import copy
import importlib.util
import inspect
import locale
import logging
import os
import re
import sys
from os.path import isabs
from pathlib import Path
from types import ModuleType
from typing import Any, Optional

from pelican.log import LimitFilter


def load_source(name: str, path: str) -> ModuleType:
    spec = importlib.util.spec_from_file_location(name, path)
    mod = importlib.util.module_from_spec(spec)
    sys.modules[name] = mod
    spec.loader.exec_module(mod)
    return mod


logger = logging.getLogger(__name__)

Settings = dict[str, Any]

DEFAULT_THEME = os.path.join(
    os.path.dirname(os.path.abspath(__file__)), "themes", "notmyidea"
)
DEFAULT_CONFIG = {
    "PATH": os.curdir,
    "ARTICLE_PATHS": [""],
    "ARTICLE_EXCLUDES": [],
    "PAGE_PATHS": ["pages"],
    "PAGE_EXCLUDES": [],
    "THEME": DEFAULT_THEME,
    "OUTPUT_PATH": "output",
    "READERS": {},
    "STATIC_PATHS": ["images"],
    "STATIC_EXCLUDES": [],
    "STATIC_EXCLUDE_SOURCES": True,
    "THEME_STATIC_DIR": "theme",
    "THEME_STATIC_PATHS": [
        "static",
    ],
    "FEED_ALL_ATOM": "feeds/all.atom.xml",
    "CATEGORY_FEED_ATOM": "feeds/{slug}.atom.xml",
    "AUTHOR_FEED_ATOM": "feeds/{slug}.atom.xml",
    "AUTHOR_FEED_RSS": "feeds/{slug}.rss.xml",
    "TRANSLATION_FEED_ATOM": "feeds/all-{lang}.atom.xml",
    "FEED_MAX_ITEMS": 100,
    "RSS_FEED_SUMMARY_ONLY": True,
    "FEED_APPEND_REF": False,
    "SITEURL": "",
    "SITENAME": "A Pelican Blog",
    "DISPLAY_PAGES_ON_MENU": True,
    "DISPLAY_CATEGORIES_ON_MENU": True,
    "DOCUTILS_SETTINGS": {},
    "OUTPUT_SOURCES": False,
    "OUTPUT_SOURCES_EXTENSION": ".text",
    "USE_FOLDER_AS_CATEGORY": True,
    "DEFAULT_CATEGORY": "misc",
    "WITH_FUTURE_DATES": True,
    "CSS_FILE": "main.css",
    "NEWEST_FIRST_ARCHIVES": True,
    "REVERSE_CATEGORY_ORDER": False,
    "DELETE_OUTPUT_DIRECTORY": False,
    "OUTPUT_RETENTION": [],
    "INDEX_SAVE_AS": "index.html",
    "ARTICLE_URL": "{slug}.html",
    "ARTICLE_SAVE_AS": "{slug}.html",
    "ARTICLE_ORDER_BY": "reversed-date",
    "ARTICLE_LANG_URL": "{slug}-{lang}.html",
    "ARTICLE_LANG_SAVE_AS": "{slug}-{lang}.html",
    "DRAFT_URL": "drafts/{slug}.html",
    "DRAFT_SAVE_AS": "drafts/{slug}.html",
    "DRAFT_LANG_URL": "drafts/{slug}-{lang}.html",
    "DRAFT_LANG_SAVE_AS": "drafts/{slug}-{lang}.html",
    "PAGE_URL": "pages/{slug}.html",
    "PAGE_SAVE_AS": "pages/{slug}.html",
    "PAGE_ORDER_BY": "basename",
    "PAGE_LANG_URL": "pages/{slug}-{lang}.html",
    "PAGE_LANG_SAVE_AS": "pages/{slug}-{lang}.html",
    "DRAFT_PAGE_URL": "drafts/pages/{slug}.html",
    "DRAFT_PAGE_SAVE_AS": "drafts/pages/{slug}.html",
    "DRAFT_PAGE_LANG_URL": "drafts/pages/{slug}-{lang}.html",
    "DRAFT_PAGE_LANG_SAVE_AS": "drafts/pages/{slug}-{lang}.html",
    "STATIC_URL": "{path}",
    "STATIC_SAVE_AS": "{path}",
    "STATIC_CREATE_LINKS": False,
    "STATIC_CHECK_IF_MODIFIED": False,
