From 39e97166b83531f3b1da69514653c7dd9e8810ff Mon Sep 17 00:00:00 2001
From: Federico Igne <git@federicoigne.com>
Date: Fri, 4 Nov 2022 22:37:00 +0000
Subject: feat: add force field component/system

This will apply continuous or instantaneus force to any object within a
certain range.
---
 raccoon.lua | 52 +++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 51 insertions(+), 1 deletion(-)

diff --git a/raccoon.lua b/raccoon.lua
index ed0eaa2..8db51ca 100644
--- a/raccoon.lua
+++ b/raccoon.lua
@@ -20,12 +20,27 @@ local util = {
     }
 }
 
+function util.signum(n)
+    if n < 0 then
+        return -1
+    elseif n > 0 then
+        return 1
+    else
+        return 0
+    end
+end
+
 function util.size(t)
     local count = 0
     for _,_ in pairs(t) do count = count + 1 end
     return count
 end
 
+function util.distance(p1,p2)
+    local vec = { p2.x - p1.x, p2.y - p1.y }
+    return math.sqrt(math.pow(vec[1], 2) + math.pow(vec[2], 2)), vec
+end
+
 --- Class factory.
 -- Creates a new class. A function
 -- ```
@@ -316,12 +331,46 @@ function Particles:spawn(pos, entities)
     end
 end
 
+local ForceField = Component()
+function ForceField:init(force,range,instant)
+    self.force = force or 1
+    self.range = range or 1
+    self.instant = instant
+    return self
+end
 
 local Metadata = Component()
 function Metadata:init(name)
     self.name = name or "Unnamed"
     return self
 end
+
+local ForceFieldSystem = System(Pos,ForceField)
+function ForceFieldSystem:exec(entity,enemies)
+    local pos = entity.get_component[Pos]
+    local ff = entity.get_component[ForceField]
+    for _,e in pairs(enemies) do
+        if e.has_component[Pos] and e.has_component[Movement] then
+            local pos1 = e.get_component[Pos]
+            local mov = e.get_component[Movement]
+            local dist,vec = util.distance(pos,pos1)
+            if dist < ff.range then
+                if e.has_component[Metadata] then
+                    local meta = e.get_component[Metadata]
+                    trace("Hit " .. meta.name .. " at position " .. pos1.x .. " " .. pos1.y)
+                else
+                    trace("Hit entity at position " .. pos1.x .. " " .. pos1.y)
+                end
+                mov.cur.x = mov.cur.x + util.signum(vec[1]) * ff.force
+                mov.cur.y = mov.cur.y - ff.force
+            end
+        end
+    end
+    if ff.instant then
+        return true, {ff}
+    end
+end
+
 local InputSystem = System(Input)
 function InputSystem:exec(entity)
     local input = entity.get_component[Input]
@@ -547,7 +596,7 @@ local player = Entity()
             local pos = entity.get_component[Pos]--:to_screen(lpos)
             table.insert(
                 game.entities,
-                Entity():with_component(Pos(pos.x,pos.y)):with_component(CircleEffect(20)))
+                Entity():with_component(Pos(pos.x,pos.y)):with_component(ForceField(5,10,true)):with_component(CircleEffect(20)))
         end,
         nil))
 
@@ -585,6 +634,7 @@ function TIC()
     MovementSystem:run(game.entities)
     ActionSystem:run(game.entities, game)
     EffectSystem:run(game.entities)
+    ForceFieldSystem:run(game.entities, game.entities)
     PosAnimSystem:run(game.entities)
     ParticlesSystem:run(game.entities, game)
     LevelSystem:run(game.levels, game)
-- 
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