Very naive knockback

1 files changed, 43 insertions, 2 deletions

diff --git a/entity.lua b/entity.lua
index caa5226..5cb52d8 100644
--- a/entity.lua
+++ b/entity.lua
@@ -29,6 +29,14 @@ function Entity:b_state(name)
     self.state_stopwatch = 0
     return self
 end
+function Entity:b_health(health)
+    self.health = health
+    return self
+end
+function Entity:b_damage(damage_spec)
+    self.damage = damage_spec
+    return self
+end
 function Entity:b_render_order(ord)
     self.render_order = ord
     return self
@@ -69,6 +77,10 @@ function Entity:build()
     assert(self.state_stopwatch)
 end
 
+function Entity:is_in_iframe()
+    return self.knockback ~= nil and self.knockback.time >= 0
+end
+
 function Entity:transition_to(state_name)
     assert(self.states[state_name])
     if self.state ~= state_name then
@@ -99,6 +111,9 @@ function Entity:update(dt)
     if self.life_time ~= nil then
         self.life_time -= dt
     end
+    if self.life ~= nil and self.life <= 0 then
+        self:kill()
+    end
 end
 
 function Entity:update_line_of_sight()
@@ -109,10 +124,11 @@ end
 
 -- prevent cobblestoning during non-manhattan movement by "lagging" the sprite
 -- behind the actual physical position
+-- this part was painful.
 function Entity:update_sprite_position()
     if self.sprite_position == nil then return end
 
-    -- step in only x or y. trivial
+    -- step in only x or y. trivial.
     if self.velocity == nil or self.velocity.y == 0 or self.velocity.x == 0 then
         self.sprite_position.x = self.position.x
         self.sprite_position.y = self.position.y
@@ -152,9 +168,34 @@ function Entity:update_sprite_position()
     return self
 end
 
+function Entity:take_damage(direction, damage_spec)
+    if self.health == nil then
+        return
+    end
+    self.health -= damage_spec.amount
+    if damage_spec.knockback ~= nil then
+        self.knockback = {
+            velocity = direction * damage_spec.knockback.magnitude,
+            remaining_time = damage_spec.knockback.time,
+            time = damage_spec.knockback.time
+        }
+    end
+end
+
 function Entity:integrate(dt)
     self.state_stopwatch += dt
-    if (self.velocity != nil) then
+
+    if self.knockback ~= nil then
+        if self.knockback.remaining_time <= 0 then
+            self.knockback = nil
+            self.velocity = vec2(0, 0)
+        else
+            self.velocity = self.knockback.velocity * (self.knockback.remaining_time / self.knockback.time)
+            self.knockback.remaining_time -= dt
+        end
+    end
+
+    if self.velocity ~= nil then
         self.position = self.position + (self.velocity * dt)
     end
 end