def read_field_names(file_name: str):
    """
    Reads the fields available in the hycom file
        file_name: str
            Complete path to the .a or .b hycom output file. It can also be the name of the file without the .a or .b ending
    """
    if file_name.endswith('.a') or file_name.endswith('.b'):
        file_name = file_name[:-2]

    b_file = open(file_name+'.b', 'r')

    # Reading the header file first 4 lines (general info)
    b_file_lines = b_file.readlines()
    all_fields = []
    for c_line in b_file_lines[10:]:
        c_field = c_line.split()[0].strip()
        if not(c_field in all_fields):
            all_fields.append(c_field)
    return all_fields


def read_field_grid_names(file_name: str):
    """
    Reads the fields available in the hycom grid file
        file_name: str
            Complete path to the .a or .b hycom output file. It can also be the name of the file without the .a or .b ending
    """
    if file_name.endswith('.a') or file_name.endswith('.b'):
        file_name = file_name[:-2]

    b_file = open(file_name+'.b', 'r')

    # Reading the header file first 4 lines (general info)
    b_file_lines = b_file.readlines()
    all_fields = []
    for c_line in b_file_lines[3:]:
        c_field = c_line.split()[0].strip()
        c_field = c_field[:-1]
        if not(c_field in all_fields):
            all_fields.append(c_field)


    return all_fields

def read_var_names(file_name: str,skipb):
    """
    Reads the fields available in the hycom file
        file_name: str
            Complete path to the .a or .b hycom output file. It can also be the name of the file without the .a or .b ending
        skipb: int
            number of lines to skip in .b files to get to variable names
    """
    if file_name.endswith('.a') or file_name.endswith('.b'):
        file_name = file_name[:-2]

    b_file = open(file_name+'.b', 'r')

    # Reading the header file first 4 lines (general info)
    b_file_lines = b_file.readlines()
    all_fields = []
    for c_line in b_file_lines[skipb:]:
        c_field = c_line.split()[0].strip()
        if not(c_field in all_fields):
            all_fields.append(c_field)
    return all_fields