    "CATEGORY_URL": "category/{slug}.html",
    "CATEGORY_SAVE_AS": "category/{slug}.html",
    "TAG_URL": "tag/{slug}.html",
    "TAG_SAVE_AS": "tag/{slug}.html",
    "AUTHOR_URL": "author/{slug}.html",
    "AUTHOR_SAVE_AS": "author/{slug}.html",
    "PAGINATION_PATTERNS": [
        (1, "{name}{extension}", "{name}{extension}"),
        (2, "{name}{number}{extension}", "{name}{number}{extension}"),
    ],
    "YEAR_ARCHIVE_URL": "",
    "YEAR_ARCHIVE_SAVE_AS": "",
    "MONTH_ARCHIVE_URL": "",
    "MONTH_ARCHIVE_SAVE_AS": "",
    "DAY_ARCHIVE_URL": "",
    "DAY_ARCHIVE_SAVE_AS": "",
    "RELATIVE_URLS": False,
    "DEFAULT_LANG": "en",
    "ARTICLE_TRANSLATION_ID": "slug",
    "PAGE_TRANSLATION_ID": "slug",
    "DIRECT_TEMPLATES": ["index", "tags", "categories", "authors", "archives"],
    "THEME_TEMPLATES_OVERRIDES": [],
    "PAGINATED_TEMPLATES": {
        "index": None,
        "tag": None,
        "category": None,
        "author": None,
    },
    "PELICAN_CLASS": "pelican.Pelican",
    "DEFAULT_DATE_FORMAT": "%a %d %B %Y",
    "DATE_FORMATS": {},
    "MARKDOWN": {
        "extension_configs": {
            "markdown.extensions.codehilite": {"css_class": "highlight"},
            "markdown.extensions.extra": {},
            "markdown.extensions.meta": {},
        },
        "output_format": "html5",
    },
    "JINJA_FILTERS": {},
    "JINJA_GLOBALS": {},
    "JINJA_TESTS": {},
    "JINJA_ENVIRONMENT": {
        "trim_blocks": True,
        "lstrip_blocks": True,
        "extensions": [],
    },
    "LOG_FILTER": [],
    "LOCALE": [""],  # defaults to user locale
    "DEFAULT_PAGINATION": False,
    "DEFAULT_ORPHANS": 0,
    "DEFAULT_METADATA": {},
    "FILENAME_METADATA": r"(?P<date>\d{4}-\d{2}-\d{2}).*",
    "PATH_METADATA": "",
    "EXTRA_PATH_METADATA": {},
    "ARTICLE_PERMALINK_STRUCTURE": "",
    "TYPOGRIFY": False,
    "TYPOGRIFY_IGNORE_TAGS": [],
    "TYPOGRIFY_OMIT_FILTERS": [],
    "TYPOGRIFY_DASHES": "default",
    "SUMMARY_END_SUFFIX": "…",
    "SUMMARY_MAX_LENGTH": 50,
    "PLUGIN_PATHS": [],
    "PLUGINS": None,
    "PYGMENTS_RST_OPTIONS": {},
    "TEMPLATE_PAGES": {},
    "TEMPLATE_EXTENSIONS": [".html"],
    "IGNORE_FILES": ["**/.*"],
    "SLUG_REGEX_SUBSTITUTIONS": [
        (r"[^\w\s-]", ""),  # remove non-alphabetical/whitespace/'-' chars
        (r"(?u)\A\s*", ""),  # strip leading whitespace
        (r"(?u)\s*\Z", ""),  # strip trailing whitespace
        (r"[-\s]+", "-"),  # reduce multiple whitespace or '-' to single '-'
    ],
    "INTRASITE_LINK_REGEX": "[{|](?P<what>.*?)[|}]",
    "SLUGIFY_SOURCE": "title",
    "SLUGIFY_USE_UNICODE": False,
    "SLUGIFY_PRESERVE_CASE": False,
    "CACHE_CONTENT": False,
    "CONTENT_CACHING_LAYER": "reader",
    "CACHE_PATH": "cache",
    "GZIP_CACHE": True,
    "CHECK_MODIFIED_METHOD": "mtime",
    "LOAD_CONTENT_CACHE": False,
    "FORMATTED_FIELDS": ["summary"],
    "PORT": 8000,
    "BIND": "127.0.0.1",
}

