import hashlib
import datetime

def stringify(*args):
    toStr = lambda x: ''.join(list(map(str,x)))
    strData = toStr(list(args))
    return strData

def hashing(stringdata):
    key = hashlib.sha256()
    key.update(stringdata.encode("utf-8"))
    return key.hexdigest()

class Block():
    def __init__(self, index, timestamp, data, prevBlockhash, selfhash):
        self.index = index
        self.timestamp = timestamp
        self.data = data
        self.prevBlockhash = prevBlockhash
        
        self.selfhash = selfhash
    def __str__(self):
        return stringify(self.index,self.timestamp,self.data,self.prevBlockhash)
    

def verify(chain):
    ChainLength = len(chain)
    print(f"{ChainLength} is length of blockchain\n")
    
    def validatePrevBlockhash(k):
        CurrBlockPresentation = chain[k].prevBlockhash
        manualHashPrev = hashing(str(chain[k-1]))
        if manualHashPrev != CurrBlockPresentation:
            print(
    f"""{k}:current-block presents PREVIOUS block hash as: {CurrBlockPresentation} 
manual hashing of the previous block in chain: {manualHashPrev} 
Current-block is malicious and tampered with chain history thus altering the previous block hash\n""")
            return False
        return True
    
    def validateCurrBlockData(k):
        CurrBlockPresentation = chain[k].selfhash
        manualHashCurr = hashing(str(chain[k]))
        if manualHashCurr != CurrBlockPresentation:
            print(
    f"""{k}:current-block presents a hash of: {CurrBlockPresentation}
Manual hashing of current blocks data shows a hash of: {manualHashCurr}
Malicious Current-block is not presenting a valid hash for it's data\n""")
            return False
        return True
                  
    def validateIndexOrdering(k):
        CurrBlockPresentation = chain[k].index
        manualChainIndex = k
        if manualChainIndex != CurrBlockPresentation:
            print(
    f"""{k}:current-block presents index of {CurrBlockPresentation}
Iterating the chain shows an index of {k}
Current-block may have been too slow to add to chain, or a malicious actor is trying to reorder chain\n""")
            return False
        return True
                  
    def validateTimeStampOrdering(k):
        if chain[k-1].timestamp >= chain[k].timestamp:
            print(
    f"""{k}:current-block presents date as {chain[k].timestamp}
previous block was dated {chain[k-1].timestamp}
Currentblock may have been too slow to add to chain, or a malicious actor is trying to reorder chain\n""")
            return False
        return True

    for i in range(ChainLength):
        validateCurrBlockData(i)
        validateIndexOrdering(i)
        if i != 0:
            validatePrevBlockhash(i)
            validateTimeStampOrdering(i)


# dummyblockhash = hashing(str("blah"))
    
mychain = []

FirstBlockData = (0,datetime.datetime.utcnow(),"Genesis","NoPrevBlockHash")
selfhash1st = hashing(stringify(*FirstBlockData))
FirstBlock = Block(*FirstBlockData,selfhash1st)
mychain = [FirstBlock]

SecondBlockData = (1,datetime.datetime.utcnow(),"afsaw",selfhash1st)
selfhash2nd = hashing(stringify(*SecondBlockData))
SecondBlock = Block(*SecondBlockData,selfhash2nd)
mychain = mychain + [SecondBlock]

ThirdBlockData = (2,datetime.datetime.utcnow(),"esfr",selfhash2nd)
selfhash3rd = hashing(stringify(*ThirdBlockData))
ThirdBlock = Block(*ThirdBlockData,selfhash3rd)
mychain = mychain + [ThirdBlock]

BadBlockData = (1,datetime.datetime.utcnow()-datetime.timedelta(seconds=2),"awefaw",selfhash1st)
selfhashBad = hashing(stringify(*BadBlockData))
BadBlock = Block(*BadBlockData,selfhashBad)
mychain = mychain + [BadBlock]


verify(mychain)

# 4 is length of blockchain

# `3:` refers the the 4th block aka BadBlock
# 3:current-block presents index of 1
# Iterating the chain shows an index of 3
# Current-block may have been too slow to add to chain, or a malicious actor is trying to reorder chain

# 3:current-block presents PREVIOUS block hash as: 4feac5456f60ae87430efc3aa70be96ad7285a897e5c2fc36240bb391ebe04bd 
# manual hashing of the previous block in chain: 2ff87d74f8f4ee982a034b916d1246364a95b6078817bcc41aa2a43f4f2b8943 
# Current-block is malicious and tampered with chain history thus altering the previous block hash

# 3:current-block presents date as 2022-04-21 05:13:07.327116
# previous block was dated 2022-04-21 05:13:09.326804
# Currentblock may have been too slow to add to chain, or a malicious actor is trying to reorder chain