#!/usr/bin/env python3

"""

Mike's Backup Rotator

A simple script to help automatically rotate backup files

Copyright 2022 Mike Peralta; All rights reserved

Released under the GNU GENERAL PUBLIC LICENSE v3 (See LICENSE file for more)

"""

import datetime
import os
import shutil
import sys
import syslog
import time
import yaml


class BackupRotator:
	
	def __init__(self):
		
		self.__dry_run = False
		self.__configs = []
		self.__config_paths = []
		self.__calculated_actions = []
	
	def run(self, configs, dry_run: bool = False):
		
		self.log("Begin")
		
		self.__dry_run = dry_run
		self.__config_paths = configs
		
		self._consume_configs(self.__config_paths)
		
		# Rotate once per config
		for config_index in range(len(self.__configs)):
			
			#
			config = self.__configs[config_index]
			
			#
			self.log("Rotating for config " + str(config_index + 1) + " of " + str(len(self.__configs)), config["__path"])
			self._do_rotate(config)
	
	@staticmethod
	def current_time():
		
		now = datetime.datetime.now()
		now_s = now.strftime("%b-%d-%Y %I:%M%p")
		return str(now_s)
	
	def log(self, s, o=None):
		
		now = self.current_time()
		
		to_log = "[" + now + "][Backup Rotator] " + str(s)
		if o is not None:
			to_log += " " + str(o)
		
		syslog.syslog(to_log)
		
		print(to_log)
	
	def _consume_configs(self, paths: list=None):
		
		assert paths is not None, "Config paths cannot be None"
		assert len(paths) > 0, "Must provide at least one config file path"
		
		# Use each config path
		for path in paths:
			
			# If this is a single path
			if os.path.isfile(path):
				self._consume_config(path)
			
			# If this is a directory
			elif os.path.isdir(path):
				
				# Iterate over each file inside
				for file_name in os.listdir(path):
					self._consume_config(os.path.join(path, file_name))
				
	def _consume_config(self, path: str):
		
		# Open the file
		f = open(path)
		if not f:
			raise Exception("Unable to open config file: " + path)
		
		# Parse
		config = yaml.safe_load(f)
		
		# Add its own path
		config["__path"] = path
		
		# Consume to internal
		self.__configs.append(config)
		self.log("Consumed config from path:", path)
	
	def _do_rotate(self, config):
	
		self._rotate_paths(config)
	
	def _rotate_paths(self, config):
		
		self.log("Begin rotating " + str(len(config["paths"])) + " paths")
		for path in config["paths"]:
			self._rotate_path(config, path)
	
	def _rotate_path(self, config, path):
		
		assert os.path.isdir(path), "Path should be a directory: {}".format(path)
		
		self.log("Rotating path: {}".format(path))
		
		found_any_rotation_keys = False
		if "maximum-items" in config.keys():
			found_any_rotation_keys = True
			self._rotate_path_for_maximum_items(config=config, path=path, max_items=config["maximum-items"])
		if "maximum-age" in config.keys():
			found_any_rotation_keys = True
			self._rotate_path_for_maximum_age(config=config, path=path, max_age_days=config["maximum-age"])

		assert found_any_rotation_keys is True, \
			"Config needs one of the following keys: \"maximum-items\""

	def _rotate_path_for_maximum_items(self, config, path: str, max_items: int):
		
		assert os.path.isdir(path), "Path should be a directory: {}".format(path)
		
		self.log("Rotating path for maximum items: {}".format(path))
		
		children = self._gather_rotation_candidates(config, path)
		
		# Do we need to rotate anything out?
		if len(children) <= max_items:
			self.log(
				"Path only has {} items, but needs more than {} for rotation; Won't rotate this path.".format(
					len(children), max_items
				)
			)
			return
		
		#
		purge_count = len(children) - max_items
		self.log("Need to purge {} items".format(purge_count))
		
		for purge_index in range(purge_count):
			
			#
			item_to_purge, item_ctime = self._pick_oldest_item(config, children)
			children.remove(item_to_purge)
			self.log("Found next item to purge: ({}) {} (ctime: {})".format(
				purge_index + 1,
				os.path.basename(item_to_purge), item_ctime
			))
			
