import os
import logging


# Constants governing config resolution:
# Path to the config file, containing key-value pairs of the other settings
CONFIG_ENVVAR = "INQUISITOR_CONFIG"
DEFAULT_CONFIG_PATH = "/etc/inquisitor.conf"

# Path to the folder where items are stored
CONFIG_DATA = "DataPath"
DEFAULT_DATA_PATH = "/var/inquisitor/data/"

# Path to the folder where source modules are stored
CONFIG_SOURCES = "SourcePath"
DEFAULT_SOURCES_PATH = "/var/inquisitor/sources/"

# Path to the folder where cached files are stored
CONFIG_CACHE = "CachePath"
DEFAULT_CACHE_PATH = "/var/inquisitor/cache/"

# Path to a log file where logging will be redirected
CONFIG_LOGFILE = "LogFile"
DEFAULT_LOG_FILE = None

# Whether logging is verbose
CONFIG_VERBOSE = "Verbose"
DEFAULT_VERBOSITY = "false"

# Subfeed source lists, with each subfeed config separated by lines and
# sources within a subfeed separated by spaces
CONFIG_SUBFEEDS = "Subfeeds"
DEFAULT_SUBFEEDS = None
SUBFEED_CONFIG_FILE = "subfeeds.conf"


def read_config_file(config_path):
    """
    Reads a config file of key-value pairs, where non-blank lines are
    either comments beginning with the character '#' or keys and values
    separated by the character '='.
    """
    # Parse the config file into key-value pairs
    if not os.path.isfile(config_path):

        raise FileNotFoundError(
            f"No config file found at {config_path}, try setting {CONFIG_ENVVAR}"
        )
    accumulated_configs = {}
    current_key = None
    with open(config_path, "r", encoding="utf8") as cfg:
        line_no = 0
        for line in cfg:
            line_no += 1
            # Skip blank lines and comments
            if not line.strip() or line.lstrip().startswith("#"):
                continue
            # Accumulate config keyvalue pairs
            if "=" in line:
                # "key = value" begins a new keyvalue pair
                current_key, value = line.split("=", maxsplit=1)
                current_key = current_key.strip()
                accumulated_configs[current_key] = value.strip()
            else:
                # If there's no '=' and no previous key, throw
                if not current_key:
                    raise ValueError(f"Invalid config format on line {line_no}")
                else:
                    accumulated_configs[current_key] += "\n" + line.strip()

    return accumulated_configs


def parse_subfeed_value(value):
    sf_defs = [sf.strip() for sf in value.split("\n") if sf.strip()]
    subfeeds = {}
    for sf_def in sf_defs:
        if ":" not in sf_def:
            raise ValueError(f"Invalid subfeed definition: {sf_def}")
        sf_name, sf_sources = sf_def.split(":", maxsplit=1)
        sf_sources = sf_sources.split()
        subfeeds[sf_name.strip()] = [source.strip() for source in sf_sources]
    return subfeeds


# Read envvar for config file location, with fallback to default
config_path = os.path.abspath(os.environ.get(CONFIG_ENVVAR) or DEFAULT_CONFIG_PATH)

configs = read_config_file(config_path)

# Extract and validate config values
data_path = configs.get(CONFIG_DATA) or DEFAULT_DATA_PATH
if not os.path.isabs(data_path):
    raise ValueError(f"Non-absolute data path: {data_path}")
if not os.path.isdir(data_path):
    raise FileNotFoundError(f"Cannot find directory {data_path}")

source_path = configs.get(CONFIG_SOURCES) or DEFAULT_SOURCES_PATH
if not os.path.isabs(source_path):
    raise ValueError(f"Non-absolute source path: {source_path}")
if not os.path.isdir(source_path):
    raise FileNotFoundError(f"Cannot find directory {source_path}")

cache_path = configs.get(CONFIG_CACHE) or DEFAULT_CACHE_PATH
if not os.path.isabs(cache_path):
    raise ValueError(f"Non-absolute cache path: {cache_path}")
if not os.path.isdir(cache_path):
    raise FileNotFoundError(f"Cannot find directory {cache_path}")

log_file = configs.get(CONFIG_LOGFILE) or DEFAULT_LOG_FILE
if log_file and not os.path.isabs(log_file):
    raise ValueError(f"Non-absolute log file path: {log_file}")

is_verbose = configs.get(CONFIG_VERBOSE) or DEFAULT_VERBOSITY
if is_verbose != "true" and is_verbose != "false":
    raise ValueError(f'Invalid verbose value (must be "true" or "false"): {is_verbose}')
is_verbose = is_verbose == "true"

subfeeds = configs.get(CONFIG_SUBFEEDS) or DEFAULT_SUBFEEDS
if subfeeds:
    subfeeds = parse_subfeed_value(subfeeds)


def get_subfeed_overrides():
    """
    Check for and parse the secondary subfeed configuration file
    """
    path = os.path.join(source_path, SUBFEED_CONFIG_FILE)
    if not os.path.isfile(path):
        return None
    overrides = read_config_file(path)
    if CONFIG_SUBFEEDS not in overrides:
        return None
    value = overrides[CONFIG_SUBFEEDS]
    if not value:
        return None
    parsed_value = parse_subfeed_value(value)
    return parsed_value


# Set up logging
logger = logging.getLogger("inquisitor")
logger.setLevel(logging.DEBUG)


def add_logging_handler(verbose, log_filename):
    """
    Adds a logging handler according to the given settings
    """
    log_format = (
        "[{asctime}] [{levelname}:{filename}:{lineno}] {message}"
        if verbose
        else "[{levelname}] {message}"
    )
    formatter = logging.Formatter(log_format, style="{")

    log_level = logging.DEBUG if verbose else logging.INFO
    handler = (
        logging.handlers.RotatingFileHandler(
            log_filename,
            encoding="utf8",
            maxBytes=2**22,  # 4 MB per log file
            backupCount=4,
        )  # 16 MB total
        if log_filename
        else logging.StreamHandler()
    )
    handler.setFormatter(formatter)
    handler.setLevel(log_level)

    logger.addHandler(handler)


def init_default_logging():
    add_logging_handler(is_verbose, log_file)