Knot Floer homology and integer surgeries

Let Y be a closed three manifold with trivial first homology, and let K⊂Y be a knot. We give a description of the Heegaard Floer homology of integer surgeries on Y along K in terms of the filtered homotopy type of the knot invariant for K. As an illustration of these techniques, we calculate the Heegaard Floer homology groups of non trivial circle bundles over Riemann surfaces (with coefficients in Z/2Z).