() = 0;
+    virtual ~AbstractTrigger() = default;
+}
+
+class ConstantTrigger {
+    public:
+    explicit ConstantTrigger (bool _val) : _val(val) {}
+    override bool eval() { return val; }
+    private:
+    bool val;
+}
+
+class AndTrigger : public AbstractTrigger {
+    public:
+    AndTrigger(std::unique_ptr<AbstractTrigger> _left, 
+    std::unique_ptr<AbstractTrigger> _right) : left(_left), right(_right) {}
+    override bool eval() { return left.eval() & right.eval(); }
+    private:
+    std::unique_ptr<AbstractTrigger> left;
+    std::unique_ptr<AbstractTrigger> right;
+}
+
+class OrTrigger : public AbstractTrigger {
+    public:
+    OrTrigger(std::unique_ptr<AbstractTrigger> _left, 
+    std::unique_ptr<AbstractTrigger> _right) : left(_left), right(_right) {}
+    override bool eval() { return left.eval() | right.eval(); }
+    private:
+    std::unique_ptr<AbstractTrigger> left;
+    std::unique_ptr<AbstractTrigger> right;
+}
+
+class XorTrigger : public AbstractTrigger {
+    public:
+    XorTrigger(std::unique_ptr<AbstractTrigger> _left, 
+    std::unique_ptr<AbstractTrigger> _right) : left(_left), right(_right) {}
+    override bool eval() { return left.eval() ^ right.eval(); }
+    private:
+    std::unique_ptr<AbstractTrigger> left;
+    std::unique_ptr<AbstractTrigger> right;
+}
+
+class NotTrigger : public AbstractTrigger {
+    public:
+    NotTrigger(std::unique_ptr<AbstractTrigger> _op) : op(_op) {}
+    override bool eval() { return !op.eval(); }
+    private:
+    std::unique_ptr<AbstractTrigger> op;
+}
+
+Trigger operator&(Trigger left, Trigger right) {
+    return Trigger(new AndTrigger(std::move(left.impl), std::move(right.impl)));
+}
+
+Trigger operator|(Trigger left, Trigger right) {
+    return Trigger(new OrTrigger(std::move(left.impl), std::move(right.impl)));
+}
+
+Trigger operator^(Trigger left, Trigger right) {
+    return Trigger(new XorTrigger(std::move(left.impl), std::move(right.impl)));
+}
+
+Trigger operator!(Trigger op) {
+    return Trigger(new NotTrigger(std::move(op.impl)));
+}
+
+}