PYGMENTS_RST_OPTIONS = None


def read_settings(
    path: Optional[str] = None, override: Optional[Settings] = None
) -> Settings:
    settings = override or {}

    if path:
        settings = dict(get_settings_from_file(path), **settings)

    if settings:
        settings = handle_deprecated_settings(settings)

    if path:
        # Make relative paths absolute
        def getabs(maybe_relative, base_path=path):
            if isabs(maybe_relative):
                return maybe_relative
            return os.path.abspath(
                os.path.normpath(
                    os.path.join(os.path.dirname(base_path), maybe_relative)
                )
            )

        for p in ["PATH", "OUTPUT_PATH", "THEME", "CACHE_PATH"]:
            if settings.get(p) is not None:
                absp = getabs(settings[p])
                # THEME may be a name rather than a path
                if p != "THEME" or os.path.exists(absp):
                    settings[p] = absp

        if settings.get("PLUGIN_PATHS") is not None:
            settings["PLUGIN_PATHS"] = [
                getabs(pluginpath) for pluginpath in settings["PLUGIN_PATHS"]
            ]

    settings = dict(copy.deepcopy(DEFAULT_CONFIG), **settings)
    settings = configure_settings(settings)

    # This is because there doesn't seem to be a way to pass extra
    # parameters to docutils directive handlers, so we have to have a
    # variable here that we'll import from within Pygments.run (see
    # rstdirectives.py) to see what the user defaults were.
    global PYGMENTS_RST_OPTIONS  # noqa: PLW0603
    PYGMENTS_RST_OPTIONS = settings.get("PYGMENTS_RST_OPTIONS", None)
    return settings


def get_settings_from_module(module: Optional[ModuleType] = None) -> Settings:
    """Loads settings from a module, returns a dictionary."""

    context = {}
    if module is not None:
        context.update((k, v) for k, v in inspect.getmembers(module) if k.isupper())
    return context


def get_settings_from_file(path: str) -> Settings:
    """Loads settings from a file path, returning a dict."""

    name, ext = os.path.splitext(os.path.basename(path))
    module = load_source(name, path)
    return get_settings_from_module(module)


def get_jinja_environment(settings: Settings) -> Settings:
    """Sets the environment for Jinja"""

    jinja_env = settings.setdefault(
        "JINJA_ENVIRONMENT", DEFAULT_CONFIG["JINJA_ENVIRONMENT"]
    )

    # Make sure we include the defaults if the user has set env variables
    for key, value in DEFAULT_CONFIG["JINJA_ENVIRONMENT"].items():
        if key not in jinja_env:
            jinja_env[key] = value

    return settings


def _printf_s_to_format_field(printf_string: str, format_field: str) -> str:
    """Tries to replace %s with {format_field} in the provided printf_string.
    Raises ValueError in case of failure.
    """
    TEST_STRING = "PELICAN_PRINTF_S_DEPRECATION"
    expected = printf_string % TEST_STRING

    result = printf_string.replace("{", "{{").replace("}", "}}") % f"{{{format_field}}}"
    if result.format(**{format_field: TEST_STRING}) != expected:
        raise ValueError(f"Failed to safely replace %s with {{{format_field}}}")

    return result


def handle_deprecated_settings(settings: Settings) -> Settings:
    """Converts deprecated settings and issues warnings. Issues an exception
    if both old and new setting is specified.
    """

    # PLUGIN_PATH -> PLUGIN_PATHS
    if "PLUGIN_PATH" in settings:
        logger.warning(
            "PLUGIN_PATH setting has been replaced by "
            "PLUGIN_PATHS, moving it to the new setting name."
        )
        settings["PLUGIN_PATHS"] = settings["PLUGIN_PATH"]
        del settings["PLUGIN_PATH"]

    # PLUGIN_PATHS: str -> [str]
    if isinstance(settings.get("PLUGIN_PATHS"), str):
        logger.warning(
            "Defining PLUGIN_PATHS setting as string "
            "has been deprecated (should be a list)"
        )
        settings["PLUGIN_PATHS"] = [settings["PLUGIN_PATHS"]]

