import c32
import hashlib
import struct

def _checksum(v):
	return hashlib.sha256(hashlib.sha256(v).digest()).digest()[-4:]

'''
String format:
- c32(Raw format) in reverse order

Raw format:
- 4 bytes checksum
- N bytes data (NOTE: encoded to prevent hidden changes)
- - for script:
- - - N bytes: varint preimage data length
- - - N bytes: preimage data
- - - N bytes: script data
- - for BIP32 HD parent key:
- - - 32 bytes: chain code
- - - 33 bytes: parent pubkey
- - for BIP32 serialized key:
- - - 1 byte: depth
- - - 4 bytes: child number
- - - 32 bytes: chain code
- - - One of:
- - - - 32 bytes: private key data
- - - - 33 bytes: public key data
- 1 byte flag (ignored if unknown)
- 1 byte type
- - 01 script (with preimage data)
- - 02 script hash preimage
- - 03 BIP32 HD parent key
- - 04 BIP32 serialized public key
- 2 bytes namespace (blockchain id)
- - 2d41 Bitcoin  ('2bc')
- - 2e01 Namecoin ('2nc')
- - 2e37 Freicoin ('FRC')
'''

class c32d:
	__slots__ = ('data', 'ns', 'dtype', 'dflag')
	
	def __init__(self, data, ns, dtype, dflag):
		self.data = data
		self.ns = ns
		self.dtype = dtype
		self.dflag = dflag
	
	@classmethod
	def decode(cls, s, raw = False):
		if not raw:
			full = c32.decode(s[::-1])
		else:
			full = s
		
		csum = bytearray(full[:4])
		v = bytearray(full[4:])
		
		# Encode the configuration bytes to simplify decoding
		pv = 0xbf
		for i in range(len(v) - 1, len(v) - 5, -1):
			pv = v[i] ^ (csum[i % 4]) ^ pv
			v[i] = pv
		
		v.append(0xbf)
		for i in range(len(v) - 1):
			v[i] ^= csum[i % 4] ^ v[i + 1]
		v.pop()
		
		v = bytes(v)
		if csum != _checksum(v):
			raise ValueError('c32d checksum wrong')
		
		o = cls(None, None, None, None)
		o.data = v[:-4]
		o.dflag = v[-4]
		o.dtype = v[-3]
		o.ns = struct.unpack('!H', v[-2:])[0]
		
		return o
	
	def encode(self, raw = False):
		try:
			v = self.data + struct.pack('!BBH', self.dflag, self.dtype, self.ns)
		except struct.error as e:
			raise ValueError(e)
		csum = bytearray(_checksum(v))
		
		v = bytearray(v)
		pv = 0xbf
		for i in range(len(v) - 1, -1, -1):
			pv = v[i] ^ csum[i % 4] ^ pv
			if i < len(v) - 4:
				v[i] = pv
		v = csum + bytes(v)
		
		if raw:
			return v
		
		return c32.encode(v)[::-1]

decode = c32d.decode

def encode(*a, **ka):
	return c32d(*a, **ka).encode()

