# Copyright (c) 2017 Pieter Wuille
# Copyright (c) 2018 Oskar Hladky
# Copyright (c) 2018 Pavol Rusnak
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
# THE SOFTWARE.

CHARSET = 'qpzry9x8gf2tvdw0s3jn54khce6mua7l'


def cashaddr_polymod(values):
    generator = [0x98f2bc8e61, 0x79b76d99e2, 0xf33e5fb3c4, 0xae2eabe2a8, 0x1e4f43e470]
    chk = 1
    for value in values:
        top = chk >> 35
        chk = ((chk & 0x07ffffffff) << 5) ^ value
        for i in range(5):
            chk ^= generator[i] if (top & (1 << i)) else 0
    return chk ^ 1


def prefix_expand(prefix):
    return [ord(x) & 0x1f for x in prefix] + [0]


def calculate_checksum(prefix, payload):
    poly = cashaddr_polymod(prefix_expand(prefix) + payload + [0, 0, 0, 0, 0, 0, 0, 0])
    out = list()
    for i in range(8):
        out.append((poly >> 5 * (7 - i)) & 0x1f)
    return out


def verify_checksum(prefix, payload):
    return cashaddr_polymod(prefix_expand(prefix) + payload) == 0


def b32decode(inputs):
    out = list()
    for letter in inputs:
        out.append(CHARSET.find(letter))
    return out


def b32encode(inputs):
    out = ''
    for char_code in inputs:
        out += CHARSET[char_code]
    return out


def convertbits(data, frombits, tobits, pad=True):
    acc = 0
    bits = 0
    ret = []
    maxv = (1 << tobits) - 1
    max_acc = (1 << (frombits + tobits - 1)) - 1
    for value in data:
        if value < 0 or (value >> frombits):
            return None
        acc = ((acc << frombits) | value) & max_acc
        bits += frombits
        while bits >= tobits:
            bits -= tobits
            ret.append((acc >> bits) & maxv)
    if pad:
        if bits:
            ret.append((acc << (tobits - bits)) & maxv)
    elif bits >= frombits or ((acc << (tobits - bits)) & maxv):
        return None
    return ret


def encode(prefix, version, payload):
    payload = bytes([version]) + payload
    payload = convertbits(payload, 8, 5)
    checksum = calculate_checksum(prefix, payload)
    return prefix + ':' + b32encode(payload + checksum)


def decode(prefix, addr):
    addr = addr.lower()
    decoded = b32decode(addr)
    if not verify_checksum(prefix, decoded):
        raise ValueError('Bad cashaddr checksum')
    data = bytes(convertbits(decoded, 5, 8))
    return data[0], data[1:-6]