From 47e823d5b97294097e988d69f01028456e9ecbc8 Mon Sep 17 00:00:00 2001
From: John McCardle <mccardle.john@gmail.com>
Date: Sun, 5 Mar 2023 22:44:39 -0500
Subject: [PATCH] Animation class (not tested)

---
 src/Animation.cpp | 81 +++++++++++++++++++++++++++++++++++++++++++++++
 src/Animation.h   | 23 ++++++++++++++
 2 files changed, 104 insertions(+)
 create mode 100644 src/Animation.cpp
 create mode 100644 src/Animation.h

diff --git a/src/Animation.cpp b/src/Animation.cpp
new file mode 100644
index 0000000..a50c047
--- /dev/null
+++ b/src/Animation.cpp
@@ -0,0 +1,81 @@
+#include "Animation.h"
+
+// linear interpolation constructor
+template<typename T>
+Animation<T>::Animation(float _d, T _ev, T* _t, std::function<void()> _cb, bool _l)
+:duration(_d), endvalue(_ev), target(_t), callback(_cb), loop(_l),
+index(-1), startvalue(*_t), elapsed(0.0f) {}
+
+// discrete values constructor
+template<typename T>
+Animation<T>::Animation(float _d, std::vector<T> _v, T* _t, std::function<void()> _cb, bool _l)
+:duration(_d), target(_t), callback(_cb), values(_v), loop(_l),
+index(0), startvalue(*_t), elapsed(0.0f), nonelapsed(0.0f) {
+    timestep = _v.size() / _d;
+}
+
+template<typename T>
+Animation<T>::~Animation() {
+    // deconstructor sets target to desired end state (no partial values)
+    cancel();
+}
+
+template<>
+void Animation<std::string>::lerp() {
+    *target = endvalue.substr(0, endvalue.length() * (elapsed / duration));
+}
+
+template<>
+void Animation<int>::lerp() {
+    int delta = endvalue - startvalue;
+    *target = startvalue + (elapsed / duration * delta);
+}
+
+template<>
+void Animation<float>::lerp() {
+    int delta = endvalue - startvalue;
+    *target = startvalue + (elapsed / duration * delta);
+}
+
+template<>
+void Animation<sf::Vector2f>::lerp() {
+    int delta_x = endvalue.x - startvalue.x;
+    int delta_y = endvalue.y - startvalue.y;
+    target->x = startvalue.x + (elapsed / duration * delta_x);
+    target->y = startvalue.y + (elapsed / duration * delta_y);
+}
+
+template<>
+void Animation<sf::Vector2i>::lerp() {
+    int delta_x = endvalue.x - startvalue.y;
+    int delta_y = endvalue.y - startvalue.y;
+    target->x = startvalue.x + (elapsed / duration * delta_x);
+    target->y = startvalue.y + (elapsed / duration * delta_y);
+}
+
+template<typename T>
+void Animation<T>::step(float delta)
+{
+    if (index == -1) {
+        // lerp function
+        elapsed += delta;
+        lerp();
+    }
+    else {
+        nonelapsed += delta;
+        if (nonelapsed < timestep) return;
+        if (index == values.size() - 1) return;
+        elapsed += nonelapsed; // or should it be += timestep?
+        nonelapsed = 0; // or should it -= timestep?
+        index++;
+        *target = values[index];
+    }
+}
+
+template<typename T>
+void Animation<T>::cancel() {
+    if (index == -1)
+        *target = endvalue;
+    else
+        *target = values[values.size() - 1];
+}
diff --git a/src/Animation.h b/src/Animation.h
new file mode 100644
index 0000000..9509876
--- /dev/null
+++ b/src/Animation.h
@@ -0,0 +1,23 @@
+#pragma once
+#include "Common.h"
+
+template<typename T>
+class Animation
+{
+    static constexpr float EPSILON = 0.05;
+    T startvalue, endvalue;
+    int index;
+    float duration, elapsed, nonelapsed, timestep;
+    T* target;
+    std::vector<T> values;
+    std::function<void()> callback;
+    bool loop;
+public:
+    Animation(float, T, T*, std::function<void()>, bool); // lerp
+    Animation(float, std::vector<T>, T*, std::function<void()>, bool); // discrete 
+    ~Animation();
+    void lerp();
+    void step(float);
+    void cancel();
+    bool isDone();
+};