"""
©AngelaMos | 2026
constants.py

Shared constants for the Caesar cipher: alphabet definitions and English letter frequency data

Defines the letter sets used by the cipher for case-aware shifting,
the expected frequency percentages for each English letter (used by
frequency analysis to score decryption candidates), and the chi-squared
threshold for filtering results.

Connects to:
  cipher.py - imports UPPERCASE_LETTERS, LOWERCASE_LETTERS, ALPHABET_SIZE
  analyzer.py - imports ENGLISH_LETTER_FREQUENCIES
"""

import string
from typing import Final


UPPERCASE_LETTERS: Final[str] = string.ascii_uppercase
LOWERCASE_LETTERS: Final[str] = string.ascii_lowercase
ALL_LETTERS: Final[str] = UPPERCASE_LETTERS + LOWERCASE_LETTERS

ALPHABET_SIZE: Final[int] = 26

ENGLISH_LETTER_FREQUENCIES: Final[dict[str,
                                       float]] = {
                                           "E": 12.70,
                                           "T": 9.06,
                                           "A": 8.17,
                                           "O": 7.51,
                                           "I": 6.97,
                                           "N": 6.75,
                                           "S": 6.33,
                                           "H": 6.09,
                                           "R": 5.99,
                                           "D": 4.25,
                                           "L": 4.03,
                                           "C": 2.78,
                                           "U": 2.76,
                                           "M": 2.41,
                                           "W": 2.36,
                                           "F": 2.23,
                                           "G": 2.02,
                                           "Y": 1.97,
                                           "P": 1.93,
                                           "B": 1.29,
                                           "V": 0.98,
                                           "K": 0.77,
                                           "J": 0.15,
                                           "X": 0.15,
                                           "Q": 0.10,
                                           "Z": 0.07,
                                       }

CHI_SQUARED_THRESHOLD: Final[float] = 50.0