"""Exchange rate CSV parser."""

import csv
from io import StringIO

from royalties.constants.error import ERROR_CSV_EMPTY


class CSVInputError(Exception):
    """Generic CSV Data Error."""

    def __init__(self, message, line_number):
        """Create exception."""
        self.message = message
        self.line_number = line_number

    def __str__(self):
        """Print exception."""
        return 'Line:{} Error: {}'.format(self.line_number, self.message)


class CSVParser:
    """CSV file parser."""

    def __init__(self, has_header, delimiter, formatter):
        """Create parser."""
        self.errors = []
        self.rows = []
        self.has_header = has_header
        self.delimiter = delimiter
        self.formatter = formatter
        self.reader = None
        self.header_values = []

    @classmethod
    def init_from_standard_format(cls, data, formatter):
        """Return an instance of parser for data in standard fx format."""
        sniffer = csv.Sniffer()
        dialect = sniffer.sniff(data)
        has_header = sniffer.has_header(data)
        return cls(
            has_header=has_header, delimiter=dialect.delimiter, formatter=formatter
        )

    def parse_string(self, data):
        """Parse a string csv representation."""
        stream = StringIO(data)
        self.reader = csv.reader(stream, delimiter=self.delimiter)
        self.iterate_lines()
        if not self.rows and not self.errors:
            self.errors.append(ERROR_CSV_EMPTY)

    def iterate_lines(self):
        """Iterate through lines."""
        for row in self.reader:
            self.parse_line(row)

    def parse_line(self, row):
        """Parse a row of data."""
        if self.has_header and self.reader.line_num == 1:
            self.header_values = row
            return
        try:
            self.rows += self.formatter.format(
                row, self.reader.line_num, header_values=self.header_values
            )
        except CSVInputError as e:
            self.errors.append(str(e))

    def get_results(self):
        """Return rows and errors."""
        return {'rows': self.rows, 'errors': self.errors}