% -----------------
% Copyright © 2020 ACK Cyfronet AGH, Poland.
%
% This work was partially funded by EPOS Project funded in frame of PL-POIR4.2
% -----------------
function csvFiles = gdf2csv(gdfFilePath)

  csvFiles = {};
  load(gdfFilePath);
  [~, resultFileNameBase] = fileparts(gdfFilePath);

  fieldNames = fieldnames(d);
  fieldTypes = getFieldTypes(FieldType, fieldNames);

  if (hasSingleData(d, fieldNames))
    if (length(d) > 1)
      M = prepareCellMatrixFromStructArrayWithScalars(d, fieldTypes);
    else
      M = prepareCellMatrixFromSingleStructWithVectors(d, fieldTypes, fieldNames);
    end
    resultFileName = [resultFileNameBase, '.csv'];
    saveCsvFile(M, fieldTypes, fieldNames, resultFileName);
    csvFiles = { resultFileName };
  else
    for i = 1:length(d)
      resultFileName = [resultFileNameBase, '-', num2str(i), '.csv'];
      M = prepareCellMatrixFromSingleStructWithVectors(d(i), fieldTypes, fieldNames);
      saveCsvFile(M, fieldTypes, fieldNames, resultFileName);
      csvFiles{i} = resultFileName;
    end
  end
end

function isSingle = hasSingleData(d, fieldNames)
  isSingle = length(d) == 1 || ~hasAnyVectors(d, fieldNames);
end

function hasVector = hasAnyVectors(d, fieldNames)
  hasVector = false;
  for i = 1:length(d)
    vectorValue = findFirstVectorValue(d(i), fieldNames);
    if ~isempty(vectorValue)
      hasVector = true;
      return;
    end
  end
end

function vectorValue = findFirstVectorValue(d, fieldNames)
  vectorValue = [];
  for i = 1:length(fieldNames)
    value = d.(fieldNames{i});
    if ~ischar(value) && ~isscalar(value)
      vectorValue = value;
      return;
    end
  end
end

function saveCsvFile(M, fieldTypes, fieldNames, filename)
  lineFormat = getLineFormat(fieldTypes);
  fid = fopen(filename, 'w+');
  fprintf(fid, '%s\n', strjoin(fieldNames', ','));
  for k=1:size(M,1)
    fprintf(fid, lineFormat, M{k, :});
  end
  fclose(fid);
end 

function M = prepareCellMatrixFromSingleStructWithVectors(d, fieldTypes, fieldNames)
  % some structures might contain vectors mixed with scalars, in that case we want to repeat the scalar values in the csv file
  d = convertScalarsToVectors(d, fieldNames);
  M = cell(length(d.(fieldNames{1})), length(fieldNames));
  for f = 1:length(fieldTypes)
    fieldType = fieldTypes{f};
    field = d.(fieldNames{f});
    if (isTime(fieldType))
      M(:, f) = formatTime(field, fieldType);
    elseif isnumeric(field)
      if (isrow(field))
        field = field';
      end
      M(:, f) = num2cell(field);
    else
      if (isrow(field))
        field = field';
      end
      M(:, f) = field;
    end
  end
end

function M = prepareCellMatrixFromStructArrayWithScalars(d, fieldTypes)
  M = squeeze(struct2cell(d))';
  M = cellfun(@handleEmptyArray, M, 'UniformOutput', false);
  for f = 1:length(fieldTypes)
    fieldType = fieldTypes{f};
    if (isTime(fieldType))
      M(:, f) = formatTime(M(:, f), fieldType);
    end
  end
end

function struct = convertScalarsToVectors(d, fieldNames)
  struct = d;
  firstVectorValue = findFirstVectorValue(d, fieldNames);
  if isempty(firstVectorValue)
    return;
  end
  count = length(firstVectorValue);
  for i = 1:length(fieldNames)
    field = struct.(fieldNames{i});
    if (isempty(field)) 
      field = nan;
    end
    if ischar(field) || isscalar(field)
      [vectorValue{1:count}] = deal(field);
      struct.(fieldNames{i}) = vectorValue';
    end
  end
end

function value = handleEmptyArray(value)
  if (isempty(value))
    value = nan;
  end
end

% creates a vector of field types written as in FieldType, but preserving the same order of fields as in the 'd'
% structure (fallback for a situation when the types in FieldType are in different order than fieldnames(d) or when
% FieldType contains more entries than fieldnames(d)
function fieldTypes = getFieldTypes(fieldTypeCell, fieldNames)
  fieldTypes = cell(1, length(fieldNames));
  for i = 1:length(fieldNames)
    for j = 1:size(fieldTypeCell, 1)
      if strcmp(fieldNames{i}, fieldTypeCell{j, 1})
        fieldTypes{i} = fieldTypeCell{j, 2};
      end
    end
  end
end