function varargout = drawDigraph(varargin)
%DRAWDIGRAPH Draw a directed graph, given as a set of vertices and edges.
%
%   drawDigraph(NODES1, NODES2, EDGES) 
%   NODES1 are originating vertices
%   NODES2 are destination vertices
%   EDGES is an array, with first column containing index of origin vertex
%   (index in NODES1), and second column containing index of destination
%   vertex (index in NODES2).
%   Edges are drawn with arrows.
%
%   H = drawDigraph(...) 
%   return handle to the set of edges.
%   

% ------
% Author: David Legland 
% E-mail: david.legland@inrae.fr
% Created: 2004-08-17
% Copyright 2004-2024 INRA - TPV URPOI - BIA IMASTE

%% Initialisations

% check number of arguments
if nargin < 3
    help drawDigraph;
    return;
end

% initialisations
sn1 = 'bo';     % nodes are red circles
sn2 = 'ro';     % nodes are red circles


%% process input arguments


% First extract the graph structure
n1 = varargin{1};
n2 = varargin{2};
e  = varargin{3};
varargin = varargin(4:length(varargin));

% extract drawing style 
if ~isempty(varargin)
    sn1 = varargin{1};
end

if length(varargin)>1
    sn2 = varargin{2};
end


%% main drawing processing

hold on;

nodes = [n1 ; n2];
e(:,2) = e(:,2)+length(n1);

% Draw a 2 dimensional directed graph

    
% Draw 2D Edges
%if ~strcmp(se, 'none') & size(e, 1)>0
%    he = plot([n1(e(:,1),1) n2(e(:,2),1)]', [n1(e(:,1),2) n2(e(:,2),2)]', se);
%end
he = drawDirectedEdges(nodes, e);

hn = [];
% Draw 2D nodes
if ~strcmp(sn1, 'none')
    hn = plot(n1(:,1), n1(:,2), sn1);   
end

 % Draw 2D nodes
if ~strcmp(sn2, 'none')
    hn = plot(n2(:,1), n2(:,2), sn2);   
end
    
   
%% format output arguments

if nargout==1
    varargout{1} = he;
end

if nargout==2
    varargout{1} = hn;
    varargout{2} = he;
end

