%--------------------------
 % @Author: Jingqiao Hu
 % @Date: 2022-01-21 10:22:36
 % @LastEditTime: 2022-01-29 15:24:37

 % WHAT I NEED for each v-cell:
 % 1. pnt-poly,              for intersection with MMC
 %      c_polyPnts: vertex of each polytope
 %      c_polyMesh: triangulation surface of each polytope 
 % 2. nodes, tets,           for simulation
 % 3. segments,              for initializing MMC
 % 4. polygon of each faces, for building Bezier surface
%--------------------------
function [c_polyMesh, c_node, c_tet, c_segs, c_polygon] = ...
    generateMesh(seeds, nelx, nely, nelz, microx, optDesign)

    path0 = "data/" + optDesign + "/";

    npnts = size(seeds, 1);
    ncvt = npnts;

    globalx = nelx * microx;
    globaly = nely * microx;
    globalz = nelz * microx;

    if strcmp(optDesign,'cantilever_hole')
        [c_segs, c_norms] = mexVD_info_file(seeds, int32(1:npnts)', globalx, globaly, globalz);
    else
        [c_segs, c_norms] = mexVD_info(seeds, int32(1:npnts)', globalx, globaly, globalz);
    end

    c_polyMesh  = cell(ncvt,  1);
    c_node      = cell(ncvt,  1);
    c_tet       = cell(ncvt,  1);
    c_polygon   = cell(ncvt,  1);

    figure; 
    % merge colinear segs
    for i = 1 : ncvt
        segs  = c_segs{i}; % [m,6]
        norms = c_norms{i};

        pnts = reshape(segs', 3, [])'; % [n,3]
        pntsFiltered = uniquetol(pnts, 1e-5, 'ByRows', true ); 
        
        faces = int32(convhull(pntsFiltered(:,1), pntsFiltered(:,2), pntsFiltered(:,3),'Simplify',true));
        vert1 = pntsFiltered(faces(:,1),:);
        vert2 = pntsFiltered(faces(:,2),:);
        vert3 = pntsFiltered(faces(:,3),:);
        c_polyMesh{i} = [vert1, vert2, vert3]; % for the following intersection

        clf;
        scatter3(vert1(:,1), vert1(:,2), vert1(:,3), 'filled'); axis equal; hold on; 
        scatter3(vert2(:,1), vert2(:,2), vert2(:,3), 'filled'); axis equal; hold on; 
        scatter3(vert3(:,1), vert3(:,2), vert3(:,3), 'filled'); axis equal; hold on; 

        [nodes, tets] = read_tet(path0, i-1);
        c_node{i} = nodes;
        c_tet{i}  = tets;

        [segsPerFace, ~] = build_polygon_surface(segs, norms);
        c_polygon{i} = segsPerFace;
    end
end

function [segsPerFace, faceID] = build_polygon_surface(segs, norms)

    % 1. detect all fnorms to find nfaces
    % 2. for each fnorm: find corresponding segs
    % 3. order these segs

    fn0 = reshape(norms', 3, [])'; % n,6
    fn1 = uniquetol(fn0, 1e-5, 'ByRows', true ); 
    
    nface = size(fn1, 1);
    nsegs = size(segs, 1);

    faceID = zeros(nsegs, 2); % each seg belongs to 2 faces
    segsPerFace = cell(nface, 1); % all segs belong to this face

    for i = 1 : nsegs
        f1 = fn0(2*i-1, :);
        f2 = fn0(2*i, :);

        [idx1, ~] = find(abs(fn1(:, 1) - f1(1)) < 1e-5 & ...
                        abs(fn1(:, 2) - f1(2)) < 1e-5 & ...
                        abs(fn1(:, 3) - f1(3)) < 1e-5);
        [idx2, ~] = find(abs(fn1(:, 1) - f2(1)) < 1e-5 & ...
                        abs(fn1(:, 2) - f2(2)) < 1e-5 & ...
                        abs(fn1(:, 3) - f2(3)) < 1e-5);                        
        faceID(i, :) = [idx1, idx2];

        segsPerFace{idx1} = [segsPerFace{idx1}; segs(i, :)];
        segsPerFace{idx2} = [segsPerFace{idx2}; segs(i, :)];
    end

%     figure(1); clf; 
    tol = 1e-2;

    % reorder segs
    for i = 1 : nface
        %% 1. reorder segs as end by end
        s0 = segsPerFace{i};

        s1 = zeros(size(s0));
        s1(1,:) = s0(1,:);

        for j = 1 : size(s0, 1) - 1
            p1 = s1(j, 1:3);
            p2 = s1(j, 4:6);

            % find seg in s0: pi != p1 && pj = p2
            [idx1, ~] = find(abs(s0(:,1) -  p2(1)) < tol & ...
                             abs(s0(:,2) -  p2(2)) < tol & ...
                             abs(s0(:,3) -  p2(3)) < tol & ...
                            (abs(s0(:,4) -  p1(1)) > tol | ...
                             abs(s0(:,5) -  p1(2)) > tol | ...
                             abs(s0(:,6) -  p1(3)) > tol) );
            if ~isempty(idx1)
                s1(j+1, :) = s0(idx1, :);    
            end

            [idx2, ~] = find((abs(s0(:,1) -  p1(1)) > tol | ...
                              abs(s0(:,2) -  p1(2)) > tol | ...
                              abs(s0(:,3) -  p1(3)) > tol ) & ...
                              abs(s0(:,4) -  p2(1)) < tol & ...
                              abs(s0(:,5) -  p2(2)) < tol & ...
                              abs(s0(:,6) -  p2(3)) < tol );
            if ~isempty(idx2)
                s1(j+1, :) = s0(idx2, [4:6, 1:3]);
            end

            if isempty(idx2) && isempty(idx1)
                error("here!");
            end
        end
        

        %% 2. detect the clockwise
        fi = fn1(i, :); % norms of this face
        v1 = s1(1, 4:6) - s1(1, 1:3);
        v2 = s1(2, 4:6) - s1(2, 1:3);
        fv = cross(v1, v2);
        fv = fv ./ norm(fv);
        
        if abs(fi(1)-fv(1)) < tol && abs(fi(2)-fv(2)) < tol && abs(fi(3)-fv(3)) < tol
        else            
            s2 = zeros(size(s1));
            for j = 1:size(s1, 1)
                jj = size(s1, 1) - j + 1;
                s2(j, :) = [s1(jj, 4:6), s1(jj, 1:3)];
            end
            s1 = s2;
        end
        segsPerFace{i} = s1;        
    end

%     x = segs(:,[1,4]);
%     y = segs(:,[2,5]);
%     z = segs(:,[3,6]);
%     figure(1); clf; plot3(x',y',z','LineWidth',2); hold on;
end

% tet file
% 1. Number of vertex, tet: n1, n2
% vertex:   n * 3
% tet:      m * 4
function [nodes, valid_tets] = read_tet(path0, i)
    
    datapath = [path0+'tet'+num2str(i)+'.txt']; 
    fileID = fopen(datapath, 'r');
    info = fscanf(fileID, '%f');

    npnts  = info(1);
    ntets  = info(2); 

    nodes = reshape(info(3 : 3 + npnts*3 - 1), 3, [])'; % all nodes coodinates of cdt
    tets  = reshape(info(3 + npnts*3 : end), 4, [])' + 1;

    fclose(fileID);

    [valid_tets] = checkValid_tetmesh(nodes, tets);
%     DT = triangulation(valid_tets, nodes(:,1), nodes(:,2), nodes(:,3));
%     figure; tetramesh(DT,'FaceAlpha',0.3);
end