% -----------------
% Copyright © 2022 ACK Cyfronet AGH, Poland.
% -----------------
%
% Get string format for the time values provided in timeVector. Format is based
% on numeric 'FieldType' (GDF) or 'type' (catalog) field
% see https://docs.cyfronet.pl/display/ISEPOS/GDF+v2.2+-+description
function timeStrVector = formatTime(timeVector, fieldType)
  % if we have '5a' and '5b', the date value is a string instead of a number)
  if (ischar(fieldType) && (strcmp(fieldType, '5a') || strcmp(fieldType, '5b')))
    timeStrVector = timeVector;
    return;
  end
  if iscell(timeVector)
    timeVector = cell2mat(timeVector);
  end
  emptyIndexes = isnan(timeVector);
  timeFormat = getTimeFormat(fieldType);
  timeStrVector(~emptyIndexes, 1) = cellstr(datestr(timeVector(~emptyIndexes), timeFormat));
  timeStrVector(emptyIndexes, 1) = { 'NaN' };
end

function timeFormat = getTimeFormat(fieldType)
  if (fieldType == 5)
    timeFormat = 'yyyy mmm dd HH:MM:SS.FFF';
  else
    timeFormat = arrayfun(@changeToMatlabFormat, fieldType(2:end));
  end
end

% Matlab uses different specification of the format than the one used in GDF files (based on Java format) - e.g., 'M' is
% used in GDF for month, while in Matlab it is used for minutes
function correctedFormatId = changeToMatlabFormat(javaTimeFormatId)
  switch javaTimeFormatId
    case 'M'
      correctedFormatId = 'm';
    case 'm'
      correctedFormatId = 'M';
    case 's'
      correctedFormatId = 'S';
    case 'S'
      correctedFormatId = 'F';
    otherwise
      correctedFormatId = javaTimeFormatId;
  end
end