Implementing monte carlo path traced refractions problem

Question

I am writing a forward monte carlo path tracer with the added feature of specular refractions for transparent materials, I have managed to come this far but something is not quite right and I am having a hard time figuring out what. I have looked at the following guide and I make sure to invert the normal, switch the refractive indices etc depending on whether we are entering a material with a lower or higher refractive index. It seems like the reflection part when I get total internal reflection works great but the problem is the refraction direction I think but I don't see the problem with it. I am using a russian roulette approach to choose either reflection or refraction and the variable p is the pdf.

This is what I achieve right now with Transparency = 1.0f, refractive index = 1.5f:

My code for calculating the sample direction looks like this:

vec3 BlinnPhongGlass::sample_wi(vec3 & wi, const vec3 & wo, vec3 & n, float & p) {
    vec3 tangent = normalize(perpendicular(n));
    vec3 bitangent = normalize(cross(tangent, n));
    float phi = 2.0f * M_PI * randf();
    float cos_theta = pow(randf(), 1.0f / (shininess + 1));
    float sin_theta = sqrt(max(0.0f, 1.0f - cos_theta * cos_theta));
    vec3 wh = normalize(sin_theta * cos(phi) * tangent + sin_theta * sin(phi) * bitangent + cos_theta * n);

    if (randf() < 0.5f) {
        // Sample a direction based on the Microfacet brdf
        // PDF for wh
        p = (shininess + 1.0f) * pow(dot(n, wh), shininess) / (2.0f * M_PI);

        // Reflect wo around wh to get wi
        wi = -(wo - (2.0f * dot(wo, wh) * wh));

        // PDF for wi
        p = p / (4.0f * dot(wo, wh));
        p = p * 0.5f;

        return reflection_brdf(wi, wo, n);
    } else {
        p = 1.0f;
        p = p * 0.5f;

        float no = 1.5f; // Glass
        float ni = 1.0f; // Air

        bool outside = dot(wo, n) < 0;
        float etaI = outside ? ni : no; // Index of medium we are currently in
        float etaT = outside ? no : ni; // Index of medium we are about to enter
        float eta = etaI / etaT;

        // Compute wi using Snell's law
        float cosThetaI = outside ? -dot(n, wo) : dot(n, wo);
        float sin2ThetaI = max(0.0f, 1.0f - cosThetaI * cosThetaI);
        float sin2ThetaT = eta * eta * sin2ThetaI;

        // Total internal reflection -> reflect instead
        if (sin2ThetaT >= 1) {
            wi = -(wo - (2.0f * dot(wo, wh) * wh));
            return reflection_brdf(wi, wo, n);
        }

        n = outside ? n : -n; // Invert normal when exiting

        float cosThetaT = sqrt(1.0f - sin2ThetaT);

        wi = normalize(eta * -wo + (eta * cosThetaI - cosThetaT) * n);

        vec3 brdf = vec3(transparency) / dot(wo, n);

        return brdf;
        // We need to attenuate the refracted brdf with (1 - F)
        //const float fresnel_term = R0 + (1.0f - R0) * pow(1.0f - abs(dot(wh, wi)), 5.0f);
        //return (1 - fresnel_term) * brdf;
    }
}