    # JINJA_EXTENSIONS -> JINJA_ENVIRONMENT > extensions
    if "JINJA_EXTENSIONS" in settings:
        logger.warning(
            "JINJA_EXTENSIONS setting has been deprecated, "
            "moving it to JINJA_ENVIRONMENT setting."
        )
        settings["JINJA_ENVIRONMENT"]["extensions"] = settings["JINJA_EXTENSIONS"]
        del settings["JINJA_EXTENSIONS"]

    # {ARTICLE,PAGE}_DIR -> {ARTICLE,PAGE}_PATHS
    for key in ["ARTICLE", "PAGE"]:
        old_key = key + "_DIR"
        new_key = key + "_PATHS"
        if old_key in settings:
            logger.warning(
                "Deprecated setting %s, moving it to %s list", old_key, new_key
            )
            settings[new_key] = [settings[old_key]]  # also make a list
            del settings[old_key]

    # EXTRA_TEMPLATES_PATHS -> THEME_TEMPLATES_OVERRIDES
    if "EXTRA_TEMPLATES_PATHS" in settings:
        logger.warning(
            "EXTRA_TEMPLATES_PATHS is deprecated use "
            "THEME_TEMPLATES_OVERRIDES instead."
        )
        if settings.get("THEME_TEMPLATES_OVERRIDES"):
            raise Exception(
                "Setting both EXTRA_TEMPLATES_PATHS and "
                "THEME_TEMPLATES_OVERRIDES is not permitted. Please move to "
                "only setting THEME_TEMPLATES_OVERRIDES."
            )
        settings["THEME_TEMPLATES_OVERRIDES"] = settings["EXTRA_TEMPLATES_PATHS"]
        del settings["EXTRA_TEMPLATES_PATHS"]

    # MD_EXTENSIONS -> MARKDOWN
    if "MD_EXTENSIONS" in settings:
        logger.warning(
            "MD_EXTENSIONS is deprecated use MARKDOWN "
            "instead. Falling back to the default."
        )
        settings["MARKDOWN"] = DEFAULT_CONFIG["MARKDOWN"]

    # LESS_GENERATOR -> Webassets plugin
    # FILES_TO_COPY -> STATIC_PATHS, EXTRA_PATH_METADATA
    for old, new, doc in [
        ("LESS_GENERATOR", "the Webassets plugin", None),
        (
            "FILES_TO_COPY",
            "STATIC_PATHS and EXTRA_PATH_METADATA",
            "https://github.com/getpelican/pelican/"
            "blob/main/docs/settings.rst#path-metadata",
        ),
    ]:
        if old in settings:
            message = f"The {old} setting has been removed in favor of {new}"
            if doc:
                message += f", see {doc} for details"
            logger.warning(message)

    # PAGINATED_DIRECT_TEMPLATES -> PAGINATED_TEMPLATES
    if "PAGINATED_DIRECT_TEMPLATES" in settings:
        message = "The {} setting has been removed in favor of {}".format(
            "PAGINATED_DIRECT_TEMPLATES", "PAGINATED_TEMPLATES"
        )
        logger.warning(message)

        # set PAGINATED_TEMPLATES
        if "PAGINATED_TEMPLATES" not in settings:
            settings["PAGINATED_TEMPLATES"] = {
                "tag": None,
                "category": None,
                "author": None,
            }

        for t in settings["PAGINATED_DIRECT_TEMPLATES"]:
            if t not in settings["PAGINATED_TEMPLATES"]:
                settings["PAGINATED_TEMPLATES"][t] = None
        del settings["PAGINATED_DIRECT_TEMPLATES"]

