Edit2D/entity.odin

package ion

import b2 "vendor:box2d"
import array "core:container/small_array"

static_index :: i32

static_index_global :: struct 
{
	index : i32,
	level : string,
	offset : b2.Vec2,
}

/*
	This file contains code to handle box2d stuffs of the game code
	Don't put game's logic here
*/

engine_world :: struct 
{
	world_id : b2.WorldId,
	
	//This in engine code?
	static_indexes          : map[static_index]int `cbor:"-"`,
	relations               : map[^static_index][dynamic]static_index_global `cbor:"-"`,
	relations_serializeable : map[ static_index][dynamic]static_index_global,
	
	/*
		Seems okay to put the joint defs in engine rather than in game because
		we don't add more attributes in joints in the game

		Can be changed later without requireing refactor
	*/
	revolute_joint_defs     : [dynamic]revolt_joint_def,
	distant_joint_defs      : [dynamic]distance_joint_def,
	joints                  : [dynamic]b2.JointId `cbor:"-"`,
}

engine_entity_flags_enum :: enum u64 {
	POLYGON_IS_BOX,
	MULTI_BODIES,
	CHAIN,
	MULTI_SHAPES,
}

engine_entity_flags :: bit_set[engine_entity_flags_enum]

engine_entity_def :: struct {
	body_def   : b2.BodyDef,
	shape_def  : b2.ShapeDef,
	shape_type : b2.ShapeType,
	
	
	radius, scale : f32,
	centers       : [2]b2.Vec2,
	size          : b2.Vec2,
	is_loop       : bool,
	vertices      : array.Small_Array(b2.MAX_POLYGON_VERTICES, b2.Vec2),
	name_buf      : [255]u8 `fmt:"-" cbor:"-"`,
	
	entity_flags  : engine_entity_flags,
	
	index         : static_index,
	
	//For chain bodies
	//It will replicate itself to the body count and connect themselves with rev_joints
	body_count    : i32,
	rev_joint     : b2.RevoluteJointDef,
	half_link_length : f32
}

engine_entity  :: struct {
	body_id       : b2.BodyId,
	shape_id      : b2.ShapeId,
	
	//This is if the entity has multiple bodies
	bodies        : [dynamic]b2.BodyId,
	shapes        : [dynamic]b2.ShapeId,
	joints        : [dynamic]b2.JointId,
	entity_flags  : engine_entity_flags,
	index         : ^static_index,
} 



engine_entity_single_body :: proc(def : ^engine_entity_def, world_id: b2.WorldId, index : i32) -> engine_entity
{
	
	def := def
	
	new_entity : engine_entity
	
	
	if def.index != 0
	{
		new_entity.index  = new(static_index)
		new_entity.index^ = def.index
	}
	
	new_entity.body_id = b2.CreateBody(world_id, def.body_def)
	
	switch def.shape_type{
	
	case .circleShape:
		{
			def.radius *= def.scale
			circle := b2.Circle{ radius = def.radius }
			
			def.scale = 1
			
			new_entity.shape_id = b2.CreateCircleShape(new_entity.body_id, def.shape_def, circle)
		}
		
	case .capsuleShape:
		{
			def.radius     *= def.scale
			def.centers[0] *= def.scale
			def.centers[1] *= def.scale
			
			def.scale = 1
			
			capsule := b2.Capsule{
				center1 = def.centers[0], 
				center2 = def.centers[1], 
				radius = def.radius
			}
			
			new_entity.shape_id = b2.CreateCapsuleShape(
				new_entity.body_id,
				def.shape_def,
				capsule
			)
		}
	case .chainSegmentShape:
		{
			chain_def := b2.DefaultChainDef()
			verts :[dynamic]b2.Vec2
			
			for &v in array.slice(&def.vertices){
				v *= def.scale
			}
			
			
			for v in array.slice(&def.vertices){
				//If it's not a looped chain then it needs two defination
				
				if !def.is_loop do append(&verts, v)
				
				append(&verts, v)
			}
			
			slice := array.slice(&def.vertices)
			
			chain_def.points = &verts[0]
			chain_def.count = i32(len(verts))
			chain_def.isLoop = def.is_loop
			
			c := b2.CreateChain(new_entity.body_id, chain_def)
			
			shapes_data :[10]b2.ShapeId
			shapes := b2.Body_GetShapes(new_entity.body_id, shapes_data[:])
			
			for shape in shapes{
				b2.Shape_SetUserData(shape, rawptr(uintptr(index)))
			}
			
			def.scale = 1
			
			
		}	
	case .segmentShape:
		{
			for &v in array.slice(&def.vertices){
				v *= def.scale
			}
			segment : b2.Segment = {point1 = array.get(def.vertices, 0), point2 = array.get(def.vertices, 2)}
			
			new_entity.shape_id = b2.CreateSegmentShape(new_entity.body_id, def.shape_def, segment)
			def.scale = 1
			
		}
	case .polygonShape:
		{
			poly : b2.Polygon
			
			if .POLYGON_IS_BOX in def.entity_flags
			{
				def.size *= def.scale
				poly      = b2.MakeBox(def.size.x, def.size.y)
				def.scale = 1
			}else
			{
				//def.size *= def.scale
				
				for &v in array.slice(&def.vertices){
					v *= def.scale
				}
				
				points := make([dynamic]b2.Vec2, 0)
				
				for p, i in array.slice(&def.vertices){
					if i >= int(def.vertices.len) do break
					append_elem(&points, p)
				}
				sort_points_ccw(points[:])
				
				hull := b2.ComputeHull(points[:])
				poly = b2.MakePolygon(hull, 0)
				delete(points)
				def.scale = 1
			}
			new_entity.shape_id = b2.CreatePolygonShape(new_entity.body_id, def.shape_def, poly)
		}
	
	}
	
	if def.shape_type != .chainSegmentShape{
		b2.Shape_SetUserData(new_entity.shape_id, rawptr(uintptr(index)))
	}
	
	return new_entity
}