Utilities.lua

-- component entity system and utility functions

-- these two functions are responsible for the entire ces
-- check if entity has all the components

function _has(e, ks)
	for c in all(ks) do
        if not e[c] then return false end
    end
    return true
end

-- iterate through entire table of entities (world)
-- run a custom function via the second parameter
function System(ks, f)
    return function(system)
        for e in all(system) do
            if _has(e, ks) then f(e) end
        end
    end
end

-- return of list with entity owning the corresponding id class
function getEntitiesByClass(_class, _world)
    local filteredEntities = {}
    for e in all(_world) do
		if not e.id then return end
		if (e.id.class == _class) then
			add(filteredEntities, e)
		end
    end
    return filteredEntities
end

function getEntitiesBySubclass(_subclass, _world)
    local filteredEntities = {}
	for e in all(_world) do
		if not (e.id) then return end
		if (e.id.subclass == _subclass) then
			add(filteredEntities, e)
		end
    end
    return filteredEntities
end

-- basic AABB collision detection using pos and box components
function coll(e1, e2)
    if e1.pos.x < e2.pos.x + e2.box.w and
        e1.pos.x + e1.box.w > e2.pos.x and
        e1.pos.y < e2.pos.y + e2.box.h and
        e1.pos.y + e1.box.h > e2.pos.y then

        return true
    end
    return false
end

function palAll(_color) -- switch all colors to target color
	for color=1, 15 do 
		pal(color, _color)
	end
end

-- switch all color to white (7) for a flashing effect when entity is damaged
function changePalForHitframe(_entity) 
	if (_entity.hitframe) then palAll(7) end
end

-- polygon draw, taken from wiki
function ngon(x, y, r, n, color)
	line(color)
	for i=0, n do
		local angle = i/n
		line(x + r*cos(angle), y + r*sin(angle))
	end
end

-- get entity's centralised x or y point
function gecx(entity)
	return entity.pos.x + entity.box.w/2
end

function gecy(entity)
	return entity.pos.y + entity.box.h/2
end
 
-- utility random method
function randomOneAmong(object)
	local die = ceil(rnd(#object))

	return object[die]
end

-- due to the max positive integer value in pico-8 being 32767
-- this function won't be able to handle distances longer than
-- 181 pixels
function measureDistance(x1, y1, x2, y2)
	local dx, dy = x2 - x1, y2 - y1
	return sqrt(dx*dx + dy*dy)
end

function getPlayer(_world)
	for e in all(world) do
		if not e.id then break end
		if (e.id.class == "player") then return e end
	end
	return nil
end

function printm(_content, _y, _color)
    print(_content, 64-#_content*2, _y, _color
)
end