# lognestmonster Copyright (c) 2019 Joshua 'joshuas3' Stockin
# <https://github.com/JoshuaS3/lognestmonster/>.


# This file is part of lognestmonster.

# lognestmonster is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.

# lognestmonster is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.

# You should have received a copy of the GNU General Public License
# along with lognestmonster. If not, see <https://www.gnu.org/licenses/>.

import struct
import os
import resource
import time
import sys

STATEMENT_START = 0
STATEMENT_END = 1
EVENT_START = 2
EVENT_END = 3

VERBOSITY_LEVELS = {
	0: "INIT",
	1: "DEBUG",
	2: "VERBOSE",
	3: "VERYVERBOSE",
	4: "WARNING",
	5: "ERROR"
}

def ulonglong(bytestr):
	return struct.unpack("@Q", bytestr)[0]
def uchar(charv):
	return struct.unpack("@B", charv)[0]
def ushort(shortv):
	return struct.unpack("@H", shortv)[0]


class EventProto:
	parent = None
	pushed = [False]
	def __init__(self):
		self.parent = None
		self.pushed = [False]

class Reader:
	fd = None

	version = 0
	timestamp = 0

	top_level = []

	event_count = 0
	statement_count = 0

	file_size = 0
	position = 0
	bad_bytes = 0

	filter_time_start = -1
	filter_time_end = -1
	filter_verbosity = -1
	filter_tag = -1

	def __init__(self, fd):
		self.fd = fd

		self.version = 0
		self.timestamp = 0

		self.top_level = []

		self.event_count = 0
		self.statement_count = 0

		self.file_size = 0
		self.position = 0
		self.bad_bytes = 0

		self.filter_time_start = -1
		self.filter_time_end = -1
		self.filter_verbosity = -1
		self.filter_tag = -1

	def size(self):
		self.fd.seek(0, os.SEEK_END) # go to end of file and get position
		newsize = self.fd.tell()
		self.fd.seek(self.position) # return to previous position

		is_diff = self.file_size is not newsize
		self.file_size = newsize
		return is_diff

	def pos(self):
		p = self.fd.tell()
		self.position = p
		return p

	def seek(self, position):
		self.position = position
		self.fd.seek(self.position)

	def read(self, byte_count):
		data = self.fd.read(byte_count)
		if len(data) == byte_count:
			return data
		else:
			return False

	def scan(self): # scan for events and statements from self.position to the end of file
		print()
		print("beginning file scan")
		if self.filter_time_start is not -1:
			print("filter time start: {0}".format(self.filter_time_start))
		if self.filter_time_end is not -1:
			print("filter time end: {0}".format(self.filter_time_end))
		if self.filter_verbosity is not -1:
			print("filter verbosity: {0}".format(self.filter_verbosity))
		if self.filter_tag is not -1:
			print("filter tag: {0}".format(self.filter_tag))
		print("file size: {0}".format(self.file_size))
		print()

		s = time.time()

		if self.position == 0: # if it's the start of the file, grab version and timestamp
			self.version = uchar(self.read(1))
			self.timestamp = ulonglong(self.read(8))

		current_statement = None
		current_event = None

		if self.pos() < self.file_size: # if the seeker is before EOF
			while self.pos() < self.file_size: # while the seeker is before EOF
				in_byte = uchar(self.read(1)) # read 1 byte

				if in_byte == STATEMENT_START: # the byte indicates a statement's start, begin interpreting
					this_position = self.position + 1 # identify and save the seeker position of this statement

					try:
						timestamp = ulonglong(self.read(8))
					
						append = True

						if self.filter_time_start is not -1 and append:
							append = timestamp > self.filter_time_start

						if self.filter_time_end is not -1 and append:
							append = timestamp < self.filter_time_end

						if self.filter_verbosity is not -1 and append:
							verbosity = uchar(self.read(1))
							append = verbosity in self.filter_verbosity
						else:
							self.seek(this_position + 9)

						tag_size = uchar(self.read(1))
						if self.filter_tag is not -1 and append:
							if tag_size > 0:
								tag = self.read(tag_size).decode("utf-8")
								append = tag == self.filter_tag
						else:
							self.seek(this_position + 10 + tag_size)

						message_size = ushort(self.read(2))
						self.seek(this_position + 12 + tag_size + message_size) # ignore the message
						
						while uchar(self.read(1)) is not STATEMENT_END and self.pos() < self.file_size: # we can afford self.pos() here because most files aren't corrupt
							self.bad_bytes += 1

						if append == True:
							self.statement_count += 1
							if current_event is not None:
								current_event.pushed.append(this_position)
							else:
								self.top_level.append(this_position)
					except Exception as e:
						self.bad_bytes += self.pos() - this_position

				elif in_byte == EVENT_START: # the byte indicates an event's start, create an event
					new_event = EventProto()
					if current_event is not None: # if an event exists, push the new event to it
						new_event.parent = current_event
					current_event = new_event


				elif in_byte == EVENT_END: # the byte indicates an event's end, close event if exists
					if current_event is not None:
						if len(current_event.pushed) > 1:
							self.event_count += 1
							if current_event.parent is not None:
								current_event.parent.pushed.append(current_event)
								current_event = current_event.parent # if the event has a parent, set the parent to current
							else:
								self.top_level.append(current_event) # event has no parent, it's a top-level log item
								current_event = None
						else:
							if current_event.parent is not None:
								current_event = current_event.parent # if the event has a parent, set the parent to current
							else:
								current_event = None
					else: # event doesn't exist, this end byte is out of place
						self.bad_bytes += 1

				else: # unknown byte, not in statement or event
					self.bad_bytes += 1

		print("finished reading, {0} bad bytes".format(self.bad_bytes))
		print()
		print("tree version: {0}".format(self.version))
		print("tree timestamp: {0}".format(self.timestamp))
		print()
		print("event count: {0}".format(self.event_count))
		print("statement count: {0}".format(self.statement_count))
		print()
		print("time elapsed: {0}".format(time.time() - s))