From a06622361d858c4d9c78c15323fc0d0e17e94110 Mon Sep 17 00:00:00 2001
From: the lemons <citrons@mondecitronne.com>
Date: Wed, 21 Dec 2022 15:46:30 -0600
Subject: collision detection and correction

---
 main.lua         |  4 +++-
 obj.lua          | 40 ++++++++++++++++++++++++++++++++++------
 objects/test.lua |  2 +-
 world.lua        |  2 +-
 4 files changed, 39 insertions(+), 9 deletions(-)

diff --git a/main.lua b/main.lua
index ebef333..392fa05 100644
--- a/main.lua
+++ b/main.lua
@@ -68,7 +68,9 @@ function love.draw()
 		end
 	end
 	-- draw all possibly visible objects
-	for o in world.iterate(cx1 - 20, cy1 - 20, cx2 + 20, cy2 + 20) do
+	for o in world.in_box(
+			cx1 - obj.max_size, cy1 - obj.max_size,
+			cx2 + obj.max_size, cy2 + obj.max_size) do
 		set_color(1, 1, 1)
 		o:draw()
 	end
diff --git a/obj.lua b/obj.lua
index 5f35755..59a68d5 100644
--- a/obj.lua
+++ b/obj.lua
@@ -29,7 +29,6 @@ function obj.load(id, data)
 	o:init()
 	return o
 end
-
 function obj.is_obj(v)
 	return getmetatable(v) == obj
 end
@@ -48,6 +47,13 @@ function obj:overload(m, ...)
 	end
 end
 
+function obj:init(...)
+	self.chunk = world.chunk(unpack(self.data.pos))
+	self.chunk.objects[self.id] = self
+	world.objects[self.id] = self
+	return self:overload("init", ...)
+end
+
 function obj:tick(...)
 	if self.data.vel then
 		local vx, vy = unpack(self.data.vel)
@@ -57,7 +63,32 @@ function obj:tick(...)
 	if self.data.avel then
 		self.data.angle = (self.data.angle or 0) + self.data.avel / pi
 	end
+
+	if self.hitbox then
+		local x, y = unpack(self.data.pos)
+		for o in world.in_box(
+				x - obj.max_size, y - obj.max_size,
+				x + obj.max_size, y + obj.max_size) do
+			if o.hitbox and o ~= self then
+				local dist = o.hitbox + self.hitbox
+				local ox, oy = unpack(o.data.pos)
+				local dx, dy = ox - x, oy - y
+				if dx*dx + dy*dy < dist*dist then
+					local angle = math.atan2(dy, dx)
+					-- reposition self outside of collided object
+					self.data.pos[1] =
+						self.data.pos[1] - math.cos(angle) * dist + dx
+					self.data.pos[2] =
+						self.data.pos[2] - math.sin(angle) * dist + dy
+					self:collision(o, angle)
+					o:collision(self, pi - angle)
+				end
+			end
+		end
+	end
+
 	self:overload("tick", ...)
+
 	local chunk = world.chunk(unpack(self.data.pos))
 	if chunk ~= self.chunk then
 		self.chunk.objects[self.id] = nil
@@ -76,11 +107,8 @@ function obj:draw(...)
 	love.graphics.pop()
 end
 
-function obj:init(...)
-	self.chunk = world.chunk(unpack(self.data.pos))
-	self.chunk.objects[self.id] = self
-	world.objects[self.id] = self
-	return self:overload("init", ...)
+function obj:collision(collided)
+	return self:overload("collision", collided)
 end
 
 function obj:remove()
diff --git a/objects/test.lua b/objects/test.lua
index d8c1a65..9d72b29 100644
--- a/objects/test.lua
+++ b/objects/test.lua
@@ -1,4 +1,4 @@
-local test = {radius = 4}
+local test = {hitbox = 4}
 
 function test:draw()
 	line(-4, 4, 0, -4, 4, 4, -4, 4)
diff --git a/world.lua b/world.lua
index c153a70..0607225 100644
--- a/world.lua
+++ b/world.lua
@@ -43,7 +43,7 @@ function world.all()
 	end)
 end
 
-function world.iterate(x1, y1, x2, y2)
+function world.in_box(x1, y1, x2, y2)
 	return coroutine.wrap(function()
 		for x = x1, x2 + world.chunk_size, world.chunk_size do
 			for y = y1, y2 + world.chunk_size, world.chunk_size do
-- 
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