    # {SLUG,CATEGORY,TAG,AUTHOR}_SUBSTITUTIONS ->
    # {SLUG,CATEGORY,TAG,AUTHOR}_REGEX_SUBSTITUTIONS
    url_settings_url = "http://docs.getpelican.com/en/latest/settings.html#url-settings"
    flavours = {"SLUG", "CATEGORY", "TAG", "AUTHOR"}
    old_values = {
        f: settings[f + "_SUBSTITUTIONS"]
        for f in flavours
        if f + "_SUBSTITUTIONS" in settings
    }
    new_values = {
        f: settings[f + "_REGEX_SUBSTITUTIONS"]
        for f in flavours
        if f + "_REGEX_SUBSTITUTIONS" in settings
    }
    if old_values and new_values:
        raise Exception(
            "Setting both {new_key} and {old_key} (or variants thereof) is "
            "not permitted. Please move to only setting {new_key}.".format(
                old_key="SLUG_SUBSTITUTIONS", new_key="SLUG_REGEX_SUBSTITUTIONS"
            )
        )
    if old_values:
        message = (
            "{} and variants thereof are deprecated and will be "
            "removed in the future. Please use {} and variants thereof "
            "instead. Check {}.".format(
                "SLUG_SUBSTITUTIONS", "SLUG_REGEX_SUBSTITUTIONS", url_settings_url
            )
        )
        logger.warning(message)
        if old_values.get("SLUG"):
            for f in ("CATEGORY", "TAG"):
                if old_values.get(f):
                    old_values[f] = old_values["SLUG"] + old_values[f]
            old_values["AUTHOR"] = old_values.get("AUTHOR", [])
        for f in flavours:
            if old_values.get(f) is not None:
                regex_subs = []
                # by default will replace non-alphanum characters
                replace = True
                for tpl in old_values[f]:
                    try:
                        src, dst, skip = tpl
                        if skip:
                            replace = False
                    except ValueError:
                        src, dst = tpl
                    regex_subs.append((re.escape(src), dst.replace("\\", r"\\")))

                if replace:
                    regex_subs += [
                        (r"[^\w\s-]", ""),
                        (r"(?u)\A\s*", ""),
                        (r"(?u)\s*\Z", ""),
                        (r"[-\s]+", "-"),
                    ]
                else:
                    regex_subs += [
                        (r"(?u)\A\s*", ""),
                        (r"(?u)\s*\Z", ""),
                    ]
                settings[f + "_REGEX_SUBSTITUTIONS"] = regex_subs
            settings.pop(f + "_SUBSTITUTIONS", None)

    # `%s` -> '{slug}` or `{lang}` in FEED settings
    for key in ["TRANSLATION_FEED_ATOM", "TRANSLATION_FEED_RSS"]:
        if (
            settings.get(key)
            and not isinstance(settings[key], Path)
            and "%s" in settings[key]
        ):
            logger.warning("%%s usage in %s is deprecated, use {lang} instead.", key)
            try:
                settings[key] = _printf_s_to_format_field(settings[key], "lang")
            except ValueError:
                logger.warning(
                    "Failed to convert %%s to {lang} for %s. "
                    "Falling back to default.",
                    key,
                )
                settings[key] = DEFAULT_CONFIG[key]
    for key in [
        "AUTHOR_FEED_ATOM",
        "AUTHOR_FEED_RSS",
        "CATEGORY_FEED_ATOM",
        "CATEGORY_FEED_RSS",
        "TAG_FEED_ATOM",
        "TAG_FEED_RSS",
    ]:
        if (
            settings.get(key)
            and not isinstance(settings[key], Path)
            and "%s" in settings[key]
        ):
            logger.warning("%%s usage in %s is deprecated, use {slug} instead.", key)
            try:
                settings[key] = _printf_s_to_format_field(settings[key], "slug")
            except ValueError:
                logger.warning(
                    "Failed to convert %%s to {slug} for %s. "
                    "Falling back to default.",
                    key,
                )
                settings[key] = DEFAULT_CONFIG[key]

    # CLEAN_URLS
    if settings.get("CLEAN_URLS", False):
        logger.warning(
            "Found deprecated `CLEAN_URLS` in settings."
            " Modifying the following settings for the"
            " same behaviour."
        )

        settings["ARTICLE_URL"] = "{slug}/"
        settings["ARTICLE_LANG_URL"] = "{slug}-{lang}/"
        settings["PAGE_URL"] = "pages/{slug}/"
        settings["PAGE_LANG_URL"] = "pages/{slug}-{lang}/"

        for setting in ("ARTICLE_URL", "ARTICLE_LANG_URL", "PAGE_URL", "PAGE_LANG_URL"):
            logger.warning("%s = '%s'", setting, settings[setting])

    # AUTORELOAD_IGNORE_CACHE -> --ignore-cache
    if settings.get("AUTORELOAD_IGNORE_CACHE"):
        logger.warning(
            "Found deprecated `AUTORELOAD_IGNORE_CACHE` in "
            "settings. Use --ignore-cache instead."
        )
        settings.pop("AUTORELOAD_IGNORE_CACHE")

