from __future__ import annotations

import logging
import os
import pathlib
import shutil
from datetime import datetime as dt
from collections.abc import Iterable

LOG_FORMAT = "%(name)s: %(message)s"
level = 20
logging.basicConfig(
    level=level,
    format=LOG_FORMAT,
    datefmt="[%H:%M:%S]",
    #handlers=[handler] if handler else [],  # for our UT benchmark, this is a pesky IT effort
)

logger = logging.getLogger('os-listdir')

logger.setLevel(level)


def clean_output_dir_original(path: str, retention: Iterable[str]) -> None:
    """Remove all files from output directory except those in retention list"""

    if not os.path.exists(path):
        logger.info("Directory already removed: %s", path)
        return

    if not os.path.isdir(path):
        try:
            os.remove(path)
        except Exception as e:
            logger.error("Unable to delete file %s; %s", path, e)
        return

    # remove existing content from output folder unless in retention list
    for filename in os.listdir(path):
        file = os.path.join(path, filename)
        if any(filename == retain for retain in retention):
            logger.info(
                "Skipping deletion; %s is on retention list: %s", filename, file
            )
        elif os.path.isdir(file):
            try:
                shutil.rmtree(file)
                logger.info("Deleted directory %s", file)
            except Exception as e:
                logger.error("Unable to delete directory %s; %s", file, e)
        elif os.path.isfile(file) or os.path.islink(file):
            try:
                os.remove(file)
                logger.debug("Deleted file/link %s", file)
            except Exception as e:
                logger.error("Unable to delete file %s; %s", file, e)
        else:
            logger.error("Unable to delete %s, file type unknown", file)


def clean_output_dir_new(path: str, retention: Iterable[str]) -> None:
    """Remove all files from output directory except those in retention list"""

    if not os.path.exists(path):
        logger.debug("Directory already removed: %s", path)
        return

    if not os.path.isdir(path):
        try:
            os.remove(path)
        except Exception as e:
            logger.error("Unable to delete file %s; %s", path, e)
        return

    # remove existing content from output folder unless in retention list
    for dir_entry in os.scandir(path):
        file = dir_entry.path
        if any(dir_entry.name == retain for retain in retention):
            logger.debug(
                "Skipping deletion; %s is on retention list: %s", dir_entry.name, file
            )
        elif dir_entry.is_dir():
            try:
                shutil.rmtree(file)
                logger.debug("Deleted directory %s", file)
            except Exception as e:
                logger.error("Unable to delete directory %s; %s", file, e)
        elif dir_entry.is_file(follow_symlinks=False) or dir_entry.is_symlink():
            try:
                os.remove(file)
                logger.debug("Deleted file/link %s", file)
            except Exception as e:
                logger.error("Unable to delete file %s; %s", file, e)
        else:
            logger.error("Unable to delete %s, file type unknown", file)
# Performance test


alphanum = 'abcdefghijklmnopqrstuvwxyz0123456789'
DIR_SEPARATOR = '/'
TEST_DIR = '/tmp/output'
shutil.rmtree(path=TEST_DIR, ignore_errors=False)
total_files = 0
total_dirs = 0
total_inodes = 0


def populate_files(test_path):
    global total_dirs
    global total_files
    global total_inodes

    def add_char_then_touch(test_dir, suffix_filename):
        global total_files
        for first_chr in alphanum:
            this_name = test_dir + DIR_SEPARATOR + suffix_filename + first_chr
            pathlib.Path(this_name).touch()
            total_files += 1
            for second_chr in alphanum:
                that_name = this_name + second_chr
                pathlib.Path(that_name).touch()
                total_files += 1

    # establish Test directory
    current_template = test_path
    try:
        os.mkdir(current_template)
    except:
        pass
    total_dirs += 1

    # populate test directory
    for first_char in alphanum:
        this_file = current_template + DIR_SEPARATOR + first_char
        pathlib.Path(this_file).touch()
        total_files += 1
        add_char_then_touch(current_template, first_char)


# prepare test area
populate_files(TEST_DIR)

# start performance test
old_start_dt = dt.now()

# Exercise target routine
clean_output_dir_original(TEST_DIR, [])

old_end_dt = dt.now()

# prepare test area
populate_files(TEST_DIR)

new_start_dt = dt.now()

clean_output_dir_new(TEST_DIR, [])

# end performance test
new_end_dt = dt.now()

# test results
old_delta_utc = old_end_dt - old_start_dt
new_delta_utc = new_end_dt - new_start_dt
print(f'Original Delta time {old_delta_utc}')
print(f'Latest   Delta time {new_delta_utc}')
print(f'Total inodes: {total_inodes}')
print(f'Total Files   {total_files}')
print(f'Total Dirs    {total_dirs}')