open Common

type t =
{
  alfa : Spindeterminant.t ;
  beta : Spindeterminant.t ;
}

type hole = int
type particle = int




let alfa t = t.alfa

let beta  t = t.beta

let vac n =
  {
    alfa = Spindeterminant.vac n;
    beta = Spindeterminant.vac n;
  }

let phase t =
  match Spindeterminant.(phase t.alfa, phase t.beta) with
  | Phase.Pos, Phase.Pos
  | Phase.Neg, Phase.Neg  -> Phase.Pos
  | _ -> Phase.Neg


let of_spindeterminants a b =
  {
    alfa = a ;
    beta  = b
  }


let is_none t = Spindeterminant.(is_none t.alfa || is_none t.beta)


let negate_phase t =
  { t with alfa = Spindeterminant.negate_phase t.alfa }

let set_phase p t =
  { alfa = Spindeterminant.set_phase p t.alfa ;
    beta = Spindeterminant.set_phase Phase.Pos t.beta
  }


let excitation_level_alfa t t' =
  Spindeterminant.excitation_level t.alfa t'.alfa

let excitation_level_beta t t' =
  Spindeterminant.excitation_level t.beta t'.beta

let excitation_levels t t' =
  excitation_level_alfa t t', excitation_level_beta t t'


let excitation_level t t' =
  (excitation_level_alfa t t') + (excitation_level_beta t t')


let of_lists n a b =
  let alfa = Spindeterminant.of_list n a
  and beta  = Spindeterminant.of_list n b
  in of_spindeterminants alfa beta


let to_lists t =
  Spindeterminant.to_list t.alfa,
  Spindeterminant.to_list t.beta


let creation spin p t =
  match spin with
  | Spin.Alfa -> { t with alfa = Spindeterminant.creation p t.alfa }
  | Spin.Beta -> { t with beta = Spindeterminant.creation p t.beta }


let annihilation spin h t =
  match spin with
  | Spin.Alfa -> { t with alfa = Spindeterminant.annihilation h t.alfa }
  | Spin.Beta -> { t with beta = Spindeterminant.annihilation h t.beta }


let single_excitation spin h p t =
  assert (h <> p);
  match spin with
  | Spin.Alfa -> { t with alfa = Spindeterminant.single_excitation h p t.alfa }
  | Spin.Beta -> { t with beta = Spindeterminant.single_excitation h p t.beta }


let double_excitation spin h p spin' h' p' t =
  assert (h <> p);
  assert (h' <> p');
  match spin, spin' with
  | Spin.(Alfa, Beta)  ->        { alfa = Spindeterminant.single_excitation h  p      t.alfa ;
                                   beta = Spindeterminant.single_excitation h' p'     t.beta }
  | Spin.(Beta, Alfa)  ->        { beta = Spindeterminant.single_excitation h  p      t.beta ;
                                   alfa = Spindeterminant.single_excitation h' p'     t.alfa }
  | Spin.(Alfa, Alfa)  -> { t with alfa = Spindeterminant.double_excitation h p h' p' t.alfa }
  | Spin.(Beta, Beta)  -> { t with beta = Spindeterminant.double_excitation h p h' p' t.beta }


let compare = compare


let pp ppf t =
  Format.fprintf ppf "@[<v>@[phase:%a@]@;@[a:%a@]@;@[b:%a@]@]@."
    Phase.pp (phase t)
    Spindeterminant.pp t.alfa
    Spindeterminant.pp t.beta