    # ARTICLE_PERMALINK_STRUCTURE
    if settings.get("ARTICLE_PERMALINK_STRUCTURE", False):
        logger.warning(
            "Found deprecated `ARTICLE_PERMALINK_STRUCTURE` in"
            " settings.  Modifying the following settings for"
            " the same behaviour."
        )

        structure = settings["ARTICLE_PERMALINK_STRUCTURE"]

        # Convert %(variable) into {variable}.
        structure = re.sub(r"%\((\w+)\)s", r"{\g<1>}", structure)

        # Convert %x into {date:%x} for strftime
        structure = re.sub(r"(%[A-z])", r"{date:\g<1>}", structure)

        # Strip a / prefix
        structure = re.sub("^/", "", structure)

        for setting in (
            "ARTICLE_URL",
            "ARTICLE_LANG_URL",
            "PAGE_URL",
            "PAGE_LANG_URL",
            "DRAFT_URL",
            "DRAFT_LANG_URL",
            "ARTICLE_SAVE_AS",
            "ARTICLE_LANG_SAVE_AS",
            "DRAFT_SAVE_AS",
            "DRAFT_LANG_SAVE_AS",
            "PAGE_SAVE_AS",
            "PAGE_LANG_SAVE_AS",
        ):
            settings[setting] = os.path.join(structure, settings[setting])
            logger.warning("%s = '%s'", setting, settings[setting])

    # {,TAG,CATEGORY,TRANSLATION}_FEED -> {,TAG,CATEGORY,TRANSLATION}_FEED_ATOM
    for new, old in [
        ("FEED", "FEED_ATOM"),
        ("TAG_FEED", "TAG_FEED_ATOM"),
        ("CATEGORY_FEED", "CATEGORY_FEED_ATOM"),
        ("TRANSLATION_FEED", "TRANSLATION_FEED_ATOM"),
    ]:
        if settings.get(new, False):
            logger.warning(
                "Found deprecated `%(new)s` in settings. Modify %(new)s "
                "to %(old)s in your settings and theme for the same "
                "behavior. Temporarily setting %(old)s for backwards "
                "compatibility.",
                {"new": new, "old": old},
            )
            settings[old] = settings[new]

    # Warn if removed WRITE_SELECTED is present
    if "WRITE_SELECTED" in settings:
        logger.warning(
            "WRITE_SELECTED is present in settings but this functionality was removed. "
            "It will have no effect."
        )

    return settings


def configure_settings(settings: Settings) -> Settings:
    """Provide optimizations, error checking, and warnings for the given
    settings.
    Also, specify the log messages to be ignored.
    """
    if "PATH" not in settings or not os.path.isdir(settings["PATH"]):
        raise Exception(
            "You need to specify a path containing the content"
            " (see pelican --help for more information)"
        )

    # specify the log messages to be ignored
    log_filter = settings.get("LOG_FILTER", DEFAULT_CONFIG["LOG_FILTER"])
    LimitFilter._ignore.update(set(log_filter))

    # lookup the theme in "pelican/themes" if the given one doesn't exist
    if not os.path.isdir(settings["THEME"]):
        theme_path = os.path.join(
            os.path.dirname(os.path.abspath(__file__)), "themes", settings["THEME"]
        )
        if os.path.exists(theme_path):
            settings["THEME"] = theme_path
        else:
            raise Exception("Could not find the theme {}".format(settings["THEME"]))

    # standardize strings to lowercase strings
    for key in ["DEFAULT_LANG"]:
        if key in settings:
            settings[key] = settings[key].lower()

    # set defaults for Jinja environment
    settings = get_jinja_environment(settings)

    # standardize strings to lists
    for key in ["LOCALE"]:
        if key in settings and isinstance(settings[key], str):
            settings[key] = [settings[key]]

    # check settings that must be a particular type
    for key, types in [
        ("OUTPUT_SOURCES_EXTENSION", str),
        ("FILENAME_METADATA", str),
    ]:
        if key in settings and not isinstance(settings[key], types):
            value = settings.pop(key)
            logger.warning(
                "Detected misconfigured %s (%s), falling back to the default (%s)",
                key,
                value,
                DEFAULT_CONFIG[key],
            )

