"""Module for pacman repository helper functions.
"""

import logging
import subprocess

# ========== Constants ==========
REPO_ADD_CMD = '/usr/bin/repo-add'
REPO_REMOVE_CMD = '/usr/bin/repo-remove'

# ========== Logging setup ==========
syslog = logging.getLogger(__name__)


# ========== Classes ==========
class RepoAddError(BaseException):
    """Exception when the repo-add or repo-remove script fails."""


# ========== Functions ==========
def gen_cmdline(operation, db, opts, *pkgs):
    """Generate a command suitable for invoking either repo-add or
    repo-remove.

    :param operation: run either repo-add or repo-remove
    :type operation: str
    :param db: the database file to operate on
    :type db: str, bytes, or path-like object
    :param opts: extra options to pass to repo-add
    :type opts: list
    :param pkgs: these arguments depend on whether the operation is
        an add or remove.
        If operation is 'add', then pkgs is all of the paths of the
        package files to add to the database. If operation is 'remove',
        then pkgs is the name of the packages to remove from the database.
    :type pkgs: any iterable
    :returns: list of command-line arguments suitable for passing to
        subprocess.run()
    :rtype: list
    :raises: ValueError if operation was invalid
    """
    if not operation == 'add' or operation == 'remove':
        raise ValueError('Invalid operation was requested')

    cmd = [f"/usr/bin/repo-{operation}"]

    if opts is not None:
        cmd.extend(opts)

    cmd.append(db)
    cmd.extend(pkgs)

    return cmd


def repo_add(operation, db, *pkgs, opts=None):
    """Run repo-add.

    Since both the repo-add and repo-remove scripts have the
    same command-line usage, it is simpler to generalize both
    operations using a single function.

    :param operation: run repo-add or repo-remove, can be
        either 'add' or 'remove'
    :type operation: str
    :param db: the database file to operate on
    :type db: str, bytes, or path-like object
    :param opts: extra options to pass to repo-add
    :type opts: list
    :param pkgs: these arguments depend on whether the operation is
        an add or remove.
        If operation is 'add', then pkgs is all of the paths of the
        package files to add to the database. If operation is 'remove',
        then pkgs is the name of the packages to remove from the database.
    :type pkgs: any iterable
    :raises: RepoAddError if repo-add failed
    """
    if operation == 'add':
        syslog.info('Adding packages to database')
    else:
        syslog.info('Removing packages from database')

    syslog.debug(f"Database: {db}")
    syslog.debug(f"Options: {opts}")
    syslog.debug(f"Packages: {pkgs}")

    try:
        cmd = gen_cmdline(operation, db, opts, *pkgs)
        process = subprocess.run(cmd,
                                 check=True,
                                 capture_output=True,
                                 text=True)
    except subprocess.CalledProcessError:
        raise RepoAddError(process.stderr)
    else:
        syslog.debug(process.stdout)
        syslog.info('Database operation complete')