""" Sensospot Data Parser

Parsing the numerical output from Sensovations Sensospot image analysis.
"""

import re
from pathlib import Path
from collections import namedtuple

import pandas

from .columns import (
    RAW_DATA_POS_ID,
    META_DATA_WELL_ROW,
    RAW_DATA_COLUMN_SET,
    META_DATA_EXPOSURE_ID,
    META_DATA_WELL_COLUMN,
    RAW_DATA_COLUMNS_RENAME_MAP,
)
from .parameters import add_optional_measurement_parameters

REGEX_WELL = re.compile(
    r"""
    (?P<row>([A-Z]+))  # row name containing one or more letters
    (?P<column>(\d+))     # column, one or more decimals
    """,
    re.VERBOSE | re.IGNORECASE,
)

FileInfo = namedtuple("FileInfo", ["row", "column", "exposure"])


def _guess_decimal_separator(file_handle):
    """ guesses the decimal spearator of a opened data file """
    file_handle.seek(0)
    headers = next(file_handle)  # noqa: F841
    data = next(file_handle)
    separator = "," if data.count(",") > data.count(".") else "."
    file_handle.seek(0)
    return separator


def _parse_csv(data_file):
    """ parse a csv sensovation data file """
    data_path = Path(data_file)
    with data_path.open("r") as handle:
        decimal_sep = _guess_decimal_separator(handle)
        return pandas.read_csv(handle, sep="\t", decimal=decimal_sep)


def _extract_measurement_info(data_file):
    """ extract measurement meta data from a file name """
    data_path = Path(data_file)
    *rest, well, exposure = data_path.stem.rsplit("_", 2)  # noqa: F841
    matched = REGEX_WELL.match(well)
    if matched is None:
        raise ValueError(f"not a valid well: '{well}'")
    row = matched["row"].upper()
    column = int(matched["column"])
    exposure = int(exposure)
    return FileInfo(row, column, exposure)


def _cleanup_data_columns(data_frame):
    """ renames some data columns for consistency and drops unused columns """
    renamed = data_frame.rename(columns=RAW_DATA_COLUMNS_RENAME_MAP)
    surplus_columns = set(renamed.columns) - RAW_DATA_COLUMN_SET
    return renamed.drop(columns=surplus_columns)


def parse_file(data_file):
    """ parses one data file and adds metadata to result 
    
    will race a ValueError, if metadata could not be extracted
    """
    measurement_info = _extract_measurement_info(Path(data_file))
    data_frame = _parse_csv(data_file)
    data_frame[META_DATA_WELL_ROW] = measurement_info.row
    data_frame[META_DATA_WELL_COLUMN] = measurement_info.column
    data_frame[META_DATA_EXPOSURE_ID] = measurement_info.exposure
    return _cleanup_data_columns(data_frame)


def parse_multiple_files(file_list):
    """ parses a list of file paths to one combined dataframe """
    if not file_list:
        raise ValueError("Empty file list provided")
    collection = (parse_file(path) for path in file_list)
    filtered = (frame for frame in collection if frame is not None)
    data_frame = next(filtered)
    for next_frame in filtered:
        data_frame = data_frame.append(next_frame, ignore_index=True)
    data_frame[META_DATA_WELL_ROW] = data_frame[META_DATA_WELL_ROW].astype(
        "category"
    )
    return data_frame


def list_csv_files(folder):
    """ returns all csv files in a folder """
    folder_path = Path(folder)
    files = (item for item in folder_path.iterdir() if item.is_file())
    visible = (item for item in files if not item.stem.startswith("."))
    return (item for item in visible if item.suffix.lower() == ".csv")


def _sanity_check(data_frame):
    """ checks some basic constrains of a combined data frame """
    field_rows = len(data_frame[META_DATA_WELL_ROW].unique())
    field_cols = len(data_frame[META_DATA_WELL_COLUMN].unique())
    exposures = len(data_frame[META_DATA_EXPOSURE_ID].unique())
    spot_positions = len(data_frame[RAW_DATA_POS_ID].unique())
    expected_rows = field_rows * field_cols * exposures * spot_positions
    if expected_rows != len(data_frame):
        raise ValueError("Measurements are missing")
    return data_frame


def parse_folder(folder):
    """ parses all csv files in a folder to one large dataframe """
    file_list = list_csv_files(Path(folder))
    data_frame = parse_multiple_files(file_list)
    data_frame = add_optional_measurement_parameters(data_frame, folder)
    return _sanity_check(data_frame)