			#
			self._remove_item(config, item_to_purge)
	
	def _rotate_path_for_maximum_age(self, config, path: str, max_age_days: int):
		
		assert os.path.isdir(path), "Path should be a directory: {}".format(path)
		
		self.log("Rotating path for max age of {} days: {}".format(max_age_days, path))
		
		children = self._gather_rotation_candidates(config, path)
		
		self.log("Examining {} items for deletion")
		children_to_delete = []
		for child in children:
			
			age_seconds = self._detect_item_age_seconds(config, child)
			age_days = self._detect_item_age_days(config, child)
			age_formatted = self.seconds_to_time_string(age_seconds)
			child_basename = os.path.basename(child)
			
			if age_days > max_age_days:
				self.log("Old enough to delete: {} ({})".format(
					child_basename, age_formatted
				))
				children_to_delete.append(child)
			else:
				self.log("Not old enough to delete: {} ({})".format(
					child_basename, age_formatted
				))

		self.log("Removing old items ...")
		for child_to_delete in children_to_delete:
			basename = os.path.basename(child_to_delete)
			self.log("> {}".format(basename))
			self._remove_item(config, child_to_delete)

		
	@staticmethod
	def _gather_rotation_candidates(config, path):
		
		candidates = []
		
		if "target-type" not in config.keys():
			raise Exception("Please provide the configuration key: target-type")
		
		for item_name in os.listdir(path):
			
			item_path = os.path.join(path, item_name)
			
			if config["target-type"] == "file":
				if not os.path.isfile(item_path):
					continue
			elif config["target-type"] == "directory":
				if not os.path.isdir(item_path):
					continue
			else:
				raise Exception("Configuration key \"target-type\" must be \"file\" or \"directory\"")
			
			candidates.append(item_path)
		
		return candidates
	
	def _pick_oldest_item(self, config, items):
		
		best_item = None
		best_ctime = None
		for item in items:
			
			ctime = self._detect_item_date(config, item)
			if best_ctime is None or ctime < best_ctime:
				best_ctime = ctime
				best_item = item
		
		return best_item, best_ctime
	
	@staticmethod
	def _detect_item_date(config, item):
		
		assert "date-detection" in config.keys(), "Please provide config key: \"date-detection\""
		detection = config["date-detection"]

		if detection == "file":
			ctime = os.path.getctime(item)
		else:
			raise AssertionError("Invalid value for \"date-detection\"; Should be one of {file}: {}".format(
				detection
			))

		return ctime

	def _detect_item_age_seconds(self, config, item):
		
		now = time.time()
		ctime = self._detect_item_date(config, item)
		delta = now - ctime
		
		return delta

	def _detect_item_age_days(self, config, item):
		
		age_seconds = self._detect_item_age_seconds(config, item)
		age_days = int(age_seconds / 86400)

		return age_days

	def seconds_to_time_string(self, seconds: float):
		
		if isinstance(seconds, float):
			pass
		elif isinstance(seconds, int):
			seconds = float * 1.0
		else:
			raise AssertionError("Seconds must be an int or float")
		
		# Map
		map = {
			"year": 31536000.0,
			"month": 2592000.0,
			"week": 604800.0,
			"day": 86400.0,
			"hour": 3600.0,
			"minute": 60.0,
			"second": 1.0
		}
		
		s_parts = []
		for unit_label in map.keys():
			unit_seconds = map[unit_label]
			if seconds >= unit_seconds:
				unit_count = int(seconds / unit_seconds)
				s_parts.append("{} {}{}".format(
					unit_count, unit_label,
					"" if unit_count == 1 else "s"
				))
				seconds -= unit_seconds * unit_count
		
		s = ", ".join(s_parts)
		
		return s

	def _remove_item(self, config, path):
		
		if os.path.isfile(path):
			self._remove_file(config, path)
		elif os.path.isdir(path):
			self._remove_directory(config, path)
		else:
			raise AssertionError("Don't know how to remove this item: {}".format(path))

	def _remove_file(self, config, file_path):
		
		if not os.path.isfile(file_path):
			raise Exception("Tried to remove a file, but this path isn't a file: " + str(file_path))
		
		if self.__dry_run:
			self.log("Won't purge file during global-level dry run: ", file_path)
		elif "dry-run" in config.keys() and config["dry-run"] is True:
			self.log("Won't purge file during config-level dry run: ", file_path)
		else:
			self.log("Purging file:", file_path)
			os.remove(file_path)
	
	def _remove_directory(self, config, dir_path):
		
		if not os.path.isdir(dir_path):
			raise Exception("Tried to remove a directory, but this path isn't a directory: " + str(dir_path))
		
		if self.__dry_run:
			self.log("Won't purge directory during global-level dry run: ", dir_path)
		elif "dry-run" in config.keys() and config["dry-run"] is True:
			self.log("Won't purge directory during config-level dry run: ", dir_path)
		else:
			self.log("Purging directory:", dir_path)
			shutil.rmtree(dir_path)