function [] = initDisturbances(opts_param)
% initDisturbances - Initialize the disturbances
%
% Syntax: [] = initDisturbances(opts_param)
%
% Inputs:
%    - opts_param -

%% Default values for opts
opts = struct();

%% Populate opts with input parameters
if exist('opts_param','var')
    for opt = fieldnames(opts_param)'
        opts.(opt{1}) = opts_param.(opt{1});
    end
end

load('./disturbances/mat/dist_psd.mat', 'dist_f');

dist_f.f = dist_f.f(2:end);
dist_f.psd_gm = dist_f.psd_gm(2:end);
dist_f.psd_ty = dist_f.psd_ty(2:end);
dist_f.psd_rz = dist_f.psd_rz(2:end);

Fs = 2*dist_f.f(end);      % Sampling Frequency of data is twice the maximum frequency of the PSD vector [Hz]
N  = 2*length(dist_f.f);   % Number of Samples match the one of the wanted PSD
T0 = N/Fs;                 % Signal Duration [s]
df = 1/T0;                 % Frequency resolution of the DFT [Hz]
                           % Also equal to (dist_f.f(2)-dist_f.f(1))
t = linspace(0, T0, N+1)'; % Time Vector [s]
Ts = 1/Fs;                 % Sampling Time [s]

phi = dist_f.psd_gm;
C = zeros(N/2,1);
for i = 1:N/2
  C(i) = sqrt(phi(i)*df);
end
theta = 2*pi*rand(N/2,1); % Generate random phase [rad]
Cx = [0 ; C.*complex(cos(theta),sin(theta))];
Cx = [Cx; flipud(conj(Cx(2:end)))];;
u = N/sqrt(2)*ifft(Cx); % Ground Motion - x direction [m]
% Dwx = struct('time', t, 'signals', struct('values', u));
Dwx = u;
theta = 2*pi*rand(N/2,1); % Generate random phase [rad]
Cx = [0 ; C.*complex(cos(theta),sin(theta))];
Cx = [Cx; flipud(conj(Cx(2:end)))];;
u = N/sqrt(2)*ifft(Cx); % Ground Motion - y direction [m]
Dwy = u;
theta = 2*pi*rand(N/2,1); % Generate random phase [rad]
Cx = [0 ; C.*complex(cos(theta),sin(theta))];
Cx = [Cx; flipud(conj(Cx(2:end)))];;
u = N/sqrt(2)*ifft(Cx); % Ground Motion - z direction [m]
Dwz = u;

phi = dist_f.psd_ty; % TODO - we take here the vertical direction which is wrong but approximate
C = zeros(N/2,1);
for i = 1:N/2
  C(i) = sqrt(phi(i)*df);
end
theta = 2*pi*rand(N/2,1); % Generate random phase [rad]
Cx = [0 ; C.*complex(cos(theta),sin(theta))];
Cx = [Cx; flipud(conj(Cx(2:end)))];;
u = N/sqrt(2)*ifft(Cx); % Disturbance Force Ty x [N]
Fty_x = u;

phi = dist_f.psd_ty;
C = zeros(N/2,1);
for i = 1:N/2
  C(i) = sqrt(phi(i)*df);
end
theta = 2*pi*rand(N/2,1); % Generate random phase [rad]
Cx = [0 ; C.*complex(cos(theta),sin(theta))];
Cx = [Cx; flipud(conj(Cx(2:end)))];;
u = N/sqrt(2)*ifft(Cx); % Disturbance Force Ty z [N]
Fty_z = u;

phi = dist_f.psd_rz;
C = zeros(N/2,1);
for i = 1:N/2
  C(i) = sqrt(phi(i)*df);
end
theta = 2*pi*rand(N/2,1); % Generate random phase [rad]
Cx = [0 ; C.*complex(cos(theta),sin(theta))];
Cx = [Cx; flipud(conj(Cx(2:end)))];;
u = N/sqrt(2)*ifft(Cx); % Disturbance Force Rz z [N]
Frz_z = u;

u = zeros(length(t), 6);
Fd = u;

Dwx    = Dwx   - Dwx(1);
Dwy    = Dwy   - Dwy(1);
Dwz    = Dwz   - Dwz(1);
Fty_x  = Fty_x - Fty_x(1);
Fty_z  = Fty_z - Fty_z(1);
Frz_z  = Frz_z - Frz_z(1);

save('./mat/nass_disturbances.mat', 'Dwx', 'Dwy', 'Dwz', 'Fty_x', 'Fty_z', 'Frz_z', 'Fd', 'Ts', 't');