def test():
	c32.test()
	for (p, s, raw) in (
		((b'', 0, 0, 0), '1111115Fd9acc', b'\xb5\xa5\x0c\xb9\x00\x00\x00\x00'),
		((b'test', 4232, 142, 219), '955OGe8hOGc97hH4EJj1', b'?V\x1e\\d/\x1cq\xdb\x8e\x10\x88'),
		((b'\xff' * 0x100, 0xffff, 0xff, 0xff), 'YYYYYYc327OYcC6F9Or6r14UYCJtc5UGt9n2YYbeH63jda5GnYjCEO3r8E53dGYFbchrG4c327OYcC6F9Or6r14UYCJtc5UGt9n2YYbeH63jda5GnYjCEO3r8E53dGYFbchrG4c327OYcC6F9Or6r14UYCJtc5UGt9n2YYbeH63jda5GnYjCEO3r8E53dGYFbchrG4c327OYcC6F9Or6r14UYCJtc5UGt9n2YYbeH63jda5GnYjCEO3r8E53dGYFbchrG4c327OYcC6F9Or6r14UYCJtc5UGt9n2YYbeH63jda5GnYjCEO3r8E53dGYFbchrG4c327OYcC6F9Or6r14UYCJtc5UGt9n2YYbeH63jda5GnYjCEO3r8E53dGYFbchrG4c327OYcC6F9Or6r14UYCJtc5UGb2cOdG3', b'\xb0\xce,*\xc7\x88\xb9j\xbf\xf0\xc1\x12\xc7\x88\xb9j\xbf\xf0\xc1\x12\xc7\x88\xb9j\xbf\xf0\xc1\x12\xc7\x88\xb9j\xbf\xf0\xc1\x12\xc7\x88\xb9j\xbf\xf0\xc1\x12\xc7\x88\xb9j\xbf\xf0\xc1\x12\xc7\x88\xb9j\xbf\xf0\xc1\x12\xc7\x88\xb9j\xbf\xf0\xc1\x12\xc7\x88\xb9j\xbf\xf0\xc1\x12\xc7\x88\xb9j\xbf\xf0\xc1\x12\xc7\x88\xb9j\xbf\xf0\xc1\x12\xc7\x88\xb9j\xbf\xf0\xc1\x12\xc7\x88\xb9j\xbf\xf0\xc1\x12\xc7\x88\xb9j\xbf\xf0\xc1\x12\xc7\x88\xb9j\xbf\xf0\xc1\x12\xc7\x88\xb9j\xbf\xf0\xc1\x12\xc7\x88\xb9j\xbf\xf0\xc1\x12\xc7\x88\xb9j\xbf\xf0\xc1\x12\xc7\x88\xb9j\xbf\xf0\xc1\x12\xc7\x88\xb9j\xbf\xf0\xc1\x12\xc7\x88\xb9j\xbf\xf0\xc1\x12\xc7\x88\xb9j\xbf\xf0\xc1\x12\xc7\x88\xb9j\xbf\xf0\xc1\x12\xc7\x88\xb9j\xbf\xf0\xc1\x12\xc7\x88\xb9j\xbf\xf0\xc1\x12\xc7\x88\xb9j\xbf\xf0\xc1\x12\xc7\x88\xb9j\xbf\xf0\xc1\x12\xc7\x88\xb9j\xbf\xf0\xc1\x12\xc7\x88\xb9j\xbf\xf0\xc1\x12\xc7\x88\xb9j\xbf\xf0\xc1\x12\xc7\x88\xb9j\xbf\xf0\xc1\x12\xc7\x88\xb9j\xbf\xf0\xc1\x12\xff\xff\xff\xff'),
	):
		(kp, pp) = ({}, p)
		for i in range(2):
			o = c32d(*pp, **kp)
			assert o.data == p[0]
			assert o.ns == p[1]
			assert o.dtype == p[2]
			assert o.dflag == p[3]
			kp = {
				'data': p[0],
				'ns': p[1],
				'dtype': p[2],
				'dflag': p[3],
			}
			pp = ()
		assert o.encode() == s
		assert o.encode(raw=True) == raw
	
	def ensureValueError(f):
		try:
			f()
		except ValueError:
			pass
		else:
			raise AssertionError('Invalid decode input did not throw a ValueError')
	ensureValueError(lambda: encode(b'', -1, 0, 0))
	ensureValueError(lambda: encode(b'', 0x10000, 0, 0))
	ensureValueError(lambda: encode(b'', 0, -1, 0))
	ensureValueError(lambda: encode(b'', 0, 0x100, 0))
	ensureValueError(lambda: encode(b'', 0, 0, -1))
	ensureValueError(lambda: encode(b'', 0, 0, 0x100))
	
	# Invalid c32d
	ensureValueError(lambda: decode('1111115Fd9adc'))
	ensureValueError(lambda: decode('11A1115Fd9acc'))
	
	# Invalid c32
	ensureValueError(lambda: decode('111x115Fd9acc'))
	ensureValueError(lambda: decode('1111115Fd9acx'))

if __name__ == '__main__':
	test()
	print("Tests passed")