"""Module handling the high-level parsing of the files"""

import csv
from enum import Enum
from functools import reduce
from typing import Iterable, Generator

import quality_control.average as avg
import quality_control.standard_error as se
from quality_control.headers import valid_header
from quality_control.errors import (
    ParseError, DuplicateHeader, InvalidCellValue, InvalidHeaderValue)

class FileType(Enum):
    """Enumerate the expected file types"""
    AVERAGE = 1
    STANDARD_ERROR = 2

def parse_strains(filepath):
    """Parse the strains file"""
    with open(filepath, encoding="utf8") as strains_file:
        reader = csv.DictReader(
            strains_file,
            fieldnames=[
                header.strip() for header
                in strains_file.readline().split("\t")],
            delimiter="\t")
        for row in reader:
            yield {
                key: (value if value != "\\N" else None)
                for key, value in row.items()
            }

def __parse_header(line, strains):
    return valid_header(
        set(strains),
        tuple(header.strip() for header in line.split("\t")))

def __parse_average_line(line):
    return (line[0],) + tuple(avg.valid_value(field) for field in line[1:])

def __parse_standard_error_line(line):
    return (line[0],) + tuple(se.valid_value(field) for field in line[1:])

LINE_PARSERS = {
    FileType.AVERAGE: __parse_average_line,
    FileType.STANDARD_ERROR: __parse_standard_error_line
}

def strain_names(strains):
    """Retrieve a complete list of the names of the strains"""
    def __extract_strain_names(acc, strain):
        return acc + tuple(
            item for item in (strain["Name"], strain["Name2"])
            if (item is not None and item != ""))
    return reduce(__extract_strain_names, strains, tuple())

def parse_file(filepath: str, filetype: FileType, strains: list):
    """Parse the given file"""
    seek_pos = 0
    try:
        with open(filepath, encoding="utf-8") as input_file:
            for line_number, line in enumerate(input_file):
                if line_number == 0:
                    yield __parse_header(line, strains)
                    seek_pos = seek_pos + len(line)
                    continue

                yield LINE_PARSERS[filetype](
                    tuple(field.strip() for field in line.split("\t")))
                seek_pos = seek_pos + len(line)
    except (DuplicateHeader, InvalidCellValue, InvalidHeaderValue) as err:
        raise ParseError({
            "filepath": filepath,
            "filetype": filetype,
            "position": seek_pos,
            "line_number": line_number,
            "error": err
        }) from err

def parse_errors(filepath: str, filetype: FileType, strains: list,
                 seek_pos: int = 0) -> Generator:
    """Retrieve ALL the parse errors"""
    print(f"seek_pos: {seek_pos}, {type(seek_pos)}")
    assert seek_pos >= 0, "The seek position must be at least zero (0)"

    def __error_type(error):
        """Return a nicer string representatiton for the error type."""
        if isinstance(error, DuplicateHeader):
            return "Duplicated Headers"
        if isinstance(error, InvalidCellValue):
            return "Invalid Value"
        if isinstance(error, InvalidHeaderValue):
            return "Invalid Strain"

    def __errors(filepath, filetype, strains, seek_pos):
        """Return only the errors as values"""
        with open(filepath, encoding="utf-8") as input_file:
            ## TODO: Seek the file to the given seek position
            for line_number, line in enumerate(input_file):
                if seek_pos > 0:
                    input_file.seek(seek_pos, 0)
                try:
                    if seek_pos == 0 and line_number == 0:
                        header = __parse_header(line, strains)
                        yield None
                        seek_pos = seek_pos + len(line)
                        continue

                    parsed_line = LINE_PARSERS[filetype](
                        tuple(field.strip() for field in line.split("\t")))
                    yield None
                    seek_pos = seek_pos + len(line)
                except (DuplicateHeader, InvalidCellValue, InvalidHeaderValue) as err:
                    yield {
                        "filepath": filepath,
                        "filetype": filetype,
                        "position": seek_pos,
                        "line_number": line_number,
                        "error": __error_type(err),
                        "message": err.args
                    }
                    seek_pos = seek_pos + len(line)

    return (
        error for error in __errors(filepath, filetype, strains, seek_pos)
        if error is not None)

def take(iterable: Iterable, num: int) -> list:
    """Take at most `num` items from `iterable`."""
    iterator = iter(iterable)
    items = []
    try:
        for i in range(0, num):
            items.append(next(iterator))

        return items
    except StopIteration:
        return items