# -*- coding: utf-8 -*-
"""Code to read in data files from Bio-Logic instruments"""

import re
import csv


def MPTfile(file_or_path):
    """Simple function to open MPT files as csv.DictReader objects

    Checks for the correct headings, skips any comments and returns a
    csv.DictReader object and a list of comments
    """

    if isinstance(file_or_path, str):
        mpt_file = open(file_or_path, 'r')
    else:
        mpt_file = file_or_path

    magic = next(mpt_file)
    if magic != 'EC-Lab ASCII FILE\n':
        raise ValueError("Bad first line for EC-Lab file: '%s'" % magic)

    nb_headers_match = re.match('Nb header lines : (\d+)', next(mpt_file))
    nb_headers = int(nb_headers_match.group(1))
    if nb_headers < 3:
        raise ValueError("Too few header lines: %d" % nb_headers)

    ## The 'magic number' line, the 'Nb headers' line and the column headers
    ## make three lines. Every additional line is a comment line.
    comments = [next(mpt_file) for i in range(nb_headers - 3)]

    mpt_csv = csv.DictReader(mpt_file, dialect='excel-tab')

    expected_fieldnames = (
        ["mode", "ox/red", "error", "control changes", "Ns changes",
         "counter inc.", "time/s", "control/V/mA", "Ewe/V", "dq/mA.h",
         "P/W", "<I>/mA", "(Q-Qo)/mA.h", "x"],
        ["mode", "ox/red", "error", "control changes", "Ns changes",
         "counter inc.", "time/s", "control/V", "Ewe/V", "I/mA",
         "dQ/mA.h", "P/W"],
        ["mode", "ox/red", "error", "control changes", "Ns changes",
         "counter inc.", "time/s", "control/V", "Ewe/V", "<I>/mA",
         "dQ/mA.h", "P/W"])
    if mpt_csv.fieldnames not in expected_fieldnames:
        raise ValueError("Unrecognised headers for MPT file format")

    return mpt_csv, comments