    # try to set the different locales, fallback on the default.
    locales = settings.get("LOCALE", DEFAULT_CONFIG["LOCALE"])

    for locale_ in locales:
        try:
            locale.setlocale(locale.LC_ALL, str(locale_))
            break  # break if it is successful
        except locale.Error:
            pass
    else:
        logger.warning(
            "Locale could not be set. Check the LOCALE setting, ensuring it "
            "is valid and available on your system."
        )

    if "SITEURL" in settings:
        # If SITEURL has a trailing slash, remove it and provide a warning
        siteurl = settings["SITEURL"]
        if siteurl.endswith("/"):
            settings["SITEURL"] = siteurl[:-1]
            logger.warning("Removed extraneous trailing slash from SITEURL.")
        # If SITEURL is defined but FEED_DOMAIN isn't,
        # set FEED_DOMAIN to SITEURL
        if "FEED_DOMAIN" not in settings:
            settings["FEED_DOMAIN"] = settings["SITEURL"]

    # check content caching layer and warn of incompatibilities
    if (
        settings.get("CACHE_CONTENT", False)
        and settings.get("CONTENT_CACHING_LAYER", "") == "generator"
        and not settings.get("WITH_FUTURE_DATES", True)
    ):
        logger.warning(
            "WITH_FUTURE_DATES conflicts with CONTENT_CACHING_LAYER "
            "set to 'generator', use 'reader' layer instead"
        )

    # Warn if feeds are generated with both SITEURL & FEED_DOMAIN undefined
    feed_keys = [
        "FEED_ATOM",
        "FEED_RSS",
        "FEED_ALL_ATOM",
        "FEED_ALL_RSS",
        "CATEGORY_FEED_ATOM",
        "CATEGORY_FEED_RSS",
        "AUTHOR_FEED_ATOM",
        "AUTHOR_FEED_RSS",
        "TAG_FEED_ATOM",
        "TAG_FEED_RSS",
        "TRANSLATION_FEED_ATOM",
        "TRANSLATION_FEED_RSS",
    ]

    if any(settings.get(k) for k in feed_keys):
        if not settings.get("SITEURL"):
            logger.warning(
                "Feeds generated without SITEURL set properly may not be valid"
            )

    if "TIMEZONE" not in settings:
        logger.warning(
            "No timezone information specified in the settings. Assuming"
            " your timezone is UTC for feed generation. Check "
            "https://docs.getpelican.com/en/latest/settings.html#TIMEZONE "
            "for more information"
        )

    # fix up pagination rules
    from pelican.paginator import PaginationRule

    pagination_rules = [
        PaginationRule(*r)
        for r in settings.get(
            "PAGINATION_PATTERNS",
            DEFAULT_CONFIG["PAGINATION_PATTERNS"],
        )
    ]
    settings["PAGINATION_PATTERNS"] = sorted(
        pagination_rules,
        key=lambda r: r[0],
    )

    # Save people from accidentally setting a string rather than a list
    path_keys = (
        "ARTICLE_EXCLUDES",
        "DEFAULT_METADATA",
        "DIRECT_TEMPLATES",
        "THEME_TEMPLATES_OVERRIDES",
        "FILES_TO_COPY",
        "IGNORE_FILES",
        "PAGINATED_DIRECT_TEMPLATES",
        "PLUGINS",
        "STATIC_EXCLUDES",
        "STATIC_PATHS",
        "THEME_STATIC_PATHS",
        "ARTICLE_PATHS",
        "PAGE_PATHS",
    )
    for PATH_KEY in filter(lambda k: k in settings, path_keys):
        if isinstance(settings[PATH_KEY], str):
            logger.warning(
                "Detected misconfiguration with %s setting "
                "(must be a list), falling back to the default",
                PATH_KEY,
            )
            settings[PATH_KEY] = DEFAULT_CONFIG[PATH_KEY]

    # Add {PAGE,ARTICLE}_PATHS to {ARTICLE,PAGE}_EXCLUDES
    mutually_exclusive = ("ARTICLE", "PAGE")
    for type_1, type_2 in [mutually_exclusive, mutually_exclusive[::-1]]:
        try:
            includes = settings[type_1 + "_PATHS"]
            excludes = settings[type_2 + "_EXCLUDES"]
            for path in includes:
                if path not in excludes:
                    excludes.append(path)
        except KeyError:
            continue  # setting not specified, nothing to do

    return settings
