function resolveCollisions()
    for i, obj1_key in ipairs(entityLib) do
        for j, obj2_key in ipairs(entityLib) do
            obj1 = obj1_key.obj
            obj2 = obj2_key.obj
            for k, obj1_id in ipairs(obj1) do
                for l, obj2_id in ipairs(obj2) do
                    if obj1_id ~= obj2_id then
                        collideEntity(obj1, obj1_id, obj2, obj2_id)
                    end
                end
            end
        end

        for j, obj2_key in ipairs(blockLib) do
            obj1 = obj1_key.obj
            obj2 = obj2_key.obj
            for k, obj1_id in ipairs(obj1) do
                for l, obj2_id in ipairs(obj2) do
                    if obj2_id["flags"]["collision"] then
                        collideBlock(obj1, obj1_id, obj2, obj2_id)
                    end
                end
            end
        end
    end
end

function collideBlock(obj1, id1, obj2, id2)
    x1, y1 = entity.getPos(id1)
    w1, h1 = entity.getSize(obj1)
    x2, y2 = block.getPos(id2)
    w2, h2 = block.getSize(obj2)

    local width = math.min(x1+w1, x2+w2) - math.max(x1, x2)
    local height = math.min(y1+h1, y2+h2) - math.max(y1, y2)

    dir = isColliding(x1, y1, w1, h1, x2, y2, w2, h2)

    if dir == "top" then
        entity.addPos(id1, 0, height)
        entity.setVel(id1, nil, 0)
    elseif dir == "bottom" then
        entity.addPos(id1, 0, height*-1)
        entity.ground(id1)
    elseif dir == "left" then
        entity.addPos(id1, width, 0)
        xVel = entity.getVel(id1)
        if xVel < 0 then
            entity.setVel(id1, 10, nil)
        end
    elseif dir == "right" then
        entity.addPos(id1, width*-1, 0)
        xVel = entity.getVel(id1)
        if xVel > 0 then
            entity.setVel(id1, -10, nil)
        end
    end
end

function collideEntity(obj1, id1, obj1, id2)
    x1, y1 = entity.getPos(id1)
    w1, h1 = entity.getSize(obj1)
    x2, y2 = entity.getPos(id2)
    w2, h2 = entity.getSize(obj2)

    local width = math.min(x1+w1, x2+w2) - math.max(x1, x2)
    local height = math.min(y1+h1, y2+h2) - math.max(y1, y2)

    dir = isColliding(x1, y1, w1, h1, x2, y2, w2, h2)

    if dir == "top" then
        entity.addPos(id1, 0, height/2)
        entity.setVel(id1, nil, 0)

        entity.addPos(id2, 0, height/2*-1)
        entity.setVel(id2, nil, 0)
        entity.ground(id2)
    elseif dir == "bottom" then
        entity.addPos(id1, 0, height/2*-1)
        entity.setVel(id1, nil, 0)
        entity.ground(id1)

        entity.addPos(id2, 0, height/2)
        entity.setVel(id2, nil, 0)
    elseif dir == "left" then
        entity.addPos(id1, width/2, 0)
        xVel1 = entity.getVel(id1)


        entity.addPos(id2, width/2*-1, 0)
        xVel2 = entity.getVel(id2)

        if obj1 ~= player and obj2 ~= player then
            if xVel1 < 0 then
                entity.setVel(id1, 1, nil)
            end
            if xVel2 > 0 then
                entity2.setVel(id2, -1, nil)
            end
        end
    elseif dir == "right" then
        entity.addPos(id1, width/2*-1, 0)
        xVel1 = entity.getVel(id1)

        entity.addPos(id2, width/2, 0)
        xVel2 = entity.getVel(id2)

        if obj1 ~= player and obj2 ~= player then
            if xVel1 < 0 then
                entity.setVel(id1, 1, nil)
            end
            if xVel2 > 0 then
                entity.setVel(id2, -1, nil)
            end
        end
    end
end


function isColliding(x1, y1, w1, h1, x2, y2, w2, h2)
    local p1x, p1y = math.max(x1, x2), math.max(y1, y2)
    local p2x, p2y = math.min(x1+w1, x2+w2), math.min(y1+h1, y2+h2)

    if p2x-p1x > 0 and p2y-p1y > 0 then
        return getCollisionSide(x1, y1, w1, h1, x2, y2, w2, h2)
    end
end

function getCollisionSide(x1, y1, w1, h1, x2, y2, w2, h2)
    local m1x, m1y = x1+w1/2, y1+h1/2
    local m2x, m2y = x2+w2/2, y2+h2/2

    if math.abs(m1x-m2x) > math.abs(m1y-m2y) then
        if m1x-m2x < 0 then
            return "right"
        else
            return "left"
        end
    else
        if m1y-m2y < 0 then
            return "bottom"
        elseif m1y-m2y > 0 then
            return "top"
        end
    end
end