#!/usr/bin/env Python3

import sys

LETTERS = {
    r"$\alpha$": "α",
    r"$\beta$": "β",
    r"$\gamma$": "γ",
    r"$\delta$": "δ",
    r"$\epsilon$": "ε",
    r"$\varepsilon$": "ε",
    r"$\zeta$": "ζ",
    r"$\eta$": "η",
    r"$\theta$": "θ",
    r"$\vartheta$": "θ",
    r"$\kappa$": "κ",
    r"$\lambda$": "λ",
    r"$\mu$": "μ",
    r"$\nu$": "ν",
    r"$\xi$": "ξ",
    r"$\pi$": "π",
    r"$\varpi$": "π",
    r"$\rho$": "ρ",
    r"$\sigma$": "σ",
    r"$\varsigma$": "ς",
    r"$\tau$": "τ",
    r"$\upsilon$": "υ",
    r"$\phi$": "φ",
    r"$\varphi$": "φ",
    r"$\chi$": "χ",
    r"$\psi$": "ψ",
    r"$\omega$": "ω",
    r"$\Gamma$": "Γ",
    r"$\Delta$": "Δ",
    r"$\Theta$": "Θ",
    r"$\Lambda$": "Λ",
    r"$\Xi$": "Ξ",
    r"$\Pi$": "Π",
    r"$\Sigma$": "Σ",
    r"$\Upsilon$": "Υ",
    r"$\Phi$": "Φ",
    r"$\Psi$": "Ψ",
    r"$\Οmega$": "Ω"}

def main(filename):
    with open(filename, "r") as f:
        text = f.read()

    for tex_letter, greek_letter in LETTERS.items():
        text = text.replace(tex_letter, greek_letter)

    with open(filename, "w") as f:
        f.write(text)

if __name__ == "__main__":
    try:
        filename = sys.argv[1]
    except IndexError as e:
        print("You must provide a filename!")
    else:
        main(filename)