import hashlib
import sys
import datetime
import sqlite3
import math
import pathlib
import itertools
import logging as log
from itertools import zip_longest
from db import DB

BLOCK_SIZE=4096
HASH_LEN=8
DB_NAME="morevna.db"
FILE_COUNT=2**21
TARGET_DIR="temp"

log.basicConfig(level=log.DEBUG)

class Pipeline:
	def __init__(self,fileName):
		self.fileName=fileName
		self.db=DB(DB_NAME)
		self.actions=[]

	def setup(self):
		self.db.setup()

	def update(self):
		log.info("starting update")
		for (i,(chunk,storedHashRec)) in enumerate(zip_longest(self.chunks(), self.db.listHashes())):
			if not chunk: break
			hash=self.hash(chunk)
			storedHash=(storedHashRec and storedHashRec["sector_hash"]) or b"\0"
			if hash==storedHash: continue
			log.info("updating sector %d, hash %s != stored %s", i, hash.hex(), storedHash.hex())
			self.copyChunk(chunk,i)
			self.db.insertHash(i,hash)
		self.db.connection.commit()
		log.info("update done")

	def chunks(self):
		with open(self.fileName, mode="br") as f: # !! buffering
			data=f.read(BLOCK_SIZE)
			while data:
				yield data
				data=f.read(BLOCK_SIZE)

	@staticmethod
	def hash(chunk):
		return hashlib.sha256(chunk).digest()[:HASH_LEN]

	def copyChunk(self,chunk,i):
		path=self.getChunkPath(i)
		if not path.parent.exists(): path.parent.mkdir(parents=True) # !! no fail? existing file named as a dir
		log.debug("writing file %s", path)
		f=path.open(mode="wb")
		f.write(chunk)
		f.close()

	def mergeChunks(self):
		log.info("starting merge")
		try: targetFile=open(self.fileName,mode="xb")
		except FileExistsError:
			log.warning("file %s already exists, aborting",self.fileName)
			return False # !! be more specific

		i=0
		while True:
			try:
				sourcePath=self.getChunkPath(i)
				sourceFile=sourcePath.open(mode="rb")
				targetFile.write(sourceFile.read())
				sourceFile.close()
				log.info("file %s merged",sourcePath)
			except FileNotFoundError: break
			i+=1
		targetFile.close()
		log.info("merge done")
		return True

	def getChunkPath(self,i):
		paddedName=("{0:0"+str(len(str(FILE_COUNT)))+"}").format(i)
		return pathlib.Path(TARGET_DIR).joinpath(Pipeline.getPath(paddedName))

	@staticmethod
	def getPath(name):
		dirs=[name]
		for i in range(2,len(name),2):
			dirs.append(name[:-i])
		return pathlib.Path(*reversed(dirs))

def initDB():
	conn=sqlite3.connect("morevna.db")

	c=conn.cursor()
	c.execute("""create table if not exists `hashes` (
		`sector_id` integer primary key,
		`sector_hash` blob not null,
		`updated` integer
	)""")
	
	c.execute("""create index if not exists `dirty_index` on `hashes` (`dirty`)""")
	conn.commit()

def initHashes(fileName):
	initDB()
			
	with sqlite3.connect(DB) as db:
		handle=db.cursor()
		handle.executemany(
			"""insert into `hashes` (`sector_id`,`sector_hash`,`dirty`) values (:id,:hash,1)""",
			({"id":i,"hash":dataHash} for (i,dataHash) in enumerate(chunks(fileName)))
		)
		db.commit()

def hashes():
	with sqlite3.connect(DB) as db:
		handle=db.cursor()
		handle.execute("""select `sector_hash` from `hashes` order by `sector_id` asc""")
		h=handle.fetchone()
		while h is not None:
			yield h
			h=handle.fetchone()

def findChanges(fileName):
	changelist=[]

	# build changelist
	# can use up to (HASH_LEN+size(int))*(filesize/BLOCK_SIZE) bytes of memory plus overhead
	# that's (8+4)*(8*2**30 / 4096) = 24MB for defaults
	for (i,(dataHash,savedHash)) in enumerate(itertools.zip_longest(chunks(fileName),hashes())):
		if dataHash!=savedHash:
			changelist.append((i,dataHash))
		if dataHash is None: break # shouldn't happen

	# write log
	with open(logFile, mode="w") as f:
		f.write("sector	hash\n")
		for (i,dataHash) in changelist:
			f.write("{0}\t{1}\n".format(i,dataHash))
			
	# update DB
	with sqlite3.connect(DB) as db:
		handle=db.cursor()
		handle.executemany(
			"""update `hashes` set `sector_hash`=:hash, `dirty`=1 where `sector_id`=:id""",
			({"id":i,"hash":dataHash} for (i,dataHash) in changelist)
		)
		db.commit()
	
def transferChanges(targetPath):
	# read changes
	with sqlite3.connect(DB) as db, open(fileName,mode="rb") as sf:
		handle=db.cursor()
		handle.execute("""select `sector_id` from `hashes` where `dirty`=1""")
			
		# transfer modified sectors and mark them as clean
		sectorIds=handle.fetchall()
		'''for (sectorId,) in sectorIds:
			path=targetPath / getPath(sectorId)
			try: path.parent.mkdir(parents=True)
			except FileExistsError: pass
			df=path.open(mode="wb")
			sf.seek(sectorId)
			df.write(sf.read(BLOCK_SIZE))
			handle.execute("""update `hashes` set `dirty`=0 where `sector_id`=?""",(sectorId,))
			db.commit()'''
		sector=sf.read(BLOCK_SIZE)
		i=j=0
		while sector and j<len(sectorIds):
			if i==sectorIds[j][0]:
				path=targetPath / getPath(sectorId)
				try: path.parent.mkdir(parents=True)
				except FileExistsError: pass
				df=path.open(mode="wb")
				df.write(sector)
				handle.execute("""update `hashes` set `dirty`=0 where `sector_id`=?""",(sectorIds[j][0],))
				db.commit()
				j+=1
			i+=1
			sector=sf.read(BLOCK_SIZE)

def getPath(index):
	nodeIds=[]
	k=1
	while k<=FILE_COUNT:
		paddedLen=int(math.log10(FILE_COUNT/k))
		nodeIds.append("{0:0{1}}",index//k,paddedLen)
		k*=FILES_PER_DIR
	nodeIds.reverse()
	return pathlib.Path(*[id for id in enumerate(nodeIds)])

action=sys.argv[1]
fileName=sys.argv[2]
baseName=".".join(fileName.split(".")[:-1])
hashFile="{0}-hash.dat".format(baseName)
isoDate=datetime.datetime.now().strftime("%Y%m%dT%H%M%S")
logFile="{0}-{1}.log".format(baseName,isoDate)

pipeline=Pipeline(fileName)
if action=="setup": pipeline.setup()
elif action=="update": pipeline.update()
#elif action=="transfer": transferChanges(sys.argv[3])
elif action=="rebuild": pipeline.mergeChunks()
else: print("bad action")