using DFTK
using Downloads
using Unitful
using Plots

PSEUDOLIB = "https://raw.githubusercontent.com/JuliaMolSim/PseudoLibrary"
COMMIT    = "56d1774708e1adfff35d30a403004cb98de4224b"
URL_UPF = PSEUDOLIB * "/$COMMIT/pseudos/pd_nc_sr_lda_standard_04_upf/Li.upf";

psp_hgh  = load_psp("hgh/lda/li-q3.hgh");
path_upf = Downloads.download(URL_UPF, joinpath(tempdir(), "Li.upf"))
psp_upf  = load_psp(path_upf);

function run_bands(psp)
    a = -1.53877u"Å"
    b = -2.66523u"Å"
    c = -4.92295u"Å"
    lattice = [ a  a  0;
               -b  b  0;
                0  0 -c]
    Li = ElementPsp(:Li; psp)
    atoms     = [Li, Li]
    positions = [[1/3, 2/3, 1/4],
                 [2/3, 1/3, 3/4]]

    # These are (as you saw above) completely unconverged parameters
    model = model_LDA(lattice, atoms, positions; temperature=1e-2)
    basis = PlaneWaveBasis(model; Ecut=24, kgrid=(6, 6, 4))

    scfres   = self_consistent_field(basis; tol=1e-4)
    bandplot = plot_bandstructure(scfres)
    (; scfres, bandplot)
end;

result_hgh = run_bands(psp_hgh)
result_hgh.scfres.energies

result_upf = run_bands(psp_upf)
result_upf.scfres.energies

plot(result_hgh.bandplot, result_upf.bandplot, titles=["HGH" "UPF"], size=(800, 400))