import codecs
import locale
import os
import platform

# Note: While we can easily inline the logic related to the constants set in this module, we deliberately create
# small functions that encapsulate that logic as this enables easy unit testing. In particular, by creating functions
# we can easily mock the dependencies during testing, which is not possible if the code is not enclosed in a function
# and just executed at import-time.

########################################################################################################################
LOG_FORMAT = "%(levelname)s: %(name)s %(message)s"

########################################################################################################################
# PLATFORM_IS_WINDOWS


def platform_is_windows():
    return "windows" in platform.system().lower()


PLATFORM_IS_WINDOWS = platform_is_windows()

########################################################################################################################
# USE_SH_LIB
# Determine whether to use the `sh` library
# On windows we won't want to use the sh library since it's not supported - instead we'll use our own shell module.
# However, we want to be able to overwrite this behavior for testing using the GITLINT_USE_SH_LIB env var.


def use_sh_library():
    gitlint_use_sh_lib_env = os.environ.get("GITLINT_USE_SH_LIB", None)
    if gitlint_use_sh_lib_env:
        return gitlint_use_sh_lib_env == "1"
    return False


USE_SH_LIB = use_sh_library()

########################################################################################################################
# TERMINAL_ENCODING
# Encoding used for terminal encoding/decoding.


def getpreferredencoding():
    """Modified version of local.getpreferredencoding() that takes into account LC_ALL, LC_CTYPE, LANG env vars
    on windows and falls back to UTF-8."""
    fallback_encoding = "UTF-8"
    preferred_encoding = locale.getpreferredencoding() or fallback_encoding

    # On Windows, we mimic git/linux by trying to read the LC_ALL, LC_CTYPE, LANG env vars manually
    # (on Linux/MacOS the `getpreferredencoding()` call will take care of this).
    # We fallback to UTF-8
    if PLATFORM_IS_WINDOWS:
        preferred_encoding = fallback_encoding
        for env_var in ["LC_ALL", "LC_CTYPE", "LANG"]:
            encoding = os.environ.get(env_var, False)
            if encoding:
                # Support dotted (C.UTF-8) and non-dotted (C or UTF-8) charsets:
                # If encoding contains a dot: split and use second part, otherwise use everything
                dot_index = encoding.find(".")
                preferred_encoding = encoding[dot_index + 1 :] if dot_index != -1 else encoding
                break

        # We've determined what encoding the user *wants*, let's now check if it's actually a valid encoding on the
        # system. If not, fallback to UTF-8.
        # This scenario is fairly common on Windows where git sets LC_CTYPE=C when invoking the commit-msg hook, which
        # is not a valid encoding in Python on Windows.
        try:
            codecs.lookup(preferred_encoding)
        except LookupError:
            preferred_encoding = fallback_encoding

    return preferred_encoding


TERMINAL_ENCODING = getpreferredencoding()

########################################################################################################################
# FILE_ENCODING
# Gitlint assumes UTF-8 encoding for all file operations:
#  - reading/writing its own hook and config files
#  - reading/writing git commit messages
# Git does have i18n.commitEncoding and i18n.logOutputEncoding options which we might want to take into account,
# but that's not supported today.

FILE_ENCODING = "UTF-8"