How can I a find the Light Direction/Ray from a Point on a surface to an Area Light? Is there a universal technique to do this for all types of lights (circle, rectangle, sphere & tube)?

This is for area lighting in a ray tracer.

For example for a point light I know it can be done like this:

class PointLight : public Light 
{ 
    Vec3f pos; 
public: 
    PointLight(const Matrix44f &l2w, const Vec3f &c = 1, const float &i = 1) : Light(l2w, c, i) 
    { l2w.multVecMatrix(Vec3f(0), pos); } 
    // P: is the shaded point
    void getDirectionAndIntensity(const Vec3f &P, Vec3f &lightDir, Vec3f &lightIntensity) const 
    { 
        lightDir = pos - P; // compute light direction 
        float r2 = lightDir.norm(); 
        lightDir.normalize(); 
        lightIntensity = intensity * color / (4 * M_PI * r2); 
    } 
};

How can I a find the Light Direction/Ray from a Point on a surface to an Area Light? Is there a universal technique to do this for all types of lights (circle, rectangle, sphere & tube)?

Although this is for area lighting in a ray tracer, is there another way to implement area lighting through an emissive value that I can apply to any object or surface (I have seen this mentioned online)? As opposed to doing it like this.

For example for a point light I know it can be done like this:

class PointLight : public Light 
{ 
    Vec3f pos; 
public: 
    PointLight(const Matrix44f &l2w, const Vec3f &c = 1, const float &i = 1) : Light(l2w, c, i) 
    { l2w.multVecMatrix(Vec3f(0), pos); } 
    // P: is the shaded point
    void getDirectionAndIntensity(const Vec3f &P, Vec3f &lightDir, Vec3f &lightIntensity) const 
    { 
        lightDir = pos - P; // compute light direction 
        float r2 = lightDir.norm(); 
        lightDir.normalize(); 
        lightIntensity = intensity * color / (4 * M_PI * r2); 
    } 
};